Solar Battery and Generator

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Another C10

Another C10

Electrical Contractor 1987 - present
Location
Southern Cal
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Electrician NEC 2020
What is a # 1 rule of integrating when installing a automatic generator to a residential service that already has a solar system with a battery backup.

I've been searching online for specific details as well as schematics.

thank you.
 
It already has battery backup?

The #1 rule is don't have the solar connected in the same panel as loads backed up by the generator. Keep the sources on separate sides of the ATS.

That said, if you already have battery backup then there's no straightforward design answer. It depends on what the goals are for the multiple backup sources as well as specs and compatability. A few battery backup systems even allow full integration of generators.
 
jaggedben said:
It already has battery backup?
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I appreciate your response, my concern through reading is the chance of ( over charging the battery ) I mentioned to the client to have a solar tech look at his equipment. I'm just installing the ATS and the necessary Generac wiring.

The solar battery won't last long enough, utilities shuts down at times for days during severe wind conditions.
 
jaggedben said:
The #1 rule is don't have the solar connected in the same panel as loads backed up by the generator. Keep the sources on separate sides of the ATS.
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I think that's exactly going to be the scenario. 1 panel- 2 separate sources connected to the 1 panels bussing .
 
Another C10 said:
What is a # 1 rule of integrating when installing a automatic generator to a residential service that already has a solar system with a battery backup.

I've been searching online for specific details as well as schematics.

thank you.
Click to expand...
Getting PV, battery backup, and a generator to play nice can be a non-trivial exercise and may require technical assistance from the battery inverter manufacturer and/or the PV system provider. The battery backup will have some sort of gateway that contains a transfer switch, and whether it is wired as a whole or partial home backup makes a difference.

As jaggedben said, what you have to prevent is the PV system backfeeding the generator.
 
Another C10 said:
I appreciate your response, my concern through reading is the chance of ( over charging the battery ) I mentioned to the client to have a solar tech look at his equipment. I'm just installing the ATS and the necessary Generac wiring.

The solar battery won't last long enough, utilities shuts down at times for days during severe wind conditions.
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Sounds like you want a simple cascading backup to the backup. ATS goes downstream of battery and solar backup output. The grid side of your ATS may be powered by either grid or battery backup, still works the same way. Generator only comes on when battery backup runs out, and it doesn't charge the battery.
 
ggunn said:
The battery backup will have some sort of gateway that contains a transfer switch
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I did notice current transformers attached on the load side of the panels 200 A breaker, I suppose that communicates with the solar/ battery gateway ? If so then maybe the generators supply won't actuate those CT"s ..?

If those CT do actuate the battery function, maybe another set of current transformers could be attached to the Generators feed to the same main panel. ?
 
Do you know the home battery system brand/model? If it's Tesla Powerwall or similar then the Generac ATS should be upstream of the PV/battery system with the grid port connected to the grid/PV/battery. The reason is the PV/battery will pick up loads quickly (<1s normally) when the grid goes down then power loads until battery reserve is reached. So the Generac ATS should only switch when the grid port is down for longer (>5s) outages.
 
analog8484 said:
Do you know the home battery system brand/model? If it's Tesla Powerwall or similar then the Generac ATS should be upstream of the PV/battery system with the grid port connected to the grid/PV/battery. The reason is the PV/battery will pick up loads quickly (<1s normally) when the grid goes down then power loads until battery reserve is reached. So the Generac ATS should only switch when the grid port is down for longer (>5s) outages.
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"Upstream" is ambiguous.
 
analog8484 said:
Do you know the home battery system brand/model? If it's Tesla Powerwall or similar then the Generac ATS should be upstream of the PV/battery system with the grid port connected to the grid/PV/battery. The reason is the PV/battery will pick up loads quickly (<1s normally) when the grid goes down then power loads until battery reserve is reached. So the Generac ATS should only switch when the grid port is down for longer (>5s) outages.
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I think I would call that 'downstream'. The ATS should be on the load side of the grid/PV/battery output.

Also 'or similar' is ambiguous.
 
Another C10 said:
I did notice current transformers attached on the load side of the panels 200 A breaker, I suppose that communicates with the solar/ battery gateway ? If so then maybe the generators supply won't actuate those CT"s ..?

If those CT do actuate the battery function, maybe another set of current transformers could be attached to the Generators feed to the same main panel. ?
Click to expand...
Usually CTs only serve on-grid functions, and won't do anything off-grid. But without knowing location of the CTs and model of the battery system it's hard to say for sure. Your description of the CT location is vauge. Service panel or somewhere else?
 
jaggedben said:
But without knowing location of the CTs and model of the battery system it's hard to say
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The CT's are attached to the bussing portion right at the load side of the 200A main breaker before hitting the distribution fins.

I'll try to get the model and brand of the battery when I return to the project or have the owner send over an image.

I'd presume the solar and battery hits the panel last ( so as to supply ) the breaker panel as would my 110 A breaker going to and/ or from the transfer switch of the generator.

everyone's input is highly appreciated. thank you.
 
You need to understand the arrangement of the existing transfer or micro-disconnect equipment, and which loads are backed up. Don't make assumptions. These systems can be configured in a number of different ways.
 
analog8484 said:
If it's Tesla Powerwall or similar then the Generac ATS should be upstream of the PV/battery system with the grid port connected to the grid/PV/battery.
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The closest point of continuity the generated power and solar power share is the breaker fins located at the 200A Meter Mains branch circuit distribution area.
 
jaggedben said:
You need to understand the arrangement of the existing transfer or micro-disconnect equipment, and which loads are backed up. Don't make assumptions. These systems can be configured in a number of different ways.
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What he said. For starters, are the PV and battery inverter in a whole or partial home backup configuration?
 
Another C10 said:
The closest point of continuity the generated power and solar power share is the breaker fins located at the 200A Meter Mains branch circuit distribution area.
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I don't follow. Where are the backup loads?
You really need a line diagram or a more complete description if you want to get sound advice here.
 
Another C10 said:
I will find out although I'm pretty certain there are no chosen loads in particular, the entire panel gets the battery power ..to be used wisely.
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IMO you should get the solar contractor involved. Again IMO, getting a PV system, battery backup, and a generator to work together effectively isn't something that a contractor who isn't familiar with all the technologies involved should try to do on their own. Free advice and worth every penny. :D
 
Avoiding "stream" references. See diagram below, it's the kind of setup for a Tesla Powerwall or "similar" home battery system that I was talking about, but with ATS instead of MTS. The "similar" refers to AC coupled home battery systems with a MID ("Backup Gateway" for Tesla).

1695831744548.png
 
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