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Topic Title: Light circuit no earth
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Created On: 03 August 2013 12:37 AM
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 03 August 2013 12:37 AM
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SKElectrical

Posts: 893
Joined: 01 February 2009

Domestic.
No earth on the lighting circuit (..there is but its been snipped)
Is it worth installing an rcd?
Do I need to be part p affiliated to do so, as it expired in May.
 03 August 2013 06:44 AM
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normcall

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Frequently you can gain enough to actually use the existing 'cut off' earthing cable. Just have to check that all can be done.
That age generally had insulated inserts for switch fixings or even wooden boxes. Always worth installing a RCD as it doesn't require an earth connection.
You haven't fallen into the Part P trap, have you?
Even the law society sellers questionnaire only mentions 'qualified and registered' people for any electrical work then goes on to ask for building control certificates etc for ANY electrical works carried out since 2005. Nuffick about older stuff.
No, you do not need to be 'Part P affiliated' to do any domestic electrical works - or commercial or industrial for that matter.

I'm getting too old for all these debates about misinformation put about by interested (financially) parties - but it won't stop me sticking my oar in.

-------------------------
Norman
 03 August 2013 01:43 PM
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SKElectrical

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I'll install an rcd to this circuit.

Part P - at first I didn't, then i did, then i didn't, then i did, and now i haven't. It has depended on work demands. Unfortunately my local BC don't pass off building work unless the elecs are part P. Can i just say now to anyone thinking of continuing this Part P debate - don't bother because im not interested, nor is norm.
 03 August 2013 01:59 PM
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SKElectrical

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Oh yeah, they do have insulated lugs on switches, BUT they have metal light fittings everywhere, hence I think rcd might be best.
Thanks norm
 03 August 2013 02:41 PM
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daveparry1

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When I do a c/unit change where there's no earth on the lighting circuit I don't worry too much about metal ceiling lights but switches I usually replace with plastic items especially if they're whithin reach of a radiator or other earthed metalwork. (whether the customer re-fits the metal ones after I've gone is up to them!) I put the appropriate label on the c/unit and also make a note on the eic that class 1 accessories shouldn't be used on these circuits. I do refuse to fit new metal lights etc. unless I can find a convenient way to earth them though,

Dave.
 03 August 2013 03:24 PM
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leckie

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The Best Practice Guide No.1 advises on the requirements for replacing a consumer unit when lighting circuits have no effective earth. It spells out the need to confirm if any class 1 switches or fittings are earthed by carrying out continuity tests. Any metal items found not to be earthed need to have an IR test between live conductors and the Extraneous conductive parts of each piece of equipment. It then says if any of the requirements are not met, eg. low IR reading between live conductors and a class1 fitting, the consumer unit should not be replaced unless an rcd is fitted as part of the work being carried out.

To me that basically reads that no matter what's wrong, you can replace the board as long as rcd's are fitted, you fit a warning label and note the non compliances on the EIC.
 03 August 2013 03:43 PM
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daveparry1

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Yes Lec so it seems they are saying that even if the i/r is low it doesn't matter provided there's an rcd fitted which of course there usually will be if the c/unit is being replaced!
This is of course the "rcd solves everything" attitude, if we used that way of thinking it would be wrong but if "they" say it it's ok!

Dave.
 03 August 2013 04:59 PM
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normcall

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Playing devils advocate, you should insulate any un-terminated bare wires due to induced voltage.
Of course, it was never a problem years ago!

-------------------------
Norman
 03 August 2013 05:07 PM
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perspicacious

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Presumably the homeowners priority over the last 50 years has been to refit the kitchen twice, along with at least one bathroom refit, fit double glazing and to brick pave the drive?

Regards

BOD
 03 August 2013 05:08 PM
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perspicacious

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Oh and I forgot, build a PVC conservatory.....

Regards

BOD
 03 August 2013 05:52 PM
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impvan

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Oh I can beat that! One of my lot is on their third outdoor hot-tub, while still enjoying lead-sheathed and VRI cables and some round-pin outlets in their farmhouse.
 03 August 2013 06:52 PM
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daveparry1

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Maybe they think it adds "character" Impvan!

Dave.
 03 August 2013 11:23 PM
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leckie

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Well I referred to the BPG regarding replacing CU's when lighting circuits have no cpc's. in actual fact it's far more risky when there are cpc's that are not connected. You have to be very careful testing to make sure that the floating cpc's do no have low IR values
 04 August 2013 10:35 AM
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SKElectrical

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Originally posted by: perspicacious

Presumably the homeowners priority over the last 50 years has been to:
refit the kitchen twice,
correct
at least one bathroom refit,
correct
fit double glazing
correct
and brick pave the drive?
correct
AND a PVC conservatory.....
correct



I'm changing the c/u now,
 06 August 2013 09:24 PM
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SKElectrical

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Hi guys im being told now (away from this forum) that installing an
RCD to circuit without a cpc is pointless. This is surely wrong isn't it?

The point of a cpc is to earth metal parts - ie protect said parts by blowing circuit fuse.
The point of RCD is to trip breaker by monitoring unbalanced current across line & neutral; ie it doesn't require a *CPC*.

Have I got that right?
Should I fit an rcd - cust is being told rewire of circuit is only option.


ps. im painting the stairs and landing now so wont be replying tonight - thx in advance.
 06 August 2013 10:18 PM
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daveparry1

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That's a typical comment of someone that doesn't understand how an rcd works! As you said, the rcd operates on seeing an imbalance between L-N, nothing to do with whether there's a cpc or not. I suppose it could be said though that if you had a metal accessory which was not earthed and it developed a fault from L or N to it's metalwork, would the rcd operate if you touched it? probably not unless you yourself were touching earth also, just a thought,

Dave.
 07 August 2013 09:33 AM
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AJJewsbury

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Hi guys im being told now (away from this forum) that installing an
RCD to circuit without a cpc is pointless. This is surely wrong isn't it?

Maybe half true before a bit of re-telling....

BS 7671 states that an RCD (even a 30mA one) doesn't provide adequate protection if a c.p.c. is missing (where it would normally be required). You get additional protection, but you're still lacking basic ADS. If you like disconnection only occurs where someone touches the faulty live part and something earthy at the same time - i.e. you need human flesh to act as a c.p.c. - not the most ethical approach.

So in terms of BS 7671 compliance, adding a RCD to a 'class 1' circuit missing a c.p.c. is pointless - as it's still won't comply. In practical terms though, then clearly no ADS but with additional protection is far better than no ADS and no additional protection.

- Andy.
 07 August 2013 09:21 PM
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leckie

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Well now, the BPG I referred to basically says just that Andy. Adding the RCD does not make the installation comply with BS7671 but makes it a bit safer. I must admit, I think the BPG should be a bit stronger, rather than say do pretty much what you want as long as you add an RCD. The BPG's are supposed to be endorsed by all the recognised bodies. IMO they should advocate a stricter set of objectives. But on the other hand an RCD is better than nothing. But only just.
 08 August 2013 02:27 AM
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SKElectrical

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it was last wired circa 1960. I don't like this customer but the husband keeps trying to stuff tenners £ in my pocket haha! I've told them il do it for £350
 11 August 2013 09:03 PM
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esspeegee

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I refer to, and hand out, this document (see link) t when there is no cpc in the lighting circuit. And then decline to replace CU unless customer agrees to a partial re-wire.
http://www.esc.org.uk/fileadmi...ractice/BPG1v2_web.pdf
IET » Wiring and the regulations » Light circuit no earth

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