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Old 12-08-2009, 07:12 AM   #1
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6/3 Romex for a 60 amp sub panel?


I'm running a 60 amp sub to my detached garage. I have #6 THW for my underground and was planning on continuing it inside in 1" conduit back to the box. Can I use 6/3 romex inside instead? I've heard individual connectors are rated higher then Romex is and 6/3 might not be large enough. Is that the case?

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Old 12-08-2009, 07:15 AM   #2
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6/3 Romex for a 60 amp sub panel?


You are not permitted to install romex underground -- even if it is in conduit.

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Old 12-08-2009, 07:44 AM   #3
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6/3 Romex for a 60 amp sub panel?


Isn't THW wet rated ?
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Old 12-08-2009, 12:12 PM   #4
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6/3 Romex for a 60 amp sub panel?


THW is rated for wet locations and was the wire of choice before THHN and THWN came on the market. It is 75 degree wire, single conductor and must be installed in conduit.
It is perfectly compliant to run the THW in conduit underground and then when you enter the structure transition to NM. However, running conduit all the way (panel to panel) and using THW, or THHN/THWN is the much better option.

#6 THW is rated for 65 amp.
#6 THHN/THWN is rated for 75 amp.
#6 NM (Romex) is rated at 55 amp.

Do a professional job and just run it all in PVC conduit and use THWN wire, unless you already have the THW wire.
You MUST run four individual conductors H-H-N-G.

For further information use the search function on this forum. Sub panels are one of the most asked questions. There is more information from previous threads. More than you will care to read.

Last edited by J. V.; 12-10-2009 at 11:45 AM.
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Old 12-08-2009, 07:40 PM   #5
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6/3 Romex for a 60 amp sub panel?


I know I can't run NM underground, I wanted to know if I could run the THW underground and transition to NM in a junction box once I got in the house, sorry if I wasn't clear on that.
I already have the THW, that's why I'm not using THWN. Someone gave it to me a few years back. I already ran the conduit in the ground but haven't run the conduit inside yet. A friend of mine just told me he has some 6/3 NM he'll give me for a what amounts to about 20 cents a foot. I'd rather run the NM as I have to go all the way across the basement and can snake the wire more easially then I can conduit. If I have to run the conduit to do the job right that's what I'll do.

The reason I ask again and beat the dead horse is some people are saying 6/3 is fine for 60 amps, others say it isn't. I think I read somewhere that you can use the next larger breaker size and since there is no 55 amp you can use a 60. I have no idea if that's true or not but their is a lot of conflicting information out there.
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Old 12-08-2009, 07:46 PM   #6
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6/3 Romex for a 60 amp sub panel?


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I already have the THW, that's why I'm not using THWN. Someone gave it to me in 1963
Fixed it for you

I started in the trade in 73 and have never used THW


To answer your question, the 6/3 NM is good for your 60 amp circuit and is proper to use inside the structure.
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Old 12-08-2009, 07:49 PM   #7
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6/3 Romex for a 60 amp sub panel?


Provided the load will not exceed 55a ?
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Old 12-08-2009, 08:10 PM   #8
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6/3 Romex for a 60 amp sub panel?


J.V. (Poster #4) In the Third paragraph you state (paraphrasing) ..You see that you can not use #6 NM. (presumably because it's rated for 55 amps only) But then you say ... You will have to use #8 NM... It must be a typographical error or a slip of the keyboard (on par with "A slip of the tongue") You probably meant to tell the OP that they will have to use #4!
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Old 12-08-2009, 08:19 PM   #9
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6/3 Romex for a 60 amp sub panel?


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Originally Posted by Scuba_Dave View Post
Provided the load will not exceed 55a ?
Correct. Deja Vu thread.
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Old 12-09-2009, 07:14 AM   #10
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6/3 Romex for a 60 amp sub panel?


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Originally Posted by 220/221 View Post
Fixed it for you

I started in the trade in 73 and have never used THW


To answer your question, the 6/3 NM is good for your 60 amp circuit and is proper to use inside the structure.
I honestly don't know how old it is. It's never been used and the jacket is in good shape is their any safety issue using this wire?
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Old 12-09-2009, 07:24 AM   #11
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6/3 Romex for a 60 amp sub panel?


K&T wire is still in use that goes back 100+ years
As long as the jacket is not brittle I don't see a problem
Some wire in my house is from the 50's & still in use
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Old 12-09-2009, 12:01 PM   #12
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6/3 Romex for a 60 amp sub panel?


Quote:
Originally Posted by spark plug View Post
J.V. (Poster #4) In the Third paragraph you state (paraphrasing) ..You see that you can not use #6 NM. (presumably because it's rated for 55 amps only) But then you say ... You will have to use #8 NM... It must be a typographical error or a slip of the keyboard (on par with "A slip of the tongue") You probably meant to tell the OP that they will have to use #4!
Yep, Thanks for the correction. #4 is what I should have said.

220/221. You say okay for 6/3 NM on a 60 amp feeder? Please explain. NM is 60 degree wire and rated for 55 amp. I agree he can/must install a 60 amp sub, but he can only use a 50 amp breaker for the feeder. I am asking. Thanks in advance.
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Old 12-09-2009, 12:08 PM   #13
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6/3 Romex for a 60 amp sub panel?


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Originally Posted by J. V. View Post
Yep, Thanks for the correction. #4 is what I should have said.

220/221. You say okay for 6/3 NM on a 60 amp feeder? Please explain. NM is 60 degree wire and rated for 55 amp. I agree he can/must install a 60 amp sub, but he can only use a 50 amp breaker for the feeder. I am asking. Thanks in advance.
Wire size is determined by calculated load. No 55A breakers means that #6 NM can be protected by a 60A. 240.4(B) I think...
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Old 12-10-2009, 11:50 AM   #14
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6/3 Romex for a 60 amp sub panel?


Quote:
Originally Posted by jerryh3 View Post
Wire size is determined by calculated load. No 55A breakers means that #6 NM can be protected by a 60A. 240.4(B) I think...
jerry. That seems to answer my question. Thanks for the code reference.

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