Powerwalls installed without CT on non-backed up loads

[njmurvin]

I have had a 10kw solar setup since 2019. I recently had 2 PWs (third party) installed awaiting PTO from SCE. City final inspection is complete. My main panel is a 400 amp service integrated with meter. The battery installers ran a 125 amp circuit to a backup loads sub panel next to the GW and moved most of my house loads to it. They left only the larger loads (sub panel to a pool house, 3 ACs, electric ovens, pool equipment, above ground spa, etc.) in the main panel (not backed up).

They did not install any CTs in the main panel at all where the non backed up loads reside. I assume that, because of this, the GW is oblivious to any power consumed by those larger loads. At least that's what it appears from the app. I have the app configured for SCE's 4-9 peak hour plan. I have the reserve for the batteries set to 50%. The plan is to charge the batteries in the early hours of the day and discharge the battery down to the reserve during the 4-9pm peak period to avoid peak hour rates. I see that it does discharge during those hours but it doesn't seem to be affected by the larger loads (that don't have CTs) when they're turned on. Does the system have the intelligence to only discharge the amount of battery energy it thinks is needed based on the CT inputs? Or should the batteries supply energy to all circuits (CT or not) during those hours? Or, will the batteries only supply energy to the backup loads even when the grid is up.

How am I negatively affected by not having CT inputs on these circuits?

If I decide that I want them, what's the best way to add CTs to account for all of my power usage? There are several circuits in the main panel (including the one that goes to the backup loads panel). Is there any way to avoid putting a CT on each and every "load" circuit in the main panel?

 

[arnolddeleon]

Well, without knowing your total loads it is impossible for the Powerwall to offset them "exactly" (it won't be exact). This costs you during the peak hours because you are paying for something that could have been offset with something presumably cheaper. You could potentially go with an "export all" option(if you are allowed by your utility agreement) during peak hours. In that situation it doesn't matter what your load are. That potentially maximizes the savings because you are dumping the maximum amount of energy during peak hours.

They can install CTs in the main that captures the net total of the load of you main panel. They presumably have CTs for your solar/powerwall and a CT for your backed up load they can have the system "do math" to calculate the load of the non-backed up circuits.

In short, a good installer should have handled this. They might have been "challenged" by the 400A main panel but there are ways to solve that too.

 

[taphil]

Also curious as to why your main house A/C isn't backed up. 125A limit? Typically A/C is the biggest power draw and running them off the battery during peak hours is a good way to avoid peak rates. And in case of prolonged power outage in hot weather like today, there's plenty of sun to charge up your batteries and run the A/C for a bit after the sun goes down, or at least to keep 1 floor or part of the house cool.

 

[njmurvin]

Well, without knowing your total loads it is impossible for the Powerwall to offset them "exactly" (it won't be exact). This costs you during the peak hours because you are paying for something that could have been offset with something presumably cheaper. You could potentially go with an "export all" option(if you are allowed by your utility agreement) during peak hours. In that situation it doesn't matter what your load are. That potentially maximizes the savings because you are dumping the maximum amount of energy during peak hours.

They can install CTs in the main that captures the net total of the load of you main panel. They presumably have CTs for your solar/powerwall and a CT for your backed up load they can have the system "do math" to calculate the load of the non-backed up circuits.

In short, a good installer should have handled this. They might have been "challenged" by the 400A main panel but there are ways to solve that too.

Yes, I have no reason to suspect the backed up loads, solar and PWs aren't being measured correctly. If the system can do math, it should be fairly straightforward to calculate the non backed up usage (assuming we know the total net usage at the main and the other measurements). Based on the history of this install, I don't think I can rely much on the installer. This whole process has been a more than a "challenge".

 

[njmurvin]

Also curious as to why your main house A/C isn't backed up. 125A limit? Typically A/C is the biggest power draw and running them off the battery during peak hours is a good way to avoid peak rates. And in case of prolonged power outage in hot weather like today, there's plenty of sun to charge up your batteries and run the A/C for a bit after the sun goes down, or at least to keep 1 floor or part of the house cool.

I have 2 ACs serving the main house. The only one that could have feasibly been connected to the backup loads panel is the 5 ton unit. I was concerned that it would drain the batteries too quickly and compromise the refrigerators and other critical circuits. If I could have included the 2 ton unit (long story why I couldn't), I probably would have.

 

[njmurvin]

So that I'm clear on this, are you saying that the PWs and/or gateway only discharge the amount of battery energy deemed necessary by the calculated demand based on readings of the CTs? This would explain why I don't see any change in the battery discharge rate during peak hours when I energize loads that are on circuits without CTs.

If so, does this extend to solar generation as well? For example, while the grid is up, does my generated solar get consumed only by loads on circuits with CTs installed or all loads?

 

[miimura]

So that I'm clear on this, are you saying that the PWs and/or gateway only discharge the amount of battery energy deemed necessary by the calculated demand based on readings of the CTs? This would explain why I don't see any change in the battery discharge rate during peak hours when I energize loads that are on circuits without CTs.

If so, does this extend to solar generation as well? For example, while the grid is up, does my generated solar get consumed only by loads on circuits with CTs installed or all loads?

The Powerwall discharge logic can only work with the information at hand. If the loads in your main panel are not measured, they cannot be offset by the batteries. There are multiple ways for the Powerwall system to add CTs and configure those measurements to match a given situation. Two of the ways are extending wires from the Gateway to the new CT location and adding a remote Neurio device in the panel where the measurement needs to be made. You should talk to your installer about installing CTs to measure your total grid draw. That is the proper way.

 

[njmurvin]

Got it for the CTs and battery discharge. I’ll discuss this with the installer.

How about solar consumption? Before the PWs and GW, my solar output ran into my panel directly where it would be consumed by all loads in the system and any excess would count as an export to the grid. Now it goes through the GW. What does the GW do with the solar output? Does it use the CT readings to determine what goes to charging, home and export to grid?

 

[arnolddeleon]

Got it for the CTs and battery discharge. I’ll discuss this with the installer.

How about solar consumption? Before the PWs and GW, my solar output ran into my panel directly where it would be consumed by all loads in the system and any excess would count as an export to the grid. Now it goes through the GW. What does the GW do with the solar output? Does it use the CT readings to determine what goes to charging, home and export to grid?

Usually there will be a CT that measures the production before it gets consumed. With the right set of CTs, the gateway configure out if there is there is net load or surplus and act accordingly. This usually means either charge the better or discharge the battery.

 

[njmurvin]

The CT measurement of the solar output seems the same as my Enphase reporting. But my loads are not all measured. That means the GW senses more surplus Solar than is really there and charges the batteries sooner? Likewise, once the batteries are charged, the GW thinks it’s exporting more to the grid than it would if it were monitoring all loads. But the non monitored loads are still consuming power from the grid. So I assume the net amount of energy exported works out the same as if the loads were monitored.

Where I think it hurts me is in the peak window. It doesn’t use as much of the batteries as it should. The non backed up loads are using grid power at the higher peak rates when there is cheaper energy sitting in the batteries.

Is my thinking straight on this?

 

[power.saver]

Where I think it hurts me is in the peak window. It doesn’t use as much of the batteries as it should. The non backed up loads are using grid power at the higher peak rates when there is cheaper energy sitting in the batteries.

Yes, that's right. You should really try to get those loads monitored so you can offset them with stored energy during the peak.

 

[njmurvin]

Thanks. If the installer refuses to cooperate, I’ll probably be asking for help here to figure out the best way to accomplish this.