Garage Consumer Unit Question - DIY Solar.

bunderoon · 03-04-2025 12:01PM #1

Afternoon folks.

Question about running a 6mm sq SWA cable between house and shed. My array will be max of 4kW (Inverter is a dual MPPT Solis 4kW) and installed on the garage roof and on the front wall. Array 1= Roof is ~20 degrees. Array 2 = Wall, 90 degrees. I will get my electrician to install a mini consumer unit in garage. An isolator switch for the board and also one 6A MCB for led lights, one for sockets (13A max, small work tools etc) and one for Inverter.

My question is, is it just a 3 core cable to connect the garage to the house CU? Not a 5 Core etc? For example, the inverter MCB DOES NOT need to connecting to the house CU and then the House CU connections to the Garage Board separately using the other cores in the 5 core cable?

Is the attached diagram correct?

Note, no fireman's switch in garage as its 30M from house. Data cables will be ran also. Will need to get creative with the Inverter Clamp connection between shed and ESB Meter Tails. I have already an Eddi, Zappi and Harvi in operation.

Thanks in advance.

bunderoon · 03-04-2025 09:20PM

Anyone dealt with similar?

graememk · 03-04-2025 10:56PM

Mines is down in the farmyard connected to the CU there.

It actually goes from house CU to first yard CU then to the barn CU, solar is connected to the barn CU.

My Solar is on a RCBO not a MCB, but as you have a RCBO in the house that should cover it.

You may run into tripping issues on a 30mA rcbo, some solar rcbos are being changed to 100mA ones

JohnySwan · 04-04-2025 11:15AM

https://www.boards.ie/discussion/2058404941/garage-consumer-unit-question-diy-solar

I would go 10sq minimum from the house. Lose the rcbo feeding the garage for a double pole mcb, give the inverter its own double pole, bi directional rcbo. 100ma as pointed out above.

bunderoon · 30-04-2025 04:31PM

Hey @graememk and @JohnySwan

To protect the 10sq as it will be under ground, then into my attic, shouldnt it need protection? I assume an RCBO and if so, a 100mA as to avoid cascading issues as the Garage CU will have 32A 30mA RCBOs for Sockets (Patio and Garage) and the solar inverter RCBO will be 100mA as advised by Solis.

I have updated my diagram.

JohnySwan · 30-04-2025 04:35PM

https://www.boards.ie/discussion/comment/123405035#Comment_123405035

An MCB is the normal method to supply a sub board.

bunderoon · 30-04-2025 04:35PM

I've an electrician to do the AC side for me, but he isnt a solar installer. Thankfully he will be signing the NC6.

Also, do I need a CT cable from the Inverter to the House CU or Meter?

I have a Zappi and Eddi. Heat water and charge car between 2am and 5am. I have two CT clamps on the Harvi and the eddi is the v2 so it is the 'hub'. I have set up the first clamp in reverse so I can see what power I am using from the grid. Works well the last years since installed. The second harvi clamp is pointing towards grid and I have the solar Icon on the myenegi App, waiting for when the electrician does the AC. Do I need a Solis CT clamp? I dont have a battery or hybrid inverter.

bunderoon · 30-04-2025 04:37PM

https://www.boards.ie/discussion/comment/123405052#Comment_123405052

Besides the RCBO being more expensive, I assume there is no harm in having it? It can protect the cable incase of a break if future owners go digging in years to come.

JohnySwan · 30-04-2025 06:15PM

https://www.boards.ie/discussion/comment/123405066#Comment_123405066

The Mcb would provide that protection. The Rcbo could cause a nuisance.

bunderoon · 30-04-2025 06:55PM

Fair enough, thanks. Mine being a 100mA shouldnt be, I guess.

JohnySwan · 30-04-2025 07:06PM

https://www.boards.ie/discussion/comment/123405531#Comment_123405531

Less likely than a 30ma but still could be. Why would you put one in if you don't require it?

bunderoon · 30-04-2025 09:16PM

Because I made the mistake of ordering all whats in the picture to ensure that the electrician stays and does the job. So hard to get one these days and especially with a diy solar sign off - NC6.

Did show him the job and it was fine. My only question mark was on the trip at the house CU.

bunderoon · 30-04-2025 09:32PM

As a matter of curiosity,

I assume it's this:

https://www.wesco.ie/products/abbnh0022-s202-b40-40a-2p-mcb-type-b-circuit-breakers.html?filter_set%5B%5D=299,305,307,1370

...Ghost... · 03-05-2025 08:33AM

https://www.boards.ie/discussion/comment/123406142#Comment_123406142

That'll do the job.

I had similar designs and mine is all done now about a month. My shed CU is just idle for now, as I opted to connect my second inverter direct to the main CU. The one mistake I made and will have corrected is that I used a spare 32A single pole MCB to supply the shed. While the shed will probably never see a load that will cause that breaker to trip, I'm going to replace with a double pole. Thankfully that particular breaker has space to the right of it, so it will be a 10 minute job next time the leccy man is in the area. I'm in no rush, because I don't need power to the shed right now anyway.

graememk · 03-05-2025 08:57AM

As far as I know the double pole mcbs are relatively new in Ireland, your single pole would be fine, if it's already wired up and done.

...Ghost... · 03-05-2025 10:43AM

https://www.boards.ie/discussion/comment/123413343#Comment_123413343

We need to add "buy me a beer" buttons here. You've just saved me a few more quid!

bunderoon · 03-05-2025 12:59PM

Thanksa million.

Will go and get a double pole MCB online for the House CU. Was in CT Electrics thismorning and they only had single poles.

Must create a DIY thread on my install when done.

JohnySwan · 03-05-2025 01:45PM

https://www.boards.ie/discussion/comment/123413864#Comment_123413864

No need for a double pole MCB, just make sure the sub board has a double pole isolator.

bunderoon · 03-05-2025 06:23PM

There is a double pole isolater going into the garage CU when it gets installed. I thought a double pole MCB was 'preferred' at house CU to isolate both live and neutral of the swa going to the garage.

JohnySwan · 03-05-2025 06:33PM

https://www.boards.ie/discussion/comment/123414741#Comment_123414741

It won't hurt anyway.

graememk · 03-05-2025 07:24PM

100ma is to counter act parasitic capacitance that can happen on solar.

Garage Consumer Unit Question - DIY Solar.

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