NEMA 10-50 to NEMA 14-50 adapter

NEMA 10-50 to NEMA 14-50 adapter

I have a question for MS owners who had a NEMA 10-50 plug in their garage. Did anyone use a NEMA 10-50 to NEMA 14-50 adapter to charge the MS? If anyone did go the adapter route, was it efficient enough?

jat | September 4, 2013

My grandmother's house had 10-50 plugs for the dryer (even though it was a 30A fuse; really old house) - when I got there, I had to find an electrician who had a 10-50 plug and cut off the end of the 10-30 adapter I had made and installed that plug (which was a convertible plug, I could replace the ground pin with L-shaped to use it as a 10-30, and of course since then Tesla has shipped the official adapter).

There is no efficiency loss, just make sure you label the outlet as only for use with Tesla since the 14-50 neutral wire won't be connected - just wire hot-hot, 10-50 neutral-14-50 ground. An adapter to 6-50 might be a better choice, as you don't have to leave neutral unconnected, which is a risk if anyone ever tried to plug an RV (for example) into it.

If it is in your garage, you could also just replace the 10-50 with a 6-50, and use the official Tesla adapter.

nsbharath | September 4, 2013

Thanks for your reply. The issue is that the current NEMA 10-50 is currently being used for a dryer, so I don't know what impact it will have if I replace the 10-50 with a 6-50. I did find that someone was selling these adapters I might try this before other choices.

Bob W | September 4, 2013

Are you guys sure you have a NEMA 10-50 outlet in your garage? It would be a violation of the National Electrical Code to use a 10-50 outlet on a 30A circuit. I've never seen a clothes dryer that required 50A.

A NEMA 10-30 plug is very common for a clothes dryer, not a 10-50. Tesla makes a handy adapter for that (as well as the more modern 14-30).

For reference, see this handy chart in Wikipedia.

Let me see if I can make it visible:

shop | September 4, 2013

Nice chart Bob. I agree, it is probably a 10-30.

Dcp9142 | September 4, 2013

It is about $20 in parts to convert the outlet to a 10-30 and the dryer to a matching 10-30 cord.

jat | September 4, 2013

@BobW - absolutely sure at my grandmother's house (none of the outlets are grounded or even have a polarized neutral plug). The welder in the shop also used the same 10-50 plug (though supplied at 50A), but it was in such bad shape I didn't want to try and use it -- it is exposed to the weather and the insulation was visibly cracking on it.

Apparently, in really old houses it was common to use 10-50 plugs on dryers and other heavy appliances, even when the fuse/wire were rated for 30A. It isn't particularly a hazard, since if you try and draw 50A from it you will blow the fuse before the wire overheats, though clearly it violates current code.

shop | September 4, 2013

That adapter from evseadapters should work fine.

nsbharath | September 5, 2013

Thanks for all the replies.
@BobW- Yes, I checked it again and it was 10-50 plug. House was built in 1981 and that probably explains it.
@shop - yes, I plan to buy that adapter.

shop | September 5, 2013

One last thing to check is what size breaker is in the panel for that plug. 30a or 50a. It'll work either way, you'll just have to manually dial down the current if it is 30a.

jat | September 5, 2013

@shop - if it is a 30A fuse/breaker, you have to dial it down to 24A, not 30A.

shop | September 5, 2013

Jat, you misread my post. Yes, you are right.

markvallaster | March 5, 2015

Just ordered from evse adapters to use at my mothers house. The way it would work is the tesla cable, to the tesla 50amp adapter to a rated 50amp extension cord to the evse adapter to the 30amp dryer plug. Charging dialed back to 24 amps. Anyone see any problems with that?


Bighorn | March 5, 2015

Should work fine--I'd minimize the length of the extension cord.

Bighorn | March 5, 2015

Does your extension cord have a 10-30/14-30 female end? Hard to tell what all your ends are to be able to advise. When I constructed mine, the extension just went between the two plug ends, 14-50 and 6-20 in my case.

Bighorn | March 5, 2015

I guess the extension cord needs the 14-50 ends, right, the way your're describing the set-up?

Rocky_H | March 5, 2015

@markvallaster, you're probably talking about an RV extension cord, right, with 14-50 plugs on the ends? Yes, several people have used that type of setup. And yes, good of you to know about pre-reducing to 24 amps on the 30 amp dryer circuit. | March 5, 2015

Instead of kludges why not wire in a 14-50 outlet and have a clean solution?

Rocky_H | March 5, 2015

@georgehawley, quote: "Instead of kludges why not wire in a 14-50 outlet and have a clean solution?"

Why not? Probably because his mother would be freaking pissed off at not being able to user her dryer after you replaced the outlet with an RV outlet. *facepalm*