3 phase panel and 1 phase panel from 3 phase source: grounded conductor termination?

[Jpflex]

People have been asking for a picture so here it is

3 phase ungrounded 300kva delta delta pad mounted transformer 4800 volt primary and 480 volt secondary to first disconnect 3/0 secondary feeders

Goes to gutter at another building to allow tap to both a 3 phase ungrounded distribution panel to power motors and other tap within gutter to single phase disconnect 200 amperes selected by boss from phases A and C

1 phase disconnect 200 ampere breaker boss selected feeds single phase 50 KVA 480 v to 240 v secondary with 3/0 wires boss selected to feed single phase distribution panel. Neutral is for the first time now derived from single 50kva transformer


What happens to derived neutral and system bonding jumper?


Does this transformer get a system bonding jumper installed with a supply side bonding jumper to 1 phase panel or does single phase distribution panel get a system bonding jumper as the first point of disconnect? (bonding neutral conductor derived from transformer to single phase distribution panel neutral bus, EGC, case and grounding conductor?

Doing the latter will also connect grounded conductor to 3 phase panel that is bonded with gutter

 

[LarryFine]

The derived neutral requires a GEC to the building electrode system just as you would with a service, including, I believe, the 1ph disconnect.

The 480v section should either be grounded or have ground-fault detection equipment. All metallic parts should be bonded to or by an EGC system.

 

[Jpflex]

The derived neutral requires a GEC to the building electrode system just as you would with a service, including, I believe, the 1ph disconnect.

The 480v section should either be grounded or have ground-fault detection equipment. All metallic parts should be bonded to or by an EGC system.

Yes I mentioned ground detectors being required at ungrounded source at ungrounded 3 phase system transformer but my coworker managed to convince company it was not required

 

[Jpflex]

Gutter connecting single phase and 3 phase panel

 

[tortuga]

Yes I mentioned ground detectors being required at ungrounded source at ungrounded 3 phase system transformer but my coworker managed to convince company it was not required

Thats odd, what was the rationale?
Are you working for a utility or somewhere the NEC does not apply?
There are no exceptions to 250.21(B)(1) in the NEC.

And unless you sized the run for voltage drop the 480V feeder from the gutter tap to the 50kVA primary can probably be smaller conductors.

 

[Frank DuVal]

And unless you sized the run for voltage drop the 480V feeder from the gutter tap to the 50kVA primary can probably be smaller conductors.

As can the 200 amp fuses. 50,000 / 480 is 104 amps. They make fuses between 100 and 200 amps.

I guess the "other guy" read 250.20 (B) (1,2 & 3) and said, well, no grounding required and didn't read 250.21

 

[Jpflex]

Thats odd, what was the rationale?
Are you working for a utility or somewhere the NEC does not apply?
There are no exceptions to 250.21(B)(1) in the NEC.

And unless you sized the run for voltage drop the 480V feeder from the gutter tap to the 50kVA primary can probably be smaller conductors.

Well I guess it’s because this is a mine sight and NEC article 90 doesn’t cover mines. However all my work so far has been on cabins, houses, outside of the mine

 

[tortuga]

Well I guess it’s because this is a mine sight and NEC article 90 doesn’t cover mines. However all my work so far has been on cabins, houses, outside of the mine

Ahh makes sense. I would be surprised if the MSHA in all those CFR's still allowed new installations to have ungrounded systems without detectors.

 

[Jpflex]

Ahh makes sense. I would be surprised if the MSHA in all those CFR's still allowed new installations to have ungrounded systems without detectors.

I actually have no idea what MSHA electrical codes are. Everything I do is according to NEC as long as I’m able. I have no interest in mining but only electrician work and obtaining enough working hours under c10 to qualify for journeyman licensing

 

[tortuga]

Everything I do is according to NEC as long as I’m able.

Well the ungrounded delta you and your coworker are installing seems like its not exclusively 'underground a mine, self-propelled mobile surface mining machinery' and/or its 'attendant electrical trailing cable', so you should fire off an email or letter citing 250.21(B)(1) and request management get you a ground detector in writing. That way you have a record, just incase.

ISOMETER® iso685 Series

ISOMETER® iso685 Series – insulation monitoring for ungrounded AC/DC systems with real-time fault detection. Learn more!

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[Jpflex]

Well the ungrounded delta you and your coworker are installing seems like its not exclusively 'underground a mine, self-propelled mobile surface mining machinery' and/or its 'attendant electrical trailing cable', so you should fire off an email or letter citing 250.21(B)(1) and request management get you a ground detector in writing. That way you have a record, just incase.

ISOMETER® iso685 Series

ISOMETER® iso685 Series – insulation monitoring for ungrounded AC/DC systems with real-time fault detection. Learn more!

www.benderinc.com

The delta pad mounted transformer is not underground but above ground and not in mine. Everything I have done has been outside the mine surface level. I believe we are under MAHA rules but as far as NEC I do t know

 

[tortuga]

I believe we are under MAHA rules but as far as NEC I do t know

If your in California, where MSHA ends the CA version of the NEC begins.
What you describe working on would be under the Cali version of the NEC, and ground detectors are required.

 

[Jpflex]

If your in California, where MSHA ends the CA version of the NEC begins.
What you describe working on would be under the Cali version of the NEC, and ground detectors are required.

Do you mean because the electrical work I’m doing at this time is NOT INSIDE a mine? All work being done so far is onsite and outside

 

[tortuga]

Yes 90.3(B) of the 2017 NEC : "Not Covered. This Code does not cover the following:"

(2) Installations underground in mines and self-propelled
mobile surface mining machinery and its attendant electrical trailing cable

It does cover everything else at a mine property. Offices, sheds, substations.

 

[petersonra]

Well the ungrounded delta you and your coworker are installing seems like its not exclusively 'underground a mine, self-propelled mobile surface mining machinery' and/or its 'attendant electrical trailing cable', so you should fire off an email or letter citing 250.21(B)(1) and request management get you a ground detector in writing. That way you have a record, just incase.

ISOMETER® iso685 Series

ISOMETER® iso685 Series – insulation monitoring for ungrounded AC/DC systems with real-time fault detection. Learn more!

www.benderinc.com

you can also just wire up three lights. the code does not require anything real fancy.

 

[Jpflex]

you can also just wire up three lights. the code does not require anything real fancy.

I’m just not sure how to install this since the windings don’t seem accessible inside pad mounted transformer. Also if it were the lights would be tapped off L1, L2, L3 to a common point but there would be no protection for tapped wires

 

[tortuga]

I would just buy a ready made product, and put it on on the wall next to the 480V main,
beaver makes one with simple indicator lights:

GIP-4

Sales and service of motors and transformers; for industrial electrical applications

beaverelectrical.com

There are others littlefuse makes one.
Keep in mind all your breakers need to be straight rated 480V. no 480/277 breakers.
The problems one can run into with ungrounded systems are numerous so when they have to be used I prefer a fancy IEC style monitoring/protection relay, but yeah they cost 10x as much as the indicator lights.

 

[RyanMP1011]

I actually have no idea what MSHA electrical codes are. Everything I do is according to NEC as long as I’m able. I have no interest in mining but only electrician work and obtaining enough working hours under c10 to qualify for journeyman licensing

To my knowledge, MSHA will reference and enforce the NEC for blatant safety violations. I don't know if they formally adopt the NEC, but they do reference it. Apparently things like raceway fill as well, but I have not personally seen someone be cited for that. Our trays are way over-filled.

Enclosures left partially latched, labeling, damaged cables, and compromised equipment (water inside light fixtures, boxes) are all common citations.

I highly doubt the MSHA inspectors are going to cite anyone for strapping EMT at 5' from a box, unless it presents an obvious hazard.

At my company, we closely follow NEC, and as soon as I'm made aware of a new code change, I adapt future projects to it.

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