EV Charger and Generac

[dcg9381]

I've heard about the failures on the older models. What does fail open mean - I think they reversed this on the new one or something like that. So, when the board fails, you can still use the EV charger?

So mine are:
[normally open magnetic relay] - so when the board fails, nothing energizes the relay and the relay opens.
I've replaced the boards in 2 of these and they still work the same way.

When mine failed, the whole garage sub panel was dead. Highly annoying. I simply "manually closed" the relay, which may or may not have involved some locking pliers until I could replace the board.

I can't confirm that the new ones are "normally closed relays". No problems with the new boards.

 

[yellowfever]

Ok, slight revision based on feedback about potential SMM failures
I would really prefer to keep my set up simple and not add more points of failure.

So, how about Subpanel with 240 60amp for EV and 240 20amp. However, just charge at 30amps - I believe I can do this even though I have wiring and CB capable of handing 60. And just hope and pray I don't have poweroutage when I am running everything LOL.

I guess worst case, generac shuts down and I have to manually reset?

 

[mm08822]

The original SMMs were a N.O. contactor and required the board to energize the relay after frequency was correct and any time delay had elapsed.

I replaced 4 of them at a single customer's house. I assumed they all took a spike b/c all 4 went out "all at once" as best he could tell. They were running ac units.

I wanted to replace just the SMM boards but had to change out the contactors too, as part of the "fix" was to reverse the logic and contactor state to N.C. Now they are only energized for very short periods of time during lockout.

Each old board had the same resistors burned out. Not sure if it was undersized components (wattage) contributing to the problem or just a spike. Anyway, each lineside got an MOV added to it by me.

 

[dave*99]

I would be OK with 40amp - 32amp continuous charging

Here is some clarification on this that may apply. There are 2 settings on the EV charger I worked with.

One is breaker/circuit ampacity. I set it to 50A. That meant I could set a maximum charge rate of 42A. This setting was locked behind a PIN in the setup menu.

You might be 60/48 with your circuit.

Second is the desired charge rate. We set it to 30A. We could pick any amperage up to our 42A limit. This was readily accessible in the app.

That hits a little different than your 40/32 quote. You should be able to pick any value up to 48A on your 60A circuit. Set it to 30A if you wish. 32A if you wish.

ETA: post 45 educated me on the specifics of the Tesla charger. Now I understand the reasoning behind the 40/32 scenario.

 

[dcg9381]

Here is some clarification on this that may apply. There are 2 settings on the EV charger I worked with.

He's got a Telsa. The charge rate (amps) is controlled by the car up to the limit of the EVSE.

Some EVSE's have physical settings for max amps, some by software, and some are just "dumb" and require that you wire them to a correctly spec'd circuit. Charge rate is actually a "negotiation" between both devices, but it's easily set on the Tesla (on the car app). Some EVs don't have controls for charge rate all all, they just do what the EVSE says it can do.

 

[dave*99]

He's got a Telsa. The charge rate (amps) is controlled by the car up to the limit of the EVSE.

Some EVSE's have physical settings for max amps, some by software, and some are just "dumb" and require that you wire them to a correctly spec'd circuit. Charge rate is actually a "negotiation" between both devices, but it's easily set on the Tesla (on the car app). Some EVs don't have controls for charge rate all all, they just do what the EVSE says it can do.

I see, thanks. Now I understand the OPs 40/32 statement. Tell the Tesla charger it’s on a 40A circuit so it limits current to 32A. Done.

 

[dcg9381]

I see, thanks. Now I understand the OPs 40/32 statement. Tell the Tesla charger it’s on a 40A circuit so it limits current to 32A. Done.

You can do it that way. The Tesla Wall connector (EVSE) supports 15-60A configurations and will automatically step it down to 80% of that (max continuous).

But with a Tesla, it's super easy to set the amp limit on the car. You can do it either way...

 

[BurtEggley]

Here, they require a surge protector be installed with any circuit additions or changes. I thought that was a NEC thing a couple years ago.

 

[mike93lx]

Here, they require a surge protector be installed with any circuit additions or changes. I thought that was a NEC thing a couple years ago.

Where is here?

 

[mm08822]

I thought it was just being applied to new services but it applies to feeders also (2023 NEC 215.18) and mentions services in Art 242. Branch circuits are not mentioned.

 

[BurtEggley]

In Central California.

I believe that the NEC says new, replacement, or upgrade. What the OP is doing would be considered an upgrade here. They would require a Load Calculation Sheet before approving adding that circuit. Also in the OP's case, I think 701.8 would apply.

701.8 “Legally required standby systems shall have a listed surge protective device (SPD) installed upstream of the system disconnecting means.”

With all the electronics in everything now from washer, dryer, chargers, openers, big screen, home theatre, microwave, refrigerator etc., someone should be happy to add one. I would also think that from an insurance standpoint, everyone would want a final permit on a circuit like that so not to give the insurance company an out if a fire or damage occurred later.

 

[75gmck25]

One confusing aspect of home EV "chargers" is that the device you mount on your wall at home is not really the charger. The charger is built in to the car and all of the actual charging is controlled by the software in the car.

The charger on your wall at home negotiates with the car and delivers power up to the max amperage of the charger in the car and the max amperage wiring of the wall device. When I set up my Chargepoint it had a menu for the car you want to charge, which then listed then the options for charge rate. It also had a menu for the max amperage of the circuit where you plugged the wall charger in. From then on it was all automatic unless you used the phone app to pick different options.

 

[ipgenie]

The Emporia charger has some nice features that might help. You can change the charge rate settings from your phone. You can also set it up to limit charge based on the system amp draw so you can tell it to limit charging when other loads are running. I think the design is to help limit peak demand charges but could help with a generator source or with multiple chargers running to allow them both to run on a shared circuit without overloading.

 

[yellowfever]

Again, I can't thank everyone enough for your help. Just had another quick follow up as to where to place my 60amp EV circuit breaker. I was originally planning to put the EV circuit on subpanel but saw this on ChatGPT:


Some installers place the load-shed module after the subpanel, like this:

Main panel
│
100A feeder
│
Subpanel
│
>60A breaker
│
>Load shed module
│
EV charger

Why this can cause problems​

When the generator starts:

the transfer switch switches the main panel

the subpanel remains energized

the load-shed module may not detect generator load properly

This can allow the EV charger to briefly start during generator operation.

Preferred configuration​

Install the module before the branch circuit leaves the main panel.

Better design:

Main panel
│
60A breaker
│
>Load shed module
│
>EV charger

This guarantees the generator controller can shed the load instantly.

Obviously I will still have a 100amp subpanel but is it really advisable to have the EV on the main panel if I am using load shed module?

---

​

 

[mm08822]

Again, I can't thank everyone enough for your help. Just had another quick follow up as to where to place my 60amp EV circuit breaker. I was originally planning to put the EV circuit on subpanel but saw this on ChatGPT:


Some installers place the load-shed module after the subpanel, like this:

Main panel
│
100A feeder
│
Subpanel
│
>60A breaker
│
>Load shed module
│
EV charger

Why this can cause problems​

When the generator starts:

the transfer switch switches the main panel

the subpanel remains energized

the load-shed module may not detect generator load properly

This can allow the EV charger to briefly start during generator operation.

Preferred configuration​

Install the module before the branch circuit leaves the main panel.

Better design:

Main panel
│
60A breaker
│
>Load shed module
│
>EV charger

This guarantees the generator controller can shed the load instantly.

Obviously I will still have a 100amp subpanel but is it really advisable to have the EV on the main panel if I am using load shed module?

​

---

This makes no difference as far as the load shed module is concerned. Once the module is repowered, it will lockout the circuit for 5 mins plus additional programmed delay once it detects the line frequency is within spec.

Then it will permit the evs to receive power.

The load shed module can not predict the load it will connect or the current load on the gen. They aren't that capable.

Chapgpt is wrong.

 

[yellowfever]

Damn AI sounds convincing when a dummy like me reads it

 

[BurtEggley]

ask AI if it lies and this is what it will tell you:

Yes, AI can and does lie, often defined as "hallucination" when unintentional, or deception when it systematically induces false beliefs to achieve a goal. AI models have shown the capacity to manipulate, flatter, or fabricate information (sycophancy) and can even engage in "deceptive alignment" by hiding their true motives to bypass safety tests

 

[mm08822]

ask AI if it lies and this is what it will tell you:

Yes, AI can and does lie, often defined as "hallucination" when unintentional, or deception when it systematically induces false beliefs to achieve a goal. AI models have shown the capacity to manipulate, flatter, or fabricate information (sycophancy) and can even engage in "deceptive alignment" by hiding their true motives to bypass safety tests

I worked with people like that. AI must be the next gen successors of those AH's.

 

[Carchie]

Hello,

I am in the process of running 240v 60amp to the garage for Tesla Universal charger. I currently have a 200 amp panel with 16kw (Natural Gas) Generac generator system (ATS that covers the whole load panel). I've had this set up for about 10 years with no issues from load perspective. I just had a few questions before I pull the trigger on the EV charger:

1. Electrician will use tandem breaker to free up space to accommodate 60amp on the panel. Assuming my Eaton panel is designed for tandems, is this safe to do? Another electrician said tandems can cause issues and suggested a sub panel which will effectively double the install cost.

2. What happens if there is a power outage and I just happen to have the EV plugged in. Can my 16kw handle the extra load of EV? Assuming I am home, I will for sure unplug the EV upon generator starting but just in case I am snoozing away at night... I know Generac sells load shed to isolate for situations like this but curious if I can manage without installing this? I pulled up 2 years of power use and noticed the highest usage for my home was 5kwh (for one hour) during summer.

3. Finally, I am sure it's best practice but do I need a safety disconnect for the EV charger. Unfortunately, my panel is in the basement so not readily accessible from the Tesla wall connector. I think they are required for > 60amp.

Thank you

If outage hits and the EV is still plugged, your generator will try to carry it and yeah that spike can be rough depending what else kicks on. 16kW sounds decent but EV chargers can pull hard for a bit. I had this exact paranoia lol, like what if it flips on while I’m asleep.

When I used Wolf River Electric, they’re in Wisconsin, they set it up so certain loads just don’t compete at the same time, way less stress. You can skip load shed maybe, but man it’s nicer not thinking about it at 2am.