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Topic Title: EICR of 1960 BE conduit Installation
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Created On: 09 March 2019 08:58 am
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 09 March 2019 08:58 am
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Nidge007

Posts: 1
Joined: 27 June 2013

Hello all, i just been asked to price rem works based on
The defects highlighted by another contractors EICR and as normal reading It while onsite i found myself not agreeing with some recommendations, but I'm not going to question their ability that's not my job.
I need Information for on knock on couplers and ends. Basically common parts in block of flats, 1960's copper (not tinned) red, black in steel BE conduit and trunking system with undated dbs with RCBOs on power only. Only some newer sub circuits have a separate CPC.
Visible parts of the conduit system have knock on couplers and ends. The old type with the spring tag. So it is obvious the conduit is the earthing system for sub circuits and has visible corrosion in some parts. I though these were with drawn as they didn't comply to standards because they can cause high impedance so fail under fault conditions
So does anyone one know where i can find reference to the use/ withdraw of this type of threadless coupler as to me they should have highlighted this and recommend sub circuits be re-wired with CPC's rather than just saying not all sub circuits have no rcd protection.
 12 March 2019 04:59 pm
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lyledunn

Posts: 1228
Joined: 13 August 2003

So the issue is that this is a periodic inspection rather than an initial verification. If Zs is ok then it would seem that the conduit is doing its job and given that the installation is dated one could conclude that the current arrangements are fine having stood the test of time. Where there is doubt, you could use a low resistance high current ohmmeter.

-------------------------
Regards,

Lyle Dunn
 12 March 2019 07:32 pm
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Zoomup

Posts: 6117
Joined: 20 February 2014

Reg. 543.2.1 (vi) allows a metal conduit system to be used as a protective conductor. B.S. 4568 (1970) is often quoted these days for threaded conduit. I suppose the concern now is how reliable is the old '60s push on fittings. Has corrosion reduced the reliability of the earth joints? A high current test should reveal any bad connections.

543.3.1 requires a protective conductor to be suitably protected against mechanical and chemical deterioration and electrodynamic effects.

I have an old electrical installation book from the 1930s showing a grip style T fitting for metal conduit. The end of the painted conduit is scraped and the paint removed to show clean metal. Some fittings clamp on by the tightening of one screw, others have two screws which tightly clamp the fitting onto the cleaned conduit ends. The system boasts making a good mechanical and electrical joint.

Z.

Edited: 12 March 2019 at 07:43 pm by Zoomup
 12 March 2019 08:15 pm
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Alcomax

Posts: 450
Joined: 12 November 2009

The EICR has been completed by others and from the OP it seems the particular flagged issue [ of the Report ] is the lighting having no RCD.

Knock on couplers are still for sale, though I am not familiar with a superseded version with spring tags. In any event, I think the expectation with the current zinc or brass knock on couplers is that they should not be the sole method of ensuring earth continuity, especially on to black enamel conduit, unless there is some kind of thread connection by say a through bolt. I get the OPs concern with knock on couplers onto original imperial black enamel conduit, likely to facilitate later additions to metric sized tube. The original install was likely all threaded and so very likely to stand the test of time as a CPC. For the OP, only concerned with "remedial", the path of least resistance is RCBO the lighting and to not get bogged down with the ins and outs of the previous add on work.
 13 March 2019 08:48 am
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Zoomup

Posts: 6117
Joined: 20 February 2014

Although R.C.D.s or R.C.B.O.s will increase safety, I believe that 415.1.2 should still be observed.

Z.
 13 March 2019 12:52 pm
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AJJewsbury

Posts: 17795
Joined: 13 August 2003

Although R.C.D.s or R.C.B.O.s will increase safety, I believe that 415.1.2 should still be observed.

Indeed - but as long as the extra resistance didn't raise Zs above say 3642 Ohms, then a 30mA RCD will be able to provide ADS as well as additional protection.

That's presuming the faulty joint doesn't blow itself apart and go completely open circuit under a fault current - like perhaps a flex core that's only got one two fine strands connected into a terminal might do - but that doesn't feel likely for a bit of oxide surrounded by a substantial amount of steel.

- Andy.
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