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wall connector mounted on top of junction box?

germasch

New Member
Jul 23, 2021
2
0
NH
Since I can't use NM-B 6/2 cable to install my wall connector at full load (48A continuous / 60A breaker), which would have made life simple, i'm now considering to run PVC conduit with THHN wires (6 for the hots, 10 for ground). The distance between panel is only about 15 feet. The problem, however, is how to transition between the PVC conduit that runs down inside the wall (normal 2x4 wall) to the actual charger? I'd like to avoid having the conduit visible, so I essentially have to have a 90 degree connection inside the wall -- obviously the usual sweeping elbows won't fit. A LB-type conduit connector doesn't appear to be a code-compliant option, either, since it needs to be accessible, ie., can't be buried in the wall.

So my current plan is to put a junction box into the wall, hopefully I can find a fitting cover plate that i drill a hole through to route the wires into the wall connector. I'd just mount the wall connector on top of the junction box, so the box itself would be hidden, but still accessible (I believe). Does that sound like a reasonable plan, or are there any other options that I've missed?

Also, it sounds like 3/4" conduit should be fine for the 3 wires, but if anyone has made the experience that pulling the wires through that is not fun, I'd be interested to know, since upgrading to 1" conduit is of course an option, too.
 

Sophias_dad

Supporting Member
Supporting Member
Jul 29, 2018
1,539
1,620
Massachusetts
Your plan sounds okay. You should put something around the inside of the hole you cut in the cover plate, so it doesn't abrade the wires if they happen to touch as they heat and cool.

Is there some reason you don't just use 4/2(if you can find it) or 4/3?

Side note: I originally installed 6/2 (40A continuous/50A breaker) and as an experiment turned the HPWC up to 48A. It runs fine, and the wire temp barely gets above ambient(88F after hours of running). Only in the rarest of circumstances would you actually need 48 amp charging, too.
 

germasch

New Member
Jul 23, 2021
2
0
NH
Your plan sounds okay. You should put something around the inside of the hole you cut in the cover plate, so it doesn't abrade the wires if they happen to touch as they heat and cool.

Thanks for your reply. Details t.b.d., but I think I'll have a short piece of PVC conduit attached to the charger but protruding into that whole, so I'll make sure to deburr that.

Is there some reason you don't just use 4/2(if you can find it) or 4/3?
It seems like 4/2 doesn't really exist, and 4/3 appears hard to come by in by-the-foot quantities. I did consider it -- I also considered just using 6/2 nm-b, which other than being not code-compliant appears to be perfectly safe (same wire, same temp rating as what I'll put into conduit), but anyway, if I do it, I might as well do it right (ie., to code, too).
Side note: I originally installed 6/2 (40A continuous/50A breaker) and as an experiment turned the HPWC up to 48A. It runs fine, and the wire temp barely gets above ambient(88F after hours of running). Only in the rarest of circumstances would you actually need 48 amp charging, too.
Yeah, I'm not surprised, I guess. And you're right, I don't think I'll need 48A, probably not ever. But there's still the issue that the nameplate says (I suppose) 60A, so even though it can be turned down in software, one interpretation of code is that it needs to be wired for 60A in any case...

Due to more complications with routing the wiring, I now purchased "smurf tube", managed to drill the first hole even though of course I hit a nail, and got the tube through that, so progress... Anyway, looks like what I'm planning to do is workable, though I'm sure i'll hit some other snag(s).
 

with_raiden

Member
Apr 11, 2021
218
176
NYC

Sophias_dad

Supporting Member
Supporting Member
Jul 29, 2018
1,539
1,620
Massachusetts
Why is there no need to wire the wall connector to 60A? Once you setup load sharing, 1 amp is reserved thus making a 60A a 59A which can be split by N number of wall connectors.

There was no mention of load sharing here in any case, but even if there was, HPWC's can be set for as low as 15 amps maximum draw, and with gen3 HPWC's there's supposed to be a dedicated breaker for every HPWC. As long as that breaker is low-current enough to protect the wire from overheating, the HPWC can do what it wants. If there's a software or configuration error that allows it to draw more than the breaker is happy allowing through, the breaker will trip and the house will stay not-on-fire.

There's a section in the HPWC wall manual describing how to set it up for circuit breakers from 15 to 60 amps. That would be just plain silly if every install requires 60 amp capable wiring, because a 15 amp breaker simply won't accept a 4 gauge wire.
 

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