wiring a 48 amp EVSE

[RustyShackleford]

I'm trying to help a friend who just bought an EV and wants to install a 48 amp charger (EVSE) for it. He's installed 120vac circuits before, but I think this is a little over his head. He wants to mount it on the edge of a deck, at a location that is about 15ft distant from a corner of the house where the main load center is located in an interior wall; thus some of the wire will be in a wet location.

The main problem is that an EVSE is considered a continuous load, and therefore the circuit must be up-sized by 25%, so a 60 amp circuit is required. Some people are under the misapprehension that 6awg NM-B (Romex) can be used for a 60 amp circuit, but this is false - see the attached ampacity table and recall that the 60-degreeC column must be used for NM-B (and UF-B). It can be used for 55 amp circuits, and the "step up" rule allows 60 amp breakers to be used on 55 amp circuits. Hence the confusion. So something else is needed.

One option is to run THWN in conduit. The problem with this is that it'd be pretty tough to run conduit up to the panel. Perhaps we could run 4awg Romex down to a junction box, and then transition to conduit with 6awg THWN. Another option would be to use armored cable (type MC), but it'd need to be the type that is sheathed in a PVC jacket (for water-resistance). This is called Teck90 cable: https://nassaunationalcable.com/pro...QRzm70dpv9KqQps6H-JOK1bJEItgghQBoC1OIQAvD_BwE

It's pretty damn expensive, and it requires special terminations (at least at the end that's exposed to weather) and those appear even more expensive.

I suppose we could just use 4awg UF-B, except I'm not sure that even exists, and it'd be a PITA to work with if it did.

So I'm wondering if there's something else I'm not thinking of.

My inclination is to tell him to exchange the 48 amp EVSE for a 40 amp one, and just use 6awg UF-B the whole way. My household has not one, but two, EVs and we are perfectly content with a 40 amp EVSE.

 

[EbS-P]

My inclination is to tell him to exchange the 48 amp EVSE for a 40 amp one, and just use 6awg UF-B the whole way. My household has not one, but two, EVs and we are perfectly content with a 40 amp EVSE.

So the Tesla wall charger allows you to set the circuit ampacity when it’s commissioned. Tell him to look at the manual and see if that it possible. I’m quite happy with my 16A charging rate. It will be easier to add a second 20A to charge a second EV and upgrade the 20A to a 40A or manage share circuit charging.

 

[RustyShackleford]

I haven't looked at the charger yet, but he said it's 48 amps. But like you say, maybe it's selectable like the Emporia one I've installed at another house:

https://shop.emporiaenergy.com/products/emporia-ev-charger?variant=44861002088703

... and I'm jumping the gun here.

 

[RustyShackleford]

Ok, just found out they DID buy the Emporia charger. So I'm gonna recommend running it at 40 amps. So we can either (1) go 6awg UF-B the whole way, or (2) come down from the panel with 6awg NM-B, and then PVC conduit with 8awg THWN to the charger.

I hate working with UF-B, but option 2 requires a junction-box, and then probably some liquid-tight for the last couple feet into the EVSE, so probably quite a bit more expense for materials.

Assuming it's ok to run UF-B un-protected along the bottom of the deck. Also might need to briefly transition to conduit to get a water-tight entrance into the bottom of the EVSE, and to protect it coming up the side of the deck.

 

[RustyShackleford]

There's much controversy over whether it's ok to use 6awg NM-B for a 48 amp EVSE. I asked my AHJ and he said no, but said if I know of any exceptions to please tell him. (He's that rare bird willing to discuss and admit he might be wrong). This thread mentions some exceptions, none relevant to me: https://forums.mikeholt.com/threads...-charging-station.2591385/page-2#post-3055762

But the beauty of that Emporia unit is that you can dial it in. I can set it to 44 amps and just meet the 55 amp spec. Or if, in the future, someone decides 48 amps really is ok, I can change it to that. But I don't really care: we have two EVs an are content with 40.

 

[EbS-P]

There's much controversy over whether it's ok to use 6awg NM-B for a 48 amp EVSE. I asked my AHJ and he said no, but said if I know of any exceptions to please tell him. (He's that rare bird willing to discuss and admit he might be wrong). This thread mentions some exceptions, none relevant to me: https://forums.mikeholt.com/threads...-charging-station.2591385/page-2#post-3055762

But the beauty of that Emporia unit is that you can dial it in. I can set it to 44 amps and just meet the 55 amp spec. Or if, in the future, someone decides 48 amps really is ok, I can change it to that. But I don't really care: we have two EVs an are content with 40.

Model 3 RWD is limited to 32 amps. What happened to teslas 80 amp charger. That’s right not available anymore. Anything over 40 amps is overkill unless you come home every night and need a full charge. And I’m sorry you’re spending that much time in thr car.

 

[EatenByLimestone]

Might be an overly simple question, but can the charger be mounted in a different spot so that the wire isn’t an issue?

 

[RustyShackleford]

Might be an overly simple question, but can the charger be mounted in a different spot so that the wire isn’t an issue?

I don't think so. But how could the wire not be an issue ?

 

[gthomas785]

I have the emporia charger. I ran 4awg aluminum SE cable on a 60A breaker to a 60A disconnect box. Hooked the whip from the evse to the disconnect. Easy peasy.

ETA: in case the benefits weren't self evident.
SE cable can be run exposed outdoors. Aluminum because... why copper? And the disconnect was $12 whereas an similar sized "junction box" is north of $30 and doesn't include lugs.

 

[EatenByLimestone]

I don't think so. But how could the wire not be an issue ?

mount it on the house. No need to route the wire through the deck underside.