whole house generator and utility connection PV

[marcs11]

Typically when installing a PV system to a house with a generator and transfer switch we do a line side tap so as NOT to back feed the generator. Is it a code violation to install the PV on the load side. If so could please site the article.

Thanks

 

[kwired]

Can't answer your question but was thinking if you backfeed the generator with a PV system - does it put fuel back into the fuel tank?

 

[jaggedben]

110.3(B) would be the most salient section. If either manufacturer says it's not okay then you're violating that one.

Another possible code violation might be 705.143.

Also the 2017 code has a whole new section about micro-grids, there might be something there as well.

 

[ggunn]

Typically when installing a PV system to a house with a generator and transfer switch we do a line side tap so as NOT to back feed the generator. Is it a code violation to install the PV on the load side. If so could please site the article.

Thanks

It's not a code violation but it's a very bad idea unless you install a system with batteries that is designed to play nice with the generator. Grid tied PV is a strategic tool to offset the electrical bill. Backup power is a tactical tool to provide emergency power during a grid outage. The overlap between them is small.

We in the solar industry get asked a lot if we can set things up so that the PV will keep running in conjunction with a backup generator during a grid outage. Yes, it can be done, but it's expensive. When you compare the cost of such a system with the generator fuel cost it would offset, it virtually never is even remotely close to being worth it.

 

[gadfly56]

It's not a code violation but it's a very bad idea unless you install a system with batteries that is designed to play nice with the generator. Grid tied PV is a strategic tool to offset the electrical bill. Backup power is a tactical tool to provide emergency power during a grid outage. The overlap between them is small.

We in the solar industry get asked a lot if we can set things up so that the PV will keep running in conjunction with a backup generator during a grid outage. Yes, it can be done, but it's expensive. When you compare the cost of such a system with the generator fuel cost it would offset, it virtually never is even remotely close to being worth it.

Out of curiosity, how do you design these if requested? Obviously you need a battery bank to dump any overgeneration from the PV side, and I see how the generator might be used to get you the 60 Hz so the inverter doesn't shut down, but when PV isn't enough to supply the load, how do you decide whether the batteries or generator provide the power, and does that shut down the PV altogether or does everyone pick up some part of the load?

 

[ggunn]

Out of curiosity, how do you design these if requested? Obviously you need a battery bank to dump any overgeneration from the PV side, and I see how the generator might be used to get you the 60 Hz so the inverter doesn't shut down, but when PV isn't enough to supply the load, how do you decide whether the batteries or generator provide the power, and does that shut down the PV altogether or does everyone pick up some part of the load?

One way is to install a SMA Sunny Boy / Sunny Island system. The Sunny Boy is a PV inverter and the Sunny Island is a battery inverter, and the Sunny Island is also the arbiter of the AC bus (microgrid) that ties them together.

 

[gadfly56]

One way is to install a SMA Sunny Boy / Sunny Island system. The Sunny Boy is a PV inverter and the Sunny Island is a battery inverter, and the Sunny Island is also the arbiter of the AC bus (microgrid) that ties them together.

So how does a generator figure into this lashup?

 

[wwhitney]

So how does a generator figure into this lashup?

If demand exceeds solar output, and the batteries get low, then the battery controller fires up the generator. Not sure how the load presented to the generator is controlled, though.

Cheers, Wayne

 

[GoldDigger]

The answer is that the generator does not factor in well at all, since the Sunny Island must be the reference waveform source for the GTI(s).
Other hybrid inverters offer specific models and configs for generator support. (Including Schneider and Outback)

Sent from my XT1585 using Tapatalk

 

[peterlarsen.suntec]

Schneider XW, Outback Radian and SMA Sunny Island can be A/C (grid) coupled with additional generators including PV, Wind, micro hydro and a Generator. The sources go through the inverter/charger and the signal is a clean sine wave. Batteries are required. On a grid tied PV system without a charger/inverter the inverter source circuit must be on the line side of the transfer switch. You cannot run the generator and grid tied PV at the same time without causing damage to the generator and possibly the inverter. Micro hydro and wind usually need a diversion load in a A/C coupled system.

Sent from my LGLS991 using Tapatalk

 

[electron_ranger]

Most grid-tie inverter manufacturers will tell you that connecting the inverter in parallel with a generator will void the warranty. Something to do with an irregular sine wave from the generator I believe.

I've used a normally closed relay that opens the hot legs from the inverter output as soon as the generator comes on. Anyone got other solutions?

 

[ggunn]

Most grid-tie inverter manufacturers will tell you that connecting the inverter in parallel with a generator will void the warranty. Something to do with an irregular sine wave from the generator I believe.

I've used a normally closed relay that opens the hot legs from the inverter output as soon as the generator comes on. Anyone got other solutions?

If you connect the PV on the line side of the transfer switch, it will shut down when the grid goes down and always be isolated from the generator.

 

[electron_ranger]

If you connect the PV on the line side of the transfer switch, it will shut down when the grid goes down and always be isolated from the generator.

Good point. The relay trick works if you have an ESS for backup power and also want a generator for redundancy.