Old building electrics

[Spark plug]

a friend of mine has bought a building to use as a workshop, and has asked me to cast my eyes over the electrics in an unofficial Cappasity.

As the building was built and wired before I was born I've never came across wording this old in an industrial setting.

At first I was very alarmed as there is no earthing but as I looked in to it a it more, every thing is wired in steel conduit all steel enclosures and steel DB's. All be it old cartridge fuse DB's with ceramic holders.

There has been a RCD fitted to the supply between the meter and the buss bar enclosure that feeds fused disconectors witch in turn feed various DB's etc.

The earthing for the water and gas has been brought up to date, I'm guessing at the same time the RCD was fitted. The building uses a TN-S earthing system.

Personly if it where me I would re wire just because of the age of the instillation, witch I have recommended but he wants to know if it's safe to use for the time being and do a rolling rewire, obviously subject to testing its hard to determin.

Basically was / is an all steel installation with no separate CPC acceptable / common place?

 

[Robotstar5]

Basically was / is an all steel installation with no separate CPC acceptable / common place?

Still acceptable (in the right conditions) today, why waste money on Green/Yellow wire inside a steel tube?.

 

[brightspark]

Still acceptable (in the right conditions) today, why waste money on Green/Yellow wire inside a steel tube?.

just make sure all the conduit conections are tight and not coroded .an earth loop test and rcd would be advisable to make sure

 

[Spark plug]

Thanks chaps I wasn't sure but that's what I was expecting once I figured it was all wired in steel.

At first I thort I was all wired PEN but I've never came across it before.

 

[brightspark]

if the systems fitted with a 30 ma rcd at source and no nuicance tripping the insulation should be half decent

 

[Spark plug]

if the systems fitted with a 30 ma rcd at source and no nuicance tripping the insulation should be half decent

Yes that's exactly it, just something I've never came across before I might call over with the merger just out of interest.

 

[dobbslc]

I tested a factory recently that makes lead acid batteries, it had lots of steel conduit feeding the metal clad sockets etc and quite a lot of the joints and bushes were loose.
Luckily it had a separate cpc running through it but if yours is that old and doesn't I would at least go round and check every joint, then get a long piece of cable and use this to test it at the far ends of each run for continuity. You want a very low resistance reading across every run.
Just a thought, running an industrial unit from one 30ma RCD could very well cause trouble with nuisance tripping, not sure what machines your mate will be running but I would check they are safe to use if the power trips!
I would do a rewire now before it's fitted out with all his kit. At least the tubing is already there and fit separate RCBO's to the necessary circuits.

 

[Spark plug]

I'd Megger / IR test it to see what state the insulation is in...if its just above 1MOhm its seriously borderline, also check the terminations for signs of degradation - could be VIR cabling (vulcanised India Rubber), also look for signs of burning / arc damage on sockets etc.

Other thing to beware of in an install of that age is Asbestos - switchgear will more than likely have asbestos flash arrestors up to the size of an A4 sheet of paper or bigger and its mostly friable so if its getting replaced, power it down,, check dead, cut cables, spray it with a pva solution and let it set, then remove, bag and dispose of it.

It's not that bad, no rubber or string insulated cables. It's all pvc, tbh apart from looking old the instigation looks to be in good condition.

 

[Pete.]

The building I'm demolishing has a number of asbestos flash arrestors (not to mention ceilings, guttering, siding). Certainly something to watch out for.