6/3 Romex for a 60 amp sub panel?

Tmb9862

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?

kbsparky

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

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Scuba_Dave

Isn't THW wet rated ?

J. V.

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.

Tmb9862

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.

220/221

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.

Scuba_Dave

Provided the load will not exceed 55a ?

spark plug

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!

jerryh3

Correct. Deja Vu thread.

Tmb9862

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?

Scuba_Dave

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

J. V.

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.

jerryh3

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...

J. V.

jerry. That seems to answer my question. Thanks for the code reference.