# Reading nameplate data



## BleedingLungsMurphy (10 mo ago)

ColbyL said:


> I have recently been given WAY too much responsibility for the little skills I have and I feel incredibly out of my depths, so I am hoping you guys can help me out a little.


You have the right to refuse work. Talk to your employer and document the interaction. They have to provide training. You are liable for the work you do. Learn to do it right or walk away until you are given the tools or knowledge that you need to safely to your job.


----------



## ColbyL (Jun 21, 2019)

I'm perfectly safe, it's just I either have to ask the bosses for what could possibly be a stupid question, or study myself on the weekend in preperation. If the answer you give isn't enough, I can still ask a question during the week.


----------



## micromind (Aug 11, 2007)

On the duct heater, L1 and L2 indicate that it's single phase. How many KW and is the KW rating 208 or 240?

The low voltage terminals may very well be a high temperature limit switch that needs to be connected in series with the contactor that controls it. They could be something else too. 

HVAC controls are typically 24AC but it could be 120.


----------



## glen1971 (Oct 10, 2012)

ColbyL said:


> I have recently been given WAY too much responsibility for the little skills I have and I feel incredibly out of my depths, so I am hoping you guys can help me out a little. I am new to reading nameplate data and I was wondering if you had any solid rules for when I need an extra circuit for a single device or when I need a control wire. I've already messed this up once with a Fan Coil/Cooler Unit combo. So I was hoping someone could tell me what to look for.
> 
> I have a Make-up-air/Duct Heater combo unit. The plans say it's just an MUA unit, not a Duct Heater and it's a 208V 1ph 12/2 device. The HVAC guy says it needs another wire for the Duct Heater. I don't know if he's just guessing or if he knows what he's doing. I thought this was suspicious so I asked someone above me to look at the nameplate data and see if he could figure out what's going on.
> 
> ...


L1 and L2 is a single phase description.

Whenever I've seen a label with a voltage of 120/208-240, that means it'll work on either 120 volt supply, with the higher of 2, or 3, current listings. Or 208 or 240 volt single phase. Some motors will list a current for either voltage, or a rating percentage to change the higher current, and even no additional note on the current.

Can you post a picture of the name plate in question?


----------



## ColbyL (Jun 21, 2019)

Sorry, I forgot to take a picture. But I believe it was a 3KW device. How can I tell which voltage rating the 3KW is related to? Anything you can offer is welcome.

I do remember one of the things that made no sense is that the nameplate said "maximum amperage=15A".

I don't expect to solve the problem today. I just want to brush up on the things that confused me before monday.

EDIT. 

I think things are a bit clearer. Tell me if my interpretation is right or not. 

120v/208-240 means that I have the option of running this device single phase either with 120v hot -> neutral, 208v red phase hot -> black phase hot or 240v hot -> neutral. 

I'll have to look at the shop drawings later, but can someone tell me, would a make-up air / duct heater combo for an apartment corridor ever need a control wire? I'm guessing that low voltage connection might be for an optional fire alarm component. Like a control relay?


----------



## micromind (Aug 11, 2007)

The nameplate max amps is most likely the max breaker or fuse size. If it's 3KW @ 240 single phase, the actual current would be 12.5 amps. It'd be lower with 208. 

There will be some sort of a contactor between the supply and the heater, the coil will be controlled by the fan unit. It'll turn the heater on along with the fan if it's needed.

The 2 control terminals are most likely a high temp. limit to shut the heater off if the temperature gets too high. They need to be connected in series with the contactor coil.


----------



## BleedingLungsMurphy (10 mo ago)

ColbyL said:


> have to ask the bosses for what could possibly be a stupid question


There are no stupid questions for an apprentice to ask.



ColbyL said:


> 208V 1ph 12/2 device


It sounds like you haven't learned 3 phase theory yet so this might be confusing.

208v 1 ph is not possible or at least not standard. He probably means 240v single phase or 208v but not all 3 phases. Looks like 2/3 phases are required if there is only an L1 and an L2 terminal.



ColbyL said:


> Opening the device, we can only find the L1 L2 terminals


For devices typically 3 phase would have L1 L2 L3

Single phase / split phase will have L1 N or L1 L2


----------



## BleedingLungsMurphy (10 mo ago)

ColbyL said:


> How can I tell which voltage rating the 3KW is related to?


Divide 3000 (3kw) by the voltage you have. 240 or 208. If you have the horsepower rating of the motor you can use tables in the code book to find the FLA.

Section 28 for motors

See Tables 29, 37, 44 or 45 in CEC 2021


----------



## glen1971 (Oct 10, 2012)

BleedingLungsMurphy said:


> There are no stupid questions for an apprentice to ask.
> 
> 
> It sounds like you haven't learned 3 phase theory yet so this might be confusing.
> ...


How is 208 volt single phase not possible? What do you get if you use a two pole breaker on a 120/208 volt, 3 phase 4 wire panel?

Edited to clarify the 2 pole breaker.


----------



## BleedingLungsMurphy (10 mo ago)

glen1971 said:


> How is 208 volt single phase not possible?


I said it isn't standard. If you have 208v to ground you better get off the high leg before you kill someone.



glen1971 said:


> What do you get if you use a pole breaker on a 120/208 volt, 3 phase 4 wire panel?


A single pole breaker from a 3 phase 120v/208v panel?

I get 120v. What do you get?


----------



## ColbyL (Jun 21, 2019)

I get 208 single phase all the time. Baseboard heaters for example. I did third year, so I understand 3ph theory. Just don't get to apply it much. Or at all yet. Pretty much nothing is 3ph, despite the fact that I'm installing every device in the building. Do you live in industrial? I'm woodframe residential. No gorilla work lifting transformers ten times heavier than I am for me thank you. 

And yes, this is single phase 208.

So micromind, you are saying that the wattage and amperage will go lower if I use one of the lower voltage options? The theory is still a bit foggy from school, but I remember them saying that the device will try to force the wattage to remain the same regardless of how low I make the voltage setting. Is this a special exception to that rule?


----------



## BleedingLungsMurphy (10 mo ago)

ColbyL said:


> And yes, this is single phase 208.


How are you getting 208v on a single phase? A 208v baseboard heater is not using a single phase. You have it connected between two phases for 208v or one phase to neutral for 120v.



ColbyL said:


> So micromind, you are saying that the wattage and amperage will go lower if I use one of the lower voltage options?


How would the wattage change? Amps will increase with lower voltage. Ohms law. Do you have your notes from 3rd year? This is basic stuff.


----------



## NoBot (Oct 12, 2019)

I've always thought that 120/208-240 means the a neutral is required. 12/3. Am I wrong?


----------



## glen1971 (Oct 10, 2012)

BleedingLungsMurphy said:


> I said it isn't standard. If you have 208v to ground you better get off the high leg before you kill someone.
> 
> 
> A single pole breaker from a 3 phase 120v/208v panel?
> ...


You said it isn't standard. A 2 pole breaker on a 120/208 volt 3 phase system gets you 208 volts line to line.

Fixed it. 2 pole breaker was what I was intending to ask..


----------



## glen1971 (Oct 10, 2012)

BleedingLungsMurphy said:


> How are you getting 208v on a single phase? A 208v baseboard heater is not using a single phase. You have it connected between two phases for 208v or one phase to neutral for 120v.


Have you worked on anything other than a light switch or a 3 phase motor?
Next thing you'll come up with is there is no such thing as 480 volt single phase.


----------



## Forge Boyz (Nov 7, 2014)

BleedingLungsMurphy said:


> How are you getting 208v on a single phase? A 208v baseboard heater is not using a single phase. You have it connected between two phases for 208v or one phase to neutral for 120v.


It's semantics. What else do you call it when you use 2 legs of a 3 phase system? You can't call it 2 phase because that describes another type of distribution system that has 2 phases 90 degrees apart. It's no longer installed new but there is a very small installed base still operating.

Sent from my SM-G970U using Tapatalk


----------



## HertzHound (Jan 22, 2019)

NoBot said:


> I've always thought that 120/208-240 means the a neutral is required. 12/3. Am I wrong?


That’s what I would think also. If it was to run on all three types of voltages, there would be some jumpers to change and or motors to re-wire. But if it meant it needs a neutral, it’s probably the controls and blower motor running on 120 and the heater running on 208 to 240, nothing to change. I would be looking for a terminal or leads that was marked N-L1-L2


----------



## NoBot (Oct 12, 2019)

HertzHound said:


> That’s what I would think also. If it was to run on all three types of voltages, there would be some jumpers to change and or motors to re-wire. But if it meant it needs a neutral, it’s probably the controls and blower motor running on 120 and the heater running on 208 to 240, nothing to change. I would be looking for a terminal or leads that was marked N-L1-L2


Yes, to the OP, is there a neutral terminal near L1 & L2?

I've wired electric furnaces and air handlers that require two circuits, usually 20Kw or larger. On the Name Plate, it would list the two circuits and breakers sizes required. Usually these are straight 240 volt, single phase units - no neutral, with 240 volt blower motors and a 240 to 24 volt transformer for the thermostat. An example would Circuit #1 60 amp 240V, Circuit #2 40 amp 240V on two pole breakers

I've also wired 3 phase units both 240 and 480V. These have always been one circuit with no neutral. The nameplate would read Volts 480, Phase 3. using a 3 pole breaker.

I've wired units similar to the OP listed as 120/208-240 single phase. These are usually smaller , with a three wire circuit. N-L1-L2


----------



## NoBot (Oct 12, 2019)

What upsets me are residential appliances. The name plate on an oven will read 240 volt only to find on installation it requires a neutral. The name plate should read 120/240V. 
On residential appliances, it's best to run a 3 wire cable with a neutral to all ovens and cooktops. Dryers are always 3 wire with ground.


----------



## glen1971 (Oct 10, 2012)

In the OP's original post, they mentioned it is a "12/2 device". @NoBot mentions a "12/3". Maybe it's early and I can't picture it, but what is that description referring to?


----------



## NoBot (Oct 12, 2019)

glen1971 said:


> In the OP's original post, they mentioned it is a "12/2 device". @NoBot mentions a "12/3". Maybe it's early and I can't picture it, but what is that description referring to?


12/2 = Romex, MC cable or conduit with hot, hot, ground
12/3 = Romex, MC cable or conduit with hot, hot, neutral, ground
with 12/3 the unit would use one hot leg and the neutral to feed the 120V blower motor and/or 120v transformer for the thermostat. Two hots feed the heating elements.


----------



## glen1971 (Oct 10, 2012)

NoBot said:


> 12/2 = Romex, MC cable or conduit with hot, hot, ground
> 12/3 = Romex, MC cable or conduit with hot, hot, neutral, ground
> with 12/3 the unit would use one hot leg and the neutral to feed the 120V blower motor and/or 120v transformer for the thermostat. Two hots feed the heating elements.


That makes sense. I don't think I've ever seen it noted like that before on the equipment. On the prints or conduit/cable, I've seen something close to that.


----------



## ColbyL (Jun 21, 2019)

I believe it was line to line. The equipment schedule said it was a 12/2 MUA system.

@BleedingLungsMurphy It's some odd rule I thought I remembered from school being an exception to that rule. Whatever, maybe I remembered the rule wrong. 

I am trying to understand how the "max amps" criteria works. It says max amps = 15A. So I have three voltage settings (120/208-230V) and one wattage setting, (3KW). If I do 3000w/120v=25a. Which is higher than max amps. So it doesn't make sense the way it is.


----------



## micromind (Aug 11, 2007)

ColbyL said:


> So micromind, you are saying that the wattage and amperage will go lower if I use one of the lower voltage options? The theory is still a bit foggy from school, but I remember them saying that the device will try to force the wattage to remain the same regardless of how low I make the voltage setting. Is this a special exception to that rule?


With a heating element, resistance stays the same therefore, lower voltage will result in lower amperage and thus, lower wattage. 

Lets say the resistance is 10 Ω. If we apply 240 volts to a 10 Ω load, the current will be 24 amps. (240 ÷ 10 = 24). in this case, the wattage would be 5760. (24 amps X 240 volts = 5760 Watts). 

Now, lets apply 208 volts. 208 ÷ 10 = 20.8 amps. 20.8 amps X 208 volts = 4326 watts. 

This applies to resistive loads only, inductive loads are different because of power factor.


----------



## MotoGP1199 (Aug 11, 2014)

I know your in Canada(so code sections will be different) but this might help understand reading HVAC rating plates.


----------



## ColbyL (Jun 21, 2019)

Okay, now it's making more sense. You just never apply actual theory doing simple installations. Then the other guy confused the hell out of me with his mistakes. Until I get another look at that nameplate, I think I have all my questions answered.


----------



## Navyguy (Mar 15, 2010)

Standard nameplate ratings…

120V = L1 and N
1 phase 208 = L1 and L2
240 = L1 and L2
120 / 240V = L1, L2 and N
120 / 208 = L1, L2 and N (can substitute an LX with L3)
3 phase 208 = L1, L2, and L3

120-240V = any voltage between 120 and 240, may require L1 and N or L1 and L2

So and anything with a “slash” like 120/240V is a three wire installation (L1, L2 and N), and thing with a “dash” like 120-240 is a two wire installation with a range of voltages, typically L1 and N or L1 and L2. If the available voltage is 208, then it could be L1 and L2 and you can substitute an LX with L3 since 208 is in the range of 120-240.

You must know your voltages…

120 = single phase
240 = single phase
208 = single phase or three phase
277 = single phase
440 = single phase or three phase
347 = single phase
600 = single phase or three phase

Cheers
John


----------



## ColbyL (Jun 21, 2019)

So when it says 120/208-240 it's saying each phase is 120, but hook it up with 2 phases and a neutral and the resulting voltage can be anywhere from 208-240v?

Or does the 240 simply mean that it also accepts a 240->N hookup as well.


----------



## Navyguy (Mar 15, 2010)

ColbyL said:


> So when it says 120/208-240 it's saying each phase is 120, but hook it up with 2 phases and a neutral and the resulting voltage can be anywhere from 208-240v?


Think of standard dryer or stove receptacles... they are 120 / 240. Some parts of them run on 120 volts (lights, timer, buzzer, etc) while other parts run on 220 or 240 (heater elements). Because there is both 120 and 240, you require a three wire (L1, L2 and N).

So if something has 120 / 208-240, it is the same as above except the range of voltage to run the other portion is somewhere between 208 and 240 volts. So the "/" means "and" _120 and 208-240_ and the "-" means "range" so _120 volts and any voltage between range of 208 to 240 volts_. This still requires a three wire (L1, L2 and N).

If the name plate just indicated 208-240, then this would be a range of voltages and only require a two wire.

Cheers
John


----------



## Viggmundir (Sep 13, 2019)

ColbyL said:


> So when it says 120/208-240 it's saying each phase is 120, but hook it up with 2 phases and a neutral and the resulting voltage can be anywhere from 208-240v?
> 
> Or does the 240 simply mean that it also accepts a 240->N hookup as well.


Like said previously, there are probably 3 terminals: L1, L2, N. It uses 120v for the controls, and maybe the blower motor. 208v or 240v for the heat. Will be installed with a 2 pole breaker.

Where will you get a 240V->N connection from? That is not a standard system used in Canada.

120/240V is 120V L-N, 240V L-L
120/208V is 120V L-N, 208V L-L
277/480V is 277V L-N, 480V L-L
347/600V is 347V L-N, 600V L-L

There is a 3 phase 240V corner grounded delta system, but I highly doubt you would find that in a residential situation.


----------



## ColbyL (Jun 21, 2019)

Okay makes sense. And I wish the HVAC guys realized we don't have single phase 240 as well. The other MUA fan they installed is rated 240 1ph.


----------



## glen1971 (Oct 10, 2012)

ColbyL said:


> Okay makes sense. And I wish the HVAC guys realized we don't have single phase 240 as well. The other MUA fan they installed is rated 240 1ph.


Voltage in a house is 240 line to line and is single phase.


----------



## ColbyL (Jun 21, 2019)

But if I stick my meter across it in voltage mode, it'll read 208 though. There's no way of actually getting it to 240. You're saying it'll accept a line to line 208?

edit

Just to backpedal onto the theory again. would for example a normal receptacle and all the appliances I plug into it be operable if I had a voltage of 70v/120v (just pretend that this voltage exists) and hooked the plug up line to line?


----------



## micromind (Aug 11, 2007)

A duct heater is just a simple resistor, if it's 240, it'll work on 208 but it'll draw less current and produce a bit less heat.


----------



## gpop (May 14, 2018)

ColbyL said:


> So when it says 120/208-240 it's saying each phase is 120, but hook it up with 2 phases and a neutral and the resulting voltage can be anywhere from 208-240v?
> 
> Or does the 240 simply mean that it also accepts a 240->N hookup as well.



240 is 2 legs of 120v 180 degrees apart. (circle is 360 degree's so 180 is half)
208 is 2 legs that are 120 degrees apart (1/3 which makes sense as its part of a 3 phase system)

Then there is 240v high leg delta and for all intents its the same as 240v 2 leg when used as single phase. 

240 to N (uk system) would work as long as it does not require a 120v to N circuit. You would simply land the N on the L2 terminal as the equipment expects 208-240 between the L1 and L2 terminals.


----------



## gpop (May 14, 2018)

ColbyL said:


> But if I stick my meter across it in voltage mode, it'll read 208 though. There's no way of actually getting it to 240. You're saying it'll accept a line to line 208?
> 
> edit
> 
> Just to backpedal onto the theory again. would for example a normal receptacle and all the appliances I plug into it be operable if I had a voltage of 70v/120v (just pretend that this voltage exists) and hooked the plug up line to line?



you can use a buck and boost transformer to get 240 when you only have 208 available but as your unit takes either there is no need.

Lots of thing can run at lower voltages but nothing is free so you can not expect to get the same amount of work at a lower voltage unless you supply more amps. On a resistance heater to get the same amount of heat you would have to reduce the resistance which would raise the amps. As this is not a option you have to except less heat at lower voltages and due to ohms law the amps will be less.
I believe the rule of thumb is 0.74 x watts if you run a 240 heater at 208 so a 3000w heater @ 240v becomes a 2220 watts heater @ 208.


----------



## Viggmundir (Sep 13, 2019)

glen1971 said:


> Voltage in a house is 240 line to line and is single phase.





ColbyL said:


> But if I stick my meter across it in voltage mode, it'll read 208 though. There's no way of actually getting it to 240. You're saying it'll accept a line to line 208?
> Just to backpedal onto the theory again. would for example a normal receptacle and all the appliances I plug into it be operable if I had a voltage of 70v/120v (just pretend that this voltage exists) and hooked the plug up line to line?


@ColbyL , don't get confused by what @glen1971 and @gpop Are saying here. Normally a house is 240V single phase. What you are working on is not a house though, correct? You sound like you are working on a multi unit residential building of some kind that is fed with 120/208V 3 phase, and that's ok, your meter will read 208V, not 240V.

If the HVAC guys supplied a 240V single phase unit, it may or may not be wrong. If it is only rated for 240V then it is the wrong unit, get your Jman to double check and deal with it. BUT many 240v residential things are also rated for 208V, and so it will work at your job site. It should be marked on the unit for both voltages.

For your imaginary 70V/120V system, yes a standard receptacle would work hooked up line to line. The receptacle and load are dumb, they don't know if it's hooked up line to line, or line to neutral, all they do is work or not, if there is enough voltage to push the proper current to do the work.

A nameplate rating exists so we can hook it up so it works properly. Hooking it up to another system(different voltage) may cause the item to burn up, or not work, or not work well.

Example:
A 120V heater hooked up to 240V will pull twice the rated current, and will burn up.
A 240V heater hooked up to 120V on the other hand won't burn up. It will work, but only at half rated current, so you only get 1/4 of the power, so not well.
That's resistive loads, inductive work a little different.


----------



## wiz1997 (Mar 30, 2021)

Some of you really need to go study electrical theory.


----------



## kb1jb1 (Nov 11, 2017)

Over 40 years of experience and I still get confused at some of the poorly written nameplates. I think they are written by 12 year olds overseas. I hooked up a pool salt generator for a built in pool the other day and the name plate said max amps 31.4 and 240 volts. ?? The pool guy said I need a 30 amp 240 volt circuit and the salt generator and the pump have to go on at the same time. No instructions in the box. Only 16 gauge wires off the terminals. I have never seen a salt generator on a 30 amp receptacle. I miss the old NEMA method of doing things.


----------



## ColbyL (Jun 21, 2019)

Thanks.Viggmundir, that cleared things up a lot. No I am working in a apartment/office complex for battered woman. The top floor is residences, and the second and third floor are offices. First floor seems like a big lobby and parking lot. Also, Canada like the US does not use 240V single phase. I don't know about the bigger commercial and industrial buildings, but all our voltages are default at 120v to neutral and 208 line to line.

I didn't check myself, but that second MUA on the first floor the other electrician said wouldn't work because it was 240v single phase. So assuming the nameplate says what the guy says it did, that means the HVAC guy needs to change his MUA right? Or do I just need to resize the breakers to match the new amperage and say "the ducts will be warm enough with 75% heat"


----------



## Slay301 (Apr 23, 2018)

Navyguy said:


> Standard nameplate ratings…
> 
> 120V = L1 and N
> 1 phase 208 = L1 and L2
> ...


240 grounded B=3 phase fyi


----------



## BleedingLungsMurphy (10 mo ago)

glen1971 said:


> Have you worked on anything other than a light switch or a 3 phase motor?


Are you even an electrician?



Forge Boyz said:


> It's semantics. What else do you call it when you use 2 legs of a 3 phase system? You can't call it 2 phase


I call it using 2 legs of a 3 phase system. What do you call it when you use 1 leg of a 3 phase system?

Line to neutral is single phase?

Line to line is single phase?

Split phase is single phase?


----------



## Forge Boyz (Nov 7, 2014)

BleedingLungsMurphy said:


> I call it using 2 legs of a 3 phase system. What do you call it when you use 1 leg of a 3 phase system?
> 
> This could work. But it's not 2 phase.
> 
> ...




Sent from my SM-G970U using Tapatalk


----------



## joe-nwt (Mar 28, 2019)

wiz1997 said:


> Some of you really need to go study electrical theory.


I bet you thought it would slow down after you posted that.......


----------



## Slay301 (Apr 23, 2018)

BleedingLungsMurphy said:


> Are you even an electrician?
> 
> 
> I call it using 2 legs of a 3 phase system. What do you call it when you use 1 leg of a 3 phase system?
> ...


You consistently say some of the dumbest stuff on this site I’m honestly amazed every time I read One of your post. It’s like omg he got more
Stupid since the last one


----------



## BleedingLungsMurphy (10 mo ago)

Slay301 said:


> You consistently say some of the dumbest stuff on this site I’m honestly amazed every time I read One of your post. It’s like omg he got more
> Stupid since the last one


Are you going to be okay? Care to elaborate which part of my post you thought was stupid? 

Can you explain how 208v line to line is a single phase? Take your time, I have all day.


----------



## Slay301 (Apr 23, 2018)

BleedingLungsMurphy said:


> Are you going to be okay? Care to elaborate which part of my post you thought was stupid?
> 
> Can you explain how 208v line to line is a single phase? Take your time, I have all day.


You’re probably one a the dumb f’s who call it 2 phase aren’t you ???


----------



## BleedingLungsMurphy (10 mo ago)

Slay301 said:


> You’re probably one a the dumb f’s who call it 2 phase aren’t you ???


Are you okay? I'm just asking how you think 208v line to line is a single phase? How would you describe one phase of a three phase system?


----------



## Slay301 (Apr 23, 2018)

BleedingLungsMurphy said:


> Are you okay? I'm just asking how you think 208v line to line is a single phase? How would you describe one phase of a three phase system?


Calling you r e t a r d e d would be an insult to the mentally handicapped.


----------



## BleedingLungsMurphy (10 mo ago)

Slay301 said:


> Calling you r e t a r d e d would be an insult to the mentally handicapped.


Okay but what exactly is your issue? What did I say that you think is incorrect?



Forge Boyz said:


> It's semantics. You can't call it 2 phase because that describes another type of distribution system that has 2 phases 90 degrees apart


As opposed to using 2 phases from a 3 phase system that are 120 degrees apart? Sounds like more semantics....


----------



## Slay301 (Apr 23, 2018)

BleedingLungsMurphy said:


> Okay but what exactly is your issue? What did I say that you think is incorrect?
> 
> 
> As opposed to using 2 phases from a 3 phase system that are 120 degrees apart? Sounds like more semantics....


This is about as simple as I can make it for a diyer on a site for electricians.

In a residential situation, you are served by a single phase (from the 3 phase distribution lines), which is stepped down to 240V in the transformer outside your house. This is split, in the transformer, by a center tap neutral into a pair of 120V legs. This means you get 120V from either pole to the neutral, and 240V from pole to pole. But either way it is still only 1 phase.


----------



## ColbyL (Jun 21, 2019)

It's the definition the scientific community settled on. You can call it something else in your private language, but the electrical and scientific institutions have declared line to line 208 as 1-phase.


----------



## Slay301 (Apr 23, 2018)

ColbyL said:


> It's the definition the scientific community settled on. You can call it something else in your private language, but the electrical and scientific institutions have declared line to line 208 as 1-phase.


Finally some one from Canada who understands electricity


----------



## Viggmundir (Sep 13, 2019)

ColbyL said:


> Thanks.Viggmundir, that cleared things up a lot. No I am working in a apartment/office complex for battered woman. The top floor is residences, and the second and third floor are offices. First floor seems like a big lobby and parking lot. Also, Canada like the US does not use 240V single phase. I don't know about the bigger commercial and industrial buildings, but all our voltages are default at 120v to neutral and 208 line to line.
> 
> I didn't check myself, but that second MUA on the first floor the other electrician said wouldn't work because it was 240v single phase. So assuming the nameplate says what the guy says it did, that means the HVAC guy needs to change his MUA right? Or do I just need to resize the breakers to match the new amperage and say "the ducts will be warm enough with 75% heat"


You are welcome.

Correction for you: Canada and the USA do use a 240V single phase system. We center tap the 240V coil to get 120V. What we don't have, is a 240V line to neutral system. That is a British/European thing, but it doesn't mean we don't have 240V single phase.

For the MUA, it all depends on what's in the unit. Any heating will run at 75% capacity, which may leave you with inadequate heat. The bigger issue, is wither the controls and the fan motors will run on 208V instead of 240V.


----------



## gpop (May 14, 2018)

BleedingLungsMurphy said:


> Are you okay? I'm just asking how you think 208v line to line is a single phase? How would you describe one phase of a three phase system?



Think less of where the power comes from and consider what you would see on a scope. On 2 legs of 208 you would have a single sine wave so its single phase.


----------



## Viggmundir (Sep 13, 2019)

BleedingLungsMurphy said:


> Okay but what exactly is your issue? What did I say that you think is incorrect?
> 
> 
> As opposed to using 2 phases from a 3 phase system that are 120 degrees apart? Sounds like more semantics....


Forge Boy is right, 2 phase is a totally different system. It has 2 phases, 90 degree apart, but uses 2 wires per phase for a total of 4 wires.
Using 2 legs of a 3 phase system is only 2 wires, its not 2 phase.


----------



## Slay301 (Apr 23, 2018)

gpop said:


> Think less of where the power comes from and consider what you would see on a scope. On 2 legs of 208 you would have a single sine wave so its single phase.


You have a better ch ace of bashing your head through a brick wall than getting him to understand this


----------



## ColbyL (Jun 21, 2019)

Alright, so I'll tell the super to tell the HVAC guy to either change the device or risk the device breaking because it doesn't have enough voltage to fully operate.


----------



## gpop (May 14, 2018)

ColbyL said:


> Alright, so I'll tell the super to tell the HVAC guy to either change the device or risk the device breaking because it doesn't have enough voltage to fully operate.



Im sorry if we have confused you.

your original post said it was labeled 120/208-240 

So 208 is fine pull a neutral if its conduit or install a 3 core cable and call it good to go. The fact it puts out less heat is not that big of a deal especially as heaters are interchangeable so they may have spec'ed a high wattage to offset the problem.


----------



## BleedingLungsMurphy (10 mo ago)

Slay301 said:


> In a residential situation, you are served by a single phase (from the 3 phase distribution lines), which is stepped down to 240V in the transformer outside your house.


You switched to 240v now? Residential 240v is a single split phase 180* degree with a neutral tapped in the middle. You probably learned that in 1st year.

We are talking about 208v though. Residential 208v drops 2 phases and a neutral to each suite and the phases are 120* apart, not 180*

So, can you explain why 208v can be called singe phase? Here's a hint.... look at the waveform on an oscilloscope when you put a load between two phases of a three phase system.



Slay301 said:


> This is about as simple as I can make it for a diyer on a site for electricians.


Ironic.......


----------



## BleedingLungsMurphy (10 mo ago)

gpop said:


> On 2 legs of 208 you would have a single sine wave so its single phase.


Finally someone who gets it


Viggmundir said:


> Forge Boy is right, 2 phase is a totally different system.


Who is calling it 2 phase? Read the thread.


----------



## ColbyL (Jun 21, 2019)

We kinda jumped to a different MUA. First one was 120/208-240 single phase. I'm done with that and happy with the answer. The second on the first floor is just 240v single phase. I'm happy with my current answer on that as well. Sorry if I wasn't clear when I switched topics a little.


----------



## HertzHound (Jan 22, 2019)

On the distribution side, two phases of a three phase system is called single phase. Probably because on the load side, a device that uses two two legs of a three phase system can only be single phase.

A little off topic, but this always irks me. 

I’ve read on here so many times, the mistake of saying that single phase 120/240 has a phase shift of 180 degrees, and that is why the current cancels out in the neutral. I just bite my toung. The typical residential single phase transformer out on the pole has only one secondary winding. It cannot be out of phase with itself. The phase angle between L1 and L2 is zero. There is no magical cancellation of neutral current because of a phase shift. The single winding is tapped in the center to give another utilization voltage, and again, is still in phase with L1 & L2.


----------



## LGLS (Nov 10, 2007)

ColbyL said:


> I have recently been given WAY too much responsibility for the little skills I have and I feel incredibly out of my depths, so I am hoping you guys can help me out a little. I am new to reading nameplate data and I was wondering if you had any solid rules for when I need an extra circuit for a single device or when I need a control wire. I've already messed this up once with a Fan Coil/Cooler Unit combo. So I was hoping someone could tell me what to look for.
> 
> I have a Make-up-air/Duct Heater combo unit. The plans say it's just an MUA unit, not a Duct Heater and it's a 208V 1ph 12/2 device. The HVAC guy says it needs another wire for the Duct Heater. I don't know if he's just guessing or if he knows what he's doing. I thought this was suspicious so I asked someone above me to look at the nameplate data and see if he could figure out what's going on.
> 
> ...


Not for nothing, but don’t your bosses or the people in charge know and realize they’ve helped a lot of responsibility onto your plate and that you are not really prepared to do it, because if they do realize this – they’re going to be expecting you to be asking lots of “stupid“ questions.

By the way there’s no such thing as a stupid question when it comes to electrical work and safety, buddy my friend… Do not allow your ego or the risk of being considered ignorant or stupid stop you from seeking out the proper information from those who know it .


----------



## ColbyL (Jun 21, 2019)

They know, but I keep on asking questions I later find in the shop drawings that I should have found earlier. I'm trying to stay proactive and learn to do things right. I also like having an answer written out rather than drawn as a piece of artwork. 

I'm also not on paper as the foreman, so it's not like I'm taking liability for the work. It's just a really big learning opportunity.


----------



## Almost Retired (Sep 14, 2021)

ColbyL said:


> They know, but I keep on asking questions I later find in the shop drawings that I should have found earlier. I'm trying to stay proactive and learn to do things right. I also like having an answer written out rather than drawn as a piece of artwork.
> 
> I'm also not on paper as the foreman, so it's not like I'm taking liability for the work. It's just a really big learning opportunity.


I agree with the learning opportunity completely (ideally you should have a designated person to guide you and answer your questions ... but ...)
as you noticed there is info on the prints that you need
i would suggest your first step is to familiarize your self with what is contained in the entire prints
you dont have to memorize it, but just like the code, you need to know where to look it up when you come to it and have that question
i think this will help you a lot


----------



## gpop (May 14, 2018)

HertzHound said:


> A little off topic, but this always irks me.
> 
> I’ve read on here so many times, the mistake of saying that single phase 120/240 has a phase shift of 180 degrees, and that is why the current cancels out in the neutral. I just bite my toung. The typical residential single phase transformer out on the pole has only one secondary winding. It cannot be out of phase with itself. The phase angle between L1 and L2 is zero. There is no magical cancellation of neutral current because of a phase shift. The single winding is tapped in the center to give another utilization voltage, and again, is still in phase with L1 & L2.



So the secondary winding is not 1/2 clockwise and 1/2 anti-clockwise with the N being in the middle.


----------



## Almost Retired (Sep 14, 2021)

gpop said:


> So the secondary winding is not 1/2 clockwise and 1/2 anti-clockwise with the N being in the middle.


just to state the same info in a different manner 
(and not because it hasnt been completely covered already by several others here)
but just because i want to

_before they center tapped it_ 
the original secondary winding of the txr had 240V across the whole winding.
one end reads 0V to ground
the other end reads 240V to ground
it is one continuous winding

when you center tap it, that does *not* break the winding into 2 halves
if you disconnect the center tap outside of the transformer it will read 240 and 0 to ground

even disconnected if you measure volts to center and end it will show 120V either way
_that is not a difference of phase .... it is a difference of potential_
we tend to forget what our meters are actually measuring

the primary is also one continuous winding
primary volts at one end, zero volts at the other end

this is the reason it is called single phase
it only requires a single phase of the primary transmission lines
*_*

120/208 is called 3 phase because it requires 3 phases of the primary transmission lines
it is symmetrical, meaning all 3 phases are exactly 120 degrees apart

Hi Leg delta is not _symmetrical_ 3 phase, it doesnt matter if you call it 3 or not, you can use it that way for loads that do _not_ use the neutral
it only uses 2 primary phases but it is not called 2 phase

(as mentioned earlier, true 2 phase is entirely different, and soon to be completely obsolete)

i now yield the floor to any one else who wishes to state it their way lol


----------



## Almost Retired (Sep 14, 2021)

one more thing 




__





what are the internal connections of a center tapped transformer - Google Search






www.google.com


----------



## joe-nwt (Mar 28, 2019)

Almost Retired said:


> _before they center tapped it_
> the original secondary winding of the txr had 240V across the whole winding.
> *one end reads 0V to ground
> the other end reads 240V to ground*
> ...



Until you ground it, you will only ever get 3 readings. 240V end to end, 120V from the center tap to either end and 0V from any part to ground.


----------



## HertzHound (Jan 22, 2019)

gpop said:


> So the secondary winding is not 1/2 clockwise and 1/2 anti-clockwise with the N being in the middle.


Not that I know of. If that was how it is wound, wouldn’t there be 0V on the secondary as the primary’s magnetic field rises and collapses?


----------



## HertzHound (Jan 22, 2019)

It’s also like you said earlier. What does the oscilloscope show?


----------



## joe-nwt (Mar 28, 2019)

gpop said:


> So the secondary winding is not 1/2 clockwise and 1/2 anti-clockwise with the N being in the middle.


Actually it is. From the center tap.

Do this. You are the center tap. Extend your arms out and rotate your arms in the direction of the winding. You will notice that from your perspective as the center tap, one winding appears to be clockwise and the other counter-clockwise.


----------



## Almost Retired (Sep 14, 2021)

joe-nwt said:


> Until you ground it, you will only ever get 3 readings. 240V end to end, 120V from the center tap to either end and 0V from any part to ground.


well if that is the only flaw you can find , i think i did pretty good for just off the top of my head


----------



## joe-nwt (Mar 28, 2019)

Almost Retired said:


> well if that is the only flaw you can find , i think i did pretty good for just off the top of my head


All I'm saying is the newbie deserves accurate information.


----------



## wiz1997 (Mar 30, 2021)

BleedingLungsMurphy said:


> Are you going to be okay? Care to elaborate which part of my post you thought was stupid?
> 
> Can you explain how 208v line to line is a single phase? Take your time, I have all day.


208 volt single phase as requested.






__





Larson Electronics - 10 kVA Transformer - 480V Primary Voltage - 208V Secondary Voltage - Single Phase - NEMA 3R - Fully Potted / Encapsulated


10 kVA Transformer - 480V Primary Voltage - 208V Secondary Voltage - Single Phase - NEMA 3R - Fully Potted / Encapsulated




www.larsonelectronics.com


----------



## Almost Retired (Sep 14, 2021)

joe-nwt said:


> Actually it is. From the center tap.
> 
> Do this. You are the center tap. Extend your arms out and rotate your arms in the direction of the winding. You will notice that from your perspective as the center tap, one winding appears to be clockwise and the other counter-clockwise.


i agree that is how it works out electrically or phase wise
but physically it is one piece of wire wound in the same direction from one end to the other


----------



## Almost Retired (Sep 14, 2021)

joe-nwt said:


> All I'm saying is the newbie deserves accurate information.


100% agreed and i am not against being corrected when wrong


----------



## HertzHound (Jan 22, 2019)

How about this mind bender. 

You have 3, 6, 9, etc. single phase loads. You connect them to a Y service so that the load is evenly proportional. To figure the load you have to do the math like it’s a Delta. 🤯


----------



## gpop (May 14, 2018)

joe-nwt said:


> Actually it is. From the center tap.
> 
> Do this. You are the center tap. Extend your arms out and rotate your arms in the direction of the winding. You will notice that from your perspective as the center tap, one winding appears to be clockwise and the other counter-clockwise.


Never thought of it that way.

Only time i really think about it is when im wiring a step down transformer and if i want full kw rating for 120 only then i have to reverse the one of the secondary coils.


----------



## LGLS (Nov 10, 2007)

ColbyL said:


> They know, but I keep on asking questions I later find in the shop drawings that I should have found earlier. I'm trying to stay proactive and learn to do things right. I also like having an answer written out rather than drawn as a piece of artwork.
> 
> I'm also not on paper as the foreman, so it's not like I'm taking liability for the work. It's just a really big learning opportunity.


Your boss is still charging the customer for an on-site foreman. Where is that money going? These are some of the questions you should also be having and getting answers to.


----------



## HertzHound (Jan 22, 2019)

But even still, the windings are all the same direction. It’s just a difference of putting the windings in series or parallel. The individual windings are rated for the lower voltage. So if the higher voltage is present, the windings need to go in series, this will create a voltage drop across the winding, bringing it to the lower rated voltage. The same series parallel thing is going on with the secondary.


----------



## joe-nwt (Mar 28, 2019)

HertzHound said:


> But even still, the windings are all the same direction.


Yes, physically they are.


----------



## Almost Retired (Sep 14, 2021)

joe-nwt said:


> Yes, physically they are.


with the center tap connected and all is powering the house like normal
would you say that the 2 halves of the 120/240 are opposite "phases" ?
as in 180 degrees apart or zero apart?


----------



## joe-nwt (Mar 28, 2019)

Split of 1 phase. 180 degrees with reference to the center tap.


----------



## TEO (Jan 17, 2020)

I've been in this game for 30+ years and now I'm confused 
But seriously there's lots of good info in here


----------



## Almost Retired (Sep 14, 2021)

TEO said:


> I've been in this game for 30+ years and now I'm confused
> But seriously there's lots of good info in here


reference this
 #81  ·  2 h ago
joe-nwt said:
Actually it is. From the center tap.

Do this. You are the center tap. Extend your arms out and rotate your arms in the direction of the winding. You will notice that from your perspective as the center tap, one winding appears to be clockwise and the other counter-clockwise.

to begin with spin both arms in the same direction
secondly look at your left hand then your right
they are opposite rotation from the center tap perspective
even tho they are the same rotation from just one end

electrically this is true, a full explanation of why would require engineering knowledge that i dont have


----------



## BleedingLungsMurphy (10 mo ago)

HertzHound said:


> On the distribution side, two phases of a three phase system is called single phase


This is where I disagree.* The load is single phase* but it is fed by 2 phases like each phase on a delta transformer. When you connect a load across 2 phases of a WYE you just create a delta. 



HertzHound said:


> The typical residential single phase transformer out on the pole has only one secondary winding. It cannot be out of phase with itself.


If you hook up a silly scope from L1 to N and N to L2 you will see 2 wave forms 180* apart on the split phase. If you measure L1 to L2 the winding will still be "in phase" with itself, whatever that means.


----------



## Navyguy (Mar 15, 2010)

Slay301 said:


> 240 grounded B=3 phase fyi


Yes I agree. In the USA that is very common, here in Canada in 30 years I have only come across it once or twice and was eventually removed for a traditional 120 / 208 or 347 / 600 install.

Cheers
John


----------



## micromind (Aug 11, 2007)

In my opinion, single phase is 2 wires regardless of the source. It can also be 3 wire if and only if the neutral is involved. 

It can be 120 2 wire from any single or 3 phase system or it can be 208 2 wire from a 3 phase Y or it can be 240 from any single phase or any 2 legs of a ∆ system.

It can even be 69,000 or 120,000 2 wire from a 120KV Y system. 

2 phase is either 4 or 5 wire.

3 phase is 3 wire with reasonably balanced voltage between any 2 wires, 4 wire if the neutral is involved.


----------



## Slay301 (Apr 23, 2018)

Navyguy said:


> Yes I agree. In the USA that is very common, here in Canada in 30 years I have only come across it once or twice and was eventually removed for a traditional 120 / 208 or 347 / 600 install.
> 
> Cheers
> John


I see it all the time here throws you through a loop when u see a phase conductor coming off the ground bar unfused


----------



## Slay301 (Apr 23, 2018)

micromind said:


> In my opinion, single phase is 2 wires regardless of the source. It can also be 3 wire if and only if the neutral is involved.
> 
> It can be 120 2 wire from any single or 3 phase system or it can be 208 2 wire from a 3 phase Y or it can be 240 from any single phase or any 2 legs of a ∆ system.
> 
> ...


💯 agree


----------



## BleedingLungsMurphy (10 mo ago)

micromind said:


> In my opinion, single phase is 2 wires regardless of the source


That's kind of a requirement. Let us know if you figure out how to make a circuit with 1 wire.

Number of wires being irrelevant a single phase load can be supplied by 1 or 2 phases from a 3 phase supply. 

There is no such thing as a 2 phase load but you can have 2 of 3 phases supplying a panel or a load. The load itself is single phase or 3 phase. No one is calling it "2 phase" so I don't know what you guys are arguing about.


----------



## Slay301 (Apr 23, 2018)

BleedingLungsMurphy said:


> That's kind of a requirement. Let us know if you figure out how to make a circuit with 1 wire.
> 
> Number of wires being irrelevant a single phase load can be supplied by 1 or 2 phases from a 3 phase supply.
> 
> There is no such thing as a 2 phase load but you can have 2 of 3 phases supplying a panel or a load. The load itself is single phase or 3 phase. No one is calling it "2 phase" so I don't know what you guys are arguing about.


1 wire = series circuit
2phase to you= single phase to everyone else 

just stop talking


----------



## HertzHound (Jan 22, 2019)

joe-nwt said:


> Split of 1 phase. 180 degrees with reference to the center tap.


Somewhat correct, but you are reversing the scope one way from the other. The phase across the whole winding is still rising and falling at the same time.


----------



## joe-nwt (Mar 28, 2019)




----------



## HertzHound (Jan 22, 2019)

So this is what it’s like talking to flat earthers?


----------



## BleedingLungsMurphy (10 mo ago)

Slay301 said:


> 2phase to you= single phase to everyone else





Forge Boyz said:


> You can't call it 2 phase





Slay301 said:


> You’re probably one a the dumb f’s who call it 2 phase


You demonstrably have no idea what you're talking about and aparently you can't follow the thread. You're the only person in this entire thread calling it "2 phase" and everyone is arguing over your assertions. You guys are hilarious.



Slay301 said:


> 1 wire = series circuit


If your series circuit only has one wire that's a dead short.
Do you know what polarity is?


----------



## Slay301 (Apr 23, 2018)

BleedingLungsMurphy said:


> You demonstrably have no idea what you're talking about and aparently you can't follow the thread. You're the only person in this entire thread calling it "2 phase" and everyone is arguing over your assertions. You guys are hilarious.
> 
> 
> If your series circuit only has one wire that's a dead short.
> Do you know what polarity is?


Lol do you no polarity doesn’t matter ??? It’s called alternating current “polarity” changes every 1/2 cycle. I bet you didn’t even know if you wire a receptacle “backwards” it still works 🤯 Here as a 1 wire diagram as simple as I can make it for you. Have you ever heard the phrase heat loop? Replace the light with any load of your choosing lmao 🤣


----------



## paulengr (Oct 8, 2017)

BleedingLungsMurphy said:


> That's kind of a requirement. Let us know if you figure out how to make a circuit with 1 wire.
> 
> Number of wires being irrelevant a single phase load can be supplied by 1 or 2 phases from a 3 phase supply.
> 
> There is no such thing as a 2 phase load but you can have 2 of 3 phases supplying a panel or a load. The load itself is single phase or 3 phase. No one is calling it "2 phase" so I don't know what you guys are arguing about.


1. The original “power distribution” which was DC from Edison’s dynamos was one wire. The return path was peg grounding. There are plenty of examples today as well of microwave or inductive power distribution. Cell phone “wireless” charging for example. These are all technically “one wire” because they launch an electromagnetic wave which has no return path.

2. Tesla’s induction motor patent was for a two phase motor and early systems were based on it. Eiffel later introduced 3 phase as an optimization to improve torque pulsation and efficiency. The Scott T transformer exists specifically to deal with 2/3 phase conversion.



https://en.m.wikipedia.org/wiki/List_of_Nikola_Tesla_patents



3. Edison/GE later introduced the GE “safety system” which is the 3 wire system so that no wire was above 120 V to ground along with the safety grounding system (bonding) that has stuck with us into modern times. This is a single phase system with a split phase distribution. Since both hits are the same phase it is clearly single phase. Would in some ways be a lot nicer if it was 2 phase like Teslas original system because capacitor start/run would have never been used or needed.


----------



## Slay301 (Apr 23, 2018)

paulengr said:


> 1. The original “power distribution” which was DC from Edison’s dynamos was one wire. The return path was peg grounding. There are plenty of examples today as well of microwave or inductive power distribution. Cell phone “wireless” charging for example. These are all technically “one wire” because they launch an electromagnetic wave which has no return path.
> 
> 2. Tesla’s induction motor patent was for a two phase motor and early systems were based on it. Eiffel later introduced 3 phase as an optimization to improve torque pulsation and efficiency. The Scott T transformer exists specifically to deal with 2/3 phase conversion.
> 
> ...


Your wasting you’re time trying to explain I fear he skipped DC/AC theory


----------



## Almost Retired (Sep 14, 2021)

HertzHound said:


> Somewhat correct, but you are reversing the scope one way from the other. The phase across the whole winding is still rising and falling at the same time.


you are both correct in every point; 
Joe specified measuring from center tap to either end
you specified measuring from end to end
it is the same inside the breaker panel
L1 to N plus L2 to N allows cancellation of neutral unbalance
L1 plus L2 allows synchronized alternation at 60Hz rather than opposing and preventing current flow

an oscope is just a meter
it cannot define a circuit for you
YOU have to understand the circuit and apply the meter accordingly
YOU have to interpret the meanings of the readings

for instance 0V across a fuse does not tell you the circuit is dead, it tells you the fuse is good


----------



## Almost Retired (Sep 14, 2021)

joe-nwt said:


> View attachment 164685


there is always that little iggy button ....
and the best part is ,,, it can be reversed any time you choose


----------



## kb1jb1 (Nov 11, 2017)

What was the OP? I forgot.


----------



## Almost Retired (Sep 14, 2021)

kb1jb1 said:


> What was the OP? I forgot.


he was trying to understand a motor tag for a MUA unit


----------



## HertzHound (Jan 22, 2019)

kb1jb1 said:


> What was the OP? I forgot.


I thought it was about north and south poles, and why we in the northern hemisphere think we’re on top?


----------



## Slay301 (Apr 23, 2018)

HertzHound said:


> I thought it was about north and south poles, and why we in the northern hemisphere think we’re on top?


The earth is flat


----------



## kb1jb1 (Nov 11, 2017)

Slay301 said:


> The earth is flat


So are we on the top , bottom or the diameter edge?


----------



## Almost Retired (Sep 14, 2021)

HertzHound said:


> I thought it was about north and south poles, and why we in the northern hemisphere think we’re on top?


all of the maps show us on top ....


----------



## kb1jb1 (Nov 11, 2017)

As related to north and south pole, when pulling a drain stopper does it create a whirlpool clockwise in the northern hemisphere and CCW in the southern hemisphere? What about the toilet?


----------



## Slay301 (Apr 23, 2018)

kb1jb1 said:


> As related to north and south pole, when pulling a drain stopper does it create a whirlpool clockwise in the northern hemisphere and CCW in the southern hemisphere? What about the toilet?


Your confusing north and south pole with the right and left pole


----------



## Almost Retired (Sep 14, 2021)

kb1jb1 said:


> As related to north and south pole, when pulling a drain stopper does it create a whirlpool clockwise in the northern hemisphere and CCW in the southern hemisphere? What about the toilet?


i cant verify the directions, but this does happen. kitchen sink, tub, anything similar
it is called the "Coriolis Effect"
a toilet when flushed has not had a drain opened, the drain is open all the time, the bowel has to be overfilled to cause a siphoning action
the fill water will disturb the effect


----------



## kb1jb1 (Nov 11, 2017)

Slay301 said:


> Your confusing north and south pole with the right and left pole


Does the metric system come into play?


----------



## Slay301 (Apr 23, 2018)

kb1jb1 said:


> Does the metric system come into play?


No it’s more of a common core math situation


----------



## BleedingLungsMurphy (10 mo ago)

Slay301 said:


> t’s called alternating current “polarity”


It's called instantaneous polarity. You should have learned that in 1st year when you learned how to wire a short circuit.

Here is a diagram with colors showing *a single phase device* connected to* 2 phases from a 3 phase supply*.

How would you get 208v from a single phase in your world?

The 2 phases are 120* apart so when phase A is at 120v phase B is at 88v giving you 208v line to line.

When you connect your oscilloscope across the device you only see 1 sine wave. If you connect your oscilloscope to the device AND the supply you can see 3 sine waves.

You guys can call it whatever you want with your special language.


----------



## micromind (Aug 11, 2007)

BleedingLungsMurphy said:


> It's called instantaneous polarity. You should have learned that in 1st year when you learned how to wire a short circuit.
> 
> Here is a diagram with colors showing *a single phase device* connected to* 2 phases from a 3 phase supply*.
> 
> ...


Can you even imagine how a motor would behave if it was connected to that waveform..........


----------



## kb1jb1 (Nov 11, 2017)

Talk about a hijacked post. ?


----------



## HertzHound (Jan 22, 2019)




----------



## gpop (May 14, 2018)

Once we figure this out im going to ask how the phase shift between delta and wye works.


----------



## BleedingLungsMurphy (10 mo ago)

micromind said:


> Can you even imagine how a motor would behave if it was connected to that waveform..........


Depends how the motor is wound. Why don't you tell the rest of the class how it would behave, Timmy?

That video is illustrates the point I have been trying to make perfectly. There is a difference between the source and the device measuring or using power.



paulengr said:


> The return path was peg grounding


Sounds like another wire to me. Your logic implies an A/C circuit using a grounded identified conductor is also one wire circuit. You spend a lot of effort _trying _to sound smart. I would love to see your google search history, I could use a laugh.


----------



## LGLS (Nov 10, 2007)

BleedingLungsMurphy said:


> Depends how the motor is wound. Why don't you tell the rest of the class how it would behave, Timmy?
> 
> That video is illustrates the point I have been trying to make perfectly. There is a difference between the source and the device measuring or using power.
> 
> ...


As for me… Two of my best friends and I have a pact, that if any one of us die, the other two are instructed to immediately clear my Internet browser history, google search history, and confiscate that big green duffel rough sack in the back of my closet.

There are just some things your family should never know. You know?


----------



## Slay301 (Apr 23, 2018)

Dude just stop talking everyone here thinks you’re a moron. You asked for a 2 wire circuit which I’ve given you multiple examples. Even on a 3 phase service delta or wye when feeding a 2 pole load your still only using 1 wire. 1 side of the transformer coil goes out to the load back to the other side of the same coil again one wire hence the phrase single phase. I don’t think it’s that difficult to understand ? Another thing that really bothers me about you is your name. It’s supposed to be Bleeding Gums Murphy FFS. The best part of you ran down your moms leg

Edit- also Paul is a EE and a pretty smart one at that I’m pretty sure he will no more about electrical theory than whatever half ass
Technical school you went to could teach you


----------



## emtnut (Mar 1, 2015)

HertzHound said:


> (youtube vid)


Well, first off ... There is a traffic cabinet in the background, so we know this guy is a genius   

I guess it's cause he's younger, but with those old style scopes, you can do the same thing as the newer isolated scopes. It's called 'floating the scope' ... You use one of these ...


----------



## Almost Retired (Sep 14, 2021)

HertzHound said:


>


your meter doesnt tell you what you are looking at
how and where you hook it up tells you what you are looking at

you can almost prove a lot of things by using partially related information

if you dont have a good understanding of the theory, a meter cant help you learn it


----------



## HertzHound (Jan 22, 2019)

Almost Retired said:


> your meter doesnt tell you what you are looking at
> how and where you hook it up tells you what you are looking at
> 
> you can almost prove a lot of things by using partially related information
> ...


I don’t need help. I was hoping to help others. This was all discussed on this forum many years ago by very smart people. I’m not going to bother looking up old posts, especially if the video didn’t change any minds. Cary on and be safe.


----------



## BleedingLungsMurphy (10 mo ago)

HertzHound said:


> I was hoping to help others


Good luck!



Almost Retired said:


> how and where you hook it up tells you what you are looking at


Exactly. The grounded conductor becomes your new reference point.

You know what grinds my gears? When people, including myself, call the grounded center tap a neutral.

By definition you need 3 phases for a neutral. When you ground the center tap you split the phase, you don't create a true neutral, but the identified conductor will carry the unbalanced load.

Semantics.



Slay301 said:


> Dude just stop talking everyone here thinks you’re a moron.


Have you ever said something useful? Rhetorical question, BTW.


----------



## Viggmundir (Sep 13, 2019)

BleedingLungsMurphy said:


> You know what grinds my gears? When people, including myself, call the grounded center tap a neutral.
> By definition you need 3 phases for a neutral. When you ground the center tap you split the phase, you don't create a true neutral, but the identified conductor will carry the unbalanced load.


Who's definition would that be?

Because my code book doesn't limit a neutral to 3 phase... You need 3 or more wires, not 3 phases!


----------



## BleedingLungsMurphy (10 mo ago)

Viggmundir said:


> Because my code book doesn't limit a neutral to 3 phase... You need 3 or more wires, not 3 phases!


----------



## BleedingLungsMurphy (10 mo ago)

Some more fuel for the fire. If a single split phase has a _neutral_ and the phases are equally spaced then wouldn't that be 180*?


----------



## Viggmundir (Sep 13, 2019)

BleedingLungsMurphy said:


> View attachment 164788





BleedingLungsMurphy said:


> Some more fuel for the fire. If a single split phase has a neutral, the phases are equally split, by definition. Wouldn't that be 180*?
> View attachment 164789


Oh hey! You found it! Well done!


----------



## BleedingLungsMurphy (10 mo ago)

Viggmundir said:


> Oh hey! You found it! Well done!


Thank you for another valuable contribution to the conversation but it seems like you've failed to interpret the definition properly. They made it really simple in Appendix B so anyone can understand. I know it's confusing so I highlighted the important parts for you.

By definition, a neutral conductor of a circuit requires *at least three conductors* in that circuit.* However, in the trade, the term “neutral conductor” is commonly applied to the conductor of a 2-wire circuit that is connected to a conductor grounded at the supply end. *Care should therefore be taken in the use of this term when applying the Code.


----------



## Viggmundir (Sep 13, 2019)

Seriously????

Grounded center tap of a transformer is part of a *3 wire circuit*, therefor it is an actual neutral.
If you use only 2 of those 3 wires, (say a 120V load), then it is not a true neutral, it is an identified conductor only.

You stated " You know what grinds my gears? When people, including myself, call the grounded center tap a neutral.

By definition you need 3 phases for a neutral. When you ground the center tap you split the phase, you don't create a true neutral, but the identified conductor will carry the unbalanced load. "

You do not need 3 phases for a neutral, code book says multi phase or 3 wire single phase (grounded center tap anyone?) is a neutral.

I can't believe this is still an argument 130 comments into a thread about reading nameplates!


----------



## BleedingLungsMurphy (10 mo ago)

Why do you keep saying 3 wire? It says 3 conductor in the definition. Are you distributing power on the neutral? Check your ego and go learn basic theory. I can't believe some of you call yourself journeymen. Pathetic.


----------



## Viggmundir (Sep 13, 2019)

BleedingLungsMurphy said:


> Why do you keep saying 3 wire? It says 3 conductor in the definition. Are you distributing power on the neutral? Check your ego and go learn basic theory. I can't believe some of you call yourself journeymen. Pathetic.


*Because the code book says 3 wire!!! *in the definition of a neutral in section 0! The appendix B explanatory note(read not definition!) says 3 conductors, to clarify that a 2 wire circuit has an identified conductor, and not a neutral conductor.


----------



## BleedingLungsMurphy (10 mo ago)

*Equal in magnitude and equally spaced in phase*

Okay then, does this mean a each half of a split phase is 180* apart for it to be a true neutral ?


----------



## BleedingLungsMurphy (10 mo ago)

Jokes aside, Viggy, an example of 3 wire with a neutral would be A phase / B phase / Neutral from a 3 phase system. You might see this on a residential 120/208v panel. I'm still not convinced that a grounded conductor is a neutral when you center tap 240v.


----------



## Slay301 (Apr 23, 2018)

BleedingLungsMurphy said:


> Some more fuel for the fire. If a single split phase has a _neutral_ and the phases are equally spaced then wouldn't that be 180*?
> View attachment 164789


No it would be 0 degrees it’s 1 phase how could something that’s single be more than 1 ? 🤔


----------



## Slay301 (Apr 23, 2018)

.


----------



## glen1971 (Oct 10, 2012)

BleedingLungsMurphy said:


> View attachment 164788


In your reply with the red square around the definition of neutral, please highlight the word "phase" as I can't seem to see it.


----------



## Almost Retired (Sep 14, 2021)

Viggmundir said:


> *Because the code book says 3 wire!!! *in the definition of a neutral in section 0! The appendix B explanatory note(read not definition!) says 3 conductors, to clarify that a 2 wire circuit has an identified conductor, and not a neutral conductor.


im gonna tell you both one more time
then i am putting you both on ignore for being irritating
go get a room you are acting like an old married couple

*IT DEPENDS ON HOW YOU MEASURE IT AND WHERE YOU MEASURE IT FROM
LI TO L2 IS IN PHASE
N TO L1,, COMPARED TO N TO L2,, IS 180 OUT OF PHASE

YOU ARE BOTH CORRECT FROM ONE POINT OF VIEW ONLY
LOOK AT THE BIG PICTURE*

bye bye


----------



## Almost Retired (Sep 14, 2021)

BleedingLungsMurphy said:


> *Equal in magnitude and equally spaced in phase*
> 
> Okay then, does this mean a each half of a split phase is 180* apart for it to be a true neutral ?


im gonna tell you both one more time
then i am putting you both on ignore for being irritating
go get a room you are acting like an old married couple

*IT DEPENDS ON HOW YOU MEASURE IT AND WHERE YOU MEASURE IT FROM
LI TO L2 IS IN PHASE
N TO L1,, COMPARED TO N TO L2,, IS 180 OUT OF PHASE

YOU ARE BOTH CORRECT FROM ONE POINT OF VIEW ONLY
LOOK AT THE BIG PICTURE*

bye bye


----------



## Slay301 (Apr 23, 2018)

Almost Retired said:


> im gonna tell you both one more time
> then i am putting you both on ignore for being irritating
> go get a room you are acting like an old married couple
> 
> ...


I tried to click the link it doesn’t work ?


----------



## Almost Retired (Sep 14, 2021)

Slay301 said:


> I tried to click the link it doesn’t work ?


what link ?
that is bold, underline, italics
i thought links were in blue ?


----------



## HertzHound (Jan 22, 2019)

Almost Retired said:


> *IT DEPENDS ON HOW YOU MEASURE IT AND WHERE YOU MEASURE IT FROM
> LI TO L2 IS IN PHASE
> N TO L1,, COMPARED TO N TO L2,, IS 180 OUT OF PHASE*


if you are getting 180 degrees out of phase on one, you are holding your test lead backwards. Watch the movie again.


----------



## emtnut (Mar 1, 2015)

Watching the video @HertzHound post, when the guy had the 2 transformers and reversed polarity, reminded me of this video.

It's on Transformer Polarity, and it relates in a way to what is going on here. This guy is dry in his presentation, but he is an absolute genius in Electrical Engineering.
I linked to the part where he creates an auto-transformer, and describes additive or subtractive transformers. Well worth watching the whole video if this type of stuff interests you.

He does mention whether a Transformer is Subtractive or Additive is listed on the *Nameplate*, so this is almost on topic too 






He has other really good videos too on his channel.


----------



## GladMech (Sep 18, 2020)

QUIT USING SLOPPY LANGUAGE!


BleedingLungsMurphy said:


> Number of wires being irrelevant a single phase load can be supplied by 1 or 2 phases from a 3 phase supply.


90% of the arguments and confusion on this forum are from one person (accidentally or deliberately) using sloppy terminology. I cringed every time you said "bring two phases of the three phase" to the device. You are NOT bringing "two phases" - you are bringing *two conductors* attached to *two legs* of the three phase supply, which will only create _*one phase*_.

I see your problem! Quit trying to bring phases! Just bring the conductors and let them bring the phases.

Come on... Be an electrician...


----------



## GladMech (Sep 18, 2020)

(I can't believe I waded through 146 posts just to say that!)


----------



## glen1971 (Oct 10, 2012)

GladMech said:


> (I can't believe I waded through 146 posts just to say that!)


I can't believe there's 8 pages here on how to read an equipment nameplate!


----------



## ComTowerSparky (May 28, 2021)

HertzHound said:


> So this is what it’s like talking to flat earthers?


🤣🤣🤣🤣


----------



## CAUSA (Apr 3, 2013)

A tooones worth.
Polar Vectors,
120V degrees 0 + 120V degrees 120 + 120V degrees 240= 0, for phase angles of 3 phase systems.

120V degrees 0 + 120V degrees 180=0, for single phase systems.


I still haven't mastered the subscript, to add symbols yet for this site addicted too much to the Iphone.

I just have to say something though EH,


----------



## GladMech (Sep 18, 2020)

glen1971 said:


> I can't believe there's 8 pages here on how to read an equipment nameplate!


It was maybe one page on how to read an equipment nameplate and seven pages on how to tell the difference in a CONDUCTOR and a PHASE.


----------



## BleedingLungsMurphy (10 mo ago)

glen1971 said:


> In your reply with the red square around the definition of neutral


Open wide, here comes the airplane!











Slay301 said:


> No it would be 0 degrees


What is the difference between 180* and 0* on an A/C system?

What does the center tap do to a single phase? 

Are you referencing from 0v?

Do you even understand what we are talking about? (rhetorical question)

A neutral can be a grounded conductor. The grounded conductor on a split phase system is not a neutral.

You guys are just contradicting yourselves now. Either it's a neutral and the each half is 180* apart or it is not a neutral and each half is "in phase with itself".....whatever that is suppose to mean.


----------



## BleedingLungsMurphy (10 mo ago)

GladMech said:


> You are NOT bringing "two phases" - you are bringing *two conductors* attached to *two legs* of the three phase supply, which will only create _*one phase*_.


Who said bringing 2 phases?

Those *two conductors *are connected to *two phases* on a wye system.

The *device* is wired one phase. The physical windings in the motor in this case.

Half of you are so obsessed with proving other people wrong that you've completely lost sight of the topic. Pathetic.


----------



## Slay301 (Apr 23, 2018)

BleedingLungsMurphy said:


> Open wide, here comes the airplane!
> View attachment 164804
> 
> 
> ...


1. 180*duhh
2. Center tap splits the coil in half duhhh
3. Referencing your mother 
4. Do you?
6. Huhhh??? (RIP Majewsji) 

What strain are you smoking I would like to know ?


----------



## glen1971 (Oct 10, 2012)

Duplicate post....


----------



## glen1971 (Oct 10, 2012)

BleedingLungsMurphy said:


> View attachment 164788





BleedingLungsMurphy said:


> Open wide, here comes the airplane!
> View attachment 164804


It would be super mega awesome if you could read the garbage you spew out, before spouting out more. Your post just before this one has no mention what so ever of "phase"...Oddly enough most of us here can read...

And you claim to be a "Master Electrician"? Wow....

A response is not expected nor warranted.


----------



## Slay301 (Apr 23, 2018)

glen1971 said:


> It would be super mega awesome if you could read the garbage you spew out, before spouting out more. Your post just before this one has no mention what so ever of "phase"...Oddly enough most of us here can read...
> 
> And you claim to be a "Master Electrician"? Wow....
> 
> A response is not expected nor warranted.


More like a master dip 💩


----------



## GrindTime.DeathGrinder (Nov 6, 2021)

1


----------



## GrindTime.DeathGrinder (Nov 6, 2021)

ColbyL said:


> I get 208 single phase all the time. Baseboard heaters for example. I did third year, so I understand 3ph theory. Just don't get to apply it much. Or at all yet. Pretty much nothing is 3ph, despite the fact that I'm installing every device in the building. Do you live in industrial? I'm woodframe residential. No gorilla work lifting transformers ten times heavier than I am for me thank you.
> 
> And yes, this is single phase 208.
> 
> So micromind, you are saying that the wattage and amperage will go lower if I use one of the lower voltage options? The theory is still a bit foggy from school, but I remember them saying that the device will try to force the wattage to remain the same regardless of how low I make the voltage setting. Is this a special exception to that rule?


So you have different types of systems. If you have a 3 phase center tapped neutral 120/240-V Delta High Leg Transformer, you could actually use any one of these voltages. This works out for you in commercial applications where you have lots of motors and other diverse loads. All phase to phase connections will provide 240 - Volts: A to B - B to C or A to C all will give you 240 V on this type of system. A phase to neutral = 120-V B- phase to neutral = 208( this is your high leg that is required to be colored orange) YOU DO NOT WANT TO MAKE THE MISTAKE OF WIRING THIS TO A 120 Volt circuit! And C phase to neutral is 120- V

IF you don't have an ugly's book you should get one. If you do have one, check out pages 13 and 14. There you will have your common distribution systems with nominal voltages and that will help you to learn and understand electrical systems.

Moving on: There is also a 120/208 Y system in three phase where line to line voltage is 208 and your line to neutral is
120-Volts. I hope this helps you to understand your options and in what applications this information would be useful to you in the future.
As someone else said earlier, higher voltage will = lower amperage draw and lower voltage = higher amperage draw. This should help. To get your amperage draw from your nameplate you would divide your wattage by your voltage. This is going to be a continuous load because typically it will be running for more than 3 hours so you want to size your conductors appropriately. (amperage x 1.25 = ??) The breaker still cannot be bigger than your MAX breaker size the nameplate allows despite the size of your conductors.
Good luck and be very careful if you are not comfortable doing this. Remember that other peoples lives may be in your hands and be as thorough as you can, but if it means you can't keep up with the pace of the job, just admit that you can't handle it and be honest with your supervisor. Your employer should understand that if you don't put your knowledge to use, you lose it. Brushing up is most definitely gonna be a requisite. Ask questions when you don't remember.That's how you learn/ remember. You could be hindering yourself if you pretend you know it all already, unless you have the time do dedicate to researching while your not on the job and you actually do it.

Alright, well I feel I've been long winded enough and will take a break from typing now. lol
Good luck!


----------



## gpop (May 14, 2018)

HertzHound said:


>



This is a great video and it does answer a few questions that that has always puzzled me.

1/ I never could work out what controlled the polarity of the 240v wave in comparison to the 120v waves if they were 180 out of phase. now it makes way more sense that if both waves are in the positive then the 240v wave would also be in the positive. 
2/ Newtons laws says that 2 opposites cancel each other out so that seems odd when you are looking at the scope (it was great to see that 2 reversed waves did in fact cancel each other out)

I also liked the fact that he explained why a lot of us have been taught wrong due to the ground reference of the old scopes. 

Being told you are wrong is frustrating. Being shown you are wrong is educational.


----------



## 12packofcorona (9 mo ago)

ColbyL said:


> I have recently been given WAY too much responsibility for the little skills I have and I feel incredibly out of my depths, so I am hoping you guys can help me out a little. I am new to reading nameplate data and I was wondering if you had any solid rules for when I need an extra circuit for a single device or when I need a control wire. I've already messed this up once with a Fan Coil/Cooler Unit combo. So I was hoping someone could tell me what to look for.
> 
> I have a Make-up-air/Duct Heater combo unit. The plans say it's just an MUA unit, not a Duct Heater and it's a 208V 1ph 12/2 device. The HVAC guy says it needs another wire for the Duct Heater. I don't know if he's just guessing or if he knows what he's doing. I thought this was suspicious so I asked someone above me to look at the nameplate data and see if he could figure out what's going on.
> 
> ...


The nameplate is say that it is using two legs of the three phase supply. The nameplate should also say what the minimum circuit/maximum fuse or breaker size is. I would say that if you use a 2 plle 20 amp breaker, and run # 12 THHN, you would be ready to go. Sometimes the bosses can "throw you to the wolves." Good luck, Sparky!


----------

