Detached Garage

[Dazzol2009]

I have a customer with a detached garage about 10meters from his house, he wants an upgrade of his CU, so that he can give power to his garage, CU is not a problem, I was going to feed 10mm SWA cable 3Core to the garage, then install a 40A rcd garage cu with (a 40 mcb at the house cu), a 16a for sockets and 6a for lights, the only confusing part is, looked at different posts and they are suggesting you need a spike for a detached garage, the system he has got is pme, they suggest do not use house earth as there may be a difference in potential between the two propertys, any suggestions guys?

 

[kung]

Hi Dazzol2009
Does the garage have any extraneous conductive parts ?
You can export earth although i never do as rats etc can knaw through concrete,metal etc and if unlucky you could have no earth plus someone could add a metal structure without knowing what could happen i TT it and put a lable next to it saying if adding any ext/con/part bond it. lots of people will its a personal pref thing.
Regards
Kung.

 

[Guest123]

Hi.

A PME system can be exported provided that the either of the following 2 conditions are met

1. There are no extraneous conductive parts within the outbuilding i.e steel frame, water service, gas service etc.

2. If there are conductive parts, then the equipotential zone needs to be extended to the outbuilding via main equipotential bonding conductors sized accordingly i.e a minimum of 10mm2 for each service back to the MET within the house, unless the sub-main is greater than 10mm2 itself.


Personally if there are conductive parts within the outbuilding then I always TT regardless of sub-main size.

 

[electricAl]

Got a similiar job - need to run 5m of SWA to detached garage. TN-C-S, so good to see no extraneous conductive.

Strange thing tho`, all the wiring for 2 way switching & 2 pendants + FCU & double skt all clipped & ready to go!?

Except for leccy to it that is.

Customer says it was there when he moved in 4 years back (house advertised as having power in the garage)

Bit of a Mary Celeste. Like someone left in a hurry just before completion. Had me wondering for a minute - did they know something i don`t yet?

Anyhow, take the point about the possibility of rodents eating your earthing, but wouldn`t they far less likely chew thru SWA & cpc WITHOUT getting barbecued, than thru a 10mm2 earthing conductor to the rod?
Just my thoughts anyway.

Al

 

[kung]

Anyhow, take the point about the possibility of rodents eating your earthing, but wouldn`t they far less likely chew thru SWA & cpc WITHOUT getting barbecued, than thru a 10mm2 earthing conductor to the rod?
Just my thoughts anyway.

Al

Anything is possible and i did say if your unlucky didnt i ?

 

[electricAl]

Ah, but what i hadn`t taken into account of course, was the well documented aversion rats have of stripes - particularily green & yellow stripes.

You never see rats wearing either green nor yellow, letalone stripes do ya. Not even Roland. Even in the 80`s when everyone was permanently clad in something stripey.

Thats why SWA is so cool. The little varmits happily nibble right thru the XLPE & armour only to recoil in horror when they spot the CPC

 

[Dazzol2009]

Kevin had a stripey tank top i beleive?
On a serious note, are we all saying that if the customer has a pms system, the best bet is to install a spike and continue the bonding from the house.
The situation of the garage is the only metal part of the garage is the bracketry that connects the reenforced concrete which the property is made of to the roof supports which is wood.
I was going to run a 10mm SWA cable from the house cu to the garage, then fit a 40A rcd with 16 and 6 A mcb, then errect metal conduit around the garage itself.
As I only getting back into the domestic game recently after being commercial and industrial for over ten years, I am very keen to pick up on given regulations, so with that in mind, whatever the answer maybe, I would be grearful for the regulation in which these rules come under.
cheers guys

 

[stretchyboy]

if the customer has a pms system,

It depends what time of month though doesn't it?

 

[Spudnik]

You dont connect ANY earthing from the house.

You do however need to bond the SWA at the house end, but not connect it at the garage CU.

Then spike the garage CU keeping ITS earthing arrangements isolated from the house.

 

[electricAl]

Previous response makes it as clear as can be.

As to which Regulation, it`s more of a ESQCR thing for the DNO`s than a Wiring Reg.

The `brackets` you mention sound as if they may well be extraneous but if you want to you could evaluate their potential with a I R test (>22k ohms)

 

[MTI]

i agree with bonding armoured at its point of supply (cu in house) but please can someone tell me where it says a spike to be added to garage/seperate building cu? regs on site so cant look now

 

[Dazzol2009]

Sorry guys for making school boy error in calling PME system a PMS, did like the pun though, I just want to understand on how to provide the best service for a friend who has a detached garage, I understand that there may be an issue for different potentials as building are not connected, just wanted to see it written down in front of me, sorry if that is a problem with some people.