3P, 3W remote bldg feeder from 3P,4W system 225.36

[smoothops10]

Hey all, I may be looking at this wrong but wanted to get some input. If I have a 3P,4W 277/480 service in building A and want to run a feeder to an MCC in building B (will be the only feeder serving the building with all loads downstream of MCC) which has no 277v line neutral loads and probably never will - does a 4W (+G) feeder with neutral need to be pulled to building B? I cannot really think of a good reason if it is not used. How does 225.36 come into play - can you get a 3P,3W MCC 'suitable for use as service equipment'? I've never seen this and utility would not supply a 3P,3W system if put on its own service in the future anyway. Is that the point of 225.36, the code is anticipating the possibly that the building will be fed from a feeder now but possibly a service in the future or is there more to it? Could I just put in a 3P,4W mcc and feed it with 3W (+G) or is that against the listing of the MCCs intended use?
The 2012 UL marking and application guide (pg12-13 on google) makes me feel like we need to run the neutral to get the 'suitable for us as service equipment'.
Is there any other benefit to having the neutral run with the feeder other than being able to serve 277v loads? I cannot think of any but I'm often proved wrong.


Any thoughts appreciated - thanks all.

 

[petersonra]

I don't think you need to run the N if it is not being used.

OTOH, it is not going to cost all that much extra to run the N wire. It can be smaller and it will not count as a CCC.

I don't understand the need for service equipment if it is not a service.

As best I can tell from looking at them, the primary difference between an MCC that is listed for use as service equipment and one that is not is having a place to land the neutral.

 

[smoothops10]

Yeah I'll probably run neutral but it upsets me that this is the reason. The issue is I may end up with a building C, D, E, F and G also served from bldg A in a similar situation. And some of these are fed with multiple sets - the costs add up. I've thought about running minimum sized neutrals but my understanding is that as you increase the quantity of different sized wires in a pull you increase the odds of something going wrong with the pull from some south wire catalog I had awhile back.

 

[augie47]

I was not aware that a MCC had to have a neutral bar to be "rated for service".
Not denying the fact, but, if that is the case, you might discuss with your AHJ that in the 2014 NEC, the requirements of 225.36 have been changed so that requirement does not seem to in place for your situation,.

 

[kwired]

Hey all, I may be looking at this wrong but wanted to get some input. If I have a 3P,4W 277/480 service in building A and want to run a feeder to an MCC in building B (will be the only feeder serving the building with all loads downstream of MCC) which has no 277v line neutral loads and probably never will - does a 4W (+G) feeder with neutral need to be pulled to building B? I cannot really think of a good reason if it is not used. How does 225.36 come into play - can you get a 3P,3W MCC 'suitable for use as service equipment'? I've never seen this and utility would not supply a 3P,3W system if put on its own service in the future anyway. Is that the point of 225.36, the code is anticipating the possibly that the building will be fed from a feeder now but possibly a service in the future or is there more to it? Could I just put in a 3P,4W mcc and feed it with 3W (+G) or is that against the listing of the MCCs intended use?
The 2012 UL marking and application guide (pg12-13 on google) makes me feel like we need to run the neutral to get the 'suitable for us as service equipment'.
Is there any other benefit to having the neutral run with the feeder other than being able to serve 277v loads? I cannot think of any but I'm often proved wrong.


Any thoughts appreciated - thanks all.

Grounded conductor is only required to be run to service equipment, it is not required to run with feeders if there is no load supplied that utilizes the grounded conductor. A feeder still is required to have an equipment grounding conductor run with it, a service doesn't need an equipment grounding conductor because it is the same thing as the grounded conductor up to point of the main bonding jumper, after that point they split up into grounded and equipment grounding conductors.

Not quite certain of the requirement of 225.36, and the issue of someday it could become service supplied instead of feeder supplied. Like anything else if changes are made down the road, you may have to change other things to comply with all codes, so IMO that alone is probably not the only reason they want a service rated disconnecting means, because you could always add a service rated disconnecting means down the road if necessary.

 

[petersonra]

I was not aware that a MCC had to have a neutral bar to be "rated for service".
Not denying the fact, but, if that is the case, you might discuss with your AHJ that in the 2014 NEC, the requirements of 225.36 have been changed so that requirement does not seem to in place for your situation,.

It does not have to have a neutral bar. Just a place to terminate the N wire at.

 

[augie47]

It does not have to have a neutral bar. Just a place to terminate the N wire at.

agree..bad wording on my part...
I do not know what it needs in order to get it's SUSE rating and after reading a few pages in the UL White Book I am not confident enough to give advice.

 

[petersonra]

agree..bad wording on my part...
I do not know what it needs in order to get it's SUSE rating and after reading a few pages in the UL White Book I am not confident enough to give advice.

we were able to get a kit from Siemens once to upgrade a MCC to be service rated.

It consisted of a distribution block like terminal for the incoming N, a sticker to label the neutral terminal, and another sticker that said something about being service rated that went on the outside.

 

[smoothops10]

I was not aware that a MCC had to have a neutral bar to be "rated for service".
Not denying the fact, but, if that is the case, you might discuss with your AHJ that in the 2014 NEC, the requirements of 225.36 have been changed so that requirement does not seem to in place for your situation,.

Looked up the rop on this. Good to know thanks...

 

[don_resqcapt19]

...

I don't understand the need for service equipment if it is not a service.

As best I can tell from looking at them, the primary difference between an MCC that is listed for use as service equipment and one that is not is having a place to land the neutral.

Prior to the 2014 code, the disconnecting means at a second building was required to be suitable for use as service equipment.

As far as I know "suitable for use as service equipment" requires a neutral connection point that is isolated from the enclosure and to have a manufacturer supplied means for the neutral terminal to be bonded to the enclosure.

Equipment that is "suitable only for use as service equipment" has the neutral terminal permanently bonded to the enclosure.