Neutral wire size

[Thomas James]

Hey guys, I hate to be a pain but I have a question about hooking up a 50 amp service. OK, first off I already have a 50 amp service to our Hot Tub. We're going to be taking that out, and I'm going to use the existing wiring to run to an RV hookup. I'll just use a 4x4 gang box form the Hot Tub area over to the RV hookup. Total run is around 65ft. I have #6 wire now, and that should work. Now, here's what I did when I originally ran the wiring. I ran the white(neutral) as #12, thinking it was not a load carrying wire. It's worked out OK tho. But what I'm thinking is I prob need to pull that #12 out(it's run under ground in conduit) and replace it with at least #10...or if I'm doing all that work, I might as well use #6. I think I read somewhere that the white needs to be able to carry 70% of the rated load which would be around 35 amps(which would be at least a #10). Is that right? Or am I OK with keeping the #12 as the neutral(prob not)? Thanks in advance for any help.

[Roy C Tyler]

This should answer your question:    http://www.myrv.us/electric/Pg/50amp_Service.htm     

[Bill Sprague]

I'm sure you know this and I don't want to sound insulting. 

That said, an RV "50 Amp" service is a pair of 50 amp breakers.  In the electricians world I think it would be considered 100 amp service.  In fact, the master breaker for our condo looks just like the breaker in the power pole at RV parks.  Our condo is considered to have "100 Amp Service". 

Somehow, RVers call it 50 amp service when it is really 100 amp service.   

[Edward Buker]

Thomas,

Generally the neutral can be downsized for a house panel and the code allows for sizing wire size reductions based on calculations of the neutral current. With 220V loads the neutral carries no current so those loads are eliminated from the neutral line current carrying calculation. Generally speaking a one or two wire size reduction can be the end result.

Our case where all loads are all 120V the neutral does carry load so generally in this case it is recommended that you use the same wire size as the hot lines for the distance and the current capacity that is required. This is my understanding from electricians posting questions and interpretations of the NEC code. Hope this helps.

Later Ed

[Thomas James]

Hey, thanks for all the good info guys. Yeah, I'm gonna just go ahead and pull the #12 neutral out that I have for the Hot Tub, and replace it with a #6. That's the right thing to do. Guess I was tryin to take the lazy way out of it. And we All know how that usually works out. I just finished up hooking up the outlet, and running #6 romex thru the wall to the Hot Tub. Now, as soon as my daughter decides to come and get that off my hands, then I can finish it up. Thank y'all very much. See ya,

[Fred Brooks]

     Hi Thomas,
   Ed is right, even though you have 2- 50amp 120 volt lines coming into your coach it has NO way back to the source except thru the neutral wire. The wire should be at least a 6 gauge or larger.
   I am repairing a coach today where the owner made an "adapter pig tail" so he could plug his 50amp coach into his clothes dryer plug in his garage, well......no neutral in that plug and of coarse he fried lots of stuff in his coach.
   Regards, Fred