Garage Power Supply

[GarethSticky]

Im planning on running in a supply to my garage (brick building no exposed metal work). I plan to have a few sockets, lights and a couple of outdoor lights. At most I’ll be running a lawn mower or some small hand held tools.

In my meter box there is already a 100A double pole breaker installed just after the meter. I was planning on installing 2 single pole Henley blocks after the braeker to split the tails with one set going to my exisiting consumer unit in the house and the second set going to the new consumer unit in the garage. The garage supply will be via a 4mm or 6mm swa cable and the run is approximately 30m. In terms of protection for the swa I was wondering what is the best way of doing it? MCB just after the Henley blocks? Also the Henley blocks, MCB and cabling will be in the meter box, is this going to cause issues with the supplier? Is there a better way of doing it?

At the garage end I will be installing a MK Sentry Consumer Unit (40A 30mA DP RCD. 1 x 6A, 1 x 16A MCB).

Thanks,
Gareth

 

[bongos]

Have you got a spare non-RCD protected way in your existing CU? This would be the easiest way to supply your submain. Use a suitable box butted next to the CU to terminate the SWA.

If you haven't then you will probably have to use a suitably rated MCB in an enclosure. But if you do this there should still be a single point of isolation which would then involve adding a switchfuse at the front of your intsall, to isolate both the garage supply and the house CU.

That's why the first option is easiest.

Also see this.

 

[ban-all-sheds]

Have you got a spare non-RCD protected way in your existing CU? This would be the easiest way to supply your submain. Use a suitable box butted next to the CU to terminate the SWA.

I would say definitely go for the idea of splitting the tails, into a switchfuse, SWA to the garage FCU.

And use 10mm² SWA - cost difference is minimal, and you don't want to ever dig that trench again.

Do you know how the trench should be prepared?

What tests will you carry out on the sub-main cable and garage circuits, and how?

But if you do this there should still be a single point of isolation which would then involve adding a switchfuse at the front of your intsall, to isolate both the garage supply and the house CU.

That's why the first option is easiest.

In my meter box there is already a 100A double pole breaker installed just after the meter.

 

[GarethSticky]

Bongos, Its a brand new house. Theres plenty of spare ways in the existing consumer unit but I dont want to be lifting floor boards or cutting into new walls etc.

I was assuming the exisitng 100A breaker was suitable for my isolation point.

Ban-all-sheds, I can get the 4mm or 6mm for free, I just as well go for the 6mm. I wont be digging a trench as i'll have to cross a patio and tarmac drive. I'll be clipping the cable to the underside of the cross beams of my wooden fence. Its approx 18 inches off the ground.

Is the mcb in a suitable enclosure within the meter box not an option? The switchfuses looks quite bulky and would require a separate enclosure next to the meter box? Is it ok to install the henley blocks or any other equipment in the meter box?

Ive not looked into testing just seeing what my options are for installation. I guess if I do the work myself I'll have trouble getting a part p approved spark to test and sign it off?

Cheers
Gareth

 

[1john]

you need an enclosure with the ability to gland off the SWA and preferabally a double pole isolator for the garage feed cable, that way it can be safely isolated and the house still be intact. henly blocks seem to be ok in the meter cupboard but the DNO tend not to like you installing other things in there, although i have never heard of anyone having to remove anything thats been put in there and myself have put things in the meter cupboard before.

you need to notify the LABC of your intended work and see what they require you to do and what they will do in regards to inspecting and testing of it, or find an electrician who is happy for you to do the donkey work and connect it up and test it.

 

[ban-all-sheds]

I was assuming the exisitng 100A breaker was suitable for my isolation point.

Are you sure it's a breaker, and not a switch?

It's double pole, and it sits between the meter and the house CU?

I'll be clipping the cable to the underside of the cross beams of my wooden fence. Its approx 18 inches off the ground.

How do you get across a drive 18" off the ground?

And generally people don't like clipping cables to wooden fences - you may find that your BCO or an electrician who does the inspection won't accept it.

Is the mcb in a suitable enclosure within the meter box not an option?

Use a double-pole one.

I guess if I do the work myself I'll have trouble getting a part p approved spark to test and sign it off?

Without his prior involvement, and agreement over what you can do under his supervision and direction you'll probably find it impossible.

 

[GarethSticky]

Had a quick look this morning it is a 100A 3 TP isolator not a breaker. Only using the 2 poles.

The cable run is easier to explian if seen. Im avoiding the drive / patio by going via the fence. Having said that the trench could be dug through the lawn but im choosing not to.

I will have to look into how informing the LABC works. How do they know what I have done if I dont tell them? Does the guy reading the meter look at anything other than the meter? The truth is if I run the swa from my exisitng consumer unit no one would be any the wiser. Obviously if the garage was being built it would need to be signed off but there'll be no one checking in my case?

Spoke to my brother in law who had a supply run to his garage last year. A 'qualified' spark ran a swa cable from a spare way in the old fuse board to a new consumer unit in the garage. I asked him did he do any testing and his reply was "he turned the lights on they worked and plugged the lawnmower in and that worked - job done!" Im not saying that makes it ok but it must go on all the time.

 

[Chri5]

It's liking saying that people get mugged all the time. That doesn't make it right.

Yes people will work outside the rules and regulations. Those regulations are designed for the safety of you the client, his family and property.

If you stay where you are it could be that no one would ever know, when you move as part of the process a survey is done and you also have to complete a form which always asks "have you had any electrical work done"- if you say no then you'd be lying, if you say yes then you have to support major works such as yours with certificates.

If you go down the route of LABC notification then there's a minimum fee, which scales up on job values.

Fences are considered temporary structures and as such it's a bit 'iffy' fixing SWA to it. Consider wind blowing the fence down and what might happen to a live cable straining against the forces of nature.

Most components do have manufactures date stamps and the cable colour code will indicate a fit date post 2004.

Call in a spark, talk to him about what you plan and see if he is prepared to allow you to supply, run and fix components of the job. You might find someone who would terminate and test a 1st fix as long as the work you have done is visible, and is done to the requirements of BS7671.

Half a day for an electrician, £150 or so to the LABC or hide the job ?

 

[1john]

half day at £150, sadly not around here anymore, much less.