Max continuous load on 30A home EVSE

[bogle_rad]

I just got my brand new MS last week (yay!) and I already had a Schneider Electric home EVSE rated at 30A continuous on 30A double pole breaker that I had been using for my Chevy Volt. Here's some info on this specific EVSE:
EVlink Indoor Home EV Charging Station - Schneider Electric USA

I heavily perused the forums prior to getting my MS and noted many warnings about dialing down the current in the car when using homemade or non-Tesla adapters based on any given NEMA outlet's rating. I'm curious if this also applies to my particular EVSE? When I first plugged in the MS to my EVSE, it charged at 30A. I dialed it down to 24A, but I'm uncertain if this was necessary or not since EVSEs have all that sophisticated communication stuff and are probably rated differently than a NEMA outlet.

 

[dhrivnak]

If you have a 30 amp breaker the charger should have been set to 24 amps. Since the volt only charges at 16 amps to there would never have been an issue. The electrician should have put in a 40 amp breaker with appropriate wire size. But dialing back the Tesla should work as it remembers the setting.

 

[bogle_rad]

Hmm - maybe I should have my electrician (my neighbor) replace the double pole 30A breaker with a double pole 40A breaker? Then I get faster charging and never have to worry that a software update resets the charge limit on the MS. It looks to me like he used 10-2 gauge wire. The instructions say to use 8 AWG. I'm kind of lost at this point.

 

[mblakele]

Charging at 24A on a 30A circuit is safer, and should give you 17-18 range mph. Overnight that adds up to quite a bit of range: unless you need more, why not leave it alone?

 

[roblab]

Hmm - maybe I should have my electrician (my neighbor) replace the double pole 30A breaker with a double pole 40A breaker? Then I get faster charging and never have to worry that a software update resets the charge limit on the MS. It looks to me like he used 10-2 gauge wire. The instructions say to use 8 AWG. I'm kind of lost at this point.

Go with the 24 amps. Don't try to push the wire size. It's only your house, maybe your life, and the car really will charge just fine at 24 amps.

IF your neighbor is convinced that you can charge at 30, well, I would still say 24. On top of all that, if you plug your car into your EVSE at 30 and the car recognizes any resistance (small wires), it will automatically cut to 24.

 

[bogle_rad]

My problem with the current wiring of the EVSE is that if there's a software update that causes the MS to forget that I dialed down the current to 24A, it will go back up to 30A and be a potential fire hazard. I delay charge the MS to start at 11pm, since I'm on hourly pricing, so I wouldn't know that this had happened. If all the safety measures in the car and the breaker work properly, fine - no fire. But as you said, it is risking my life to some small degree. Plus, if I ever sell the house, a less observant homeowner may simply use the EVSE as is and risk their life and property.

I think I should just ask my neighbor if he made an error in originally wiring the EVSE and if he's willing to fix it.

 

[FlasherZ]

Hmm - maybe I should have my electrician (my neighbor) replace the double pole 30A breaker with a double pole 40A breaker? Then I get faster charging and never have to worry that a software update resets the charge limit on the MS. It looks to me like he used 10-2 gauge wire. The instructions say to use 8 AWG. I'm kind of lost at this point.

You cannot legally do this. In the code, a #10 circuit must be protected with a maximum breaker size of 30A. To make this device installation legal, you have to replace the wiring with #8 and a 40A breaker. The user-selectable current setting in the Tesla does not count to reduce the load, for a few reasons: the main is that it's known to reset occasionally on updates or when location is misdetected.

It sounds like your neighbor wasn't familiar with the continuous load requirement with EV charging. I've found many residential electricians that aren't aware of the continuous load rules, because few of them deal with it. What he should have done is taken the device's load (30A) and multiplied it by 1.25 for continuous load (37.5A). Then choose a wire accordingly (#8) and the next-size-up breaker (37.5A -> 40A).

The NEC also requires (110.3) that you follow manufacturer's instructions. From their document located here: http://download.schneider-electric....&p_File_Id=682103408&p_File_Name=HRB38095.pdf

Preparation

Power Requirements
— Input Voltage: 208–240 Vac (See Figure 4 on page 4.)
— Input Current: 30 A
— Frequency: 60 Hz
— Feeder Circuit Breaker: two-pole, 40 A

NOTE: A ground fault circuit interruptor (GFCI) circuit breaker will override the automatic reset function built into the charging station.

NOTE: Use AWG 8 copper or aluminum wire rated 90 degrees C or higher.

So yes, it was a mistake to use #10. But don't beat on him too hard, many residential electricians hear "30A" and immediately think "#10" because most loads aren't continuous loads in your home.

 

[miimura]

If the wiring is a long run, it may be cheaper to change the charging station to one that is proper for a 30 amp circuit. The Clipper Creek LCS-30 is a good match.

 

[Boatguy]

FlasherZ is spot on and continuous draw should not exceed 80% of the breaker rating.

 

[davewill]

Unfortunately, your EVSE is not one that can be configured for a 30a circuit (24a charging). If it were my house, I would either upgrade the circuit to 40a (1st choice *) or replace the EVSE with one that can be configured for a 30a circuit (2nd choice). All you need is one glitch that causes the car to start charging at 30a and you may find yourself in trouble.

* In fact, you might as well go with wire big enough for at least a 50a circuit, so you can support 40a charging when/if you replace your EVSE.

 

[skip8jj]

The other option is to purchase the Tesla Wall Connector where in the electrition or you can set the dip switches to 24 amps. No major residing and no danger of the car forgetting what amperage it should draw.

 

[skip8jj]

Sorry, I meant desiring, not residing. SJ

 

[Boatguy]

The other option is to purchase the Tesla Wall Connector where in the electrition or you can set the dip switches to 24 amps. No major residing and no danger of the car forgetting what amperage it should draw.

This certainly an option, though you may want an estimate from the electrician first since the $750 spent on a Tesla charger, which will also need to be installed which is additional expense. The money might be better spent upgrading your wiring as suggested by davewill.

 

[Rocky_H]

I would think redoing the wiring to up the circuit size would be more expensive than changing the EVSE. Buy one meant for a 30A breaker and sell the current one you have on Craigslist or Ebay. You’re buying one and selling one, and are actually moving down in the capability of the unit, so it shouldn’t be much out of pocket cost.

 

[brkaus]

The new tesla HPWC is less expensive now.