Expecting delivery first week of Jan. HPWC back ordered by several months so they recommended Nema 6-50 till HPWC comes in since All NEMA 6 devices are three-wire grounding devices and contain same wire needed for HPWC. Will convert once HPWC comes in.
Yep, this is the recommendation. A 14-50 would require 4 wires to be in code even though the UMC only uses 3 wires.
Of course, if you are a belt and suspenders person you will install both a 14-50 and a HPWC so that in the event the HPWC is incapacitated you'll have a backup. It shouldn't add much to the price. (and it also allows you to check that the UMC is working correctly before that trip)
I did this to account for a future EV as well. 125A panel in the garage above the HPWC location fed by #2, with one 100A (via #2) to the HPWC and one 50A (fed with #6) to the 14-50. I have room in the future to replace that small panel in case I'd need 2 100A charging stations. I suspect, though, that would require me to do some more work with the service feeding my home - I suspect the PoCo would want to change things again as my transformer is rated only at ~150A (37.5 kVA) and the feeders are 350 kcmil. 160A of continuous charging in the evening plus the other home loads might push them to do some more major construction. (Note that I"m not arguing for/against the need for fast charging, etc., or whether a 14-50 only is sufficient for charging. I have need for the HPWC, and I'm thinking forward to the day where charging convenience is desired; whether it's a single "supercharger" like "fuel pump" in the home for all your vehicles, or multiple fast chargers.)
Except that in my case I only have 100A service to the house so the best I could manage without a MAJOR upgrade was 2 30A circuits. I've been charging the Roadster at 24A for 2 years and never needed more. Model S will be fine w/ 24A as well.
I don't doubt that for a second. But if someone is already going to the expense of putting in a HPWC, then the little extra it takes to put in the 15-40 is likely to prove helpful down the road.
Yup. A load calculation on a 100A service won't pass with an HPWC. In most situations it won't even pass with a 125A service (unless your home is VERY small, has all-gas appliances, and no AC or resistive heating).