System Safety Using a Standby Generator

[ak.jamills]

We are building a new home on property that already has a cabin and separate garage/workshop. The plan is to install a grid tie solar system on the new house. Utility power is tied first to the cabin that also has a standby generator with an automatic transfer switch. Power then runs from the cabin to the garage/workshop and then to the new house.

In the event of a power outage, the transfer switch will isolate the system from the grid and the standby generator will start. My concern is with the solar system feeding power to the system while the standby generator is running. I have spoken with the company that I will likely use to install the system and they did not seem to have much input as to whether this is a problem or not. I also spoke to the utility and their engineer said that the solar system should not feed into the local system while the generator was running but he did not know how the solar system would "know" to shut down when the generator is running. Note that the distance from the cabin with the standby generator and the new house is ~ 120 yards.

I would appreciate any input the subject matter experts in this forum have with regards to how to ensure this system is safely installed.
JAM

[azdave]

A grid-tie inverter will not be fooled into turning on when it sees power from your generator. It must see stable grid power before the inverter will begin to function. That's a very common feature that anyone in the grid-tie biz should know instantly.

[oregon_phil]

There is a post from littleboss that describes almost the same thing as you are trying to do.

I have the opposite issue where I have solar and will be adding a standby generator with ATS. Since you are getting a grid tied system (not hybrid with batteries), you will want to totally isolate the solar inverter from the generator.

I have a similar situation with a Kohler generator (yet to be installed). I have a Siemens MC0816B1200EFN meter breaker panel that feeds two electrical panels. The electrician is going to wire the M1 service connect like a line side tap to the solar inverter while the M2 service connect will be routed to through the ATS. This effectively isolates the solar inverter from the generator, but an electrician has to rewire the M2 side of the meter breaker panel.

I am not an electrician so please make sure you review any suggestions with the appropriate people.

[solardreamer]

We are building a new home on property that already has a cabin and separate garage/workshop. The plan is to install a grid tie solar system on the new house. Utility power is tied first to the cabin that also has a standby generator with an automatic transfer switch. Power then runs from the cabin to the garage/workshop and then to the new house.

In the event of a power outage, the transfer switch will isolate the system from the grid and the standby generator will start. My concern is with the solar system feeding power to the system while the standby generator is running. I have spoken with the company that I will likely use to install the system and they did not seem to have much input as to whether this is a problem or not. I also spoke to the utility and their engineer said that the solar system should not feed into the local system while the generator was running but he did not know how the solar system would "know" to shut down when the generator is running. Note that the distance from the cabin with the standby generator and the new house is ~ 120 yards.

I would appreciate any input the subject matter experts in this forum have with regards to how to ensure this system is safely installed.
JAM

Depending on the specific generator, it may or may not be able to activate or sustain activation of grid-tied solar which can potentially cause damage. To be on the safe side, grid-tied solar should to be isolated from generator by connecting to line side of the ATS.