Garage Consumer Unit Supply

[Claudio]

Guys,

Do these units needs to be hooked up to the supply of the main consumer unit or an MCB or can it just take a feed from the cable effectively coming staight from the meter? (instructions are lost)

Also, what are the implications of this garage consumer unit being under the stairs feeding the SWA cable in the garden as opposed to being located in the garage itself? Obviously it is more convenient to locate it in the garage incase it trips. (My garage is as the bottom of the garden).

My existing set-up has two SWA cables (lights + Power) feeding the garage with the consumer unit under the stairs. I wanted to spread the load over two cables because I had the spare SWA cable anyway.

Cheers
Claudio

 

[electronicsuk]

Do these units needs to be hooked up to the supply of the main consumer unit or an MCB or can it just take a feed from the cable effectively coming staight from the meter? (instructions are lost)

That would depend whether the CU you speak of has both DP isolation and overcurrent protection. You certainly can't joint the meter tails straight into your cable without overcurrent protection. I'm worried that you think you need the instructions, and this is probably why nobody else has replied to this topic!

Also, what are the implications of this garage consumer unit being under the stairs feeding the SWA cable in the garden as opposed to being located in the garage itself? Obviously it is more convenient to locate it in the garage incase it trips. (My garage is as the bottom of the garden).

Surely locating the garage CU under away from the garage defeats the object of the game. Doing so means you have two runs of SWA, which you then also have to terminate seperately at the garage and then move onto T+E or whatever you've wired your lights and sockets in. You'd be better glanding the two SWA cables into a split load board which also feeds the rest of the house, or better still feeding the garage down a single length of armoured from an MCB on the non-RCD side of your main CU and then locating the garage CU in the garage itself.

Seriously advise you get an electrician in to look at the job.

 

[Claudio]

Thanks for the note. That makes sense. I'm not an electrician - I'm the wrong type of engineer

My main CU is out of capacity and the main motivation for the Garage CU was to add the needed capacity. I guess I saw the "Garage" consumer unit and made too hasty a purchase.

I think I should bite the bullet and get a new modern primary split load CU that is big enough to handle circuits I need including an MCB for the garage circuit. The existing CU is an old one with (I think) replacement plug-in MCBs subbed in for the old fuses. So at least I would get some RCD protection for the house.

I suppose that would also free up one of my SWA cables and I could use that for Garden lighting.

Question:
With a standard garage CU with a 40A RCCB and 16A and 6A circuits, should I use something like a 50A MCB supply?

Cheers,
Claudio

 

[electronicsuk]

Question:
With a standard garage CU with a 40A RCCB and 16A and 6A circuits, should I use something like a 50A MCB supply?

No. The RCCB in a garage CU protects the entire unit, and protecting the supply with an MCB of rating >40A would potentially allow the RCCB to be overloaded. A protective device rated at 40A or less must be used, but the exact rating will depend on the cable type, size, length, method of installation, etc.