50 Amp Receptacle on 30 Amp Breaker

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vermilye

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Had a question that comes up regularly on a RV forum: "I have a 30 amp 240v outlet (14-30R) in my garage. Want to change the receptacle to a 50 amp 240v RV outlet (14-50R) so I can plug in my RV. Will it meet code if I keep the 30 amp 2 pole breaker & 10/3 with ground wire?" If not, where is it disallowed?

Thanks!
 
If the RV comes with a 50 amp cap, then it would seem that it needs a 50 amp rated circuit and receptacle.
 
10/3 with ground on a 50 amp circuit or is it a 50 amp receptacle on a 30 amp OCPD.EITHER WAY YOU HAVE A PROBLEM !!!!!Call a qualified EC.
 
I am not so sure that this is not allowed. If that is the only load on that circuit, then 210.21(B)(1) allows the use of a 50 amp receptacle in a 30 amp branch circuit.

If there are two or more receptacles (or other types of outlets) on that circuit, then Article 210.21(B)(3) and its associated Table apply. But it is not clear, to me at least, that it is saying you can not use a receptacle that is larger than the one listed in the table. There are two "hints" that I interpret as allowing the use of a receptacle that is no smaller than the one shown in the table. In this case, for example, a 50 amp receptacle on a 30 amp branch circuit is OK, because 50 is not smaller than the 30 that appears in the table.

Hasn't this been discussed (argued???) on this Forum before? It sounds familiar, but I was not involved in the earlier discussion.
 
vermilye said:
Had a question that comes up regularly on a RV forum: "I have a 30 amp 240v outlet (14-30R) in my garage. Want to change the receptacle to a 50 amp 240v RV outlet (14-50R) so I can plug in my RV. Will it meet code if I keep the 30 amp 2 pole breaker & 10/3 with ground wire?" If not, where is it disallowed?

Thanks!
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Best bet is to buy an adapter. RV stores have them.
 
petersonra said:
Best bet is to buy an adapter. RV stores have them.
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Right. Any self respecting RVer will have a dozen adaptors to plug anything into anything. Seems to be standard fare. Not that I like it, but the camping stores all sell such adaptors. I'm sure they're recognized by the finest Chinese Republic Electrical Testing Labratories.
 
I agree with Charlie, a 50 amp single receptacle on a 30 amp circuit is permitted.
 
Is a dedicated single 20 amp receptacle allowed on a 15 amp breaker ? No,so why would this be allowed.Its indicating 50 amps is available but is not.Now personally i dont see it as a hazard because the breaker will trip.It also is safer than using an adaptor.Legally i think its a no go.Would i do it if i know my load will not be that high,yes.
 
infinity said:
I agree with Charlie, a 50 amp single receptacle on a 30 amp circuit is permitted.
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There are situations where one must do this; e.g., upconverting the plug and receptacle, when used on a motor circuit, in order to meet Disconnecting Means horsepower ratings. 430-109(F).
 
Well, it is good to see there is a question here as well. The reason for not using an adapter to go from a 14-30R to the 14-50P on the RV is it's not standard - the user would need to make it. A 30 amp RV is 120v only, using a NEMA TT-30P. The 50 Amp RV uses the 14-50P. Most people carry the standard adapters but it would be unusual to find a 14-30R at a campground.

I agree with Steve that table 210.21(b)(3) says you can't. Not because it's unsafe, but because when the next homeowner plugs a stove into the outlet he is going to have nuisance tripping of the 30 amp breaker.
 
Jim W in Tampa said:
Is a dedicated single 20 amp receptacle allowed on a 15 amp breaker ? No,so why would this be allowed.Its indicating 50 amps is available but is not.Now personally i dont see it as a hazard because the breaker will trip.It also is safer than using an adaptor.Legally i think its a no go.Would i do it if i know my load will not be that high,yes.
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Jim a single 20 amp receptacle is permitted on a 15 amp CB. Not a very good design but permitted.

210.21(B) Receptacles.
(1) Single Receptacle on an Individual Branch Circuit. A single receptacle installed on an individual branch circuit shall have an ampere rating not less than that of the branch circuit.
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vermilye said:
Well, it is good to see there is a question here as well. The reason for not using an adapter to go from a 14-30R to the 14-50P on the RV is it's not standard - the user would need to make it. A 30 amp RV is 120v only, using a NEMA TT-30P. The 50 Amp RV uses the 14-50P. Most people carry the standard adapters but it would be unusual to find a 14-30R at a campground.

I agree with Steve that table 210.21(b)(3) says you can't. Not because it's unsafe, but because when the next homeowner plugs a stove into the outlet he is going to have nuisance tripping of the 30 amp breaker.
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Then I'm sorry to say that you would both be wrong. 210.21(B)(3) is for "two or more receptacles or outlets". This does not apply to a single receptacle.


210.23(B)(3) Receptacle Ratings. Where connected to a branch circuit supplying two or more receptacles or outlets, receptacle ratings shall conform to the values listed in Table 210.21(B)(3), or where larger than 50 amperes, the receptacle rating shall not be less than the branch-circuit rating.
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vermilye said:
Well, it is good to see there is a question here as well. The reason for not using an adapter to go from a 14-30R to the 14-50P on the RV is it's not standard - the user would need to make it. A 30 amp RV is 120v only, using a NEMA TT-30P. The 50 Amp RV uses the 14-50P. Most people carry the standard adapters but it would be unusual to find a 14-30R at a campground.

I agree with Steve that table 210.21(b)(3) says you can't. Not because it's unsafe, but because when the next homeowner plugs a stove into the outlet he is going to have nuisance tripping of the 30 amp breaker.
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There are all types of adapters available for rv`s and campers
http://www.pplmotorhomes.com/parts/rv-power-cords/power-grip-dogbone-adapters.htm
 
Thanks, Goldstar, for confirming my memory. What I find amazing is that I remembered a discussion that took place 3 years ago, but I can't remember if I took my medications this morning.
 
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