Tesla Powerwall 2 and PV System install with Solar Ready Load Center...Advice needed...

[Spatters805]

I just moved into a house and contracted with a Solar Company in CA just before the Net Energy Metering deadline passed. The house is a large one and I am contracted to receive 30 400-watt panels (Panasonic) with Enphase IQ8 inverters. I am also adding a Powerwall 2. My solar installer and my electrician required me to upgrade my load center panel and the electrician recommended a Siemens MC2442S1200SC panel, which has a 100 amp breaker for solar backfeed and ample space for the breakers I need. I had the electrician install a NEMA 6-50 40-amp outlet for my wife's Volvo hybrid and he installed a hardwired Tesla wall charger (50 amp) for my 2017 MS 75D. I also have a inlet for a portable gas/propane 13 kWh generator because I live in a fire zone in CA with lots of brown outs.

Unfortunately the solar company said the install would work, then backtracked a month later (after the install) and said I can't install a powerwall on my solar ready load center because the load center will not allow the battery to be charged by the solar panels. The electricians first refuted this, but we called Siemens and they confirmed it. The electricians never did their homework on how my proposed system would work together. Now I am stuck with a solar ready panel I can't use, a 200 amp busbar that now must be de-rated to 150 amps and a completely stalled solar install project until this all gets figured out.

My options at this point (as explained to me are)
1. Derate the panel to 150 amps and move forward (have 2 EV chargers and 2 AC units, pool pump, and a 4600 sq ft house to power).
2. Force the electricians to swap out the panel for a panel with 225 amps on the busbar (they are refusing to just do this without a fight)
3. Go without the powerwall 2 which I absolutely don't want to do.

Any suggestions from any of you with more experience than me? Will a Powerwall Plus change or remedy this situation? I am desperate to resolve this and move forward.

Thanks in advance for any advice!

 

[jjrandorin]

Maybe some of our more technical members will chime in, but unless you are doing something like ony connecting a part of the PV to the powerwall, 1 powerwall is not enough for that much solar.

 

[power.saver]

Maybe some of our more technical members will chime in, but unless you are doing something like ony connecting a part of the PV to the powerwall, 1 powerwall is not enough for that much solar.

Nor is it enough to power that much house.

 

[arnolddeleon]

I believe the IQ8 can respond to the frequency shift for curtailing their production so it should work with the single Powerwall.

I'm not sure what the objection is with the Powerwall. Based on the comment about derating the panel (which I take to mean install a smaller main breaker) then I'm guessing they are concerned about the total feed exceeding the bus bar ratings. Why aren't they using the PCS (Power Control System) of the Powerwall to prevent it from overfeeding the panel?

Here is a thread with some background: Microgrid Article by Bill Brooks Explaining Gateway 2 PCS

 

[h2ofun]

Maybe some of our more technical members will chime in, but unless you are doing something like ony connecting a part of the PV to the powerwall, 1 powerwall is not enough for that much solar.

The install is so messed up in so many ways, there really is no where to start.

 

[h2ofun]

I just moved into a house and contracted with a Solar Company in CA just before the Net Energy Metering deadline passed. The house is a large one and I am contracted to receive 30 400-watt panels (Panasonic) with Enphase IQ8 inverters. I am also adding a Powerwall 2. My solar installer and my electrician required me to upgrade my load center panel and the electrician recommended a Siemens MC2442S1200SC panel, which has a 100 amp breaker for solar backfeed and ample space for the breakers I need. I had the electrician install a NEMA 6-50 40-amp outlet for my wife's Volvo hybrid and he installed a hardwired Tesla wall charger (50 amp) for my 2017 MS 75D. I also have a inlet for a portable gas/propane 13 kWh generator because I live in a fire zone in CA with lots of brown outs.

Unfortunately the solar company said the install would work, then backtracked a month later (after the install) and said I can't install a powerwall on my solar ready load center because the load center will not allow the battery to be charged by the solar panels. The electricians first refuted this, but we called Siemens and they confirmed it. The electricians never did their homework on how my proposed system would work together. Now I am stuck with a solar ready panel I can't use, a 200 amp busbar that now must be de-rated to 150 amps and a completely stalled solar install project until this all gets figured out.

My options at this point (as explained to me are)
1. Derate the panel to 150 amps and move forward (have 2 EV chargers and 2 AC units, pool pump, and a 4600 sq ft house to power).
2. Force the electricians to swap out the panel for a panel with 225 amps on the busbar (they are refusing to just do this without a fight)
3. Go without the powerwall 2 which I absolutely don't want to do.

Any suggestions from any of you with more experience than me? Will a Powerwall Plus change or remedy this situation? I am desperate to resolve this and move forward.

Thanks in advance for any advice!

I have 4600 sq feet, all electric house. I have 30kw of solar, 7 powerwalls, and a 22kw generator. 400 amp service with 2 subpanels. I also put 5 EV charges in my garage, I have one EV now. Yes, derating is normal if you do not have a PW gateway, I had to derate I think from 200 to 125 until I put in my GW and put the 200 back in

 

[Spatters805]

With a Solar ready load center you do not have to derate the panel because the solar breaker bypasses the busbar. That was the whole point. It back feeds back to the main input. The issue from Siemens is that the solar breaker cannot receive backfeed AND push power to charge the Powerwall. I don’t understand enough about the gateway to see if there is a solution from Tesla that they just don’t know about, which is why I am posting to the forum now. I need to know if it is worth my time to replace the panel or just de rate now that I can’t use the 100 amp solar breaker to cover the backfeed. Sound like if the gentleman with the same sized house ran his panel at 150 amps (I only have 200 amp service though) then maybe it won’t matter??? According to the solar installer the PV system can’t be separated from the Powerwall because it has to be connected to the same breaker to directly charge the battery. I just imagine the gateway should solve that issue. What do y’all think?

 

[Spatters805]

By the way, the single Powerwall is meant to power only critical loads for a short duration during a power outage and not meant to provide whole house backup.

 

[miimura]

By the way, the single Powerwall is meant to power only critical loads for a short duration during a power outage and not meant to provide whole house backup.

If that's the case, you can put most of the solar on the solar ready panel and put a small portion, like 5kW, connected directly to the Powerwall Gateway. You will have to move your backup loads out of the main panel into a backup loads panel anyway and you won't have to de-rate the main breaker.

 

[Vines]

With a Solar ready load center you do not have to derate the panel because the solar breaker bypasses the busbar. That was the whole point. It back feeds back to the main input. The issue from Siemens is that the solar breaker cannot receive backfeed AND push power to charge the Powerwall. I don’t understand enough about the gateway to see if there is a solution from Tesla that they just don’t know about, which is why I am posting to the forum now. I need to know if it is worth my time to replace the panel or just de rate now that I can’t use the 100 amp solar breaker to cover the backfeed. Sound like if the gentleman with the same sized house ran his panel at 150 amps (I only have 200 amp service though) then maybe it won’t matter??? According to the solar installer the PV system can’t be separated from the Powerwall because it has to be connected to the same breaker to directly charge the battery. I just imagine the gateway should solve that issue. What do y’all think?

Your installer may have chose a service upgrade panel poorly, this solar-ready load center says right on the sticker "Parallel power Source" for the solar ready breaker slot. There is no case where loads should be on this connection, and Powerwalls can charge from the grid, so are sometimes loads.

You cannot do anything with the solar ready slot except backfeed a parallel energy source. Even if it could power both PV and powerwalls, where would your loads go?

Your installer shouldn't be putting this much PV on a system on a single powerwall. They are risking any warranty issue not being covered by Tesla due to not following design rules. The maximum PV allowed will depend on the IQ8 that is used but even the smallest reasonable one (IQ8plus-72-2-us) with max continuous output of 290W will be about 1 kW too much PV for your Powerwalls and somewhat small for your panels.

It sounds like your installation will use the Backup gateway, but maybe it will use the backup switch? If you use the backup gateway, you don't have a big issue. I would connect 7.6 kW of the PV and the PW to the backup gateway internal subpanel through a 125A breaker on the distribution bus of the main service and then leave the rest of the non-backup loads on the msp bus. Then put the balance of the PV on the solar-ready slot. This pv power wouldn't be used off grid, but could still be used without derating the main breaker.

If you are using the backup switch, then all the PV will be on the backup side no matter what and you might have to reduce the PV system size, or install a second powerwall. You would also use PCS control over the batteries to only have to downsize the main breaker to 175A.

 

[Bendude]

I just moved into a house and contracted with a Solar Company in CA just before the Net Energy Metering deadline passed. The house is a large one and I am contracted to receive 30 400-watt panels (Panasonic) with Enphase IQ8 inverters. I am also adding a Powerwall 2. My solar installer and my electrician required me to upgrade my load center panel and the electrician recommended a Siemens MC2442S1200SC panel, which has a 100 amp breaker for solar backfeed and ample space for the breakers I need. I had the electrician install a NEMA 6-50 40-amp outlet for my wife's Volvo hybrid and he installed a hardwired Tesla wall charger (50 amp) for my 2017 MS 75D. I also have a inlet for a portable gas/propane 13 kWh generator because I live in a fire zone in CA with lots of brown outs.

Unfortunately the solar company said the install would work, then backtracked a month later (after the install) and said I can't install a powerwall on my solar ready load center because the load center will not allow the battery to be charged by the solar panels. The electricians first refuted this, but we called Siemens and they confirmed it. The electricians never did their homework on how my proposed system would work together. Now I am stuck with a solar ready panel I can't use, a 200 amp busbar that now must be de-rated to 150 amps and a completely stalled solar install project until this all gets figured out.

My options at this point (as explained to me are)
1. Derate the panel to 150 amps and move forward (have 2 EV chargers and 2 AC units, pool pump, and a 4600 sq ft house to power).
2. Force the electricians to swap out the panel for a panel with 225 amps on the busbar (they are refusing to just do this without a fight)
3. Go without the powerwall 2 which I absolutely don't want to do.

Any suggestions from any of you with more experience than me? Will a Powerwall Plus change or remedy this situation? I am desperate to resolve this and move forward.

Thanks in advance for any advice!

I Think one easy solution is swap the equipment to tesla powerwall plus, ( remove enphase iq8s) it is battery and solar integradted, your power may clip a little, may not clip at all it depends on how your roof is oriented and how much temperature factor affects its installation. since you have already installled 200A siemens soalr ready ,you cannot use the parallel input breaker but you can connect it to your Main Panel bus bar. on the grid mode 32A continues , 40A backfeed just enough for your main pabel without derating.

 

[Spatters805]

If that's the case, you can put most of the solar on the solar ready panel and put a small portion, like 5kW, connected directly to the Powerwall Gateway. You will have to move your backup loads out of the main panel into a backup loads panel anyway and you won't have to de-rate the main breaker.

It sounds like your installation will use the Backup gateway, but maybe it will use the backup switch? If you use the backup gateway, you don't have a big issue. I would connect 7.6 kW of the PV and the PW to the backup gateway internal subpanel through a 125A breaker on the distribution bus of the main service and then leave the rest of the non-backup loads on the msp bus. Then put the balance of the PV on the solar-ready slot. This pv power wouldn't be used off grid, but could still be used without derating the main breaker.

If you are using the backup switch, then all the PV will be on the backup side no matter what and you might have to reduce the PV system size, or install a second powerwall. You would also use PCS control over the batteries to only have to downsize the main breaker to 175A.

We decided to go with the solution provided by Vines (thank you!). Once the gateway is installed, will the app tell you how much energy is returned to the load center?

 

[Vines]

We decided to go with the solution provided by Vines (thank you!). Once the gateway is installed, will the app tell you how much energy is returned to the load center?

You are welcome.
The gateway will show in the app all the power that is generated and that is used, as long as the CT's are correctly installed. This will be up to your installer, and in some cases will require Y-splitters and multiple meters depending on the configuration of the service panel, service conductors and branch circuits.

 

[Spatters805]

Update:

So as a potential solution, since the PV line diagram had 22 panels in 1 bank and 8 panels in another bank, I decided to run the 22 panels through the gateway and terminate on the MSP bus. The remaining 8 panels will go to the solar ready breaker, removing that backfeed from the MSP bus. The solar installer says I still need to derate panel down to 175A - See below

**********************
I would like to thank you again for your kind patience and we are working hard to have a new layout sent to you such that you are able to see how the new solution proposed by our senior project manager would look. Your sales coordinator had forwarded me an email regarding the queries that you may have regarding the proposed solution and I would like to address those issues.

In order to utilize the solar ready panel that you have already installed, our project manager has proposed that we connect 22 panels along with the battery to the main bus portion of the Main Service Panel while connecting the remaining 8 panels to the solar ready portion of your panel. These 8 panels will not be able to charge the battery. Doing this will allow us to derate to only 175A instead of 150A. We need to derate to 175A as we need a total of 65A of available backfeed. ( 37.125A from the 22 panels as well as 26A from the battery itself thus putting the total backfeed at 63.125A)

Initially we did not want to move forward with this design as the 8 panels will not be charging your battery however in this specific case I believe this is the best option we could go for as it does not compromise the other loads of your house by derating to 150A as well as preventing another main service panel upgrade.
******************************

Does this sound right? I want to optimize the system without having to add cost - The electrician that installed my panel will swap the breaker for free. I still think there are options to avoid having to derate the MSP at all given the feedback I have seen on this thread, though.

 

[Vines]

Update:

So as a potential solution, since the PV line diagram had 22 panels in 1 bank and 8 panels in another bank, I decided to run the 22 panels through the gateway and terminate on the MSP bus. The remaining 8 panels will go to the solar ready breaker, removing that backfeed from the MSP bus. The solar installer says I still need to derate panel down to 175A - See below

**********************
I would like to thank you again for your kind patience and we are working hard to have a new layout sent to you such that you are able to see how the new solution proposed by our senior project manager would look. Your sales coordinator had forwarded me an email regarding the queries that you may have regarding the proposed solution and I would like to address those issues.

In order to utilize the solar ready panel that you have already installed, our project manager has proposed that we connect 22 panels along with the battery to the main bus portion of the Main Service Panel while connecting the remaining 8 panels to the solar ready portion of your panel. These 8 panels will not be able to charge the battery. Doing this will allow us to derate to only 175A instead of 150A. We need to derate to 175A as we need a total of 65A of available backfeed. ( 37.125A from the 22 panels as well as 26A from the battery itself thus putting the total backfeed at 63.125A)

Initially we did not want to move forward with this design as the 8 panels will not be charging your battery however in this specific case I believe this is the best option we could go for as it does not compromise the other loads of your house by derating to 150A as well as preventing another main service panel upgrade.
******************************

Does this sound right? I want to optimize the system without having to add cost - The electrician that installed my panel will swap the breaker for free. I still think there are options to avoid having to derate the MSP at all given the feedback I have seen on this thread, though.

Your installer can do as they plan and leave the Powerwalls as an uncontrolled backfeed, just like the solar is.

As an alternative, if you do not want to derate the main breaker, they can set Conductor Export Control at 32A and then the Powerwall will be controlled so that the Powerwalls only output up to 32A depending on what the solar is doing.

If the solar is backfeeding at maximum (uncontrolled), then the powerwall (controlled) wouldn't backfeed power while the sun is shining. As the sun goes down, the Powerwalls would be allowed to backfeed up to 32A.

 

[Spatters805]

Excuse my ignorance on this...Will setting the Conductor Export Control at 32A allow me to still get the 5kW continuous and 7kW peak as stated on the technical data sheet or does this cap the performance of the powerwall in some way?

 

[Vines]

Excuse my ignorance on this...Will setting the Conductor Export Control at 32A allow me to still get the 5kW continuous and 7kW peak as stated on the technical data sheet or does this cap the performance of the powerwall in some way?

32A @ 240V = 7680w