Sub panel, Delta/Wye requirements.

[W-Cummins]

Hello, I need to add a few sub panels to my shop. I have one square d NF 250 amp 480/277 panel and I need to get another NF panel. So I have been looking for another (probably used panel) I assume I can use a higher rated panel ( 600v/348 ) on my system? Also the panel I have and most of them I'm looking at are / rated. My service is 4 wire Wye 480, but I don't need 277V from these sub panels, so I'm not going to run 4 wires to them, and probably will remove the grounded conductor bus from them. I have noticed some panels are marked 480/277 4 wire and 240v 3 wire ( I assume for a delta service and 240v to ground). I also assume that I don't need a 480v delta 3 wire rated panel as I can't not generate the 480v to ground that requires one even though I will only be running 3 wires??

Thoughts??

Thanks
William.....

 

[nadogail]

I would not touch you job, IMHO you are being unreasonable in your expectations.

 

[W-Cummins]

I would not touch you job, IMHO you are being unreasonable in your expectations.

Well I'm not looking for some one to wire the sub panels.... can you expand on why you think I have unreasonable expectations? You don't think the Square D NF panel's are up to the task?

 

[nadogail]

Well I'm not looking for some one to wire the sub panels.... can you expand on why you think I have unreasonable expectations? You don't think the Square D NF panel's are up to the task?

Electrical Equipment is required to be installed and used inaccordance with the manufacturers instructions.

 

[Bert_]

I don't see an issue with it. I would assume you are planning on a ground wire even though it's not mentioned. I would bond the neutral buss and mark it equipment ground only.

Downside of a higher rated breaker is if you need to purchase a new breaker, the cost will be more.

 

[Norcal]

You can't use slash rated equipment, 480/277V, on 480V systems, since your 480/277V, your good to go on that point. BTW it's 600/347V, common in Canada.

 

[Steve from Socal]

What do you need for used? I have a nice 400 amp main lug I-line panel and several three pole breakers These are in Hutchinson, Ks they could sip via Fastenal freight

 

[mike93lx]

I would not touch you job, IMHO you are being unreasonable in your expectations.

This response is confusing to the point I initially thought your were in the wrong thread. Can you elaborate on the problem you see with the OP's questions?

 

[micromind]

I've been a commercial/industrial electrician for more than 30 years. I've installed a number of panels like you're describing.

I make some sort of a placard that states '480 VOLTS 3Ø 3 WIRE. 277 VOLTS NOT AVAILABLE.'

Also, I remove the neutral bus.

A lot of my work is inspected, never had a problem.

The ratings are maximum, actual conditions can be lower. I've done jobs that were 120/208 and the available fault current exceeded what 120/240 breakers could handle. The engineer specified 277/480 panels and breakers and a placard stating '120/208 VOLTS 3Ø 4 WIRE Y'.

I would have no problem at all doing what you describe, just mark the 3 wire panels as having no 277.

 

[wyliesdiesels]

Hello, I need to add a few sub panels to my shop. I have one square d NF 250 amp 480/277 panel and I need to get another NF panel. So I have been looking for another (probably used panel) I assume I can use a higher rated panel ( 600v/348 ) on my system? Also the panel I have and most of them I'm looking at are / rated. My service is 4 wire Wye 480, but I don't need 277V from these sub panels, so I'm not going to run 4 wires to them, and probably will remove the grounded conductor bus from them. I have noticed some panels are marked 480/277 4 wire and 240v 3 wire ( I assume for a delta service and 240v to ground). I also assume that I don't need a 480v delta 3 wire rated panel as I can't not generate the 480v to ground that requires one even though I will only be running 3 wires??

Thoughts??

Thanks
William.....

nope you dont need a straight rated delta 480v panel because you have 4870Y/277v service. The straight rated delta panels have higher ratings because 240v and 480v to ground has higher fault current.

But a slash rated 480v panel is the proper panel to use.

 

[wyliesdiesels]

I would not touch you job, IMHO you are being unreasonable in your expectations.

huh?

 

[wyliesdiesels]

This response is confusing to the point I initially thought your were in the wrong thread. Can you elaborate on the problem you see with the OP's questions?

yeah im lost with his responses as well

 

[PCustoms]

yeah im lost with his responses as well

Damnit, I had to un-ignore him to see what you're all talking about

 

[cycle61]

I would not touch you job, IMHO you are being unreasonable in your expectations.

Feel free to not bid on this one.

 

[klassenl]

The ratings are maximum, actual conditions can be lower. I've done jobs that were 120/208 and the available fault current exceeded what 120/240 breakers could handle. The engineer specified 277/480 panels and breakers and a placard stating '120/208 VOLTS 3Ø 4 WIRE Y'.

I find that interesting. In my part of Canada that would not pass.


I will ask my inspector or engineer about this kind of thing the next time they are chatty.

 

[Norcal]

I find that interesting. In my part of Canada that would not pass.


I will ask my inspector or engineer about this kind of thing the next time they are chatty.

It may have been that 42K or 64K interrupting current rated breakers were impossible to get w/ a 120/240V rating, but were in stock with a 277V or 480/277V rating, I cannot see operating a panelboard, & breakers under their rated voltage as a safety issue.

 

[Bert_]

It may have been that 42K or 64K interrupting current rated breakers were impossible to get w/ a 120/240V rating, but were in stock with a 277V or 480/277V rating, I cannot see operating a panelboard, & breakers under their rated voltage as a safety issue.

The breakers and panels are usually rated and tested for the lower voltage as well as the higher voltage.

Pretty sure the breakers usually list AIC for 480 and then separate line listing a higher AIC at 240

 

[W-Cummins]

I don't see an issue with it. I would assume you are planning on a ground wire even though it's not mentioned. I would bond the neutral buss and mark it equipment ground only.

Yes I'm planing on a 4 gauge ground conductor ( for >200amps).
I'm planing on running main breaker panels w/225 amp 480v 65ka KLC34255's

So sense I started on this Delta power, down the internet rabbit hole journey, and I now have been looking into ungrounded delta systems, I have a new question

If I run the 3 wires from my 4 wire Wye system to a sub panel serving my plasma table ( with an additional at the table ground rod) and some how the ground feeding the panel from the main switch board gets cut/removed/etc... will I have a un-grounded delta at that sub panel??

You can't use slash rated equipment, 480/277V, on 480V systems, since your 480/277V, your good to go on that point. BTW it's 600/347V, common in Canada.

I was reading some place that there are also some 600/347 systems in up state New York, that might be why I'm seeing panels for sale with that rating in the NE US?

I've been a commercial/industrial electrician for more than 30 years. I've installed a number of panels like you're describing.

I make some sort of a placard that states '480 VOLTS 3Ø 3 WIRE. 277 VOLTS NOT AVAILABLE.

That sounds like a good idea I will mark them

Also, I remove the neutral bus.

So I have one vote for remove and one for re-use for the eq grounds, I was thinking that I will only have 14 breakers in the boxes, I would not need the HD connections of the grounded conductor bus bar, and if I cut the can/eq ground bus off to 14 positions it would discourage anyone from using it as a neutral.

 

[wyliesdiesels]

No you wouldn't have an ungrounded delta simply because an EGC is missing. The neutral is still bonded at the main switchboard.

If you wanted ungrounded delta you would have to setup a separately derived system along with ground fault detection equipment which could be as simple as 3 480v industrial bulbs wired in wye.

 

[micromind]

Ungrounded means there's no connection to ground at the source. If the source is grounded then the entire system is considered grounded.

Also, if the system is Y at the source, it is always Y unless there's a transformer with a ∆ secondary.

 

[wyliesdiesels]

Ungrounded means there's no connection to ground at the source. If the source is grounded then the entire system is considered grounded.

Also, if the system is Y at the source, it is always Y unless there's a transformer with a ∆ secondary.

not for a separately derived system that is isolated.

yes he would need a delta-delta transformer.

 

[Snapped-off]

I was reading some place that there are also some 600/347 systems in up state New York, that might be why I'm seeing panels for sale with that rating in the NE US?

There's also 415/240, where the 240 has 1 hot and 1 neutral.