Electric For New Shed

[cono]

Hi Big Spark

I am having power taken to my shed. It is 24 metres from the house consumer unit, which is located in the garage. I have dug the duct to 750mm and laid in 10mm 3 core armoured cable, placed suitable protection and laid warning tape. I understand (I apologise if I have misunderstood) that if the building earth is taken to the shed then an earthing rod will not be required. I am having a professional electrician do the installation who is qualified etc to issue the Part P certification. He will not be doing this to sometime in January as very busy at the moment. I am very cautious where electric is concerned and it would seem a great idea to take the building earth to the shed (prior to this I assumed that an earthing rod would be required), however, can the existing building earth be checked to ensure it is OK? I have looked in the garage and can see that there are earth wires going from the meter housing to the consumer box and the gas meter pipe. The electrician will be popping in to see me sometime so I know I can ask him then, but just wish to set my mind at rest.

Cheers Con

 

[Steve]

what sort of earth do you have? can you take a picture of the meter box?

 

[cono]

Hi Crafty

No don't have a digital camera or scanner. I have looked in the meter housing, there are four earth wires approx 5mm in diameter coming from a unit which has on the face of it the following: WARNING Protective Multiple Earthed Installation, Do not interfere. 1 of the earth wires goes to a timer unit (I have economy 7 meter), 1 to gas meter pipe, 2 to consumer unit. Does this help?

Cheers Con

 

[Steve]

protective multiple earth is shortened to PME, a type of earthing which involves connecting the main earth in your property to the main neutral terminal in the service head. The neutral is then grounded at every opportunity back to the substation.

The box that these 4 earths come out of - does it have an 80 or 100A fuse on it (stuck out a bit) with metal seals wrapped round it, with the main 'lectric cable coming into the bottom of it, and 2 thick grey or red and black cables comeing from the top? If so, it is PME and this box is the service head, normally grey or black.

It has been known for installations to be labelled as PME, but the supplier or electrician "forgets" to connect the main earth to the service head.

timer units dont normally have earth terminals, of the ones i've seen. i'm thinking the "timer unit" is actually the service head.

 

[cono]

Hi Crafty

Yes. The rating states 60/80 A 415 volts. To the left of this is a safeclip with seal (appears to be 32A) with a cable going from this in to the top of the service head and a cable coming from the bottom of the safeclip to the time clock (this has a 24 timer) and a cable goes from the timer to the meter which has a low and normal readout (economy 7).

Cheers Con

 

[sam8364]

I have been down this route - electrics to the shed, very long garden etc.

You need to get part p as it is external work - this means using someone registered or notifying council and getting it inspected.

To give you some idea of costs.....we needed an additional consumer unit, cabling through house and down 100ft of garden, 3x double sockets and 2 x bulkhead lights.

I dug the filled the trench myself - get a specialist trench digging / cable laying spade as it maked life easier.

I had quotes ranging from £500 to £1000. Got an excellent job done for £500 in the end. Took a bloody age to get the quotes in and book someone to do the job but worth it in the end.

 

[cono]

Hi Sam
I think perhaps you have misunderstood my post.
I am getting in an electrician to do the installation who is qualified to test and issue certification to Part P, see previous page. The question that I was asking is whether you can take the building earth to the shed thus avoiding the need for an earth rod. Basically I have done all the labouring, i.e. dug the trench and laid 3 core 10mm cable to Part P. Also installing 10 double metal clad socket outlets (not wired up) in the position that I want them to be for ease of working and placing 4 x 6ft flourescent low energy lights (I got these free from where I worked when all the existing lights were replaced as planned maintenance-so was quiet lucky) where I want them (again not wired up), the consumer box will also be placed in the best location for my use. As to cost, the estimate I have been given is 240.00 plus the dreaded VAT this also includes replacing the existing house consumer unit (which has rewireable fuseways) with a split load one, (the cost of this consumer box is not included in the price of materials below) to this must be added the cost of my materials, circa 300.00 which I obtained at trade price, all materials I have used are top quality, I could have done it cheaper by using lower quality materials. Yes I know that they comply with relevant standards but I guess that is what personal choice is all about.

Cheers Con

 

[Taylortwocities]

Your chosen sparky will advise you on the earth rod. There are a number of factors involved like: whats in the shed (waterpipes , other exraneous conductive parts), is the earth fault lop impedance low enough, etc etc.

If you want to read it there's a nice article at http://www.iee.org/Publish/WireRegs...matters_electrical_installations_outdoors.pdf

TTC

 

[cono]

Hi TTC

Thanks for that link. I am interested in how and why it is necessary to adopt certain procedures for an installation. Although I'm getting a professional electrician to do the work (hopefully sometime in January) it is still educational to get other peoples views.

Cheers Con