Standby Generator

CtOldman

Can anyone provide some more details regarding how a grid tied solar installation interfaces with an automatic standby generator? We sometimes get violent storms here that can knock out grid power for several days at a time.

Thanks in advance for any enlightenment.

Cariboocoot

Re: Standby Generator

Welcome to the forum.

It doesn't.

A standard grid-tie system has no batteries and when the grid is down it is down. It can not be AC coupled to a generator without a huge potential for disaster; the gen and/or inverter will fry. Your Enphase inverters fall into this category.

A hybrid grid-tie system will have batteries and thus can make use of a generator for recharging them and supplying loads when PV is not enough. For some they can also supplement the generator if it is not up to the load demand.

CtOldman

Re: Standby Generator

Thanks for the reply.

If the solar system quits producing when the grid goes down, then the transfer switch would isolate everything until the grid came back, wouldn't it?

BB.

Re: Standby Generator

To follow up with Marc's information... You would have your "protected loads" on their own sub panel. The GT Solar would be connected to the main panel.

When the grid is up, the sub panel is powered by the grid + GT solar power system.

When the grid is down, the sub panel is connected (through a transfer switch) to your backup power source (genset and/or off grid AC inverter+battery bank). The GT solar power system will be shut down at this point (no power on the main panel).

There are other ways you can setup GT power + off grid/hybrid AC inverters--But it takes a bunch more planning and explanation. You would normally not connect a GT inverter output to your AC generator output... The GT inverters can (and will) feed power backwards through the genset and could cause electrical damage. For most mechanically governed backup generators, their frequency/voltage is not stable enough and usually GT Inverters will not even start up when powered by a genset.

-Bill

Cariboocoot

Re: Standby Generator

CtOldman wrote: »

Thanks for the reply.

If the solar system quits producing when the grid goes down, then the transfer switch would isolate everything until the grid came back, wouldn't it?

Only if it is wired right.
If the inverter output is connected to the main service panel and the gen output is connected to the main service panel ... boom.

As Bill says the critical loads need to be isolated so that only they are powered by the gen and the inverter is not connected to this when the transfer switch is set for generator.

KenZ71

Re: Standby Generator

CT Old Man, welcome from another CT resident a couple towns up the river.

Having 50 solar panels sitting idle during a week-long outage would drive me nuts!

Unfortunately the conventional wisdom here seems to be grid tie solar dont work without the grid being available.

gww1

Re: Standby Generator

Ken

Most of the week long grid outages I have know about wouldn't give much from 50 panels anyway. I always hope that the thing that took out the electric doesn't take my stuff out too.
Cheers
gww

BB.

Re: Standby Generator

You can make a hybrid solar+inverter system that will work fine.

It is just a pretty complex and expensive. There are several ways to connect the panels and inverters.

-Bill

CtOldman

Re: Standby Generator

Thanks for all the help. I think I'll just go with the simple solution for the present and put up with idle panels as Ken said.