code questions

Status
Not open for further replies.
R

rickl

Senior Member
?1 225.39d does this mean i can't run a 50 amp feed to a outbuilding?

?2 i'll be feeding 4 pieces of 3phase 240 volt equipment from a 3 phase panel through a phase converter the question is do i need to bring a neutral to the panel? this panel mainbreaker will be sized for the 240 volt equipment only.

?3 if i use indivual direct burial wire (use ) the equipment grounding conductor can be any wire type (thhn, xhhn) or does it need to be USE too.
(i know it doesn't but maybe i'm wrong)
?4 what temperature rating is URD al conductor same as USE?

just some question i have and having a hard time finding the answers in the code book
please give code numbers if you have them
 
Re: code questions

?1: I?d say yes.

?2. I?d say no. I can't cite a code section, because it?s a design choice, not an code issue.

The other two ?s are out of my area.
 
Re: code questions

225.39(D) requires the disconnecting means to be rated for a minimum of 60 amps. It doesn?t say that the feeder is required to be rated for 60 amps. With 4 pieces of 3 phase equipment I?m surprised that this installation doesn?t require a feeder larger than 60 amps.

Are you planning to have any lights or 120 volt convenience receptacles in this building? If so a grounded conductor would be required.

You can directly bury bare copper so I don?t see any reason that THHN or other insulated wire can not be directly buried.

Most USE cable I see is also rated as RHH/RHW so the 75C column could be used. Make sure your terminations at each end are rated for 75C conductors or use the 60C column.
 
Re: code questions

You can have a 50A feed to a separate building, however the rating of the disconnect can't be less than 60A.

Grounded conductors are only required to be brought to service equipment, after that, only when used.

Conductors used for direct burial must be identified for such use. THHN is not.

I have never heard of URD insulation.
 
Re: code questions

Bryan, we use URD cable all the time. URD cable is Underground Residential Distribution cable, it is not listed, and it is made for the use of electric utilities. Most of it is cross-linked polyethylene insulation and is essentially USE cable. It may be used by electrical contractors in the same locations that USE is permitted as long as the AHJ approves the material. It is not recognized by the NEC. :D
 
Re: code questions

#1 225.39 is requirements about the minimum circuit capacity. This only sets a minimum size the circuit has to be to an out building. Not max.
Keep in mind if your 3-phase circuit/with neutral is a branch circuit and not a feeder it can be called a single circuit.

#2 I would hold out to see what others say as 200.2 would seem to require one but would this be considered a premises wiring system?

#3 110.54(B) allows the grounding conductor to be bare only if it is in a race-way or inside of a cable jacket. But not in direct contact with Earth. so If in contact with Earth I would say it would need to have a W sufix?

#4 I'm not sure.
 
Re: code questions

338.100 permits a bare EGC to be run with type USE cable/conductors. If bare wire is acceptable I don?t see why any type of insulated wire couldn?t be used.
 
Re: code questions

thanks
they's are questions from 2 different jobs, i'm thinking if i label the panel[ 240 volt 3phase only] i should be able to get away from having to pull a neutral.
 
Re: code questions

Rick Bryan did state that we are only required to bring the neutrals to service equipment. One thing to keep in mind that you need to read 455 as there are some requirements for Phase Converters and depending on the wiring, grounding it is simular to an SDS system.
 
Re: code questions

Originally posted by rickl:
thanks
they's are questions from 2 different jobs, i'm thinking if i label the panel[ 240 volt 3phase only] i should be able to get away from having to pull a neutral.
Click to expand...
I am not so sure thats the case. I seem to recall that if you have 4 wire service you have to pull all 4 wires to the panel even if you are not using them. but maybe I am remembering wrong.
 
Re: code questions

250.24(B) requires the grounded conductor (neutral in most cases) to be taken to the service equipment. Past that, it is your option. :D
 
Status
Not open for further replies.
Top