Have a 240V plug on dual circuits - one 30A, one 20A

[rklau]

Just picked up my Model S this morning, and adore it. Have a question about charging: we're almost certainly moving in the next couple months, so I didn't bother spending money to upgrade the garage to support a 50A circuit, and was just planning on topping off at home and using the chargers at work or the supercharger down the road from us. But I had a thought tonight: the house was built in 2007 and has a 240V plug which was included in the original construction of the house. In our breaker box, it's supported by two circuits - one 30A, one 20A. I don't think I can treat that as a 50A circuit, but could I set the charge limit in the car to 20A and use the plug as is? If so, that would certainly be faster than using the 110V plug in the garage... anyone have an informed opinion on this?

Thanks in advance!

 

[green1]

If it's truly one plug, fed from 2 differently rated breakers, that's very against code. That said, I'd use it, but I'd consider it a 20a plug and charge at 16a (80% rule for continuous loads)

To meet code the two breakers would have to be the same rating and have a bar between them such that when one trips it trips both.

 

[pgiralt]

Just picked up my Model S this morning, and adore it. Have a question about charging: we're almost certainly moving in the next couple months, so I didn't bother spending money to upgrade the garage to support a 50A circuit, and was just planning on topping off at home and using the chargers at work or the supercharger down the road from us. But I had a thought tonight: the house was built in 2007 and has a 240V plug which was included in the original construction of the house. In our breaker box, it's supported by two circuits - one 30A, one 20A. I don't think I can treat that as a 50A circuit, but could I set the charge limit in the car to 20A and use the plug as is? If so, that would certainly be faster than using the 110V plug in the garage... anyone have an informed opinion on this?

Thanks in advance!

Can you post a photo of the breaker and the plug? Something doesn't sound right. A breaker for a 240V outlet should be a dual-pole breaker which can never have two different current ratings.

 

[rklau]

Well, I took the picture and double-checked... sure enough, it's not a 20a and 30a circuits, it's two 20a joined circuits w/a 30a circuit between them. So this is conclusively a 20a circuit, and I'm a moron.

Carry on... and apologies for the unnecessary post! Really appreciate the quick replies.

 

[Rocky_H]

I recommend to use the chart on this page to find out exactly what kind of outlet it is. If it is a 20A outlet, then you could build an adapter cable from the Tesla 5-20 adapter to whatever kind of outlet that is (probably a 6-20).
NEMA connector - Wikipedia, the free encyclopedia

 

[FlasherZ]

Well, I took the picture and double-checked... sure enough, it's not a 20a and 30a circuits, it's two 20a joined circuits w/a 30a circuit between them. So this is conclusively a 20a circuit, and I'm a moron.

Carry on... and apologies for the unnecessary post! Really appreciate the quick replies.

Ah yes, the quad 240V breakers... unnecessarily confusing.

Downside of this is that Tesla doesn't make a 6-20 adapter. They do make a 6-15 adapter which should work in the receptacle you have (6-20 receptacles generally also support 6-15 plugs)...

Tesla Accessories and Charging Adapters Charging and Adapters

As Rocky noted, you can use the Tesla 5-20 adapter and build an adapter to make the 5-20 plug into the 6-20 (the car doesn't care about the voltage difference), but that requires some additional skill (and labeling!)

 

[Cosmacelf]

Can you post a picture of the plug? I agree with FlasherZ that buying Teslas 5-20 adapter and then making (or buying) an adapter from your plug (we are assuming it is a 6-20, but would be nice to check) to a 5-20 would be ideal.

 

[TexasEV]

Ah yes, the quad 240V breakers... unnecessarily confusing.

Downside of this is that Tesla doesn't make a 6-20 adapter. They do make a 6-15 adapter which should work in the receptacle you have (6-20 receptacles generally also support 6-15 plugs)...

Tesla Accessories and Charging Adapters Charging and Adapters

As Rocky noted, you can use the Tesla 5-20 adapter and build an adapter to make the 5-20 plug into the 6-20 (the car doesn't care about the voltage difference), but that requires some additional skill (and labeling!)

You don't need to make it yourself, evseadapters.com offers a 5-20P to 6-20R adapter for this purpose.