EV Charger and Generac

[yellowfever]

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

 

[mike93lx]

Tandems are fine when the panel is rated for it.

Assuming you are charging at 48A, it may cause your generator to overload, if other high load items are on. Your highest load while running may be 5kw,but the startup of an HVAC unit (if applicable for you) is much more.

A disconnect near the evse would be prudent. HVAC disconnects are very cheap and it's a good place to install a surge suppressor as well.

 

[mike93lx]

Obviously all power outages aren't predictable, but it may be prudent to drop the charge rate when storms are coming through. Also, charging off a generator is expensive and inefficient, so I'd try to minimize it unless necessary

 

[yellowfever]

Obviously all power outages aren't predictable, but it may be prudent to drop the charge rate when storms are coming through. Also, charging off a generator is expensive and inefficient, so I'd try to minimize it unless necessary

Thanks so much mike - any thoughts on Generac SMM to isolate EV from the rest of the house when generator is running.

 

[mike93lx]

Thanks so much mike - any thoughts on Generac SMM to isolate EV from the rest of the house when generator is running.

I have no first hand experience, but I think it would be prudent. Avoids an overload and will reduce fuel consumption. I assume that you can manually activate the circuit should you need to charge?

 

[yellowfever]

I have no first hand experience, but I think it would be prudent. Avoids an overload and will reduce fuel consumption. I assume that you can manually activate the circuit should you need to charge?

Yes, I believe so. However, I am leaning towards just not charging the car at all during outage.

Info per their site:

Generac's Smart Power Management System is designed to optimize the performance of a standby generator or PWRcell energy storage system (ESS). The system can consist of up to eight individual Smart Management Modules (SMM). Unlike other load management systems that depend on another control device, the SMM is self-aware and operates autonomously.

Frequency is the true measure of system performance, and does not need to factor in increased ambient temperatures, elevation changes, or generator fuel type. SMM monitors the frequency (Hz) of the power being produced by Generac's standby generators or PWRcell ESS. If frequency falls below a certain threshold of a correctly sized system, the SMM will automatically shed the managed loads to allow the system to recover.

The SMM can be set to a load priority between 1-8, or be set in a lock-out only mode for loads that do not need to run in an outage. This reduces the minimum size of system required for a more cost effective solution.

It is recommended to size the generator or PWRcell ESS with appropriate excess capacity to allow starting of the largest managed loads (i.e. loads with the highest starting currents). Each managed load of the SACM and SMM must be assigned a unique priority setting, so no two managed loads attempt to start simultaneously.

 

[mm08822]

If your panel accepts tandems/quads, I would combine 4 lower draw circuits on to the tandems/quad. Use a full size 2 pole 60a cb for the evs.

Also try to have low draw circuits fed from the same panel buss stabs.

Not an absolute must have, but reduces the stab loading feeding a high demand crt.

 

[yellowfever]

I just double checked with Eaton and my panel can definitely accept tandems. I will definitely pick the circuits not used regularly.

 

[dcg9381]

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.

What's going to happen is you'll lose power and the EVSE / Car connection will disconnect. When power is restored, it's likely that the EVSE/car will ramp charge up to prior charging status as high as 48A. In almost every case, the "ramp up" is slow, so it's not like throwing on the HVAC.

If you're worried about it generac has an easy solution, you can put this in-line with the EVSE:



It's a "dumb" device. It basically detects under frequency (generator going low on RPM) or under-voltage and will "disconnect" for a pre-set time period.

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.

You have a breaker, that's a disconnect... I wouldn't do more than that.
Note, if you have a wall connector (not hard-wired) you end up with a 50A circuit (40A continuous) not 60A (48A continuous).
For us, really no difference that we notice... But it's nice to be able to take the EVSE with us.

 

[yellowfever]

Thank you dcg9381. I am leaning towards Tesla wall charger that's hard wired in as it can handle additional power but probably negligible during over night charging. I could be wrong but I think it may have some additional protection built in? I wish it had a function like - if it loses power, it doesn't engage in charge cycle automatically. This way, I decide when to use the EV charger (upon grid power restoration).

​

 

[dcg9381]

I could be wrong but I think it may have some additional protection built in? I wish it had a function like - if it loses power, it doesn't engage in charge cycle automatically. This way, I decide when to use the EV charger (upon grid power restoration).

Tesla Wall Connector (EVSE) is designed to automatically resume charging within 1 to 3 minutes after power is restored following an outage. I cant find a way to configure it alternately... You'll get a push-notification on your Tesla app that the car stopped charging.

Another way to manage it would be to set the "charge rate" on your Tesla to be something less than 48A if you're charging overnight.

40A is about 31 miles of charge per hour... So you could knock it down to 20A, etc...

 

[JohnX14]

I would do what om08822 suggested regarding re-arranging the breaker locations and putting tandems in other locations and running the 60 from a 'full sized' 2 pole breaker. Also realize that those panels are only rated for 100 amps per bus, so a tandem 60 paired with another breaker, across the aisle from another breaker, may be more than the buss is rated for.

As far as the OP, you can use the Generac SMM to isolate the EV charger, and that is what should be done, code-wise. Or you can just make sure you don't plug in the car when power is out.

 

[dave*99]

Do your research on the Generac SMM. I read they had some reliability issues in the past. I discussed it with the Generac installer (18 months ago) when someone I know was having an 18 kW Generac unit and Level 2 charger installed. The installer did not have good things to say about the SMM. The SMM may have improved since then.

He chose to program the charger to run at 30A and could bump it up if ever needed.

 

[wyliesdiesels]

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.

post a pic of your panel diagram and we can check if panel is listed for tandems. most are so it shouldnt be an issue. some panels only allow them in specific bus spaces so keep this in mind.

you should ask the other electrician what issues theyre referring to

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.

no way for us to answer that as we have no clue what loads you have in the house.

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 the charger will not be cord and plug connected (instead hardwired), I would install a disconnect since the breaker panel is not within site of and more than 50' from the charger. It will make servicing the charger safer.

 

[wyliesdiesels]

I just double checked with Eaton and my panel can definitely accept tandems. I will definitely pick the circuits not used regularly.

model # of panel?

 

[wyliesdiesels]

You have a breaker, that's a disconnect... I wouldn't do more than that.
Note, if you have a wall connector (not hard-wired) you end up with a 50A circuit (40A continuous) not 60A (48A continuous).
For us, really no difference that we notice... But it's nice to be able to take the EVSE with us.

however its not within site of the charger so it presents a safety issue if the charger needs to be disconnected from the feed (for hardwired setup).

 

[Dewaynep]

I can't speak to any of the electrical questions, but I can answer you on the EVSE and charge rate. I have a 30 amp circuit running my EVSE (24 amp charge rate due to the 80% rule). My commute is 130 miles round trip and I charge between the hours of 11pm and 5:30am only due to a reduced electricity rate. I have never needed more than the 24 amp charge rate (5.7KW) to charge my car, 2018 model 3 LR DM, from near 0% to 100% when needed. I know we all want more and faster, but on the daily you won't need that fast of a charge so you could lower the charge rate if you suspect the generator will be kicking on overnight.

 

[yellowfever]

model # of panel?

Eaton BR4040BC200 is the model number.

Two slots are taken up by Eaton Surge protector. Was tempted to just remove it and free up slots for EV charger...
I just realized I need a 240v 20amp for my lift as well so I will need 4 tandem breakers unless I remove the surge protector.

Thanks again everyone for all of your help!

 

[wyliesdiesels]

have a pic of the panel diagram?

you can get 2 quads....

 

[dave*99]

Is the surge protector on a breaker by itself? Some of them can share a breaker with a load. Maybe your lift can connect to that.

 

[mm08822]

That panel will not handle tandems......40/40.

 

[yellowfever]

have a pic of the panel diagram?

you can get 2 quads....

 

[yellowfever]

That panel will not handle tandems......40/40.

Yikes... should it say 40/80 or something like that?

Yes, the surge protectors are on two separate breakers.

 

[mm08822]

Yes, 40/60, 40/80.

 

[yellowfever]

Yes, 40/60, 40/80.

That's a bummer - so not many options other than sub panel?

 

[dave*99]

Check the breaker on the lower left. Is it a Square D breaker? If so, it should not be in an Eaton panel. Hard to see in the photo.

 

[JohnX14]

Panel isn't rated for tandems. Just add a subpanel next to it. I see it's flush mount, how much space is next to it?

 

[yellowfever]

Check the breaker on the lower left. Is it a Square D breaker? If so, it should not be in an Eaton panel. Hard to see in the photo.

Wow - Nice catch. I saw that as well and planning to swap out with Eatons. I think I saw a Siemens up a the top - evidently BR breaker was made by a few other companies.

 

[dave*99]

There are a few different breaker types you can physically stab into the panel. But the only ones that belong there are those listed for that panel.

 

[JohnX14]

BR is a line that started as Bryant, and expanded to Challenger, T&B, General switch (I think or it was a knock off in the early '900's) and landed at Eaton.

A number of breakers will fit the BR panels. Siemens/ ITE, Homeline, Murray, as Dave stated.

I wouldn't lose sleep if I had one of these in my BR series panel.













7

 

[yellowfever]

So... I got bored and called Eaton. Mentioned the part number and they said while local codes wouldn't allow it since load center isn't designed to have more than 40 circuits, it would be OK to use non CTL (BR1515 for example) tandems in this load center.

 

[wyliesdiesels]

That panel will not handle tandems......40/40.

yup

40 circuits max

https://uselectrical.vtexcommercestable.com.br/api/dataentities/SD/documents/500158f3-fbce-11ef-b37f-e0291e56df90/file/attachments/255225_USESI_255225_specification_sheets.pdf

 

[yellowfever]

Thank you everyone. To summarize, I need 4 open slots in my current panel to allow 2 x 240V double pole (one rated at 60amp EV charger and the other at 20amp 4 post lift). Given the restrictions on my current 40 circuit, I am thinking about removing the surge protector for one double pole (Bottom left) However, I also have a double oven taking up 240V (Top right) that never gets used. Is there something I can do safely with that circuit without disconnecting it all together - sort of like sharing it with 4 post lift power that will get intermittent use.

I guess I can always use addition capacity with a new subpanel but wanted to see if there are other options.

 

[mike93lx]

Thank you everyone. To summarize, I need 4 open slots in my current panel to allow 2 x 240V double pole (one rated at 60amp and the other at 20amp). Given the restrictions on my current 40 circuit, I am thinking about removing the surge protector for one double pole (Bottom left) However, I also have a double oven taking up 240V (Top right) that never gets used. Is there something I can do safely with that circuit without disconnecting it all together - sort of like sharing it with 4 post lift power that will get intermittent use.

I guess I can always use addition capacity with a new subpanel but wanted to see if there are other options.

I would not get rid of the surge and, no, you cannot share the oven circuit. You should put in a subpanel and then you could move the oven over to that, if you wanted.

 

[larry4406]

Dumb question from a non-sparky...

Premise: Panel is full and we have hit the 40 circuit limit. We need 4 more spaces (2 for the 60A car charger, and 2 for the 240V car lift).

What if the 2-pole oven breaker where replaced by 30A BR Surge Breaker? This still powers the oven and is now the surge protector as well; the other surge protector can be removed, and this then frees up 2 spaces for his 60A240V car charger.


Then, what if he identifies some lightly loaded 120V circuits. For example, reading his panel schedule, I see the following 15A120V lighting circuits:

• Kitchen Lights
• Master Bedroom Lights
• Hallway Lights
• Hallway Lights (yes a 2nd one)

I also see the following 15A120V outlet circuits:

• Bedroom 1&2
• Bedroom 3
• Master Bedroom
• Office
• Great Room
• Basement Bedroom

So, perhaps 2 lighting circuits are wire nutted together in the panel (combined) and then a single black pigtail to only 1 breaker is used. This frees up one breaker space and reduces circuit count by 1. Perhaps also, 2 outlet circuits were similarly wire nutted together in the panel (combined), and then a single black pigtail to only 1 breaker is used. This frees up yet another breaker space and reduces circuit count by 1. Now we have 2 spaces which could be used by his 240V lift breaker.

Thoughts?

 

[yellowfever]

I am going to get a couple more electricians out soon but I think this is what I am leaning towards to avoid tandem and over loading generator:

1. Subpanel - 100amp (for both 240V 60amp EV and 220V 20amp Lift)
2. Install Generac 7006 100amp load shed (for the entire subpanel with both EV and Lift to be locked out during power outage to ensure my generator isn't overloaded)
3. No changes to the Eaton panel.

 

[dave*99]

The following plan was mentioned by a Generac installer in a conversation I had. I don’t know if it helps you but here goes.

He recommend installing a meter main. From that main he would put the EV charger on that panel. EV could only run on utility power. Other loads that would only run on utility power could also be connected there.

The Generac ATS would be fed from the meter main.

Drawback is the EV will never be able to be charged from the generator. He recommended this in conjunction with his distrust of the load shed module.

We did not implement this plan. We set the EV charger to 30A knowing the generator could support it.

YMMV

 

[dcg9381]

He recommend installing a meter main. From that main he would put the EV charger on that panel. EV could only run on utility power. Other loads that would only run on utility power could also be connected there.

There's nothing wrong with that, other than the expense of installing a new main, de-bonding the existing main, etc. Could be a bunch of money, especially with a long run. Personally, if this board won't take the new breakers, I'd do a sub-panel with a 100A load-shed, almost certainly less than a new main.

He recommended this in conjunction with his distrust of the load shed module.

I have 3 of the load shed modules. Early ones had a pretty decent failure rate, but at their core they are just a relay/contactor managed by a board. When mine failed, they "fail open" which is annoying. It was board failures, not the contractor and the newer ones haven't given me any problems, I just swapped the boards.

I think they are great solutions, relatively inexpensive and don't need any "control" wiring.
Setting the EV to 30A is a great solution if you don't want this drama.

 

[yellowfever]

I am not quite following installing a meter main but running the charger at 30amp is interesting. I guess I can always crank it up to 60amp when I need a quicker charge once in awhile but I would be OK with 40amp - 32amp continuous charging. I do wonder if my 16kw generac can handle this extra load... I would never use the lift during a power outage so not worried about that one.

I know for the last 7 years, my generac has been able to handle the load on the panel above.

I can't wait for this project to end

 

[yellowfever]

When mine failed, they "fail open" which is annoying.

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?