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Can I install a 240 Volt NEMA 14-30 outlet off my 30 Amp garage subpanel?

sewing1

2020 Model Y LR AWD
Sep 10, 2019
50
51
Florida
I've ordered a Model Y LR AWD.

I have a 100 Amp electrical service panel in my house basement. In my detached garage I have a 30 Amp subpanel that currently contains two 20 amp and one 15 amp circuit breakers for the lighting and outlets.

I'm thinking I could have an electrician install a 30 Amp breaker in the garage subpanel and wire a 240 Volt NEMA 14-30 outlet to it. I'll purchase a NEMA 14-30 adapter for my mobile connector from Tesla.

Before a contact an electrician I wanted to run this plan past this forum. Thanks for your input.
 

nwdiver

Well-Known Member
Feb 17, 2013
7,771
9,996
United States
I've ordered a Model Y LR AWD.

I have a 100 Amp electrical service panel in my house basement. In my detached garage I have a 30 Amp subpanel that currently contains two 20 amp and one 15 amp circuit breakers for the lighting and outlets.

I'm thinking I could have an electrician install a 30 Amp breaker in the garage subpanel and wire a 240 Volt NEMA 14-30 outlet to it. I'll purchase a NEMA 14-30 adapter for my mobile connector from Tesla.

Before a contact an electrician I wanted to run this plan past this forum. Thanks for your input.

I guess your electrician will let you know for sure;

If not... IMHO even 16A @ 240v is plenty and that should hopefully be viable. That would be a NEMA 6-20.
 

frankvb

Supporting Member
Feb 29, 2020
838
517
San Diego, CA
Up to the electrician indeed.

Considering the sub-panel is 30A total, and charging the car would be at 24A constant (80% of 30A) that would only leave 6A available for all the other circuits hooked up to it. Not sure if that's acceptable or not, if I had to guess I would say it's not ok.
 
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WhyYesPlease

Supporting Member
Aug 22, 2020
46
28
Toronto
I don't have any expertise, but I have a similar situation to yours. The electrician who visited and is now preparing an estimate said when he was here that with my 40A sub-panel he could install a 14-50 (to draw only 40A though). When I asked about a garage door opener running at the same time, for example, he said that since they only run for ten seconds, should be no problem. Hope that helps.
 
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user212_nr

Active Member
Aug 26, 2019
1,407
741
US
I have a 100 Amp electrical service panel in my house basement. In my detached garage I have a 30 Amp subpanel that currently contains two 20 amp and one 15 amp circuit breakers for the lighting and outlets.

Your garage is wired with a lot of power. Is there some appliance that is powered by the 20A breakers? If so, then you have not enough power to charge a Tesla and use that appliance.

You can consider upgrading the wire that feeds the panel. It may not be very difficult to run a new wire where one already exists, and the panel is probably good for 100A.
 
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sewing1

2020 Model Y LR AWD
Sep 10, 2019
50
51
Florida
Your garage is wired with a lot of power. Is there some appliance that is powered by the 20A breakers? If so, then you have not enough power to charge a Tesla and use that appliance.

You can consider upgrading the wire that feeds the panel. It may not be very difficult to run a new wire where one already exists, and the panel is probably good for 100A.

No, there are no appliances in my garage. Just four 100 watt light bulbs and 2 garage door openers on the 15 amp circuit, and lots of outlets with nothing plugged into them on the two 20 amp circuits.
 

Pilot1226

Member
Dec 20, 2019
355
158
USA
This seems like a bad idea. If you have a subpanel with 30A devoted to it, and you're going to put that onto a 14-30 outlet, this seems like an overload scenario.

It might make more sense to try to replace the 30A subpanel with a 50A subpanel, which would give you at least an extra 20A.

I'd personally change the light bulbs to LED's immediately, to free up that much... (400 watts @ 120V is like 1/4 of your 15A circuit)

The garage door openers could be an issue if activated while you're pulling 30A. I'd consider the 50A changeover I mentioned above, then you can designate a 6-20 for that. If you really wanted to be "ballsy" you could push a 14-30 and just make sure you didn't use the garage door openers simultaneously and have something in the outlet.

The problem will be that with a 6-20 you're essentially "reserving" 16A of the 30A subpanel for the car charging. That only leaves you with 14A.
 
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paulk

Member
Jan 26, 2019
91
109
hartford, ct
an electrician can use a clamp meter to see how much power your garage door openers are actually using, and you can replace your light bulbs with LEDs. if your openers only use a few amps each, a 24 amp draw from your car isnt bad.

you could also set the car to always draw just 15-20 amps, and then on that one day you need to charge faster, make sure to not use the opener until unplugging the car.
 

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