New garage supply

[Martin606]

Hi
I am wishing to get power to my garage. I live in a terraced new build house and the garage is about 20m away from the house but the cable run will need to be about 60m. I will be installing a 40A 2 way distribution board to provide lighting and socket outlets.
I have calculated that I will need to use 10mm cable to allow for volt drop due to the length of the cable run.
Can someone please assist with the following queries.
The house DB is at the front of the house so I will need to take a feed from a spare gang on this through the first floor to the rear garden.
I believe the correct way would be to run SWA in a trench to the garage.
1. Is it ok to run normal 10mm cable internally and convert to SWA on the wall outside?
2. As an alternative is it ok to run 10mm cable in conduit on the fence line?
3. As another alternative, is it ok to run 10mm cable from a socket outlet as a spur at the rear of the house rather than from the house distribution board?
4. Is it even possible or allowable to spur off a socket outlet to get power to the garage?
Thanks.

 

[Pete999]

Are you an Electrician, do you have any electrical experience? your first two questions, are easy to answer yes the SWA should be installed in a trench, and it is OK to run 10mm twin and cpc in the house and change to SWA in an appropriate IP rated enclosure, I say yes, to the 10mm but how have you arrived at this size of cable?

I don't like the idea of running anything along the fence line.

Assuming the Ring Final Circuit you intend to spur from is wired in 2.5mm cable it would be pointless running the supply to your Garage in 10mm cable, that would be for both question 3 and 4.

The next things to take into consideration is what is the Earthing system in your house? will there be any other services in your Garage water, gas, oil etc because if there is you will need to consider bonding these services, hence you may have to run a separate bonding conductor, assuming of course, the Steele wire used as armoring isn't big enough to act as a main earth conductor and a bonding conductor.

 

[Martin606]

Hi Pete
Thanks for your reply.
I have arrived at the cable size as follows
Max load X cable length X volt drop per metre/1000
40a X 60 X 4.4/1000
This gives volt drop of 10.56V which is within the accepted volt drop of 5%(11.5V)
I arrived at the cable size of 10mm by assuming max load at the garage DB OF 40A.
Is this correct?
Am I right in my assumption that it is correct to use 10mm in a trench rather than the fence line?
Am I also right to assume that it is not acceptable to spur off the final ring circuit in these circumstances.
Thanks
Martin

 

[Andy78]

As Pete says, are you an electrician ?

 

[westward10]

If you spur from the ring final you will have to fit a 13A fuse connection unit which restricts you to 13A, this would probably be adequate with a lighting and socket radial in the garage.
The other way I would definitely trench the cable, why 60m if garage is 20m from the house.

 

[Martin606]

The house is a mid terrace and the garage is in a block 20m away.
The cable would need to be run around the garden and down a path to prevent it going across the neighbours garden hence the run would be 60m. Hence I came to the 10mm sizing

 

[Wilko]

Hi Martin - just checking, but when you say 'down a path' is this piece of land on your title? (A shared path may not be yours to dig up for example).

 

[Octopus]

No he's not a spark.

Tin hat on

 

[westward10]

If that is a council path I would be scrapping this idea right now.

 

[Octopus]

If it goes over any 3rd party property you will need to investigate this with all legal avenues covered.

And it falls under part P too!

 

[Pete999]

Hi Pete
Thanks for your reply.
I have arrived at the cable size as follows
Max load X cable length X volt drop per metre/1000
40a X 60 X 4.4/1000
This gives volt drop of 10.56V which is within the accepted volt drop of 5%(11.5V)
I arrived at the cable size of 10mm by assuming max load at the garage DB OF 40A.
Is this correct?
Am I right in my assumption that it is correct to use 10mm in a trench rather than the fence line?
Am I also right to assume that it is not acceptable to spur off the final ring circuit in these circumstances.
Thanks
Martin

You don't appear to have used any correction factors in your cable calcs..

 

[Martin606]

I am aware of part P and am aware that it would need to be my land. Not that much of a tin hat thanks Murdock.
A little more help than criticism would have been nice after all this is a forum for assistance?

 

[telectrix]

another ting to bear in mind as regards cost and ease of installation is.... depending on the load, you could possibly run 10mm T/E through the house into an adaptable box at the back of the house, then reduce the cable size for SWA, caclulating VD on the 10mm then on the SWA. OCPD selected to suit the SWA, of course.just a thought.

 

[Octopus]

I am aware of part P
A little more help than criticism would have been nice after all this is a forum for assistance?

For fellow sparks yes...??? And I've not criticised you

 

[Spoon]

I am aware of part P and am aware that it would need to be my land. Not that much of a tin hat thanks Murdock.
A little more help than criticism would have been nice after all this is a forum for assistance?

We do help on this forum. It also helps if you answer our questions. You didn't like to answer the one about of you are an electrician.
The reply to this can help us tailor our replies so that they are suitable to the OP.
You might be someone who knows nothing about new circuits, testing and proper installation and just reads bits on the web.

 

[telectrix]

talking about the web. here's one i took earlier.

View attachment 35162

 

[westward10]

Don't you do any housework.

 

[westward10]

So is this path your land.

 

[telectrix]

Don't you do any housework.

i got 'er indoors for that.

 

[DPG]

Bead in mind the volt drop figure for lighting. Daz