wiring up electrickery to new garage

[Jon Nicoll]

Hi there we've just got a new concrete garage built - 40sqm, situated about

10m from the house and around 15m from our consumer unit.

I would like to run mains to this garage, to supply lighting and light power. I only intend this to be for 'domestic DIY' power, no plant machinery or anything like that.

I'm competent in actually doing the wiring but a little rusty on modern practice. My plan #1 is to run a new circuit of 4mm 3core armoured cable to the garage, then fit a 2-way consumer unit and run lighting and power off that.

Quick question - is this feasible/sensible? & if not, can anyone suggest a better alternative?

Thanks for any suggestions Jon N

[Mike Harrison]

Sounds reasonable - It would be a good idea to fit an RCD on the garage socket supply (not the lights - you don't want them going out when you jigsaw through the cable..!). Garage supply should have its own MCB in the main house CU

[BigWallop]

socket supply (not the

If you can make it sub-main supply from the house with its own switch gear, then you'll stop any nuisance tripping of the circuits in the house.

It is easily done with use of Henley blocks (16mm Terminal block) to split the tails from your meter to another single way consumer unit dedicated to the garage supply.

I would also advise you, if using an RCD, to make a separate earth point from the consumer unit in the garage and on to a ground spike at the garage end of the new supply.

[BillR]

I did this and used one of those garage consumer units as sold by the likes of Screwfix. Now you mention it the lights are fed from the RCD as well as the power....

[Christian McArdle]

A quick check shows that 4mm should be fine for a 32A radial with cable length of 20m. This should be run off a separate MCB at the consumer unit. Probably best on the non-RCD side.

You need to decide on earthing arrangements. A TT might be suggested in these circumstances as it is really a separate building far from the house. This requires you to isolate the earth on the cable at the garage end. Then use a whole garage RCD and an earth rod.

Best is a 100mA Type S for the entire supply and a further 30mA immediate on the socket circuits. However, you might not bother and just use a 30mA immediate for the entire lot. Obviously, this cheaper option would mean you lose lighting when the power trips.

Christian.

[Jon Nicoll]

Hi Gents Thanks for all your suggestions - very useful. I meant to suggest an RCD, and was wondering about using a separate earth, so your replies are spot on for me.

Thanks again Jon N

[Mark Atherton]