Running Power to a Garage

[BathSparks]

Hello fellow sparkys
The customer would like me to install A small 2 way CU in his garage. This is for him to use a few power tools, lights and possible an electric door motor. The Armoured cable run is about 25 metres. I am planning to put an RCBO in the house C.U. to protect to cable to the garage.
All's well so far. He showed me his House CU, a 12 way Hagar board with RCD protection on All circuits. A previous electrician had by-passed the RCD and told the customer it was faulty. This I intend to re-instate (with new RCD if necessary). There will be one way spare in the board after I remove an old cable (dodgy 1.5mm cable that went to garage for a light) to install the new circuit and RCBO

The question is this: Do I install the RCBO in the slot even though this is protected along with all other circuits by an RCD. The RCD at the garage end could cause "discrimination" problems between the two.

One solution would be to use a Henley block and split the tails to another main switch/RCBO and run the garage circuit from this. I cannot split the bus-bars in the old CU because there are not enough ways.

Another solution would be to try to persuade the customer to have a new 17th edition CU with all the benefits this brings. This, however tends to elicit the response "It has been working fine for the last xxxx yrs" Given that the Armoured cable will probably cost £60 or £70 + £50 for the garage mini CU, the cost is adding up.

Any helpful suggestions?

 

[malcolmsanford]

Why are you wanting to RCD protect the SWA is the earthing system TT.

Won't the customer get a bit peeved if in the middle of winter he trips the RCD in the house and have to walk those 25mts in the dark to reset it, or more to the point won't the wife watching Home and away be equally as peeved if he trips the RCD while Howard is getting it on with Madge

Seriously though I would not want the garage on the same RCD as the house, can you avoid this.

 

[Octopus]

IMHO You have 2 basic choics:

1. spilt the tails in a henley block, add an enclosure with MCB at garage end, then garage CU with RCD other end

or

2. Get the customer to agree to let you sort his board first, then fit a board at the garage (without a RCD)

Plus get a look at the bonding etc

Have fun

 

[cheeky_blue]

If you are going to replace the RCD in the Hager then why not stick a 32A MCB in that board as garage supply.
It will be already RCD protected so install Main SW, 20A MCB and 6A MCB other end in the garage CU?
Before you quote I'd make sure that the previous spark didn't bypass the RCD because there is a fault somewhere on one of the existing circuits.

 

[ian.settle1]

If the board already has a RCD and you want to fit a RCBO what discrimination will there be betwwen them?

 

[BathSparks]

Thanks for comments guys. The RCD in the Garage should not be able to trip the house supply so I reckon the only option is to split tails via Henley block and give the garage it's own supply. As this will be SWA 6mm cable, this can be protected by 32A MCB and the Garage has it's own CU for lights and sockets. Is this the best option given that He is not keen about replacing the CU. Yes cheeky_blue you are right about the RCD. This matter has to be cleared up first. I did ask the customer whether the tripping was related to any appliance use and I think a light came on (in his head of course). Again thanks for tips

 

[malcolmsanford]

Will you need to provide RCD protection for the SWA ?

 

[BathSparks]

If I split the tails with a Henley block and provide a mainswitch with 32A MCB at the house end and a garage/shed CU with one 20A and one 6A way protected by RCD in the garage I reckon that should do it. They also want one outside socket for garden appliances etc. So this method will not trip the house RCD

 

[BathSparks]

Well I was trying to avoid the possibility of tripping the house RCD as malcolmsanford

has pointed out. I think the Henley block solution solves the problem of dodgy garden/garage appliances tripping the house RCD.