garage consumer unit

[ceejay]

Is it necessary to install a garage consumer unit with an rcd if the feed is coming from an rcd protected main board? i don't think it is but want to make sure. It will be running a small ring and a lighting circuit.

 

[i=p/u]

no theres no need, but have seen it done few times.

 

[ceejay]

Thanks for the confirmation, so what size main switch would you put in it? 80A? Not sure they go smaller

 

[Johnny-G]

Definitely no need.
Chances are the RCD at the main board will have more leakage on it anyway so will trip before the garage one reaches it's threshold.

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The main switch isn't a fuse so the 'larger' the better.

 

[i=p/u]

well the switch is only for double pole isolation

 

[ceejay]

cant find anything smaller than 100A anyway, thanks Johnny.
I know i sound a little unsure, that's because i qualified 3 years ago but have not been an electrician for my main day job so i'm a little rusty and my mate has just bought a house that needs a fair bit of work

 

[ceejay]

1 last question on this subject, the feed is SWA so will a plastic MK garage 2 way 4 module consumer box be ok or should i use metal?

 

[Johnny-G]

Terminating SWA in to a plastic CU is a pain in the arse and metal CU's are expensive so a common workaround is terminating the SWA in to an adaptable/junction box and running T&E from there to the CU.
Wiska boxes are great for this as you can get a dedicated earth clamp for the SWA glands.

 

[Sav]

Hi Ceejay,

the way I would do a garage supply is
1/ Henley block and split the tails into say a 63 amp isolator (metal), so you have from the incoming supply to your meter and from your meter into a henley block. Tails to your isolator and tails to the house consumer unit.

2/ Make off your swa into the isolator (remember to earth the armour as well )

3/ the other end of the swa into your garage consumer unit. If its a plastic consumer unit, then I would put some plastic trunking, say 3" x 3" across the top of the consumer unit, use a hole saw to cut a 20mm (or whatever your swa is), make off the swa (again earth the armour as well ), then into your consumer unit. Main switch and then say RCBO's for lights and ring.

It seems long winded, but its not really that bad, also, if there is a problem with any circuit in the garage, it wont trip the RCD in the house consumer unit.

thats how I would do it (tin hat on) !!!!

Hope this is of some help,

Sav

 

[sparky-s-w]

i installed a ccu in a large garage unit, used an RCD although one at the main CCU, not a problem but the main RCD usualy trips first as more leakage, used this installation as part of my assesment, assor had no issues with the 2 RCD's
2= use 2 steel conduit through box each end to wire in the SWA and earth the armoured to that then to a plastic CCU, job done.

 

[Taylortwocities]

Terminating SWA in to a plastic CU is a pain in the arse and metal CU's are expensive so a common workaround is terminating the SWA in to an adaptable/junction box and running T&E from there to the CU.
Wiska boxes are great for this as you can get a dedicated earth clamp for the SWA glands.

I agree that WISKA boxes, with the SWA gizmo is a great solution.

No need to reterminate onto T&E though. Butt the WISKA box up to the plastic CU and, when you strip back the SWA, leave a good long length on the conductors. These then can be routed into the CU and terminated directly onto the MAIN SWITCH without needing another join.

You'll need to add an earth conductor, if you are only using 2-core SWA and have done your sums and the armour is being used as the earth.

 

[Strima]

Is it necessary to install a garage consumer unit with an rcd if the feed is coming from an rcd protected main board? i don't think it is but want to make sure. It will be running a small ring and a lighting circuit.

The only pain in the hoop with this method is if the RCD trips it's a trip back to the house and will take other circuits with it, depends on garage location and length of run etc.

 

[Octopus]

For what its worth, I'd use a metal CU for better protection, and mount the board a little higher up the wall than I would in a house.

Sector/Senate do a 2 way metal cu with 63A main switch for £28.80 + VAT so that's hardly expensive, especially as its quicker to install 1 item, than terminate the SWA into a metal enclosure etc, etc.

 

[AndyL]

not wishing to offend, but if you are not registered this is notifiable works ceejay

 

[ceejay]

not wishing to offend, but if you are not registered this is notifiable works ceejay

I realise this and whatever i carry out will be inspected by a qualified registered person