Subpanel Install

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Eagle126

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I am installing a 50 amp 4 wire subpanel in a home, can i install 8/3 romex with ground, I checked the insulation on the number 8 's is THHN?
 
I don't believe you can. Per 334.80, the ampacity of NM, NMC, and NMS must be in accordance with the 60degC conductor temperature rating.
 
david luchini said:
I don't believe you can. Per 334.80, the ampacity of NM, NMC, and NMS must be in accordance with the 60degC conductor temperature rating.
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I agree you need 6/3nm and if the calculated load is 55amps or less put it on a 60 amp breaker but 8/3 NM would need to be on a 40 amp OCPD
 
Subpanel Install

Thanks for that information, I am going to install # 6 conductor. Do i need to install a main breaker in my subpanel or does my main breaker in my main panel in the basement enough?
 
Eagle126 said:
Thanks for that information, I am going to install # 6 conductor. Do i need to install a main breaker in my subpanel or does my main breaker in my main panel in the basement enough?
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If the subpanel is in the same building then No but if the panel is in a detached structure then te 6 disco rule or main breaker is required.
 
probably for the same reason that our "State Licensed Electrical Engineer" thinks that one of the main reasons a ground rod is used is for personal protection by raising the ground in the area of the fault to the same potential as the equipment so people won't get shocked when touching it.
 
We all know the profiles are just a technicality. Anyone can post, get turned down for no experience and then create a new account with the correct credentials. I am not thumbing my nose at the forum or the people who post I am just describing it how it is.
 
dana1028 said:
I usually don't do this, but I just have to ask: Why doesn't a master electrician know the answer to either of these questions?
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There is such a wide spectrum in our industry; some may work predominately on commercial work and be lost stringing romex or wiring a hot tub or pool. (I was in this business 25 years before i drilled my first 2x4, but I could install a 4000amp service in my sleep). On the other hand, residential guys may never have had the opportunity to bend cut and thread 4" RMC.

What may seem obvious or second nature to some may be foreign to others.
 
forman400b said:
There is such a wide spectrum in our industry; some may work predominately on commercial work and be lost stringing romex or wiring a hot tub or pool. (I was in this business 25 years before i drilled my first 2x4, but I could install a 4000amp service in my sleep). On the other hand, residential guys may never have had the opportunity to bend cut and thread 4" RMC.

What may seem obvious or second nature to some may be foreign to others.
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I almost agree with you completely...however Romex is not unique to residential work - I see it frequently in commercial applications...so even commercial only electricians should know the rules for NM cable.

And the rules for a main disconnect on a subpanel in the same structure are not unique to residential work - this is universal for all types of work.

I know there are often residential-type questions posted by commercial electricians who explain their lack of experience in the arena...but these two questions are not unique to residential work - that was the only reason for my comment.
 
I don't know if it has been mentioned ,..but here in Mass we only have to use the 60c when Nm cable is run in thermal insulation... if not in insulation the ampacity is back to 50 amps ,. if the terminals are rated for 75c ..Are you in Massachusetts?
 
M. D. said:
I don't know if it has been mentioned ,..but here in Mass we only have to use the 60c when Nm cable is run in thermal insulation... if not in insulation the ampacity is back to 50 amps ,. if the terminals are rated for 75c ..Are you in Massachusetts?
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IMO this is a sensible amendment inline with the 2011 ampacity of SE cable.
 
Regardless of background in different areas of the trade, a qualified person should be able to use a code book to find what they are looking for. Especially something as critical as table 310.16. Then again i had no idea that even existed for my first 5 years in the trade. Even now I still ask what are probally considerd by most to be really stupid questions, but thats how some people learn.
 
Not a licensed electrician

Not a licensed electrician

I seriously doubt that the OP is a licensed electrician, much less a Master.

The way the original question was written, I suspect that the OP is a DIYer, trying to make a proper installation.

I just send them to licensed electricians in their area.
 
The reactions I am seeing are incredible. Thank goodness Mike has set up this forum and so many very experienced experts don't take that attitude. I have been helped so many times and I am sure anyone here can pick apart my questions and choose many of them as stupid.

BTW I am now technically qualified to take the masters exam and I have no doubt whatsoever I could pass it easily (thanks to Mike's books and DVDs). But I suspect a lot of people think I don't have the knowledge to be called a master.
 
I think the OP's questions have been addressed so I think it's time to to close this thread.

Roger
 
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