Moving EV Circuit from Backed Up to Non-Backed Up

[GHTech]

Greetings,

When my 8.16 kW PV and 2 PW's were installed (Sep 2020), we went with backing up all the circuits, including the EV (Honda Clarity Electric), which I mostly charge at work, so it has not been too much of an issue. I am thinking that it might be best to move the EV circuit to the non-backed up panel. Do I need to inform Tesla or anyone else?

Regards,

GHTech

 

[Ampster]

I have EV charging circuits on both panels. I don't have Powerwalls so I can only answer your question with a guess that it is not necessary. A building permit might be required if you were adding a circuit.

 

[jjrandorin]

Greetings,

When my 8.16 kW PV and 2 PW's were installed (Sep 2020), we went with backing up all the circuits, including the EV (Honda Clarity Electric), which I mostly charge at work, so it has not been too much of an issue. I am thinking that it might be best to move the EV circuit to the non-backed up panel. Do I need to inform Tesla or anyone else?

Regards,

GHTech

I dont think you would need to do anything other than have the circuit moved by someone knowledgeable enough to do it. Moving from backed up to non backed up isnt really an issue. The other direction (non backed up to backed up) likely would be, though.

 

[h2ofun]

Greetings,

When my 8.16 kW PV and 2 PW's were installed (Sep 2020), we went with backing up all the circuits, including the EV (Honda Clarity Electric), which I mostly charge at work, so it has not been too much of an issue. I am thinking that it might be best to move the EV circuit to the non-backed up panel. Do I need to inform Tesla or anyone else?

Regards,

GHTech

Why do you want to move? everything is on my batteries, why not

 

[aesculus]

Greetings,

When my 8.16 kW PV and 2 PW's were installed (Sep 2020), we went with backing up all the circuits, including the EV (Honda Clarity Electric), which I mostly charge at work, so it has not been too much of an issue. I am thinking that it might be best to move the EV circuit to the non-backed up panel. Do I need to inform Tesla or anyone else?

Regards,

GHTech

You may need to have another set of CT's put on the charger circuit depending on what was measured before.

In my case everything but my chargers were backed up. There is a set of CTs on the backup loads and another set that is split on the gateway going to the charger circuit. Without this you won't see your grid consumption from the charger circuit.

If you have other non backed up circuits this may be covered depending on how they are installed but I think I would ask Tesla to come and check it out (and bring another set of CTs and the spits with them just in case).

 

[h2ofun]

You may need to have another set of CT's put on the charger circuit depending on what was measured before.

In my case everything but my chargers were backed up. There is a set of CTs on the backup loads and another set that is split on the gateway going to the charger circuit. Without this you won't see your grid consumption from the charger circuit.

If you have other non backed up circuits this may be covered depending on how they are installed but I think I would ask Tesla to come and check it out (and bring another set of CTs and the spits with them just in case).

What do the comments mean adding more CT? How does this work? What functionality is changing or being added. Since my setup is whole house,
I only have the grid CT's and solar. Just 3. nice am simple. But, am I missing something?

 

[aesculus]

What do the comments mean adding more CT? How does this work? What functionality is changing or being added. Since my setup is whole house,
I only have the grid CT's and solar. Just 3. nice am simple. But, am I missing something?

You are only missing something if you have circuits that are not backed up. If you have a circuit that is not backed up and not measured by the load CT, then your Home load will never show your true value and also your grid draw will be wrong too.

Tesla will put a splitter on the gateway where the load CTs are plugged in and it will allow two sets to be input.

BTW they did the same for me for another circuit that later had solar put on it. In that case it was for the solar CTs. So now I have 4 sets of CTs.

 

[wwhitney]

When my 8.16 kW PV and 2 PW's were installed (Sep 2020), we went with backing up all the circuits, . . . I am thinking that it might be best to move the EV circuit to the non-backed up panel.

If all the circuits are currently backed up, why is there a non-back up panel?

Note that if your service panel was emptied of breakers except a single large branch breaker feeding the Gateway, and all your circuits were moved to a backed up panel on the load side of the Gateway, then your service panel is subject to the following rule: the sum of the breakers in the panel (excluding the main breaker) can not exceed the rating of its bus. So if it's, say, a panel with a 125A main breaker, a 125A bus, and a 125A branch breaker feeding the Gateway, you can't add any breakers to that panel.

Cheers, Wayne

 

[holeydonut]

If all the circuits are currently backed up, why is there a non-back up panel?

Note that if your service panel was emptied of breakers except a single large branch breaker feeding the Gateway, and all your circuits were moved to a backed up panel on the load side of the Gateway, then your service panel is subject to the following rule: the sum of the breakers in the panel (excluding the main breaker) can not exceed the rating of its bus. So if it's, say, a panel with a 125A main breaker, a 125A bus, and a 125A branch breaker feeding the Gateway, you can't add any breakers to that panel.

Cheers, Wayne

Yeah, I think the OP with a whole home backup just has a MSP with a single branch feeding the gateway (maybe through a blade disconnect ).

When I had electricians out to my home (whole house backup), most didn't want to add the charger to the backup side. But they were more than happy to add a 48A rated Tesla HPWC by plopping the 60A OCPD on my MSP's busbar. The MSP currently has a 200A feeding my TEG2 (service entry from PG&E is also 200A).

But nobody would add a CT from the TEG2 to the MSP, which meant I could never get ESS energy upstream to charge the car while the utility was operational. Of course, all bets would be off if the grid went down and the TEG2 relay kicked over.

 

[GHTech]

Why do you want to move? everything is on my batteries, why not

Hi h2ofun,

With the EV on the backed up circuit, if there is a power outage, the EV could wipe out the batteries to charge the car. No way to have the car stop charging if there is a power outage.

Regards,

GHTech

 

[GHTech]

You may need to have another set of CT's put on the charger circuit depending on what was measured before.

In my case everything but my chargers were backed up. There is a set of CTs on the backup loads and another set that is split on the gateway going to the charger circuit. Without this you won't see your grid consumption from the charger circuit.

If you have other non backed up circuits this may be covered depending on how they are installed but I think I would ask Tesla to come and check it out (and bring another set of CTs and the spits with them just in case).

Hi aesculus,

Didn't think of this are all. I have no non-backed up circuit.

Thanks,

GHTech

 

[h2ofun]

Hi h2ofun,

With the EV on the backed up circuit, if there is a power outage, the EV could wipe out the batteries to charge the car. No way to have the car stop charging if there is a power outage.

Regards,

GHTech

So, you always have the car plug in when not driving?

And if a power outage, why cannot you not stop charging the car? Just pull the plug.

Just seems other options than deal with what you are trying to do which might not be able to get a permit for

 

[jhn_]

I considered doing this a few weeks ago and even had an appointment with Tesla to do it, then I changed my mind. I’m still not sure if I want to do it or not. I really want the flexibility of having an EV charger that I can choose if it charges from grid or chargers from Powerwalls.

For me it’s not the day to day EV driving, I’ll plug that in each time home and an hour or two later it’s done and the Powerwalls are down a bit.

But if my Model 3 has low battery after a weekend road trip or something, plugging it in on a Sunday night will drain the Powerwalls completely and if sun isn’t great the next day that might mean more than a day running the house from the grid.

Somoene above suggested two EV charging circuits, one behind the TEG and one in front of it. I might just do that and leave my existing on in the whole house backup arrangement, and have the other one grid only.

Just wish there was a software way to do this by telling the TEG and Model 3 that there was a limit I wanted to pull from the Powerwalls to charge it even when the grid was operational. There is a setting for that when the grid is down.

 

[h2ofun]

I considered doing this a few weeks ago and even had an appointment with Tesla to do it, then I changed my mind. I’m still not sure if I want to do it or not. I really want the flexibility of having an EV charger that I can choose if it charges from grid or chargers from Powerwalls.

For me it’s not the day to day EV driving, I’ll plug that in each time home and an hour or two later it’s done and the Powerwalls are down a bit.

But if my Model 3 has low battery after a weekend road trip or something, plugging it in on a Sunday night will drain the Powerwalls completely and if sun isn’t great the next day that might mean more than a day running the house from the grid.

Somoene above suggested two EV charging circuits, one behind the TEG and one in front of it. I might just do that and leave my existing on in the whole house backup arrangement, and have the other one grid only.

Just wish there was a software way to do this by telling the TEG and Model 3 that there was a limit I wanted to pull from the Powerwalls to charge it even when the grid was operational. There is a setting for that when the grid is down.

could this not be done by setting reserve level?

 

[jhn_]

could this not be done by setting reserve level?

Backup reserve means that the house won’t run from the Powerwalls either if the grid is still up.

 

[wwhitney]

But they were more than happy to add a 48A rated Tesla HPWC by plopping the 60A OCPD on my MSP's busbar. The MSP currently has a 200A feeding my TEG2 (service entry from PG&E is also 200A).

Does your MSP not have a label on it that says "do not add breakers"? Because you should not add breakers to that panel, and hopefully an electrician would know that, or at least be able to read the label.

Cheers ,Wayne

 

[h2ofun]

Backup reserve means that the house won’t run from the Powerwalls either if the grid is still up.

Yep, cannot have every option. For Calif it is easy under ev2-a. Just plug in from 12pm to 3pm. Cheapest rates. Everytime I have about EV's with solar/batteries it seems folks do not have enough of either if they want to use PV for charging. Nothing is free.

 

[wwhitney]

I really want the flexibility of having an EV charger that I can choose if it charges from grid or chargers from Powerwalls.

This is what I have, although I've never needed it.

If you want to do it, one way is this: have a non-backed up panel with main breaker (properly connected into the feeder from the service to the Gateway). Put manual transfer switch hardware on the cover of the non-backed up panel. Run a feeder from the backed up panel to the non-backed up panel, interlocked with the non-backed up panel's main breaker (you need to avoid creating a neutral loop of non-backed up panel -- feeder to Gateway -- feeder to backed up panel --feeder to non-backed up panel). Put your EVSE in the non-backed up panel.

Now your loads in this panel can be either non-backed up (when supplied through the panel's main breaker) or backed up (when supplied through the interlocked feeder).

Cheers, Wayne

 

[h2ofun]

This is what I have, although I've never needed it.

If you want to do it, one way is this: have a non-backed up panel with main breaker (properly connected into the feeder from the service to the Gateway). Put manual transfer switch hardware on the cover of the non-backed up panel. Run a feeder from the backed up panel to the non-backed up panel, interlocked with the non-backed up panel's main breaker (you need to avoid creating a neutral loop of non-backed up panel -- feeder to Gateway -- feeder to backed up panel --feeder to non-backed up panel). Put your EVSE in the non-backed up panel.

Now your loads in this panel can be either non-backed up (when supplied through the panel's main breaker) or backed up (when supplied through the interlocked feeder).

Cheers, Wayne

Things like this seem to add a lot of complexity to things as you say, you have but have never needed

 

[GHTech]

If all the circuits are currently backed up, why is there a non-back up panel?

Note that if your service panel was emptied of breakers except a single large branch breaker feeding the Gateway, and all your circuits were moved to a backed up panel on the load side of the Gateway, then your service panel is subject to the following rule: the sum of the breakers in the panel (excluding the main breaker) can not exceed the rating of its bus. So if it's, say, a panel with a 125A main breaker, a 125A bus, and a 125A branch breaker feeding the Gateway, you can't add any breakers to that panel.

Cheers, Wayne

Hi Wayne,

Hopefully I can answer your questions without messing it up. I had a 200 amp panel that I upgraded in 2016. Tesla mounted the backed up panel just behind my panel (back to back) inside the garage. I have attached 2 pictures of it. They left some of the old breakers in place (on the old panel) as they didn't have enough blanks to cover it. The Service Disconnect is a 200 amp breaker. The Main Disconnect (which I believe feeds the backed up panel has a 100 amp breaker. The breaker that is on the backed up panel says it is a 200 amp breaker. So, I am not sure.

Regards,

GHTech