Circuits earthed on metal box/conduit: Does it need a rewire?

[davesparks]

If it's a point for point rewire then it should be relatively cheap as its just pulling new cable in to existing conduit.

 

[rewireIT]

Get a spark in that knows what he's doing. Suggest he read the regs book that he's supposed to keep in his van.

 

[Ratmeister]

If it's a point for point rewire then it should be relatively cheap as its just pulling new cable in to existing conduit.

There's so many sockets and circuits though, it would cost a fortune in labour I assume. There's 8 offices within the warehouse in total that are all done the same way.

 

[Ratmeister]

Get a spark in that knows what he's doing. Suggest he read the regs book that he's supposed to keep in his van.

He told me straight out that metal conduit used as earth is not allowed in new installs.
He also told me that changing the CU meant the entire install had to be treated as a new install.
I'm trying to work with it for now and I hope he'll have a read of the regs before he returns after my subtle prompting.

 

[littlespark]

The regs ask for a cpc on every circuit... whether that be a separate earth wire, steel conduit, or the steel strands around a heavy duty armoured cable. Steel conduit, properly installed, is the most substantial of any of these.

 

[James]

I have had similar discussions with clients and other electrical contractors working the same site.
sometimes it comes to a meeting with a client and contractor and myself.

I normally stay fairly quiet, just put my point across at times.
Eventually it will come down to the other guy telling me in front of the customer that I am wrong and it has to be done "this way" because it is "against the regs" to do what i suggest and that i should go away because i don't understand.

it always makes for an interesting few minutes when I place a copy of the regs book on the table and ask them to point it out.

I have found over the years that a lot of people confuse the way they were taught it should be done with an imaginary regulation specifying that it must be done that way.

p.s. To this day, I have never walked out of a meeting like that feeling embarrassed that i had got it wrong, you can normally tell you are on a winner when your opponent keeps telling you its against the regs but will never tell you which one.

 

[rewireIT]

Exactly as James says - just ask him to point out what regs it contravenes and where it specifies a DB change means existing wiring, accessories and containment has to be treated as new. He won't be able to show you them because they don't exist.

 

[davesparks]

He told me straight out that metal conduit used as earth is not allowed in new installs.
He also told me that changing the CU meant the entire install had to be treated as a new install.
I'm trying to work with it for now and I hope he'll have a read of the regs before he returns after my subtle prompting.

Someone like that is unlikely to change their mind based on a customers research from the Internet or advice from a forum.

The second point is an unfortunately common misconception which is quite prevalent in domestic work but usually less so in commercial.

It should be pretty obvious that replacing a distribution board on an existing installation does not magically change anything about the existing installation or somehow turn it into a new one.
Yes whoever does the job will need to ensure that the installation is in a safe condition for continued use, but they don't have to do everything that would be necessary to make it fully compliant as if it was installed today.

 

[Risteard]

Thanks Dave, if you were my electrician my life would be a lot easier. I've asked them to fully test the circuits today. If the readings are too high and he insists on a rewire then I'll get someone else in for a second look.

In fairness very few electrical contractors would have test equipment to perform high current continuity tests on containment now.

 

[davesparks]

In fairness very few electrical contractors would have test equipment to perform high current continuity tests on containment now.

Yes but it can be hired for a relatively small cost.