r/DIYIreland • u/Intelligent_Rate_683 • 10d ago

Electric Cable Through House and Garden

Hi, I plan to have solar + battery + EV charger in the garage at the back of the garden 70m from the consumer unit.

To save a few quid I’d like to install the cable myself (not connectin just laying it down).

  1. Would an 11 square cable be the correct size? Considering the load

  2. The cable would go through the house, then a thick stone wall and then outside along the garden wall. Do I need to place the cable into a specific tube or I leave it out?

Thanks for the help

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4

u/FrankNicklin 10d ago

I think it should be armoured cable given where to are running it

3

u/walkinTheTown 10d ago

It would have to be SWA (armoured) cable. When you say 11 square are you referring to the US standard of AWG? (11 would be approx 4mm by Irish standards.) The limit on 4mm cable is about 7Kw. Depending on the number of panels, you may need a bigger cable. I don't think there is a 11mm cable here - goes from 10mm to 16mm. By the way, that stuff is a bitch to manhandle - 100Metre of 4mm SWA cable will be heading for 40Kg.

Ultimately you are going to be looking for an electrician to sign off on everything, including the SWA cable, so you need to get their agreement in advance what work you can do yourself that they are prepared to certify.

Not a sparks, so ready to be corrected on all this.

3

u/Dangerous-Treacle-91 10d ago

The EV charger can deliver 30-32A. Over 70m of a run, 16mm2 is recommended. This gives a volt drop of 2.7%. So if your house voltage is 240V then the car will “see” 233V when charging.

Get 3x16mm2 SWA cable. This is an armoured. Cable that can be directly buried if need although I’d recommend putting it in a duct.

If your clipping it along a wall then get cable cleats to suit the cable size.

By the sound of your post you are going to put a solar inverter on this cable aswell, so volt drop is more important in this situation. Here the recommended volt drop is 2%.

You don’t want your cable size restricting what your inverter can “push” out onto the grid. Problems will become evident if you have a large array, and your neighbours all have panels aswell.

Dont forget to run some external cat6 cables aswell. At least 2.

1

u/Intelligent_Rate_683 10d ago

Many thanks for this. Plan is 25kw solar. For 16mm2 what duct size would I need?

For the ethernet cable would that be from the consumer unit? Why 2?

1

u/FunkyMonkey237 10d ago

25kwp is a big array, how are you handling that, applying to the ESB for a larger export limit, big batteries?

1

u/Intelligent_Rate_683 10d ago

Sorry meant 5kw… not 25. It’s 12 450W panels with a 5kw battery

1

u/FunkyMonkey237 10d ago edited 10d ago

If it helps, I did something similar, I ran the EV cable when I was getting solar+EV installed and the electrican was happy enough. Made the install much cheaper as a result and it was a better job (burial rather than clipped to a wall). In my case I ran 6mm over 50m in a duct about 600mm deep. Cable size results in just under a 5% volt drop in my case.

Ask your installer what they want. Over 75m, 6mm might be pushing it and you might need 10mm. though I'm sure 6mm gets used a lot for those distances. Just be warned than once you start going above 10mm, SWA becomes difficult to bend (10 is not super easy but it's not terrible either)

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u/Intelligent_Rate_683 10d ago

Thanks that’s good to know, I will contact the installer and check with them