Domestic generator with PV?

[littlespark]

Just a query. As people have been asking me about changeover switches and generators.

If a domestic house already has PV solar, and customer wants a changeover switch in case of powercut… should the supply to the PV be turned off while the generator is running?

Situation;
Powercut.
Customer shuts off all non-essential circuits, starts up his genny and flicks over the changeover switch, thus disconnecting the installation from the head, fuse and meter.

Normally, the PV would generate some usable electricity in the house during daylight hours, and any excess would be pushed back into the network, past the meter and main fuse.

If the installation was being powered by a generator…. Where would the excess PV generated electricity go?

Obviously not back through the meter.


Could it damage the genny?
Could it damage the inverter?

 

[James]

I have actually considered the exact same issue at home and have not yet put any solar panels up.

I have been thinking about a bank of resistance heaters that I could use to ensure the generator is always under some load.
i.e. Current monitor feeds plc and this decides what is best,
disconnect solar for house load less than 1kw
connect solar if house load is over 1kw
assusing a 5kw solar system, I would want 2 x 500w heaters and 1 x 2kw and 2 x 1kw.
this means I could add load from 500w to 5000w in 500w increments.
not sure if I am on the right line of thought as it is currently a project that is still in my head.

 

[plugsandsparks]

You can simply connected the Solar feed to the changeover switch - Grid side,
If Grid fails, Solar will loose sync and drop out as normal.
Genny feeds house and is separate from Solar, other wise Solar would see genny as grid and start an argument with the genny as to whose the Daddy, not sure who would win, lol

 

[davesparks]

If the PV remains connected I would expect the PV to backfeed into the generator and kill it.

 

[littlespark]

So you’re thinking it will damage the inverter or the genny?

So if the PV is simply fed from a breaker in the CU, it would be best to change the set up, so the PV is also disconnected with the mains… leaving only the genny and the CU

 

[James]

Small generators do not have the capability of absorbing excess generation from the solar (or any other source)
the avr (automatic voltage regulator) will not be able to cope.

however, if the generator is always under load then it should be ok.

there are some battery storage systems that will allow for
a grid connection (input)
a generator connection (input)
a solar supply (dc input)
a battery bank (both input and output)

2 outputs for ac
1 for permanent supply
1 only available when grid is connected.

this will give you the best of both worlds.
when grid is available it will use solar and grid to keep batteries charged
when grid fails, battery supplies the loads supported by solar if available.
when battery gets low, can signal generator to start for battery charging.

 

[kropaske]

There are devices that can restrict export to 0 and some inverters have this function build in. Still i think it would be better for generator to work on its own as PV power can fluctuate significantly in sunny/cloudy day and generator would have to work much harder.

 

[Rockingit]

If the PV remains connected I would expect the PV to backfeed into the generator and kill it.

agreed, unless it was a syncing generator and even then I think at a domestic level the generator wouldn't be able to go 'low enough' to cope.

 

[Electro-tech]

Maybe Transfer Switch with time delay

 

[richy3333]

just read 712.551 (and a few other characters)