Earthing type

[silve]

Can someone advise on earthing type for the following:-

1950s house, supplier cable (old lead/paper) type - incoming earth to consumer unit attached to sheath on that cable. A second incoming earth to the gas pipe. Other earth bonds made on the other side of consumer unit to various pipes around the house.

Is this TN-S ?

 

[RF Lighting]

Sounds like it

 

[kai]

It should be Tn-S, but don't count on it, as properties like these have a reputation for an ineffective earth, due to the sheer age of the system!

 

[Taylortwocities]

PICTURES we need PICTURES

 

[silve]

Thanks for the clarification. I have a follow up question relating to running power to an external and separate garage, on a TN-S supply.

I have 3 core 6mm SWA terminated each end into 6mm t+e with an extra 6mm cable for earth to compensate for the thin earth in the t+e.

Plan to connect into the house CU on RCD protected side. At garage end will be a MCB also with (more discriminitive) RCD protection. Earth from house is connected through to garage (and to SWA armouring) and into garage MCB.

Is this sufficient earthing? Do I need an earth rod at the garage end (bearing in mind this is TN-S supply and I guess connecting out of zone as garage about 30m away as separate building).

 

[Spark123]

Are there any extraneous conductive parts in the garage such as metalic water pipes, gas, metal structure?
I take it you are aware this work is notifiable under part p of the building regs?

 

[silve]

Pictures hot off the press!

Untitled

• silve
• 1 Jul 2010
• 2

@spark123: No pipework, metalwork etc. only the metal up and over door at opposite end of garage. Yes I'm aware thanks.

So, to rod or not?

 

[RF Lighting]

It's a TN-S. The connection to the sheath doesn't look the best. I'd like to have seen a crimped lug used for that connection.

You are fine to export the earth to the garage, and do not need to install an earth rod.

Personally I'd leave the supply off RCD if possible, and just have a local RCD in the garage for the sockets, assuming none of the wiring will be concealed wihin the wall fabbric.

 

[silve]

Thanks all

 

[spark1]

Your Main Bonding appears to be connected to the incoming side of the Gas meter is that right ?...if so it needs to be on the other side.
It also looks a bit undersized.

 

[silve]

At first glance I thought this too. However the gas incoming is on the left. It comes along a fairly long pipe running out of shot horizontaly beneath the CU, where the shut-off is also located. The righthand side with the earth bonding on it exits the meter and goes back under the concrete to the boiler.

As for the earth cable size I will check it out and report back.
[Follow-up: both are 10mm]

 

[Guitarguy]

We at the DNO just to be confusing call that earthing type SNE (seperate neutral earth) or lead sheath earthing. Like other's have said I wouldn't trust the earth on it though due to the Cable network/joints being the best part of 60 years old! Chances are it will still be ok but it's just as likely that it's not. Without the Loop impedance being tested, you won't know!

 

[LoveRocket]

You HAVE to ask the DNO. Only they can tell you what the earthing arrangement is on that supply.

You can NOT make even an educated guess purely by looking at the incomer.