Steel conduits acceptable for earthing in domestic property ?

[NEB Electrical]

Evening

Just been to quote for a consumer unit upgrade. Found that the board was from circa 1960 and wiring looked original also. No alterations have been made with exception of a few faceplates renewed in the kitchen. Red and black single cores going into an adaptable box at the back and then down the relevant conduits. No CPC's for any circuit. The only thing providing an earth is the conduits themselves.

My question is does this provide an adequate earth and would this be deemed acceptable once the new 18th edition unit is installed ?

I am of the opinion that it does not as there is technically only one earth point at the main board and if that were to fail, nothing in the house would be earthed, there is also no guarantee that the conduit system is 100% complete, although a long lead test could verify continuity ?

Any advice/opinions welcome.

Thanks in advance.

Nick
NEB Electrical Ltd

 

[7029 dave]

IMO, if it is a full conduit installation then it will be ok, do some continuity testing, having said that I used run in cpc on all my installs. (even on rewires)

 

[davesparks]

Yes steel conduit is still just as acceptable as a CPC today as it was when that was installed, see regulation 543.2.1 (vi)
Also note the requirement of regulation 543.2.7 must be complied with in this case, so an earth flylead must be taken from the backbox to every accessory with an earth terminal.

How you test the continued integrity of the conduit is up to you, you need to apply your technical knowledge to decide this as there is no 'paint by numbers' method as far as I know. personally I would use a high current Zs test as a bare minimum but would much prefer to test with a high current milliohmmeter (aka ductor) wherever possible.

 

[NEB Electrical]

IMO, if it is a full conduit installation then it will be ok, do some continuity testing, having said that I used run in cpc on all my installs. (even on rewires)

Yes i think it is a full conduit install.

Just gives me the heeby jeebys looking at a board and there is no earths connected to the bar!

Thanks for your reply

 

[MJPD29]

If it's from 1960 check what kind of cable it is whether it's pvc or rubber

 

[NEB Electrical]

Yes steel conduit is still just as acceptable as a CPC today as it was when that was installed, see regulation 543.2.1 (vi)
Also note the requirement of regulation 543.2.7 must be complied with in this case, so an earth flylead must be taken from the backbox to every accessory with an earth terminal.

How you test the continued integrity of the conduit is up to you, you need to apply your technical knowledge to decide this as there is no 'paint by numbers' method as far as I know. personally I would use a high current Zs test as a bare minimum but would much prefer to test with a high current milliohmmeter (aka ductor) wherever possible.

Dave

Superb, yes i carry out a complete test of the installation any time a consumer unit upgrade is done. I think in this case thought every switch/socket will have to be opened to make sure fly leads are in place.

I appreciate your advice on this matter.

Nick
[automerge]1572380229[/automerge]

If it's from 1960 check what kind of cable it is whether it's pvc or rubber

Matthew

Is there a way to tell the difference ? As it just looks like old single core wiring. I suppose just by the feel of it ?

If it is rubber does this constitute a non-compliance ? In my eyes it should be fully rewired due to the age of the system, but customer only wants it done if it is absolutely necessary.

Nick

 

[davesparks]

Just gives me the heeby jeebys looking at a board and there is no earths connected to the bar!

Why? there's plenty of boards out there with no cpcs, or far less cpcs than the number of circuits connected.
Circuits wired in steel conduit, trunking, SWA or MICC can all result in no,or very few, cpcs in the earth bar.

 

[NEB Electrical]

Why? there's plenty of boards out there with no cpcs, or far less cpcs than the number of circuits connected.
Circuits wired in steel conduit, trunking, SWA or MICC can all result in no,or very few, cpcs in the earth bar.

Dont know why, think its just the way i was taught.

Not everything is black and white though as i have learned over the past 5 years running by business

 

[7029 dave]

Why? there's plenty of boards out there with no cpcs, or far less cpcs than the number of circuits connected.
Circuits wired in steel conduit, trunking, SWA or MICC can all result in no,or very few, cpcs in the earth bar.

The best method because it at mass, in my day no fly leads etc, get your file out an give it a bloody good clean down to the metal.

 

[davesparks]

Superb, yes i carry out a complete test of the installation any time a consumer unit upgrade is done.

Is there a way to tell the difference ? As it just looks like old single core wiring. I suppose just by the feel of it ?

If it is rubber does this constitute a non-compliance ? In my eyes it should be fully rewired due to the age of the system, but customer only wants it done if it is absolutely necessary.

Its possible to carry out a complete test without effectively testing the conduits, for example carrying out only low current/anti trip type Zs test instead of a high current test may well result in a false pass result.

VIR singles look very different to any pvc insulated cable, i'm sure you could find many pictures if you search but the dead give away would be the woven fabric outer surface of VIR. Also the smell, waxy feel and high chance that it has perished and gone crispy should give it away.

Why would you rewire purely due to the age of the system? There are good valid reasons why you might rewire if there were a lot of additions to be made or significant alterations, altering a flush mounted steel conduit system isn't all that convenient,
but just because it is old it doesn't necessarily mean it must be replaced.