Chargers (EVSEs) and whole-house generators

[RMoore]

Those of you who have whole-house generators, did you add any module that prioritizes the EVSE if the power goes out and there is load shedding? For example, with a Generac generator and transfer switch (that I think does some load shedding or prioritizing) would you add the Smart Management Module (shown here if you scroll down)? I'll ask my generator guys but curious what folks here have done.

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[ZuleMME]

My intent would be to manually switch the loads as needed. If it's truly a whole house generator you don't need to shed loads as it should handle anything your main panel could pull. But most get over-zealous with that term and don't have more than a partial load generator. Hopefully an inverter. Otherwise DON'T CONNECT TO THE EV!

 

[AKgrampy]

The day I retired as the VP of Transmission and Distribution of our local utility I purchased a whole house generator. Had to use it a few times since then. (Really reliability just as good as it was when I worked there) We are on a well so that takes a bit of surge when it kicks in. Also we wanted to be able to live “normally” during an outage. So our generator is large enough to run our range/ stove, dryer, etc just like normal. We could charge our car when any other large load is on line but not the stove, dryer and charger at the same time but that is easy enough to control. We also have an ICE vehicle so would be OK even if we could not charge our EV. If you think about it though you would probably hunker down a bit during a major outage so you would have time to even use 110V charging for an emergency if your generator is not sized for the 240v charge.

 

[babgvant]

We have a whole house Generac, so I am interested in what others are doing there. I hadn't really thought about what would be required to make it work properly, my assumption was that when they installed it they sized it for the service and panels that we have, so additional loads would be fine (not saying that assumption is correct, just that is what I was working with ).

 

[RMoore]

Mine is 20kW and there are times where we lost power and the generator had two central a/c units running plus fridges and other appliances. Just wondering if this Smart Management Module that General makes is worth it. My guess is I don’t need it since my usual drives are short and I can likely get buy with the level of charge that will have been there before a power outage.

 

[mkhuffman]

I am planning to install a 20 or 22 kW generator and I know in the summer it probably won't be able to charge my car, run both HVACs and support cooking in the kitchen at the same time. I have a power monitor and I have hit 18 kW while charging and my AC units were not running (I have a NG furnace).

One exception from your situation is I am using a 48 Amp charger which pulls 11 kW. Probably when on the generator if I had to charge the car I would use the Ford 240V charger to reduce the load on the generator.

 

[RMoore]

I am planning to install a 20 or 22 kW generator and I know in the summer it probably won't be able to charge my car, run both HVACs and support cooking in the kitchen at the same time. I have a power monitor and I have hit 18 kW while charging and my AC units were not running (I have a NG furnace).

One exception from your situation is I am using a 48 Amp charger which pulls 11 kW. Probably when on the generator if I had to charge the car I would use the Ford 240V charger to reduce the load on the generator.

That may not be an exception to my situation since I’m planning to have a similar set up charging wise. But you did make me think of something. If you have a 48A charger doesn’t that mean it’s on a 60A circuit and doesn’t that need to be hardwired? If so, do you have a separate circuit that has 14-50 receptacle? How would you plug in your Ford charger?

My impression is that if my power goes out on a hot day in summer I’d rather use the a/c than charge the car.

 

[mkhuffman]

That may not be an exception to my situation since I’m planning to have a similar set up charging wise. But you did make me think of something. If you have a 48A charger doesn’t that mean it’s on a 60A circuit and doesn’t that need to be hardwired? If so, do you have a separate circuit that has 14-50 receptacle? How would you plug in your Ford charger?

My impression is that if my power goes out on a hot day in summer I’d rather use the a/c than charge the car.

I ran a 60 Amp circuit from my main breaker box to a new sub panel. In the sub panel I put a 60 Amp breaker and a 50 Amp breaker. I hardwired the 48 Amp charger to the 60 Amp breaker and connected a 14-50 outlet to the 50 Amp breaker.

Obviously I can't use both the outlet and the 48 Amp charger at the same time, but I can use either one. When I first got my MME I used the Ford charger on the 14-50 outlet and later got the EVSE and wired that up. I have not used the 14-50 outlet since I got the 48 Amp charger, but it is there if I need it.

On a side note I didn't use a GFCI breaker on the 14-50 outlet mainly because I couldn't find one. Shortages of everything these days.

 

[RMoore]

I ran a 60 Amp circuit from my main breaker box to a new sub panel. In the sub panel I put a 60 Amp breaker and a 50 Amp breaker. I hardwired the 48 Amp charger to the 60 Amp breaker and connected a 14-50 outlet to the 50 Amp breaker.

Obviously I can't use both the outlet and the 48 Amp charger at the same time, but I can use either one. When I first got my MME I used the Ford charger on the 14-50 outlet and later got the EVSE and wired that up. I have not used the 14-50 outlet since I got the 48 Amp charger, but it is there if I need it.

On a side note I didn't use a GFCI breaker on the 14-50 outlet mainly because I couldn't find one. Shortages of everything these days.

Got it, makes sense. I figured you knew what you were doing so likely had a second circuit. I know there is much discussion about not needing a GFCI on the 14-50 circuit given that the chargers have one (not code yet, but will be). I talked to the electrical inspector in my town and he said I wouldn't need one if I go that route but also said that he researched the issue and his impression was that the issue of nuisance tripping was mostly specific to Tesla's charger. He said he had read that their self test circuitry somehow sends out a signal in a way that lets current go to ground (at least I think that's what he said) thereby tripping the GFCI that protects the 14-50 outlet.

 

[mkhuffman]

Got it, makes sense. I figured you knew what you were doing so likely had a second circuit. I know there is much discussion about not needing a GFCI on the 14-50 circuit given that the chargers have one (not code yet, but will be). I talked to the electrical inspector in my town and he said I wouldn't need one if I go that route but also said that he researched the issue and his impression was that the issue of nuisance tripping was mostly specific to Tesla's charger. He said he had read that their self test circuitry somehow sends out a signal in a way that lets current go to ground (at least I think that's what he said) thereby tripping the GFCI that protects the 14-50 outlet.

Sounds like your electrician knows what he is talking about and I would trust his advice. What he said is consistent with what others have reported here in this forum.

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