HPWC charging at 40 amps - (Resolved)

[tezco]

The DIP switches set your branch circuit rating, which is 125% of the current drawn by the car; or, the car knows to draw 80% of what the DIP switches are set to.

I don't use "derated output", that term is incorrect in the context of the NEC here.

I suppose from the NEC point of view (that focuses more on new design), this is correct -- a "standard" branch circuit needs to be "upgraded" for continuous load, but then it really just becomes a larger "standard" circuit capable of supplying a lower continuous load. On the other hand, if you have an existing circuit to which you want to attach a continuous load, then the reverse operation needs some sort of name. I suppose you could use the terms "reduced" or "downgraded", but the NEC seems to use terms like "derate factor" etc.

 

[FlasherZ]

I suppose from the NEC point of view (that focuses more on new design), this is correct -- a "standard" branch circuit needs to be "upgraded" for continuous load, but then it really just becomes a larger "standard" circuit capable of supplying a lower continuous load. On the other hand, if you have an existing circuit to which you want to attach a continuous load, then the reverse operation needs some sort of name. I suppose you could use the terms "reduced" or "downgraded", but the NEC seems to use terms like "derate factor" etc.

Right. The NEC is purely about sizing infrastructure from the perspective of the required load. It does speak of "derating" but for adverse conditions. The reason I bring it up is that when you need to compound some derating calculations (say, you have a combination of attic temperature, raceway conductor fill, and some other derating factors), it can make a big difference in the equation.

 

[tezco]

Right. The NEC is purely about sizing infrastructure from the perspective of the required load. It does speak of "derating" but for adverse conditions. The reason I bring it up is that when you need to compound some derating calculations (say, you have a combination of attic temperature, raceway conductor fill, and some other derating factors), it can make a big difference in the equation.

Getting a bit off topic, but thanks for all the electrical advice you have given everyone. This continuous load situation is of particular interest to me since I'm in the early throes of planning some electrical upgrades out here on the farm. We're having a solar array put on the roof of the garage and need to send that power back to the meter via conduit, At the same time I'd like to get more power out to the garage in case I decide to upgrade to the HPWC. The current 100A service requires a bit of a juggle with the requirements of the Leaf, the S, various welders, an industrial air compressor etc. Since I'll be digging the trench for the solar guys, perfect time for a joint use plan, but you are right, the conduit sizing gets more complicated with multiple wire sizes, underground and in-air raceways, continuous loads, PVC thermal limits etc. Still have a lot to learn before I pow-wow with the electricians, but want to appear at least halfway intelligent, so I've broken out my old (1987) copy of the NEC. I's been a long time since I've plowed thru that book!

 

[NigelM]

Mod Note: edited thread title to show the original issue is resolved.

 

[RNG]

Thanks MitchL, Banahogg and Clmazin! I was ignorant enough to think my electrician would read directions… I had unrealistically left the work up to the guy who charged me $2500 to run the line and install the charger… He had not read or tested. I took it apart, read the directions, and now it works. Just hope it stays at the 80 I set (keep hearing people have trouble making it stay at 80…).

Hi Bruce, Tesla has been having problems with the fusing in the HPWC. They say it is due to the car trying to get too much power too quickly. They are working on the problem and suggest limiting the HPWC to the 60 amp level until they have redone the software. Just got mine installed and it is working very well, even at the 60 amp level. Cheers, RNG