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Domestic Supply to garage

Discuss Supply to garage in the Electrical Forum area at ElectriciansForums.net

J

jimlin

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I've inherited a mess that needs sorting. It's a supply to a garage. At the moment it looks like this:
Company Fuse into house is 60 A
Tails to CU are 16mm
Earthing is TN-S
Supply comes into the house on the ground floor by the the front door.
To get the supply to the garage, somebody has put 10mm T+E cable into the consumer unit with a 32A MCB
This cable goes into the roof space, is laid unsecured on the rafters and runs to the back of the house.
The cable exits the house by being shoved through a gap in the eaves, drops into the back garden, runs in small bore drainage bike to the bottom of the garden, under a narrow lane (buried to 50cm) and then into an ancient 4 way consumer unit in the garage.
It looks lethal. I've disconnected it.
This is what I propose to do:
  1. Ask the DNO to upgrade the company fuse to 100A, upgrading the supply cable if necessary
  2. Fit an 80A switch fuse
  3. Connect this to the supply using 16mm tails
  4. Run 16mm swa three core cable from the switch fuse as per the existing route but support it every 600mm with cleats and raise it off the floor in the roof space so that it is attached to the brickwork.
  5. Clip the cable with cleats every 600mmin a clearly visible position to the robust fence which runs the length of the garden.
  6. Take it under the lane at a depth of 1m
  7. Take in into a new CU at the garage end
  8. Earth at either end using the earth conductor.
  9. Replace all the cabling and accessories in the garage on the basis that if the feed out there is that bad, then the rest is going to be quite poor too.

All comments and suggestions gratefully received.

Thanks.

Jim
 
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AndyL

-
Arms
16mm seems very big for a garage, what loads are you expecting there, also 500mm is deep enough in most cases for SWA cable, 600 at most, 1000mm alot of unnecessary work
 
E

Engineer54

  • Thread Starter Thread Starter
  • #4
You haven't given us the most important parts of your design ... Distance from house CU to the garage CU, (in terms of actual cable length)?? Or what your intending to supply in this remote garage??
 
Last edited by a moderator:
E

Engineer54

  • Thread Starter Thread Starter
  • #6
We'll maybe never know, ...he's just disappeared!! lol!!! Which is typical just lately, ....ask a question and ...Gone!!
 
J

jimlin

  • Thread Starter Thread Starter
  • #9
Lets hope excavating that extra dep trench,it hasn't collapsed and buried him
Nope, it's not a weed farm but it will be running a kiln, a compressor and a TIG welder (not all at once.

Thanks for the advice on the trench. That's saved me a load of back ache.

Cable length in total is 60 metres assuming I still run it through the roof space.

Thanks for all the information.

- - - Updated - - -
 
Last edited by a moderator:
If all the factors are correct, including the 60amps, then Ive worked it out at 16mm cable, with10.44 vd at full load which equates to 4.54%.

I used 60 Amps, with 60mtrs, reference method C, with a BS 60898, type B ambient temp of 25c.

I hope Ive done this right........
 

Strima

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Arms
Esteemed
If you split the circuit down on your calcs you may come out a bit better off i.e T&E from CU to adaptable box the SWA to garage. The SWA would be at a lower ambient temp than the T&E so you may be able to drop a cable size or two and save a few quid.
 
J

jimlin

  • Thread Starter Thread Starter
  • #14
Yes, that's what I came up with too although I cheated and used the AEI cable calculator.
 
J

jimlin

  • Thread Starter Thread Starter
  • #15
If you split the circuit down on your calcs you may come out a bit better off i.e T&E from CU to adaptable box the SWA to garage. The SWA would be at a lower ambient temp than the T&E so you may be able to drop a cable size or two and save a few quid.
Thanks Strima, it's worth a look.

Thanks to everyone here too. It's my first post on this forum and the responses have been very helpful.
 
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