adding micro inverter for additional panels

[xcentric]

I have a standard solar array with a grid-tied inverter and batteries, in the UK

I also have a wood store that I need to put a new roof on, and am thinking of putting old used solar panels on it - similar cost to roofing it, really. However they are not in an ideal position and get odd shading - there's not enough to generate enough power for a string inverter, so thinking of controlling them with a micro inverter, but am unclear how this is wired into house circuit. Does it have to go back to the consumer board? or can I feed it in somewhere else (cos the wiring to get there is a long way away and through the house)?

 

[MisterSandals]

them with a micro inverter, but am unclear how this is wired into house circuit.

The micros usually daisy chain together with proprietary cabling. The output can connect to standard 12/3 wire and run to s pair of 15A (or whatever your micros recommend) breakers in the electrical panel; one wire on L1 and one wire on L2.

Surprisingly simple.

 

[BentleyJ]

Does it have to go back to the consumer board? or can I feed it in somewhere else (cos the wiring to get there is a long way away and through the house)?

The microinverters should feed into the electrical system via dedicated, properly sized wires & breaker either in a sub-consumer panel or main consumer panel.
That doesn't mean you can't get creative. For example if there is an unused outlet, with no other loads, you could plug the microinverters into that and backfeed the consumer unit with an existing circuit. NOTE: DEDICATED & PROPERLY SIZED breaker. Not sure it would pass an inspection but would be safe if the wiring and breaker were appropriate.

 

[xcentric]

so is it ok (practically, and inspection wise - 2 different things!) to run a spur from an existing plug socket ring, with a breaker, and connect into that? Cos that's simpler to wire up

 

[zanydroid]

I would recommend tagging one of the UK folks. Only US replies on your thread.

Understanding the risks of shared circuits with multiple points where power can come in is not for the faint of heart. I don’t even think EEs or electricians should get creative vs just parroting what the code book and install manual says.

We don’t have rings in the U.S.

 

[Sigunas]

so is it ok (practically, and inspection wise - 2 different things!) to run a spur from an existing plug socket ring, with a breaker, and connect into that? Cos that's simpler to wire up

Microinverters can work that way. I tried cheap gmi-700 (700 chinese watts, 400-500 real watts, ~90 euros from ali 2 years ago), connected to ~600W half cut panel. They work. I don't think they would pass inspection.

 

[zanydroid]

Of course it will work and generate power provided the breaker is rated for backfeed (you can’t backfeed GFCI breakers in the US) and it probably won’t burn down 100% of the houses that hack it in this way.

It might burn down 5% though because the fusing needs to be done in a particular way to provide overcurrent protection up to code standard

 

[Sigunas]

Of course it will work and generate power provided the breaker is rated for backfeed (you can’t backfeed GFCI breakers in the US) and it probably won’t burn down 100% of the houses that hack it in this way.

EU, UK has different grid, code and standards. Post autor stated, that he already has grid tied solar, so he already has covered that side of things, if he will not exceed his backfeed capability as per agreement.

It might burn down 5% though because the fusing needs to be done in a particular way to provide overcurrent protection up to code standard

It would be interesting to know more about the "particular way to provide overcurrent protection" if that's aplicable not only for US, CA grid.

 

[shavermcspud]

so is it ok (practically, and inspection wise - 2 different things!) to run a spur from an existing plug socket ring, with a breaker, and connect into that? Cos that's simpler to wire up

UK installer here and Electrician. under no circumstances do this. solar PV in the UK needs to bed fed from its own consumer unit with is own RCD type rated for DC imposition. No solar PV system should share the main house CU. Have a read of the IET guidelines for this.

 

[zanydroid]

It would be interesting to know more about the "particular way to provide overcurrent protection" if that's aplicable not only for US, CA grid.

If you have multiple power sources on a single circuit then it’s a matter of physics and electrical engineering that the OCPD analysis is much more complex.

Suppose you have a 13A load circuit protected by a 13A breaker from mains. If you add a microinverter string of 13A onto that circuit protected only by the AC overcurrent protection baked into the microinverter then it is possible with some arrangements to have a max of 26A (micros and grid same end of wire) traversing a unit of wire while with others only 13A (micros and grid opposite ends of wire. In either case the circuit is capable of sending 26A into outlets instead of the 13A with grid only feed.

 

[Sigunas]

UK installer here and Electrician. under no circumstances do this. solar PV in the UK needs to bed fed from its own consumer unit with is own RCD type rated for DC imposition. No solar PV system should share the main house CU. Have a read of the IET guidelines for this.

Interesting. There are talks in my country to let anyone produce up to 600W without any special agreement. Implying there will be connections to nearest wall socket.

 

[Sigunas]

If you have multiple power sources on a single circuit then it’s a matter of physics and electrical engineering that the OCPD analysis is much more complex.

Suppose you have a 13A load circuit protected by a 13A breaker from mains. If you add a microinverter string of 13A onto that circuit protected only by the AC overcurrent protection baked into the microinverter then it is possible with some arrangements to have a max of 26A (micros and grid same end of wire) traversing a unit of wire while with others only 13A (micros and grid opposite ends of wire. In either case the circuit is capable of sending 26A into outlets instead of the 13A with grid only feed.

Thanks. Additional 600W@230V would be 2.6 Amps and perhaps is not considered a big problem where I live, because required minimum for copper wire is 2.5 sq.mm (12-14 AWG) to any power socket.

 

[kommando]

First off are you G98 certified, if so you can only exceed 3.68kw inverter capacity by asking the DNO via a G99/G100 application and only adding the additional capacity after approval.

If you use the panels to solely charge batteries isolated from the mains then you are ok, but adding it to a grid tied will require a dedicated circuit feeding a dedicated breaker in the CU as long as you are either still within G98 or have G99/G100 approval for the extra capacity.