[Quiksilver22]

One of my clients has a 3 phase grounded service. It's 240v from line a and c to ground and line b is a grounded conductor.
My question is do I tap into the bar line b on the panel and run a lug with a wire to a ground bar. Or just install a ground bushing and use the pipe as a ground.
My clients meter is one of 5 coming off a main trough fed by a main disco.

I'm just swapping the panel out to a 3 phase panel because the other idiot assumed it was a single phase panel when he found the grounded conductor. He actually put it on the neutral bar and used it as such.

 

[Quiksilver22]

On top of that.
My Client also had a transformer to generate 120/240v with neutral.
Problem is the so called idiot ran 1#6cu off a 2pole breaker to feed this transformer (with a ground).
This is causing the ground to deteriorate.
My question is do f you think a transformer already getting 240v on one line can handle a second 240v so the transformer load would be balanced better.

 

[Jlarson]

Is this your first corner grounded delta?

 

[varmit]

As long as the panel and breakers are rated for 240 volts, a single phase panel is an acceptable way to do this install. This was the only acceptable method in the days of fuse type panels, as there should be no fuses in the grounded conductor. With multipole breakers, if the breaker trips, it opens the ungrounded and grounded conductors simultaneously.

Your transformer will not care what two phases are suppling it. 240 volt is 240 volt. The grounded phase to any other phase still equals about 240 volt. Yes, down stream of the panel you do need a bonding conductor. The grounded phase is treated the same as a neutral on a wye system.

 

[Ultrafault]

I have never seen that setup. Would a person just use a 2 pole breaker to hook up a 3 phase load in that case?

 

[retiredsparktech]

I have never seen that setup. Would a person just use a 2 pole breaker to hook up a 3 phase load in that case?

After reading this highly interesting post, I'm trying to recall, how we did it, in a few places in our plant.
One area, we had a Square D, QO panel, that was used for lighting and a few light three phase loads. I distinctly remember that the labeling on the panel stated that it was intended for corner grounded delta 240 volts.
The breakers used, were the regular QO breakers, both single and double pole, available anywhere.
I do recall, that the three phase loads, did use a double pole breaker for the A&C phase.

 

[Ultrafault]

After reading this highly interesting post, I'm trying to recall, how we did it, in a few places in our plant.
One area, we had a Square D, QO panel, that was used for lighting and a few light three phase loads. I distinctly remember that the labeling on the panel stated that it was intended for corner grounded delta 240 volts.
The breakers used, were the regular QO breakers, both single and double pole, available anywhere.
I do recall, that the three phase loads, did use a double pole breaker for the A&C phase.

This is very interesting I never considered that. I learn something new every day here.

 

[retiredsparktech]

One of my clients has a 3 phase grounded service. It's 240v from line a and c to ground and line b is a grounded conductor.
My question is do I tap into the bar line b on the panel and run a lug with a wire to a ground bar. Or just install a ground bushing and use the pipe as a ground.
My clients meter is one of 5 coming off a main trough fed by a main disco.

I'm just swapping the panel out to a 3 phase panel because the other idiot assumed it was a single phase panel when he found the grounded conductor. He actually put it on the neutral bar and used it as such.

Exposure to all kinds of installations and wiring practices is the name of the game. I guess, I was fortunate to be exposed to the very bizarre way the plant was wired, where I worked as an electrician for 20 years. There was so many additions to the complex, in the 70 years, the plant was in existence.
Getting back to the original post, I wonder if the panel installed, is intended for 250 volts, to ground.
IIRC, panels intended for single phase, 120/240 volts are listed for no more than 125 volts to ground, per leg.

 

[Ultrafault]

I did some digging and found this gem.
http://static.schneider-electric.us...n/Molded Case Circuit Breakers/2700DB0202.pdf

 

[Quiksilver22]

My client needs the 3 phase for new machinery so I was going to change it either way. I had 2 PSEG inspectors come out and they were both shocked to see the setup and said to change it to 3 phase.
So I guess the real question is, is the grounded phase a neutral or ground? The existing panel used it as a neutral which doesn't seen right

 

[Quiksilver22]

This is the panel I'm changing

 

[Quiksilver22]

This is another panel coming from the same trough

 

[Ultrafault]

Did you read the tech bulletin I posted? It has all the answers you need. A grounded conductor must be marked in accordance with art. 200.

 

[Meadow]

After reading this highly interesting post, I'm trying to recall, how we did it, in a few places in our plant.
One area, we had a Square D, QO panel, that was used for lighting and a few light three phase loads. I distinctly remember that the labeling on the panel stated that it was intended for corner grounded delta 240 volts.
The breakers used, were the regular QO breakers, both single and double pole, available anywhere.
I do recall, that the three phase loads, did use a double pole breaker for the A&C phase.

that sounds more like 120/240 midpoint grounded delta.

 

[Meadow]

If you could Id change all this to 208Y/120 or 240Y/139. A lot safer and easier to work with.

 

[Quiksilver22]

Ultra-thanks for the post. I thoroughly read through it and I can't believe the panel he has is ok. My only question is it pretty much states you can use a 2p breaker to feed a 3 phase system as long as it's labeled "1 phase- 3 phase"

What would you do for the ground bar?
Use a grounding bushing with a #6 to the ground bar or if it's legal/possible use a breaker from the grounded phase with a wire to a ground bar. Only problem is couldn't that breaker technically trip?

 

[Ultrafault]

Ultra-thanks for the post. I thoroughly read through it and I can't believe the panel he has is ok. My only question is it pretty much states you can use a 2p breaker to feed a 3 phase system as long as it's labeled "1 phase- 3 phase"

What would you do for the ground bar?
Use a grounding bushing with a #6 to the ground bar or if it's legal/possible use a breaker from the grounded phase with a wire to a ground bar. Only problem is couldn't that breaker technically trip?

Varmit said you treat it like any other neutral. That makes sense to me.

 

[varmit]

Your first question: Yes, for three phase loads you would use a 2 pole breaker and connect the third phase to the grounded phase on the "neutral bar". For 240 volt single phase loads you could either use a two pole breaker to both of the ungrounded phases or a single pole breaker on one ungrounded phase and the other lead connected to the "neutral bar". You, of course, CAN NOT CONNECT ANY 120 VOLT LOADS TO THIS PANEL.

As for bonding: It would be the same as any other service or separately derived system. The grounded phase (aka Neutral) would bond to the GEC, panel can, etc. You would use a standard bonding method - wire sized by NEC 250.122, metal conduit or any other code compliant method to bond the equipment fed from the panel, back to the panel.

This type system works the same as any other 240 volt three phase service equipment

 

[Quiksilver22]

Varmint thanks for all the information.
It sounds like changing the panel to a 3 phase would be pointless. And even harder to get the neutral on the b phase and on a neutral bar.

 

[Quiksilver22]

The client already has a 120/240 transformer fed from this panel, I'm just looking into running the second line to balance the load of the transformer.