# mixed voltage



## Buddha In Babylon (Mar 23, 2009)

it's a bad idea. i'm not certain if it's a code violation, but i know that anytime you have 120 and 277 in the same box/wiremold/etc., and do not have them seperated by some means, you have the potential for people to try to splice them together which is a bad idea too.


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## Mac Hine (Apr 28, 2009)

nick said:


> Well question mixed voltage 120 volt with 277 volt same raceway same box ? what is your rule on the job or whats your comments about mixing these ? Take care


As long as the insulation of the conductors are rated for the highest voltage then it is code compliant to mix voltages under 600 volts. Art. 300.3(C)(1) & (2)


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## RePhase277 (Feb 5, 2008)

nick said:


> Well question mixed voltage 120 volt with 277 volt same raceway same box ? what is your rule on the job or whats your comments about mixing these ? Take care


It is legal as long as the conductors are rated for the same voltage and the neutrals are identified separately. However, I generally try to avoid it as a general principle, The only time I would do it is if 120 and 277 went to the same equipment. For example, if I had a pipe from a lighting control center that fed 120 V and 277 V lighting.


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## bigredc222 (Oct 23, 2007)

Like the others said, it is leagal but generally not done if it can be helped. It could be a problem if you tried to put like a 120 volt and a 277 volt switch in the same box. Your not allowed more than 300 volts in a switch box. You would need to use a devider in that case.


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## LGLS (Nov 10, 2007)

Is the issue you naysayers have the intermingling of 2 different systems, or the different voltages, or the potential for someone to make up the splices incorrectly?


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## acmax (Apr 20, 2009)

LawnGuyLandSparky said:


> Is the issue you naysayers have the intermingling of 2 different systems, or the different voltages, or the potential for someone to make up the splices incorrectly?


Today out in the field their are more hacks than licensed electrician. If there's a way to blow it up they find it. I've been set on big jobs to do final and punch out and could write a book on the reasons ONLY licensed electrician and qualified appretices should be installing electrical systems.
ART. 90.1(A) (B) (C) (D).


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## brian john (Mar 11, 2007)

acmax said:


> Today out in the field their are more hacks than licensed electrician. If there's a way to blow it up they find it. I've been set on big jobs to do final and punch out and could write a book on the reasons ONLY licensed electrician and qualified appretices should be installing electrical systems.
> ART. 90.1(A) (B) (C) (D).


 
Many places do not have licenses. And I have seen a ton of hack work completed by licensed electricians. A license does not guarantee quality work.

In my expierence the biggest issue I have seen from mixing voltages is crossing the neutrals and the ground current associated with this practice.

While it is as noted NEC permissible, IMO it should be avoided when possible.


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## acmax (Apr 20, 2009)

brian john said:


> Many places do not have licenses. And I have seen a ton of hack work completed by licensed electricians. A license does not guarantee quality work.
> 
> In my expierence the biggest issue I have seen from mixing voltages is crossing the neutrals and the ground current associated with this practice.
> 
> While it is as noted NEC permissible, IMO it should be avoided when possible.


 ? what states do not require licensing.OR are you referring to only romex jerking.I want to know my son just passed the fireman's test and has not decided where to work.


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## dawgs (Dec 1, 2007)

Nick, Like the others said, I do not recommend it, but you will need to identify your conductors with color code, and install a divider in the box, along with what others said you will be compliant.


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## brian john (Mar 11, 2007)

acmax said:


> ? what states do not require licensing.OR are you referring to only romex jerking.I want to know my son just passed the fireman's test and has not decided where to work.


Pennsylvania, and New York for two that I have heard of, other posters will chime in.

And commercial electricians are as hacky as residential.

And why would electrical licenses affect where you son does work as a fireman?


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## bigredc222 (Oct 23, 2007)

He's being sarcastic. No licence more fires. I live in Pa. and can attest to the fact that our state has no requirement for a licence. However the cities do. If you want to work in Philly you have to pass a test. Many small towns and municipalities make you get a licence from them. That's usually a joke. They just want to collect 60 bucks from you then they give you a card that say's you can work there. This stuff has been hashed over a hundreds of times. Your as good as you want to be. If you have enough drive and care about what your doing licence or not you'll be good. If your just in it for a pay check and don't give a crap. you'll be a hack. I've worked for few owners of companies that were the worst electricians. They studies enough to pass the test for the licence then proceeded to do the worst crap. I quit both of them because I couldn't work like that. Guy's just throwing High hat's on ceiling tiles without supporting them from the grid. That's one of my pet peeves. All his guys did that. When I wouldn't they would tease me about it. I got pulled off the job because I wouldn't do it there way. That's when I knew I had to leave.
Chris


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## LGLS (Nov 10, 2007)

acmax said:


> Today out in the field their are more hacks than licensed electrician. If there's a way to blow it up they find it. I've been set on big jobs to do final and punch out and could write a book on the reasons ONLY licensed electrician and qualified appretices should be installing electrical systems.
> ART. 90.1(A) (B) (C) (D).


I agree but a hack is gonna hack no matter what you do anyway. Are you really not installing different systems together for their future benefit? On one job I ran multiple 3/4 from the EC to AHUs that required single phase 208 #12s and 1 120v circuit for a condensate pump. These AHUs were all around the perimeter of the space, furthest from the El Closet you could get. I got grief because of old-school thinking - why run 1 conduit when you can double the work and run 2, and "justify it" in the name of safety - not mixing systems.

F that. Got fed up, told the Jman to run it or there's the door, and the layoff won't be a pretty one...

I'm sure the inspector loved it, but I've still yet to see on in the City of New York...


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## RePhase277 (Feb 5, 2008)

LawnGuyLandSparky said:


> I agree but a hack is gonna hack no matter what you do anyway.


So true. I couldn't give a crap what the next guy down the road might do.



> On one job I ran multiple 3/4 from the EC to AHUs that required single phase 208 #12s and 1 120v circuit for a condensate pump. These AHUs were all around the perimeter of the space, furthest from the El Closet you could get. I got grief because of old-school thinking - why run 1 conduit when you can double the work and run 2, and "justify it" in the name of safety - not mixing systems.


Huh? the 208 V system and the 120 V system are the same system...


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## william1978 (Sep 21, 2008)

You can mix voltages as long as you meet the requirements that others have posted, but not normal and emergency.


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## acmax (Apr 20, 2009)

brian john said:


> Pennsylvania, and New York for two that I have heard of, other posters will chime in.
> 
> And commercial electricians are as hacky as residential.
> 
> And why would electrical licenses affect where you son does work as a fireman?


I'll agree licensing does not give a man a pass on being a hacker. Seen it first hand. Difference is the permit pull should show under who is responsible for the install. No license ? Who cares. Why bother calling for an inspection.How can one pull a permit on property they don't own. Who becomes liable in bad event. When I pay somebody for any kind of services,I always want them to be registered in some form simply on principle to show thier responsible. As an example, I would never buy meats from the guy parked in side lot and feed it to my kids.What if it turned out poisoned people would think Hey you got what you payed for.Those types of dealers are always around.There's a good reason for licensing.It would cut out a lot of scammers.


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## LGLS (Nov 10, 2007)

InPhase277 said:


> So true. I couldn't give a crap what the next guy down the road might do.
> 
> 
> 
> Huh? the 208 V system and the 120 V system are the same system...


Whoops, I meant the AHUs were 480 and the condensate pumps (all on the same 120v circuit) were 120.


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## acmax (Apr 20, 2009)

LawnGuyLandSparky said:


> Whoops, I meant the AHUs were 480 and the condensate pumps (all on the same 120v circuit) were 120.


? Why combine two different panels.What about the derating factor on conduit fill.Would like to know this, because it sounds like a big money saver. Did you get it blessed before by inspector.


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## sparkyboys (May 3, 2009)

separate conduits for all. except for in electrical room where all pipes meet.
can run all pipes into a raceway/pullbox for all the different panels. just separate and identify with white tape and label. easier for maintenance.


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## brian john (Mar 11, 2007)

sparkyboys said:


> separate conduits for all. except for in electrical room where all pipes meet.
> can run all pipes into a raceway/pullbox for all the different panels. just separate and identify with white tape and label. easier for maintenance.


 
Actually if they do not meet at a load why would they meet in an electrical room?

Seems to me if they are separate in the electric room they might meet at a riser or at a load requiring both voltages.

If they go no way near each other at the load why combine in the electric room?


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## sparkyboys (May 3, 2009)

brian john said:


> Actually if they do not meet at a load why would they meet in an electrical room?
> 
> Seems to me if they are separate in the electric room they might meet at a riser or at a load requiring both voltages.
> 
> If they go no way near each other at the load why combine in the electric room?


you can have 120 and 277 in the raceway not 480. and it allows the maintenance men to easier identify. easier for design as well, you want everything to look uniform


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## RePhase277 (Feb 5, 2008)

sparkyboys said:


> you can have 120 and 277 in the raceway not 480.


How do you figure?


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## brian john (Mar 11, 2007)

InPhase277 said:


> How do you figure?


 
Thank you for beating me to the response.


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## bigredc222 (Oct 23, 2007)

InPhase277 said:


> How do you figure?


Let me get in on that???


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## sparkyboys (May 3, 2009)

bigredc222 said:


> Let me get in on that???


I have never seen it.
so show me?


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## bigredc222 (Oct 23, 2007)

sparkyboys said:


> I have never seen it.
> so show me?


We were just saying how can you have 277 and not 480. As soon as you add a second 277 volt circuit you have 480.


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## RePhase277 (Feb 5, 2008)

sparkyboys said:


> I have never seen it.
> so show me?


300.2(A) says that we can have voltages up to 600 V for chapter 3 wiring methods.

200.6(D) specifies how we are to identify neutrals and other grounded conductors of different systems where installed in the same conduit or box.

Nowhere does it say that we are not to mix 480 and 120.


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## sparkyboys (May 3, 2009)

bigredc222 said:


> We were just saying how can you have 277 and not 480. As soon as you add a second 277 volt circuit you have 480.


ok, ok, ok, you got me on that one:laughing:


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## sparkyboys (May 3, 2009)

InPhase277 said:


> 300.2(A) says that we can have voltages up to 600 V for chapter 3 wiring methods.
> 
> 200.6(D) specifies how we are to identify neutrals and other grounded conductors of different systems where installed in the same conduit or box.
> 
> Nowhere does it say that we are not to mix 480 and 120.


ok, but what inductance?


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## brian john (Mar 11, 2007)

Not an ISSUE AT ALL. But here it is SORRY MH members.


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## RePhase277 (Feb 5, 2008)

sparkyboys said:


> ok, but what inductance?


Inductance depends on current, not on voltage. 20 A at 120 V has as much inductance as 20 A at 5000 V.


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## bigredc222 (Oct 23, 2007)

brian john said:


> Not an ISSUE AT ALL. But here it is SORRY MH members.


 Brian What are you showing us? It apears to be thermal images but I have never seen internal framework of gear get that hot.


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## RePhase277 (Feb 5, 2008)

bigredc222 said:


> Brian What are you showing us? It apears to be thermal images but I have never seen internal framework of gear get that hot.


Notice how some conductors are on one side of the framing, while others are on the other side. And the two neutrals in the bottom pic are all by themselves. What does that tell you?


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## sparkyboys (May 3, 2009)

InPhase277 said:


> Notice how some conductors are on one side of the framing, while others are on the other side. And the two neutrals in the bottom pic are all by themselves. What does that tell you?


I am not sure either.
please explain o holy ones.


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## RePhase277 (Feb 5, 2008)

sparkyboys said:


> I am not sure either.
> please explain o holy ones.


Well, when current flows, an electromagnetic field is created around the conductors, right? When all the circuit conductors are grouped together the effect is canceled because the current is flowing in opposite directions in different conductors. Like your clamp-on ammeter. If you clamp the meter over both wires of a circuit, you will read zero amps. But if you clamp it on either conductor by itself, you get a reading. Try it, it's an easy experiment.

Anyway, in Brian's pics, some of the phase conductors are on opposite sides of the gear framing. What this means is that the net field created around the conductors isn't canceled before it crosses the metal frame. Basically, we have created a transformer out of the frame. A circulating current is induced in the metal frame by the un-canceled field of the lone conductors. This current heats the metal.

This is why the code requires all circuit conductors to be routed together in the same raceway or cable.

I hope that makes sense. I'm not a great articulator of ideas...


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## sparkyboys (May 3, 2009)

I hope that makes sense. I'm not a great articulator of ideas...[/quote]

that makes a lot of sense. it kinda blew my mind for second.
was this done with one of those oscilliscopes?
And is that why the gear room needs adequate ventilation? 
And does this current flow to ground as well?


Man, its nice to be able to learn something new, I love this site!!!


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## acmax (Apr 20, 2009)

That's a great example. Thanks for info this is what I surf this site for:thumbsup: A picture is always better than 1000 words.Keep it simple,simply works.


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## RePhase277 (Feb 5, 2008)

sparkyboys said:


> that makes a lot of sense. it kinda blew my mind for second.
> was this done with one of those oscilliscopes?


Thermal camera.



> And is that why the gear room needs adequate ventilation?


Not really. Most gear rooms have transformers in them. These are the primary producers of heat in these rooms.



> And does this current flow to ground as well?


No, because there is not a complete circuit to the earth. The circuit consists of the short piece of metal frame that is perpendicular to the field in line with the conductors. Electrodynamic effects are most pronounced at 90° to the field, so there is a horizontally circulating current in the part of the metal that is at 90° to the length of the conductor.

In essence, what we get is a one-turn transformer with a 1:1 ratio. If 10 A flows in the conductor, then 10 A flows in the short section of frame. Notice in Brian's pics how the hottest spots are very short and in line with the conductors.


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## bigredc222 (Oct 23, 2007)

Very interesting. I knew when running parallel set's of wires in pipe you needed to have one of each phase in each pipe. I don't think I would have thought about it in the gear. Now I'm wondering if I ever did something like that.
Chris


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## LGLS (Nov 10, 2007)

Oops! :whistling2:


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## brian john (Mar 11, 2007)

InPhase277 said:


> Well, when current flows, an electromagnetic field is created around the conductors, right? When all the circuit conductors are grouped together the effect is canceled because the current is flowing in opposite directions in different conductors. Like your clamp-on ammeter. If you clamp the meter over both wires of a circuit, you will read zero amps. But if you clamp it on either conductor by itself, you get a reading. Try it, it's an easy experiment.
> 
> Anyway, in Brian's pics, some of the phase conductors are on opposite sides of the gear framing. What this means is that the net field created around the conductors isn't canceled before it crosses the metal frame. Basically, we have created a transformer out of the frame. A circulating current is induced in the metal frame by the un-canceled field of the lone conductors. This current heats the metal.
> 
> ...



You did a better job than I would have.

Basically a single winding transformer


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## drsparky (Nov 13, 2008)

bigredc222 said:


> Very interesting. I knew when running parallel set's of wires in pipe you needed to have one of each phase in each pipe. I don't think I would have thought about it in the gear. Now I'm wondering if I ever did something like that.
> Chris


Dito.


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