Garage earth

Last plumber · Oct 27, 2016

Good afternoon, I'm new here, as some know, I'm from the other side, ( plumbers forum ).
I've had a couple of different opinions on this from three very experienced electrical engineers.
I've read regs but curious on whether you agree and what you think is safest way of doing this or how you would do it if it were your own property.

Supply to garage runs from RCBO in house consumer unit through the house in twin and earth.
Supply is PME.
It changes to SWA before exiting the house and runs 20 meters up the garden to the garage.
The garage has a steel door.
The question is, is it safer to use the earthing from the SWA ( house earth) or is it safer to use an earth rod and separate earthing system.

Pete999 · Oct 27, 2016

Does your garage have any other services, gas, water etc? if so you need to consider a bonding conductor as well

Bobster · Oct 27, 2016

Any extraneous metal in the garage?

Perfectly fine using the armor as the earth if not.

Earth rod will not do any harm, but getting a resistance low enough (Ra) to be useful isn't particularly easy.

Barry White · Oct 27, 2016

It is safer to use the PME earth. The problem is if there are extraneous conductive parts in the garage (water or gas services usually) they require bonding back to the met with a 10mm csa or equivalent armourings may comply depending on cable size .
The steel door is not usually extraneous.

Last plumber · Oct 27, 2016

I did wonder about the door, if it's not classed as extraneous that's fine. Thank you.

There are no other extraneous parts at the moment.
I think in future ( and this is part of the five year plan as my mrs calls it, sarcastically), there may be a storage tank ( rainwater) with a pump housed inside the garage and an outside tap.

To be honest I was going to use the earth supplied from house. In my mind it was the safest way. It is supplied from an RCBO too so I didn't contemplate another way until a commercial spark said it was a no no !

Last plumber · Oct 27, 2016

If the pump and tap would create a head ache in future, it can be struck off the five year plan

Barry White · Oct 27, 2016

Last plumber said:
If the pump and tap would create a head ache in future, it can be struck off the five year plan

Dont you now use plastic? ??? plastic guttering plastic tank plastic pipes dont see how they could ever be a problem unless they LEAK

telectrix · Oct 27, 2016

mykey said:
Dont you now use plastic? ??? plastic guttering plastic tank plastic pipes dont see how they could ever be a problem unless they LEAK

he's a plumber. they're bound to leak.

Barry White · Oct 27, 2016

The word Plumber comes from the Latin PLUMBUM why it changed to Plumber i dont know as the original was more realistic !
Wont be long before they are known as plastic surgeons

Spoon · Oct 27, 2016

If you want to future proof your garage you could always add the following along with the power cable.

Ethernet cable.
Alarm cable.
Phone cable.
TV signal cable.

ruston · Oct 27, 2016

In your situation I too would go with the PME earthing . If you have to add a tank etc , do as Mykey says and use plastic. A nice sturdy narrow oil tank would suffice for that. The rest of non conductive plumbing stuff you will be well aware of.
As a matter of interest what were you recommended to do . Keep it clean

Last plumber · Oct 27, 2016

FYI , all of you !
I don't use plastic unless it's absolutely necessar. That's because it's crud !

You've all been very helpful, thank you. I knew however, that it would turn to this, pathetic immature behaviour !

There's enough on the other side. I thought over here I'd find intellectual conversation, alas ''twas not to be

ruston · Oct 27, 2016

Lol , I know what you mean about plastic, but you could relent on this occasion.
are you not going to tell us what you were advised regarding earthing?

Last plumber · Oct 27, 2016

ruston said:
In your situation I too would go with the PME earthing . If you have to add a tank etc , do as Mykey says and use plastic. A nice sturdy narrow oil tank would suffice for that. The rest of non conductive plumbing stuff you will be well aware of.
As a matter of interest what were you recommended to do . Keep it clean

I was recommended to:-
Terminate the SWA in a box ( plastic)
Continue through into another box with just L + N
Install an earth rod
Connect all earths in garage to that rod
Test the earth resistance through the ground.

I see the aim but I didn't think it was as safe as how I was going to do it

I know if you lost your incoming neutral you in effect have lost earth too in theory but how likely is that ?
Is it not more likely that your earth rod will be a poorer earth during the devastatingly long hot summers of Lancashire ?