Earthing Issue

[DDAS]

Hi Folks

My Sister just bought a house and it needs loads of work doing to it, new roof, windows, plumbing, central heating, rewire and so. Its one job at a time as she needs to save for each one and it’s a matter of prioritising. Windows and central heating are her first priority as it will soon be winter.
Anyway, as I said it does need a rewire but it will have to wait its turn. In the meantime I am not convinced that she has an adequate earth for the house at the moment. Most of the pipe work is lead and I think the original earth was via the water supply pipe however the water supply to the house was changed last year to the new plastic blue stuff thus removing the grounding. I was looking to connect a new earth to the CU via the supply but cannot find a connection for this. The consumer unit (Wylex re-wirable fuse type) is situated at the bottom of the stairs high up on the stairwell wall. The supply cables (meter tail type, but old) for the meter appears to come through the wall from the kitchen area or maybe down the wall from upstairs and appear to pass through a ceramic type of oblong block. There is a multi-stranded unsheathed cable coming from the supply cable direction to the earth block on the CU but I don’t know if this is the earth or not. . This supply doesn’t appear to be anything like TN-C-S or TN-S but I think is more like TT but without an earth rod. Would I be better putting an earth rod in for the time being just to be on the safe side?

Thanks in advance

 

[Steve]

Dont put an earth rod in. You need an electrician to come and test your Ze, the effectiveness of the earthing. Chances are, the stranded cable carries the earth from the supply somehow. What sort of supply cable is it? can we have a picture of the service head?

 

[DDAS]

I will get you a picture 2 morrow

 

[breezer]

i must admit most people do think the earth comes from the water pipe, since they know the pipe is in the ground and see an earth wire connected to it

 

[plugwash]

and iirc it was considered acceptable to use the water pipe as the main earth at one stage

 

[Steve]

i used to think the water pipe was the main earth when i was a kid, in fact then it probably was. but then we had equipotential bonding put in and they put one to the gas pipe, i thought this was the main earth then!!! In fact, they had also put an earth to the service head and made it TNCS

 

[DDAS]

Just asked admin to post some pics for me. Hope they help

 

[DDAS]

Dont put an earth rod in.

Forgive me, but what problem would this cause if I did? Even if there is already an adequate earth I cant think what the issue would be, but then I ain't an electrician

Pictures :
Picture 1
Picture 2

 

[DIYnot]

Pictures added ^^^

 

[plugwash]

any idea where the wires go after passing through that ceramic block?

 

[slippyr4]

my (TN-S) supply has an unsheathed stranded earth brazed onto the incoming cable sheath - looks identical to that. Although on mine, I can see for sure it's the earth.

You need to follow that and see where it goes.

 

[DDAS]

any idea where the wires go after passing through that ceramic block?

I assume you mean passing through the block into the wall? I don't know they appear to go into the kitchen area (the kitchen is on the other side of the wall) but I cant see where they go. I assume they are buried in the wall but where they actually come into the house I have no idea. The floors downstairs are concrete so I cant see if they arrive that way. It looks like the power supply to the houses used to run along the outside walls once upon a time as there is still some evidence of this.

my (TN-S) supply has an unsheathed stranded earth brazed onto the incoming cable sheath - looks identical to that. Although on mine, I can see for sure it's the earth.

You need to follow that and see where it goes.

I have considered taking away some of the plaster work/ brickwork to see if there is any evidence that this stranded cable may be earth.

 

[DDAS]

Pictures added ^^^

Thanks

 

[sparkybird]

I agree with crafty - get the Ze test (external earth loop impedance) and this will tell you if your sis has adequate earth or not. If not, this then gives you some ammo to use with the supply company which should provide an earth. I battled with mine for some time but finally got a result which I didn't have to pay for
SB

 

[Steve]

Some of the stuff in that picture looks very old. I would consider getting a new consumer unit very soon.

What is that switch for right in the middle? Where do its wires go?

While the REC are out, get them to fit a new service head. That old 2-piece one looks absolutely knackered.

Putting an earth rod in and connecting it to a TNCS or TNS earth can cause problems because there can sometimes be a voltage on a TNCS earth, in other words, TNCS, whilst being protective earth, is sometimes not actually at true earth voltage. Connecting this to a true earth could cause a current to flow. I think thats about right anyway!!!