Running new cable to supply garage from sub-board

[kmulcahy1994]

Hi guys. I have recently come across a N-E fault on the garage supply. the cable that was used is a 2-core SWA 6mm. However due to the house it is not possible to run a new cable to the garage. However there is a sub-board upstairs which is fed off a 40A MCB from the main lighting board, non rcd-protected. The sub board has a 100A main switch with a 63A rcd which protects 3 circuits. x2 rings and a lighting circuit. I was thinking of running the new garage supply from this board? Is this allowed? The run is about 15M and will be clipped direct. The garage runs a hot tub protected by a B32A MCB, a 16A radial and a 6A lighting circuit. I was thinking of running 6mm 3-core SWA to supply the garage. Which will be protected by a type b 32A mcb from the upstairs sub board. Just need confirmation please. Thanks.

 

[telectrix]

OMG another get it working without spending necessary.

 

[westward10]

Well you have no discrimination between the two 32As but you wouldn't have it anyway with mcbs protecting mcbs.

 

[Des 56]

You can run your new supply to the garage from wherever it takes your fancy
Before you decide from what location, you need to assess the existing cable size,the protection it affords, the present load and whether it has the capacity to cope with the calculated additional load and the earthing requirements and protection of that load

These questions are often encountered by electricians who have trained to obtain the skill to adequately answer so that the installation is safe for the user

There are people who just add cables to connections points and get things working, safety is not considered and/or mostly understood,but there are people who seek help or advise from those with the training to assess these installations
Shoving loads on systems willy nilli is not recommended

 

[westward10]

Don't cross Des today

 

[buzzlightyear]

The garage runs a hot tub protected by a B32A MCB, a 16A radial and a 6A lighting circuit. I was thinking of running 6mm 3-core SWA to supply the garage. Which will be protected by a type b 32A mcb from the upstairs sub board.

However there is a sub-board upstairs which is fed off a 40A MCB from the main lighting board, non rcd-protected. The sub board has a 100A main switch with a 63A rcd which protects 3 circuits. x2 rings and a lighting

over load if done !

 

[kmulcahy1994]

Well currently the cable that supplys the garage is a 2-core and they have used the sheath as the earth. It then goes into a 2-way garage unit. The hot tub people have linked a bit of 6mm from the main switch into there rcd unit to supply the hot tub. Will probaly install a 4-way board when i run the new supply cable to the garage.

 

[buzzlightyear]

delete

 

[kmulcahy1994]

???

 

[buzzlightyear]

N-E fault on the garage supply. the cable that was used is a 2-core SWA 6mm.

garage is a 2-core and they have used the sheath as the earth.

if it is twin and using the swa earth
then is fine ,but it confusing to say.

The hot tub people have linked a bit of 6mm from the main switch into there rcd unit to supply the hot tub.

 

[kmulcahy1994]

My description is confusion i apologies. The sub main is supplied from a 40A McB using 10mm T+E. It has a ring circuit and a lighting circuit. So if i were to calculate total load of them circuits + the total load of the circuits for the garage, aslong as thats under 40A it should be fine? My question is can you run a sub main off another submain?

 

[buzzlightyear]

there is a loading factor for the amount that is used the sub main 40amp
by adding extra load on it will not be wise .

 

[Wilko]

Outside power to a hot tub, where already an SWA cable has failed ... hmmm, isn't this something you'd like to have an expert look at? What type of earthing system do you have, how will you handle bonding? Not to mention this work requires building approval, for very sound safety reasons in this case.

 

[kmulcahy1994]

The swa for the hot tub supply hasent failed. Its the swa that supplys the garage fuse board tripped out the main rccb due to a neutral-earth fault. Its an old cable and it probaly has deterioated over years thats why there is a fault on it. So now i need to replace the cable, however the route it takes is covered by expensive hard flooring and routes under the house and paving slabs. Therefore an easier route to take would be off the sub-board upstairs, however that is supplied from a 40A MCB. The system is TN-S.

 

[buzzlightyear]

are you a qualified spark!

 

[kmulcahy1994]

Yes. However the advice I am receiving is not clear at all, very hard to understand.

 

[buzzlightyear]

we on this forum can not do the job for you ,we can( only advise .)
having you read all the posts it is down to you how you do the job.
but if I was you, which I'm not I would put a new feed to the garage
and tell your customer .

 

[kmulcahy1994]

Thats fair enough. Ive only been qualified for a year, so im still gaining experience and learning new things every day. Thats why i posted this just for advice, I just wanted to know if what i proposed to do was safe and complys with regs.

 

[kmulcahy1994]

I do appreciate everyones advice.

 

[buzzlightyear]

Thats fair enough. Ive only been qualified for a year, so im still gaining experience and learning new things every day.

you must crawl before you can walk you need somebody to
advise you on the job.