Hello All! I'm new here - Question about grid-tie solar sy w/ whole house generator

[MikeForrestGump]

Hi, we are about to install a solar system on a house with a natural gas whole house generator. I understand that the system will automatically shut down in the event of an outage and the generator will power up. My question si do I have to do something manually to power up the solar system again when the power is restored, or will everything be managed somehow without me having to do anything?

[sensij]

Hi, we are about to install a solar system on a house with a natural gas whole house generator. I understand that the system will automatically shut down in the event of an outage and the generator will power up. My question si do I have to do something manually to power up the solar system again when the power is restored, or will everything be managed somehow without me having to do anything?

What grid-tie inverter are you using with the solar panels?

[MikeForrestGump]

I believe its a solaredge inverter (DC optimizer)

[MikeForrestGump]

I am only guessing but it is crazy how there doesn't seem to be much information out there on a "simple" best practice protocol for a system like this. Perhaps there are different configuration..I mean do I need a particular inverter, an automatic transfer switch, a charge controller, and an isolated critical loads circuit in order to make this all work. Or different devices, different configuration, what? Any advice or links to where I can view best practices or example of a good setup, etc. would also suffice.. sincerely appreciated - Thank you.

[sensij]

I believe its a solaredge inverter (DC optimizer)

The SolarEdge inverter will automatically begin delivering power from the panels when it detects the grid has been restored. You may want to verify that your transfer system will shut the generator down and return to powering your house from the grid automatically, as well.

[sensij]

I am only guessing but it is crazy how there doesn't seem to be much information out there on a "simple" best practice protocol for a system like this. Perhaps there are different configuration..I mean do I need a particular inverter, an automatic transfer switch, a charge controller, and an isolated critical loads circuit in order to make this all work. Or different devices, different configuration, what? Any advice or links to where I can view best practices or example of a good setup, etc. would also suffice.. sincerely appreciated - Thank you.

There are lots of feasible configurations. If you are not using batteries, a charge controller is not necessary. The SolarEdge inverter is grid-interactive, so the panels connect directly to it and it connects directly to the grid. The critical loads panel is probably to help make sure the generator (your backup source) is sized for the load it might need to power. Lots of types of transfer switches, with more or less automation available to operate other equipment like the generator.

[MikeForrestGump]

Thank you for clarifying the charge controller is only for battery back up. This is a whole house generator with the transfer switch supplying the main line in, not wired in detail to each circuit. So if the generator fires up and electricity is coming in again, then how will the panels know not to fire up again and try to feed their electricity back in, thus harming my generator? Or does the inverter handle this and manages the "Switch on / Switch off" aspect of generator and keep the systems isolated. When the power comes back on, will the panels restart automatically? Maybe I am complicating this issue and please forgive my ignorance - you have been really helpful though and I really appreciate it.

[sensij]

Thank you for clarifying the charge controller is only for battery back up. This is a whole house generator with the transfer switch supplying the main line in, not wired in detail to each circuit. So if the generator fires up and electricity is coming in again, then how will the panels know not to fire up again and try to feed their electricity back in, thus harming my generator? Or does the inverter handle this and manages the "Switch on / Switch off" aspect of generator and keep the systems isolated. When the power comes back on, will the panels restart automatically? Maybe I am complicating this issue and please forgive my ignorance - you have been really helpful though and I really appreciate it.

Without knowing the exact wiring, it is hard for me to be sure. A well designed system would have the utility power and the grid-tie inverter connected on one leg of the transfer switch, and the generator on the other, and the main service panel on the output. That way, the main service panel would only get power from either the generator or the utility (+ solar), and there would be no way for the generator to be connected to the other power sources.

If this is not how your system is wired, your concerns might be founded. If the solar inverter is connected directly to the service panel through a breaker, for example, and the other end of the panel is supplied by the generator or the power company (depending on the state of the transfer switch), it would be important to shut the breaker to the solar inverter off whenever the generator is activated. There are automatic ways to do this... again, it is hard to know exactly how your system is configured.

The SolarEdge inverter will try to AC couple to anything that looks like grid power. If it is in fact connected through a breaker to the main panel and that breaker is not shut off, and the generator output is within the AC specs that the inverter recognizes as "grid power", it is possible that the inverter will try to deliver the power available from the solar panels. If it supplies more power than what is consumed by your loads, then yes, damage to the generator is likely to occur.

[MikeForrestGump]

Great response and really helpful too - Thank you SO much!!

[MikeForrestGump]

FYI, I also just received an email from an installer who said: "If we go to the fuse box we have a relay in the circuit that comes from the solar panels. The relay is powered from the grid power before the main breaker. When the grid goes down the relay opens its circuit to the panels. Another way we have done it is bringing the power from the solar panels into the customer side of the meter. This being up stream from the main breaker and automatic transfer switch allow for a much easier install. Depending on what SolarEdge recommends will determine which one of these two, or possibly a third option we use.."

[sensij]

FYI, I also just received an email from an installer who said: "If we go to the fuse box we have a relay in the circuit that comes from the solar panels. The relay is powered from the grid power before the main breaker. When the grid goes down the relay opens its circuit to the panels. Another way we have done it is bringing the power from the solar panels into the customer side of the meter. This being up stream from the main breaker and automatic transfer switch allow for a much easier install. Depending on what SolarEdge recommends will determine which one of these two, or possibly a third option we use.."

Sounds like your installer knows what they are doing. Never hurts to ask, though, and the more you know about your system, the better off I think you will be.