eprosenx
Active Member
I don't think it's a good idea to advocate something like this. In most cases it's not easily possible for a layman to verify the installation. Seems like a big risk for a small reward, given that charging from a 5-20 is still just a trickle.
I bet in many cases the cabling and outlets in older houses even have trouble safely sustaining a constant 12A load (I know that was the case in my house, where a 120V outlet in the garage got pretty warm when used to charge the car) ...
Yeah, I struggle with what to recommend. Many of the things we discuss on this forum are not code compliant, or at least not UL compliant, or perhaps are just a really big grey area.
I throw it out there since when on a "trickle" charging source, another 33-50% charging speed might mean the difference between your car charging sufficiently overnight vs. having to let the car dictate your schedule (which is never a place I want to be).
But you are completely correct. Charging a Tesla on really any 120v circuit should really just be reserved for the situations where there is no other option. There is a reason 2017 NEC says any circuit installed for EV charging can only have one receptacle on it. EV's are high amperage devices that max pretty much whatever circuit they plug into, they run for many hours, and often operate at night when a house fire would be most dangerous.
The big risk on 120v random circuits you might plug into is that they are "daisy chained" from one receptacle to another and often times you might find a loose connection somewhere. You don't want to be the one to find a latent defect in someones home electrical system that causes their house to burn down (even if you don't "cause" the issue).
In using an adapter like the one I mentioned, we are defeating several safely mechanisims:
- The UMC is not supposed to draw more amps than the receptacle you are plugging into is rated for - it knows what the allowable amperage is due to a resistor of a specific value in the adapter.
- By using any kind of 3rd party adapter or extension cord you loose some of the value of having a temperature probe in the end of the adapter which can detect overheating in the receptacle.
- You are drawing more than 15a (12a continuous) through a receptacle itself that is only rated for 15/12a even though the wire and branch circuit is rated to 20/16a.
So everyone needs to make their own decisions and to understand that this is not professional advice. Anything that you do carries risk.
I have used this adapter in two situations so far:
- One was in a residence where there was a receptacle right next to a panel that was modern construction and I verified it was the only pair of receptacles (quadplex) on the circuit and the wire was 12 gauge. Nothing else was on it. The only issue was the receptacle type was 5-15 not 5-20. I have seen teardowns of 5-15 receptacles from at least one vendor that have shown that internally 5-15's and 5-20's are literally identical. Only the plastic moulding that determines what prong types are accepted were different. In this use case I checked the receptacle and adapter frequently for any signs of heating for the first hour, but it ran totally cool so I stopped worrying about it.
- The other time was at a hotel where again, the receptacle was directly below the panel on a 20a circuit, but only a 15a receptacle. I knew there were some other lights on the circuit as well, so even though I used the adapter, I chickened out and set the charge rate to 12a since I did not need it to be faster. I wanted the option of cranking it up to 16a, but I set it low to reduce the chances of blowing the breaker.