Type of Earth for consumer unit

[CaptT]

I have been told that the earth connection to my consumer unit, older mcb unit, is inadequate. The company supply cable has exposed multi wire sheathing, i would say like armoured cable, and a clamp has been fixed around this to which an earth wire is fixed. I assumed as the cable then goes underground it provides earthing. If this is now said to be insufficient, and i cant think why that should be, what else can the earth wire be clamped to. The water pipes are no doubt blue plastic and i think gas is now yellow plastic so what is the answer?

I noticed at a friends house the similar calmp had been removed and a wire was in stead connected to the gas meter inlet pipe??

A bit of advise would be welcome...thanks.

 

[ricicle]

Try this for starters

 

[ban-all-sheds]

I noticed at a friends house the similar calmp had been removed and a wire was in stead connected to the gas meter inlet pipe??

That was, I hope, a bonding connection, not an attempt to provide an earth via the gas pipe...

 

[CaptT]

Try this for starters

OK taken most of that onboard so i guess that i have the TT system...should have mentioned its a late 1950`s house in case it helps...how can i be sure the earth is adequate and was my friend wrong about using the "armoured" cable sheath as earth is inadequate??

 

[ricicle]

You could get half an answer from your DNO (District Network Operator) but that will only be what they think/assume you have and only if their records are up to date.
An electrician, with an earth fault loop impedance tester should be able to confirm the suitability with a glance and a test.

 

[stillp]

Capt, could you post a photo of your incoming supply and consumer unit?

 

[CaptT]

Capt, could you post a photo of your incoming supply and consumer unit?

You can just see behind the gas meter the original fuse box and in the next image an early consumer unit put in to handle shower and kitchen (oven) electrics.

The earth clamp can be seen, in new col for the new consumer unit plus the thin earth as originally used by the buliders i preseume.

 

[Chri5]

It's TN-S, earth via supplier.

Who ever did the 16mm sq that feeds the board has cheated.

The normal would be the earth from the supply on to a MET block

The stranded earth should be covered in green yellow sleeve.

Then from the MET you feed the 16 mm to the board. Additional cables in 10 mm sq should be used to connect the gas system and also the main water pipes (unless it is plastic pipe feeds in from the street).

Your system may well function adequately, if in doubt get a ECR done. Why are 3 of the mcb's off?

 

[ban-all-sheds]

The company supply cable has exposed multi wire sheathing, i would say like armoured cable, and a clamp has been fixed around this to which an earth wire is fixed.

i guess that i have the TT system

I think you should read that article again.

was my friend wrong about using the "armoured" cable sheath as earth is inadequate??

Yes.

What makes him think he knows about electricity supplies?

 

[CaptT]

It's TN-S, earth via supplier.

Who ever did the 16mm sq that feeds the board has cheated.

The normal would be the earth from the supply on to a MET block

The stranded earth should be covered in green yellow sleeve.

Then from the MET you feed the 16 mm to the board. Additional cables in 10 mm sq should be used to connect the gas system and also the main water pipes (unless it is plastic pipe feeds in from the street).

Your system may well function adequately, if in doubt get a ECR done. Why are 3 of the mcb's off?

I suppose you must follow your conventions for regs etc..so you screw a Met block to the wall. Clamp a wire to the incoming supply "strands" and terminate it in the block. You then run cables from the block to each CU in turn. You then run two more cables from the Met block to Gas and water pipe. Hope ive got that right. (Stranded earth cable to old CU does seem poor though)

The corner CU is original circa 1955. 10 years ago I upgraded the house with an electric shower and an electric oven and added sockets to the kitchen. The plan was to install a modern CU to handle all that and have enough space left to transfer the rest of the house circuits over as well. That never happened so i left the mcbs on place to cover the din rail. Now i find that CU is old fashioned..no rcd..so am faced with changing it all over to a new wylex unit ex Bq bought a few years back which has a slit board with one rcd which should be adequate. A man needs a hobby..

 

[CaptT]

was my friend wrong about using the "armoured" cable sheath as earth is inadequate??

Yes.

What makes him think he knows about electricity supplies?[/quote]


He had a new CU fitted by proper sparky who removed the earth cable from his sheathed cable and all he can see is a new earth taken to a water pipe behind the gas meter. So he made an assumption that was the right thing to do.

Thanks for all your help

 

[flameport]

He had a new CU fitted by proper sparky who removed the earth cable from his sheathed cable and all he can see is a new earth taken to a water pipe behind the gas meter

Can't imagine any circumstances where disconnecting a DNO provided earth would be appropriate.
The gas is probably correct, but not as an earth.

 

[westie101]

The clamp on the cable is actually round the lead sheath which is the accepted way. Why one was removed at another house is beyond me and was an unacceptable move.

The provision of the clamp and connection to the MET is the responsibility of the DNO

 

[mfarrow]

He had a new CU fitted by proper sparky

No he didn't. That connection onto the earth sheath isn't the electrician's, or your friends to touch. It belongs to the DNO who run electricity to your home.

removed the earth cable from his sheathed cable and all he can see is a new earth taken to a water pipe behind the gas meter.

Make sure there isn't one also to the main cut-out where the mains fuse is. There are unfortunately idiots around who think they can create a DIY PME earthing arrangement.

The other possibility is that there is a fault with the DNO's earthing system which resulted in a high external earth impedance being recorded. If that's the reason why the earth has been disconnected, he should have installed an earth rod into the ground instead, and not relied on the incoming water supply.

 

[SimonH2]

And for good measure, at first glance it looks like unsheathed cables used between meter and CU as well.

It would be a good investment to get a qualified sparky in to advise. Given these issues, you also have to wonder what else isn't right - so a full EICR (electrical installation condition report) wouldn't be a bad idea.