16 ATS's all 3 pole and the matter of Ground Fault

[__dan]

See 210.6...

Loads on the dual source bus, three pole ATS, solidly connected neutrals on the dual sorce bus, multiple assumed existing, haphazard, N to G connections, can be cleanly loaded if the loads are all line to line.

So if it is found during an existing conditions survey, that there exists lighting loads on that neutral at 277 V, those loads can be moved downstream of a transformer, and clean up the stray neutral current (going all over the place on the dual source bus). The tap itself on the neutral for loads, I would consider it wrong, but it's something that may be commonly done (causing neutral current on the grounding system).

 

[mbrooke]

Loads on the dual source bus, three pole ATS, solidly connected neutrals on the dual sorce bus, multiple assumed existing, haphazard, N to G connections, can be cleanly loaded if the loads are all line to line.

So if it is found during an existing conditions survey, that there exists lighting loads on that neutral at 277 V, those loads can be moved downstream of a transformer, and clean up the stray neutral current (going all over the place on the dual source bus). The tap itself on the neutral for loads, I would consider it wrong, but it's something that may be commonly done (causing neutral current on the grounding system).

It would be nice if they made 480 volt exist signs.

See, with our resources we could truly have a system where N-G connections do not exist.

 

[dy11]

If this is an art 700 or 701 system, 700.31 or 701.26 allows for alarm only on a gf with no trip required.

 

[__dan]

exist signs.

a system where N-G connections do not exist.

I'm still lost on the reference to lighting, 210.6. I don't see it.

You have a three pole ATS, dual source bus, multiple assumed N to G connections, more than one creates the parallel path for neutral curent.

You have a three pole ATS, and one of them downstream has the 3 phase 4 wire panelboard with the lighting at 277V. You can load it on the neutral with the only code reference would be "objectionable current", and it would not surprise me to find it that way. In a large older existing installation, Amp clamp the system bonding jumpers to see something (existing).

That panelboard and the lighting load would go dowstream of a line to line connected transformer, cleaning up the stray neutral current on the dual source bus.

 

[mbrooke]

My understanding is that code does not allow for 480 volt lighting in typical applications like an office or hall with a low drop ceiling.

 

[__dan]

My understanding is that code does not allow for 480 volt lighting in typical applications like an office or hall with a low drop ceiling.

The 16 three pole ATS's, the majority of it will be all line to line connected and very clean on the solidly connected neutral, actually not connected to the neutral. It's a great system.

One or two of those ATS's will have the lighting panel on it at 3 phase 4 wire 277 V to the neutral. Directly on the dual source bus with the neutral in the panel and the facility lighting on it. The system is 3 phase 3 wire for most but not all of the load.

I would consider it wrong, but easy to correct by moving any neutral connected loads, downstream of a line to line connected transformer. It's a great system if you can keep it to 3 phase 3 wire.

 

[mbrooke]

The 16 three pole ATS's, the majority of it will be all line to line connected and very clean on the solidly connected neutral, actually not connected to the neutral. It's a great system.

One or two of those ATS's will have the lighting panel on it at 3 phase 4 wire 277 V to the neutral. Directly on the dual source bus with the neutral in the panel and the facility lighting on it. The system is 3 phase 3 wire for most but not all of the load.

I would consider it wrong, but easy to correct by moving any neutral connected loads, downstream of a line to line connected transformer. It's a great system if you can keep it to 3 phase 3 wire.

I know

 

[drktmplr12]

we have an Owner down here who insists on 3 phase, 4-wire plus ground from service transformer all the way to main distribution. they don't even use the neutral, but that has been a losing argument to have them see reason. just a waste of (taxpayer) dollars to install unneeded copper "in case" they want 277 lights I guess.

otherwise, we do everything 3phase+G for these very reasons.

 

[JoeStillman]

This one of the many reasons why I advocate everything being connected phase-phase.

What code article mandates GF protection on a gen?

GF Sensing only - 700.31 and 700.6

 

[hillbilly1]

we have an Owner down here who insists on 3 phase, 4-wire plus ground from service transformer all the way to main distribution. they don't even use the neutral, but that has been a losing argument to have them see reason. just a waste of (taxpayer) dollars to install unneeded copper "in case" they want 277 lights I guess.

otherwise, we do everything 3phase+G for these very reasons.

I worked on an ice plant that had only 480 volt loads and no neutral, although the bank was 277/480. They were having issues with their drives, so they had us pull in a reduced neutral in all of the pipes to the transformer. Don’t know if it fixed their problem, but never heard back from them afterwards. Plant had been that way for at least 40 years.

 

[drktmplr12]

I worked on an ice plant that had only 480 volt loads and no neutral, although the bank was 277/480. They were having issues with their drives, so they had us pull in a reduced neutral in all of the pipes to the transformer. Don’t know if it fixed their problem, but never heard back from them afterwards. Plant had been that way for at least 40 years.

to clarify, we have a neutral from the Xfmr to the service entrance equipment, but no neutral distribution at 480.