# Very old 480V 3p service



## Almost Retired

I do occasional work at a small mill in the next town. They dont employ electricians. 

The service is 3 wire, no neutral, no ground, just the 3 hot legs. The secondary of the transformers is wye connected. 

What do you call that configuration?


----------



## joe-nwt

∆Y


----------



## Almost Retired

joe-nwt said:


> ∆Y


It probably is delta on the primary, I really didnt look at that. but isnt there some word like floating or some such to differentiate from normal Y ?


----------



## joe-nwt

I guess ungrounded Y. What does it feed?


----------



## 460 Delta

I’d call it dangerous if you aren’t careful. With that said, it’d be called a floating Star here. Generally speaking when you see them, and I worked at a r-mix co that had three, they are in Delta configuration. The Star configuration gets you a neutral to get a lower single phase voltage for lighting and what not.


----------



## gpop

You can have a Y with no neutral it just means you can not use 277. Normally you would still have 3 phases and a ground which means you can still clear a single phase to ground fault. 

So are you saying you only have 3 wires on the poles going to the transformers or 3 wires coming from the transformer?


----------



## cuba_pete

gpop said:


> You can have a Y with no neutral it just means you can not use 277. Normally you would still have 3 phases and a ground which means you can still clear a single phase to ground fault.
> 
> So are you saying you only have 3 wires on the poles going to the transformers or 3 wires coming from the transformer?


Yeah…is the wye grounded X0? They didn’t really explain the secondary. Plus, aren’t there any convenience outlets in the entire mill, or is the entire thing ungrounded with no detection?


----------



## 460 Delta

cuba_pete said:


> Yeah…is the wye grounded X0? They didn’t really explain the secondary. Plus, aren’t there any convenience outlets in the entire mill, or is the entire thing ungrounded with no detection?


I’m going to guess it’s a floating system with no alarm or lights. The three plants I had before were that way and the owners were oblivious to the hazards. I told them finally the guilt, when something goes wrong was theirs alone.
Back to the OP, I wouldn’t be surprised if the original Delta bank died at some point and the poco replaced it with a Star bank made out of lot stock 277 xformers. The net effect is the same, they just didn’t have to ground the Star center.


----------



## Almost Retired

joe-nwt said:


> I guess ungrounded Y. What does it feed?


a small mill. built around 1960, i think. they do wood treating .... wolmanized


----------



## Almost Retired

gpop said:


> You can have a Y with no neutral it just means you can not use 277. Normally you would still have 3 phases and a ground which means you can still clear a single phase to ground fault.
> 
> So are you saying you only have 3 wires on the poles going to the transformers or 3 wires coming from the transformer?


3 wires leaving the 3 transformers, one wire each transformer. about a 20 foot drop to the first weatherhead/mast down to the feed to the MCC. no ground wire, no neutral wire, just 3 hots going to the mill


----------



## micromind

I'd call it 3Ø 3 wire. 

The configuration doesn't matter if there's no neutral or ground, it's simply 3Ø 3 wire.


----------



## Almost Retired

460 Delta said:


> I’d call it dangerous if you aren’t careful. With that said, it’d be called a floating Star here. Generally speaking when you see them, and I worked at a r-mix co that had three, they are in Delta configuration. The Star configuration gets you a neutral to get a lower single phase voltage for lighting and what not.


I agree, normally it is delta. BUT this is definitely Wye. I am looking for some one who is familiar with seeing this configuration to tell me what the common trade name is. I saw a post by someone, somewhere that talked about a floating delta but this is Y


----------



## gpop

If it was un-grounded how do you tell if its a Y.


----------



## Almost Retired

cuba_pete said:


> Yeah…is the wye grounded X0? They didn’t really explain the secondary. Plus, aren’t there any convenience outlets in the entire mill, or is the entire thing ungrounded with no detection?


there are 120V circuits in the mill, derived from 2 phase fed dry transformers


----------



## Almost Retired

460 Delta said:


> I’m going to guess it’s a floating system with no alarm or lights. The three plants I had before were that way and the owners were oblivious to the hazards. I told them finally the guilt, when something goes wrong was theirs alone.
> Back to the OP, I wouldn’t be surprised if the original Delta bank died at some point and the poco replaced it with a Star bank made out of lot stock 277 xformers. The net effect is the same, they just didn’t have to ground the Star center.


you are probably correct, i dont know. and there are no alarms or lights as you said. i have already had the call where a motor shorted to ground and the supervisor says "the supply is bad, i get 0V phase to ground." Luckily i remembered there is such an animal at a mill i used to work for : 1 phase to ground, no problem. but fix it before the 2nd phase shorts or you will trip the main


----------



## Almost Retired

gpop said:


> If it was un-grounded how do you tell if its a Y.


that is how the secondary of the three pots is connected. BUT there are only 3 hot wires going to the mill


----------



## Almost Retired

All I am looking for is someone who is familiar with these configurations to tell me the commonly used trade name for it


----------



## Almost Retired

460 Delta said:


> I’d call it dangerous if you aren’t careful. With that said, it’d be called a floating Star here. Generally speaking when you see them, and I worked at a r-mix co that had three, they are in Delta configuration. The Star configuration gets you a neutral to get a lower single phase voltage for lighting and what not.


so floating is probably the term that i want. I saw it somewhere else in reference to a delta system, but i am trying to verify that through common knowledge of common terminology. It is actually more forgiving than a grounded system, IF you know what it is. The immediate/last ocpd will trip with a short, but it is different to trouble shoot if you dont know what you are working on


----------



## Almost Retired

Almost Retired said:


> 3 wires leaving the 3 transformers, one wire each transformer. about a 20 foot drop to the first weatherhead/mast down to the feed to the MCC. no ground wire, no neutral wire, just 3 hots going to the mill


Bye the way, believe it or not there is one 30 amp disconnect, single phase, feeding overhead liting. Dont ask me, I dont know how it is working either, other than earth path back to the service entry


----------



## CAUSA

Almost Retired said:


> 3 wires leaving the 3 transformers, one wire each transformer. about a 20 foot drop to the first weatherhead/mast down to the feed to the MCC. no ground wire, no neutral wire, just 3 hots going to the mill


This is the pole transformers that you are mentioning?? From the utilities?? 
If yes.
The Center tap does it have a bare conductor to the shell with a taped conductor/that circular runs behind the pole transformer to attach to a lower common wire, per transformer?


----------



## Almost Retired

It is a normal metal building on a concrete slab. standard construction


CAUSA said:


> This is the pole transformers that you are mentioning?? From the utilities??
> If yes.
> The Center tap does it have a bare conductor to the shell with a taped conductor/that circular runs behind the pole transformer to attach to a lower common wire, per transformer?


HOLD UP, no center taps. yes, these are the pole transformers/ POCO xfmrs. 480V 3 phase. the secondary of the pots has ONLY 2 connections. #1 is to the other 2 pots and then ground #2 is to the 3 hot wires to the mill


----------



## Almost Retired

GUYS .... READ THE ORIGINAL POST OR THIS ONE : utility feed to the mill is 3 hot wires, no ground , no neutral

WHAT IS THE COMMON NAME FOR THIS CONFIGURATION ???


----------



## Almost Retired

all i want is the common name for the configuration/ supply


----------



## emtnut

Almost Retired said:


> GUYS .... READ THE ORIGINAL POST OR THIS ONE : utility feed to the mill is 3 hot wires, no ground , no neutral
> 
> WHAT IS THE COMMON NAME FOR THIS CONFIGURATION ???


It's Delta. Re-read posts #2 and most important #7


----------



## Almost Retired

I appreciate the interest. Yes it is rare, that is because it is at least as old as 1960, that is why I dont know what to call it. I guess i should say im looking for someone who is already retired, they might be old enough to have heard the common name for it


----------



## joe-nwt

Almost Retired said:


> the secondary of the pots has ONLY 2 connections.* #1 is to the other 2 pots and then ground* #2 is to the 3 hot wires to the mill


Grounded Wye. What do I win?


----------



## Almost Retired

emtnut said:


> It's Delta. Re-read posts #2 and most important #7


I am not going to debate that with you


----------



## Almost Retired

joe-nwt said:


> Grounded Wye. What do I win?


the mill supply does not receive a ground from the service, so i doubt it........... ONLY 3 WIRES GO TO THE MILL


----------



## Almost Retired

micromind said:


> I'd call it 3Ø 3 wire.
> 
> The configuration doesn't matter if there's no neutral or ground, it's simply 3Ø 3 wire.


I agree


----------



## Almost Retired

@Dennis Alwon or another moderator please close this thread. it isnt working


----------



## emtnut

Almost Retired said:


> @Dennis Alwon or another moderator please close this thread. it isnt working


What's not working is your description and/or understanding of a transformer.

I get the feeling, you think the secondary is 'floating' because it's a Delta primary.

That set up is common as dirt ....










If what you have is different, then tell us what it is !


----------



## Almost Retired

emtnut said:


> What's not working is your description and/or understanding of a transformer.
> 
> I get the feeling, you think the secondary is 'floating' because it's a Delta primary.
> 
> That set up is common as dirt ....
> 
> View attachment 158450
> 
> 
> If what you have is different, then tell us what it is !


I dont know what the primary is and it doesn matter, or what the secondary is and I dont care. the secondary has 3 hot wires going to the mill................ no ground............. no neutral........ just 3 hot wires .......... that is it


----------



## Almost Retired

Almost Retired said:


> I dont know what the primary is and it doesn matter, or what the secondary is and I dont care. the secondary has 3 hot wires going to the mill................ no ground............. no neutral........ just 3 hot wires .......... that is it


what is the common trade name for that configuration ?


----------



## oldsparky52

Almost Retired said:


> what is the common trade name for that configuration ?


As far as I know there is no "common trade name for that configuration", probably because it's not so common. I've lived a somewhat sheltered electrical life, but until your post I had never heard of this being done the way you say. I don't doubt you, I just don't believe there is an answer to your question.


----------



## Almost Retired

oldsparky52 said:


> As far as I know there is no "common trade name for that configuration", probably because it's not so common. I've lived a somewhat sheltered electrical life, but until your post I had never heard of this being done the way you say. I don't doubt you, I just don't believe there is an answer to your question.
> [/
> you may well be right. one of the replies i got said they thought it used to be delta secondary, (which makes sense) and the only pots the poco had on hand when it burned up had to be connected wye (not sure why).
> however i am currently looking for a post that i saw a day or 2 ago (i had been stalking this site for 3 days before i joined today) and he called a service "floating delta".... if i can find him, i will ask him. i am not exactly well exposed myself, thus the question


----------



## gpop

You can have a ungrounded whe as long as no wires on the secondary side are connected to ground. If the secondary is connected to ground what you have is dangerous.


----------



## Almost Retired

gpop said:


> You can have a ungrounded whe as long as no wires on the secondary side are connected to ground. If the secondary is connected to ground what you have is dangerous.


i dont know if the secondary is grounded at the pots. i saw it weeks ago and im working from memory and not looking at much else but the 3 hot wires to the mill


----------



## 460 Delta

Almost Retired said:


> It is a normal metal building on a concrete slab. standard construction
> 
> HOLD UP, no center taps. yes, these are the pole transformers/ POCO xfmrs. 480V 3 phase. the secondary of the pots has ONLY 2 connections. #1 is to the other 2 pots and then ground #2 is to the 3 hot wires to the mill


All right A-R slow down, what is causing some confusion is this small statement about the connections. If the Star center is grounded like you say, then a phase ground at say a motor JB will cause a breaker/fuse to trip.


Almost Retired said:


> you are probably correct, i dont know. and there are no alarms or lights as you said. i have already had the call where a motor shorted to ground and the supervisor says "the supply is bad, i get 0V phase to ground." Luckily i remembered there is such an animal at a mill i used to work for : 1 phase to ground, no problem. but fix it before the 2nd phase shorts or you will trip the main


If you have a grounded xformer bank outside, whether it be a grounded phase, or a center tap, or a Star center, and a phase to ground in a motor, you will clear a fuse or a breaker. This is regardless of the fact that you only have 3 phase wires coming into the building. The current will find a path back to the xformer bank one way or another if indeed it's grounded as you say.


----------



## Almost Retired

460 Delta said:


> All right A-R slow down, what is causing some confusion is this small statement about the connections. If the Star center is grounded like you say, then a phase ground at say a motor JB will cause a breaker/fuse to trip.
> 
> If you have a grounded xformer bank outside, whether it be a grounded phase, or a center tap, or a Star center, and a phase to ground in a motor, you will clear a fuse or a breaker. This is regardless of the fact that you only have 3 phase wires coming into the building. The current will find a path back to the xformer bank one way or another if indeed it's grounded as you say.


Agreed. I have already experienced a single phase ground in the system. How or why it works was not the question


----------



## five.five-six

This thread should be moved to : “gems of the trade”.


----------



## CAUSA

Almost Retired said:


> It is a normal metal building on a concrete slab. standard construction
> 
> HOLD UP, no center taps. yes, these are the pole transformers/ POCO xfmrs. 480V 3 phase. the secondary of the pots has ONLY 2 connections. #1 is to the other 2 pots and then ground #2 is to the 3 hot wires to the mill


I just need to ask one more question as annoying as it may seem.

two individual pole transformers?

or 3 individual pole transformers?


----------



## Almost Retired

CAUSA said:


> I just need to ask one more question as annoying as it may seem.
> 
> two individual pole transformers?
> 
> or 3 individual pole transformers?


 3 individual pots on the pole, only 2 secondary connections each, wye connected, service feeder is 3 hot wires ONLY ... no ground... no neutral


----------



## splatz

Almost Retired said:


> 3 individual pots on the pole, only 2 secondary connections each, wye connected, service feeder is 3 hot wires ONLY ... no ground... no neutral


At the pole, is the X0 / center of the secondary wye grounded?


----------



## Almost Retired

splatz said:


> At the pole, is the center of the secondary wye grounded?


it has been several weeks since i looked at it. i actually dont remember. i was mostly interested in trying to believe what i was looking at .... 3 hot wires only, no other connections at the infeed weather head. Further more, if i had known how many questions this would generate, i would have brought pics and precise detailed explanations to start with. i brought all of this on myself for going off half cocked


----------



## Almost Retired

I want to thank every one for their interest, comments, and information. The next time i go to that mill (next town a half hour away). I WILL have pics and a detailed explanation of the connections for this service. Until then, i have already told you more than i know LOL


----------



## 460 Delta

Almost Retired said:


> Agreed. I have already experienced a single phase ground in the system. How or why it works was not the question


That’s not how it works here on ET, you may ask what time it is, but you’re going to get someone who’s going to tell you how a watch works.


----------



## Almost Retired

460 Delta said:


> That’s not how it works here on ET, you may ask what time it is, but you’re going to get someone who’s going to tell you how a watch works.


that has become crystal clear to me. i have experienced it in other forums as well. guess i just forgot about that when i joined/asked


----------



## wcord

Why don't you look thru all of the different transformer connection diagrams, then post a picture of the one you are describing?
As they say, a picture says a thousand words


----------



## Almost Retired

wcord said:


> Why don't you look thru all of the different transformer connection diagrams, then post a picture of the one you are describing?
> As they say, a picture says a thousand words


im sorry, but its because i dont remember all the details of the connections. one day i will go back to that mill and gather all the details and pics


----------



## joe-nwt

Almost Retired said:


> im sorry, but its because i dont remember all the details of the connections. one day i will go back to that mill and gather all the details and pics


While you're there, dig the ground up and make sure there is no ground connection to the building.


----------



## Almost Retired

joe-nwt said:


> While you're there, dig the ground up and make sure there is no ground connection to the building.


can you explain further ? or are you joking ? of course the building is grounded, its metal on a cement slab. however there is no hard-wired ground connection from the poco


----------



## Almost Retired

OK .... I finally found the thread that i was looking at before i joined yesterday (and a lot of you that have commented here also commented there)









This Monf***ingstrostity


So, I came across this at a diner that I ate at, the diner is connected to a car parts factory, so it’s going to have a heavy load. In this photo, 7,200/12,470Y goes into a set of cutouts, then goes into the 3phase bank of transformers, the transformers have 2 HV on top and only 2 secondary...




www.electriciantalk.com





this is the thread that prompted me to ask a question about the hook up i had ... this thread is in linework


----------



## Almost Retired

now to ask the question in a different way ..... is there such a thing as floating Y ?


----------



## joe-nwt

A connection from the X0s that ran along side the phase conductors would be called a neutral. You claim there is no "ground" from the utility. How do you know the utility ground and building ground are not bonded underground?


----------



## Almost Retired

joe-nwt said:


> A connection from the X0s that ran along side the phase conductors would be called a neutral. You claim there is no "ground" from the utility. How do you know the utility ground and building ground are not bonded underground?


ok its a serious question. answer, i dont. around here i have never seen poco do it that way. but then again i have never investigated this type of old service before. there is a bare neutral/ground wire in the 4plex service drop from transformer pole to weather head infeed pole. i have visually verified that it is not connected at either end.
it doesnt make sense to me that they would leave that unconnected and then bury a ground connection however


----------



## Almost Retired

@SteveBayshore .... you were in that thread and seemed to have the most familiarity with it. is there such a thing as 480V 3P floating Wye ?


----------



## splatz

Almost Retired said:


> now to ask the question in a different way ..... is there such a thing as floating Y ?


Yes.


----------



## Almost Retired

splatz said:


> Yes.


T H A N K Y O U !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!


----------



## Almost Retired

splatz said:


> Yes.


T H A N K Y O U !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!


----------



## joe-nwt

Almost Retired said:


> ok its a serious question. answer, i dont. around here i have never seen poco do it that way. but then again i have never investigated this type of old service before. there is a bare neutral/ground wire in the 4plex service drop from transformer pole to weather head infeed pole. i have visually verified that it is not connected at either end.
> it doesnt make sense to me that they would leave that unconnected and then bury a ground connection however


The neutral support wire you describe is a neutral, not a ground. If they didn't need the neutral it wasn't connected. 

If the 480V service is supplying loads that do not require a neutral, say an MCC, why would one be installed? But normally you would still bond it to ground.

Back to the buried ground. Yes that's not the way it would be done today, but back in the day who knows what they did? There may be an entire ground grid installed at that location. Tell you what, instead of digging up the ground next time you're there, how about you string out a piece of wire between the utility and the buildings's ground and take a measurement. I don't have to tell you to check for voltage first.


----------



## Almost Retired

joe-nwt said:


> The neutral support wire you describe is a neutral, not a ground. If they didn't need the neutral it wasn't connected.
> 
> If the 480V service is supplying loads that do not require a neutral, say an MCC, why would one be installed? But normally you would still bond it to ground.
> 
> Back to the buried ground. Yes that's not the way it would be done today, but back in the day who knows what they did? There may be an entire ground grid installed at that location. Tell you what, instead of digging up the ground next time you're there, how about you string out a piece of wire between the utility and the buildings's ground and take a measurement. I don't have to tell you to check for voltage first.


LOL. Could be a shocking revelation


----------



## joe-nwt

Give us an update when you go back, please. Pics would be nice.


----------



## Almost Retired

joe-nwt said:


> Give us an update when you go back, please. Pics would be nice.


I do plan to get pics and a detailed explanation of them, next time i go. speaking of which, can i load a video to here from my phone ? and i will also check the ground potentials


----------



## Almost Retired

SteveBayshore said:


> I work on a couple of sites that look like that. Sorry I didn't take any pictures. On one, the customer owns the 2400v un-grounded Delta primary distribution and our three tubs give us 480v un-grounded Delta. There are (12) 120 volt type A lamps wired in series/parallel as a ground fault indicator connected to the 480v circuit. All constructed some time in the '50s.
> On another site we also have installed a few custom built pad mounted transformers with customer owned 26kv un-grounded delta primaries to 480v un-grounded delta secondaries. Eaton made some custom built ground fault indicators for our new MCCs for these, no 120v type A lamps in the new installations.
> These un-grounded type of services are designed/installed where continuous processes are critical. First short to ground anywhere on the plant only sets off an alarm and doesn't blow any fuses or trip any circuit breakers or shutting down a continuous process. It allows for clearing of belts and crushers for an orderly manual shutdown after an alarm is sensed..


----------



## micromind

Almost Retired said:


> now to ask the question in a different way ..... is there such a thing as floating Y ?


Yes, as long as the center of the Y is not connected to anything, it'd be a floating Y. 

An example of this would be when back-feeding a 480∆ - 120/208Y transformer in order to get 480 from a 208 service. If X0 is connected to either the neutral or the ground, there'll be circulating currents that will eventually burn up the transformer. But if X0 is isolated there are no circulating currents, therefore this is the proper way to connect it.


----------



## 460 Delta

joe-nwt said:


> If the 480V service is supplying loads that do not require a neutral, say an MCC, why would one be installed? But normally you would still bond it to ground.


Had this happen a few years ago at my former job. Disconnected a floating Delta in the MCC, good old Unitrol, and powered it up with a Star. The neutral was landed on the grounded ground bar and off we went. There were no 277 loads so it was just grounded and that was that.
There were ground rods driven in addition to the steel deep well casing and the de facto Ufer from the rebar work all lashed together 
to the iron work. This was already present. The ground system on r-mix plants are what some consider over the top, but the 75’ tall silo or silos make great lightning rods that we have to dissipate the energy quickly.


----------



## yankeejoe1141

Holy cannoli a lot of all caps posts and frustration to read through in the beginning of this thread.

I make a motion to re-name this configuration after the OP, the A.R. Special.


----------



## WannabeTesla

I bet it's grounded through a tin roof two towns over...


----------



## Almost Retired

460 Delta said:


> Had this happen a few years ago at my former job. Disconnected a floating Delta in the MCC, good old Unitrol, and powered it up with a Star. The neutral was landed on the grounded ground bar and off we went. There were no 277 loads so it was just grounded and that was that.
> There were ground rods driven in addition to the steel deep well casing and the de facto Ufer from the rebar work all lashed together
> to the iron work. This was already present. The ground system on r-mix plants are what some consider over the top, but the 75’ tall silo or silos make great lightning rods that we have to dissipate the energy quickly.


So .... you started with "had this happen a few years ago" i follow your description of the situation, but i dont find your description of what happened?


----------



## Almost Retired

WannabeTesla said:


> I bet it's grounded through a tin roof two towns over...


GOOD ONE !!!! I see you are making a connection between my 2 posts LOL


----------



## Almost Retired

yankeejoe1141 said:


> Holy cannoli a lot of all caps posts and frustration to read through in the beginning of this thread.
> 
> I make a motion to re-name this configuration after the OP, the A.R. Special.


After enough replies, I found a way to rephrase the question and got an immediate answer that answered my op perfectly

as far as the AR Special, you might want to reserve that title for my post Odd Problem - Voltage on Metal Roof.


----------



## 460 Delta

Almost Retired said:


> So .... you started with "had this happen a few years ago" i follow your description of the situation, but i dont find your description of what happened?


My post was a response to @joe-nwt query/statement about a MCC with no neutral load, just phase to phase loads.
BTW, everything worked out just perfectly at that plant.


----------



## Almost Retired

460 Delta said:


> My post was a response to @joe-nwt query/statement about a MCC with no neutral load, just phase to phase loads.
> BTW, everything worked out just perfectly at that plant.


My bad ... this has generated so much response that i am scrambling to keep up. I did not notice that was not directed to me. however i am curious so i will go back and read the whole thing


----------



## Mbit

Ungrounded wye is standard on ships and is also very common in Europe, it's called an IT system over there.


----------



## Almost Retired

Mbit said:


> Ungrounded wye is standard on ships and is also very common in Europe, it's called an IT system over there.





Mbit said:


> Ungrounded wye is standard on ships and is also very common in Europe, it's called an IT system over there.


When i was working off shore drilling. I discovered that you needed a 2 pole breaker for 120V. The panel was 2 phases (same as our common single phase panels at home) the voltage was 60/60/120. the panel had a 4 wire feed. I had no clue about the txr, i didnt even know there were choices at that time. I recognized the methods of wiring as ship board from my time in the navy


----------



## Mbit

Almost Retired said:


> When i was working off shore drilling. I discovered that you needed a 2 pole breaker for 120V. The panel was 2 phases (same as our common single phase panels at home) the voltage was 60/60/120. the panel had a 4 wire feed. I had no clue about the txr, i didnt even know there were choices at that time. I recognized the methods of wiring as ship board from my time in the navy


That's awesome, that's one area I haven't worked. Although typically I will see 69 volts to ground on a well functioning system. Or 277 if it's a 480VAC system.


----------



## Almost Retired

Mbit said:


> That's awesome, that's one area I haven't worked. Although typically I will see 69 volts to ground on a well functioning system. Or 277 if it's a 480VAC system.


ok ,,, that 69V has me intrigued. Are you talking about an ungrounded system? 120V phase to neutral?


----------



## micromind

I've seen 69/120 for metering in medium-voltage switchboards. 

It's 3 - 120 volt transformers connected 4 wire Y. 69 phase to neutral and 120 phase to phase. 

Fairly common for voltage and KVA/KW metering.


----------



## Mbit

Almost Retired said:


> ok ,,, that 69V has me intrigued. Are you talking about an ungrounded system? 120V phase to neutral?


Yes sir, ungrounded. Phase to ground, no neutral is brought out from the generators to the switchgear. 
Some ships will use equipment grounding and some have no ground bus or EGCs.


----------



## WannabeTesla

Mbit said:


> Yes sir, ungrounded. Phase to ground, no neutral is brought out from the generators to the switchgear.
> Some ships will use equipment grounding and some have no ground bus or EGCs.


This is true. Ask any ship electrician.


----------



## greenpro

Almost Retired said:


> I do occasional work at a small mill in the next town. They dont employ electricians.
> 
> The service is 3 wire, no neutral, no ground, just the 3 hot legs. The secondary of the transformers is wye connected.
> 
> What do you call that configuration?


That’s an ungrounded system, some facilities used to keep running if ground fault happens in one phase because probably will be very expensive stop production without scheduling or in some cases lives can be in danger, in that system you two phase fault to trip breaker, but they should have ground fault monitors so they know one fault occurs and scheduled repairs as soon as they can


----------

