UL Service Entrance Panels

[lbarnes]

I am currently designing a multi-building school, with a single main switchboard, and feeder panels in the outlying buildings. There is a counterpoise ring around each building, and each ring is bonded together. The system is 480Y277 volts.

Citing Article 225.36, the plans reviewer has required that I make these feeder panels "suitable for use as service equipment". This brings up a concern for me in that I believe there will be a bonding strap between the neutral bus and ground bus in the ULSE panels. There would therefore be a parallel path for neutral current flow back to the main switchboard, a situation clearly prohibited by Article 250.32(B)(1).

Can anyone provide some clarification? Should I have the installer remove the bonding strap in the panels, and if so, wouldn't this invalidate UL's listing? Should I simply not pull in an EGC with the feeder?

Thanks in advance for your help with this problem.

 

[ryan_618]

Re: UL Service Entrance Panels

I beleive you are right in your thoughts, in that there should be no bonding in the panels IF you pull an EGC.

As far as the phrase "suitable for use as service equipment" goes, if the panel includes a device that may be used as a main bonding jumper (screw, strap or other) it is listed as service equipment.

If there is an EGC, yes the installer needs to remove the bond at the panels, and no, it wouldn't void the listing.

If you do not have an EGC, make sure there are no metallic paths between the strucures. Also, you mentioned this is a 480Y/277 setup. If you have a breaker in the main that is over 1000 Amps, GFPE will be required as per 230.95, making the EGC between the two buildings a requirement, not an option.

 

[ron]

Re: UL Service Entrance Panels

Definately pull an equipment grounding conductor to each of the "subpanels".
No n-g bond at the subpanels.
In my opinion, no service entrace marking needed on the "subpanels", as they are not the first disconnect from the service.
Removing the n-g bond at these "subpanels" would not violate the listing. Panels with or without an SE marking can have a n-g bond or not, depending on their application.

 

[don_resqcapt19]

Re: UL Service Entrance Panels

See 225.36. The building disconnect panels are required to be listed as "suitable for service equipment". If there are other metallic paths between the buildings then EGCs are required and the bonding screw or strap is not to be installed.
Don

 

[ron]

Re: UL Service Entrance Panels

Don,
Good catch!

 

[eprice]

Re: UL Service Entrance Panels

Originally posted by lbarnes:
...There is a counterpoise ring around each building, and each ring is bonded together...

If I am understanding this correctly, wouldn't the bonding of the rings between buildings constitute a "...continuous metalic paths bonded to the grounding system in both buildings..." refered to in 250.32(B)(2)? So that section can't be used. 250.32(B)(1) will need to be followed and an equipment grounding conductor will need to be included in the feeders.