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See my FAQ in my signature or here:
FAQ: Home Tesla charging infrastructure QA
Nowhere in the written instructions does Tesla restrict the HPWC to "permanent wiring methods only", the magic words required - therefore they have not prohibited it and it is indeed legal (per several AHJ's I've spoken with). You are correct that some Tesla employees will tell you that it is not intended for such, but that does not matter. NEC 110.3 requires you to follow written instructions provided with the equipment.
Until Tesla changes the instructions, it will be legal to do so. But as you've rightly pointed out, you're limited to a 12" cord and it's generally going to be a pain in the rear.
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Those appliances are typically installed more permanently, and in dry locations. The 12" maximum cord requirement is designed to keep most of the cord subject to the interlock and ground-fault protection offered by the EVSE, especially since they're used in damp/wet locations.
Canuck
Well-Known Member
I put a 14-50 on a HPWC and set it to 64 amps by the dip switches but then dialed it down to 42 amps in the car. That way, the load is split 50/50 on my dual chargers for less wear on each since after 40 amps the car splits the load.
Been working good for many months now.
Been working good for many months now.
mknox
Well-Known Member
I'm not 100% sure, but I don't think it works that way. I think it utilizes the full capacity of the primary charger first, then engages the secondary. I've noticed that when I connect to an 80 amp source, it will ramp up to 40 amps, then hold for a bit, then continue ramping up to 80.
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I'll have to check if the Canadian Electrical Code has the same 12" provision, but I suspect it does. The Canadian and US codes are largely harmonized. Still seems odd considering a stove and a dryer can, and often are, pulled out for cleaning and such, but the HPWC would be firmly bolted to the wall.
Soolim
Member
If you want to draw 80A from the HPWC, the NEMA receptacle is not capable of more than 60A. That is the reason why HPWC is direct connected. But you can of course limit your HPWC current draw to something that is within the capacity of the receptacle, but there is always the danger of having a wrong setting and causing circuit overload that will lead to overheating and possible fire. I am speaking of the electrical installation external to the car, i.e. cables, circuit breakers, receptacle, connectors, etc.
Unless there is a need for portability, I would prefer hardwired connection over plug/receptacle.
Unless there is a need for portability, I would prefer hardwired connection over plug/receptacle.
The NEMA 14-50 is not rated for anything more than 40A of charging current, as code requires continuous load headroom. I have seen 30A receptacles melt when 30A continuous loads were applied for more than 30-45 minutes. If you attach a 50A plug to the HPWC you MUST set it to the 50A setting for it to be a legal install.
mknox
Well-Known Member
Yes, you must set the internal dip switches for a 50 amp circuit (40 amps delivered). But remember, you can hard-wire an HPWC into circuits of lower capacity too... right down to a 20 amp (16 amps delivered) circuit and you must also set the dip switches accordingly. Not all HPWCs are wired into 100 amp circuits.
Canuck
Well-Known Member
That tells you it's splitting the load. Try it at 56 amps and watch it ramp up to 28, then hold for a bit, then go to 56.
Question on power distribution using dual chargers at 40 amps charging current.
mknox
Well-Known Member
Thanks for the link. I hadn't caught that other thread. I'll try a lower setting next time I plug in to my 80 amp charger at work.
Soolim
Member
True, but if all I want is 20A or my panel cannot handle the 50A for full capacity UMC, then I will not get a HPWC, an UMC with the proper adapter will suffice for me. This is according to Tesla Sales Advisor.
llavalle
Member
There are adapter cables available that will convert a NEMA 6-20 to a NEMA 5-20, and then you can use the Tesla 5-20 adapter. The UMC and car don't care whether it's 120V or 240V. The adapter is fairly dangerous, though, and needs to be labeled thoroughly so someone doesn't blow up 120V-only appliances with it.
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You cannot trust the current reduction from the touchscreen for safety or code purposes. I have had my charging current reset twice over the past couple of years with software releases, and sometimes when the car detects a new location. Always use the correct adapter or check the charging current each time you charge on a non-standard set-up with an adapter cable.
llavalle
Member
Yeah... I have a couple of those... I was referring to an actual UMC connector.
You're really allowed to feed a Nema 14-50 with less than 50amp? I know this is technically legal for a regular 14-50 but here in Canada, if a outlet is used for an EVSE, regulations are not the same.
Yes. Circuit ratings must match the load intended to be served. Circuit ratings are determined by the conductor size, and the conductors are protected by the OCPD (breaker). For a single load / receptacle, you are permitted to size the conductors and OCPD to the load. Multiple receptacles on a single circuit permit 50A receptacles only on 40A or 50A rated circuits. In the US, it's a very common configuration for the range outlet (14-50) protected by a 40A breaker, as long as the range's nameplate load says 40A breaker is fine.
Arc welders are another matter - you can legally use a breaker 2x the size of the rated conductor on a NEMA 6-50 when used for an arc welder. You should never plug EV's into a welder circuit without knowing the conductor behind it.
HOWEVER, attaching a Tesla UMC to one of these circuits (of less than 50A rating) is not permitted, because the nameplate (installer configuration) of the car is a 40A continuous load, which requires 50A circuit rating. "Dialing down" the current on the touchscreen does not qualify as reducing the load, because it's user-configurable rather than installer-configured.
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