Plumbers. Bless them.

[Spark123]

The thing is RCDs play no part in protecting from differing potentials across metalwork.

No, but the supplementary bonding is for protection under fault conditions when the RCD will disconnect the supply.

No, it's not. Supplimentary cross bonding is to ensure all metalwork is at the same potential.

What fault would rely on pipework?

Electrical equipment will be earthed in its own right, not protected by someone elses pipework and supplimentary bonding.

Supplementary bonding was (and still is unless certain regs are met) required to connect together all CPCs of circuits and all extraneous metalic parts within certain special locations such as bathrooms. The intention is to limit the voltage between parts when there is a fault.
If you have a nice earthy extraneous part such as a metallic bathtub connected via metal pipes and your electric shower faults you can end up with nigh on mains potential between the shower and the bathtub for the duration of the fault (up to 5s in the 16th edn regs for a water heater iirc), with wet naked bodies and a low resistance could be fatal. If you supplementary bond the two together then this potential difference is limited.
RCDs can be used to limit the duration of the fault which is one of the requirements of the 17th edn regs.

 

[EFLImpudence]

From our ( heating) side of things the Part P must be the biggest farce of all?

No one will disagree about that.

Quals are dished out in a day or so, equipment (£5/700) purchased for testing etc - then NOBODY ever asks if u r Part P approved nobody checks anything and no body gives a toss if u report any think even life threatening? Certainly a gas inspector will not look or care.

That's Britain.
Laws are only enforced if profitable and to exonerate the authorities because 'It was the fault of someone who broke the law".

I am with NIC and all they want to do is sell Van insurance & more worthless courses ( they now do plumbing and various HVAC courses including Gas)
How do they justify an annual £375 with competition when Gas Safe charge £175 for the same service with no competition?

Gas Safe are bit slow, then.
There isn't really any competition - only one cheap 'unknown' provider.

Having installed a boiler the (electrical) installation stops at the FSO. The lead to the boiler is no different than the lead on your TV and part of the appliance. From the wiring centre (within the boiler) comes a 4 ( now 5!) core cable to the WiFi room stat. Would u interparate that needs testing?

The fixed wiring should be tested - how do you ensure the OPD will operate in the event of a fault and the RCD won't prevent you being able to switch on?

How about a combi with an added S plan (for extra Hot Water Cyl) . The supply for the 10 way box comes from the FSO (the end of the electrical installation) . It only controls the cyl in the airing cupboard next to the FSO with a 230v cyl stat and zone valve? are they 'appliances' or an addition to the electrical instalation therefore requiring minor works chitty etc? what are your opinions on that?( I am NOT after a fight but would appreciate your opinions)

As above.
Plus - As you have fitted these items with new flex I assume you think everything is alright but isn't it your responsibility to ensure that it IS and doesn't burst into flames an hour after you leave.

How do you do this?
Would you even test that the CPCs are actually connected to earth?
Would you test to see if the metal parts are earthed or live?

 

[RF Lighting]

An FCU isn't an automatic demarcation point for fixed wiring to end.

If you've installed fixed wiring, regardless of whether it's in twin and earth or flex, if it supplies a socket or cylinder stat, and if it's fed through an FCU or direct from the consumer unit it still needs to be fully tested as per BS7671 to ensure it is safe to be put into service.

FCUs do not prevent duff wiring from electrocuting people or starting fires.

I worked on four houses last year which had failed incomming earths. Everything looked fine, but my tester proved otherwise. In the event of a fault, every piece of metalwork within the house would have come live and remained live until someone got hurt. I would have been in the dock for leaving an installation in an unsafe condition.

 

[ecowarrior]

Ok so my WiFi stat isnt double insulated - but doesn't need an earth - but there is one in the flex (now) would u do ELI from there? do u do ELI having fitted a light bulb flex? That does throw some logic on needing an earth in every flexi?

If installing a new fridge say - would u ELI etc the socket it was going into?
I think everyone checks there is an earth, having said that it might be only via the pipework & not the installation wiring.

Rf - i was at a boiler that tingled last year - TT system with earthing pole disconnected!
So socket & see make a very small ELI tester ( rather than lugging all that multi testing stuff about)
would u say that if I checked from the very end of 'what ever I had installed' and it was within the limits of what ever earthing system it was that my obligation to electrical safety had been forfilled? ( this is what I am trying to get to)
Your patience appreciated! Oh - 'CPS' - having a senior moment with that one

 

[Spark123]

A lampholder with no exposed conductive parts has a specific exception to the rule, 411.3.1.1 in the 17th edn red book, probably the same no in the green.

 

[viewer]

Neither plumber nor electrician I hereby put my head in the lion's mouth, by confessing what I've done.

The water supply to a shower in my cottage comes from above through copper pipework which itself is buried in a wall. The metal bath has plastic H&C supplies so no bonding there. Likewise the radiator uses plastic pipework. The enamel bath is bolted to the concrete floor. There is no obvious way to bond within the bathroom. All equipment (shavers, lights etc) have their normal earths and all metal face plates are connected to the earth. I have taken a dedicated 6mm earth cable from the point where I see the pipe disappear into the wall above the ceiling and have taken this to the MET. I have taken a similar connection from the bath to the backplate of the shower. The backplate is earthed via the T&E.
Not really bonding I know, but is this the most sensible answer?

 

[EFLImpudence]

Ok so my WiFi stat isnt double insulated - but doesn't need an earth - but there is one in the flex (now) would u do ELI from there? do u do ELI having fitted a light bulb flex? That does throw some logic on needing an earth in every flexi?

YES - we really would.
It's a quick simple test which shows you the voltage is correct, the polarity is correct, the OPD will operate in time, the CPC is connected to earth.
Before that an IR test to show it won't short-out and the RCD will stay on or there is a fault.

You seem to be dismissing a need for a CPC but it is THE most important conductor.

If installing a new fridge say - would u ELI etc the socket it was going into?
I think everyone checks there is an earth, having said that it might be only via the pipework & not the installation wiring.

Yes to ELFI test and that is not a satisfactory earth - it does not count, it may be replaced with plastic tomorrow.

Rf - i was at a boiler that tingled last year - TT system with earthing pole disconnected!

There you go. What if you hadn't noticed the tingle?

So socket & see make a very small ELI tester ( rather than lugging all that multi testing stuff about)
would u say that if I checked from the very end of 'what ever I had installed' and it was within the limits of what ever earthing system it was that my obligation to electrical safety had been forfilled? ( this is what I am trying to get to)

They are not accurate enough.

Your patience appreciated! Oh - 'CPS' - having a senior moment with that one

Sorry - have corrected - CPCs - just testing.

 

[RF Lighting]

If you're installing new fixed wiring then you must carry out the full set of dead and live tests as set out in BS7671 and issue the apropriate certificate.

Just testing the EFLI is not acceptable.

What if you've trapped a wire when you've screwed the stat case on, or the cable you got has a fault in it, or you've made a human error and crossed your terminations?

I don't know, but I expect you're supposed to pressure test your gas pipework before putting it into service and then check for leaks once the system is full of gas?

It's the same with electrical installations.


CPC's are the circuit protective conductors. This is the proper name for what is often miscalled an 'earth wire' with in the installation. A disconnected / broken CPC is still there in the installation but it is not connected to earth so 'earth wire' is not an accurate term.

 

[EFLImpudence]

I have taken a dedicated 6mm earth cable from the point where I see the pipe disappear into the wall above the ceiling and have taken this to the MET.

That's pointless.
Supplementary bonding should connect all extraneous and exposed conductive parts within the bathroom - doesn't have to go to the met.
This may be done outside the bathroom.

I have taken a similar connection from the bath to the backplate of the shower. The backplate is earthed via the T&E.

The bath (because it is in the concrete floor) should be tested for continuity with the met (your connection removed, obviously).
If less than 23kΩ it should be bonded as above. If >23kΩ it should NOT be bonded.
This should be done with an IR test first. It may be a very high reading.

Not really bonding I know, but is this the most sensible answer?

No.


PS. if all circuits in the bathroom are protected by an RCD then SB may be omitted if disconnection times are met and main bonding is satisfactory.

 

[viewer]

Many thanks. Yes all RCD (Shower RCBO), but will do tests and alter appropriately.

 

[ecowarrior]

CPC's are the circuit protective conductors. This is the proper name for what is often miscalled an 'earth wire' with in the installation. A disconnected / broken CPC is still there in the installation but it is not connected to earth so 'earth wire' is not an accurate term.

It was the CPS that got me lol serves me right for the R17 issue!

Ok the - so the furthest point from the CU is my WiFi stat now with its unused cpc. so - If I have you right - Insulation test, polarity test. ELI and RCD (if Applicable) and we are safe?

Assuming no cpc wire in the WiFi stat flexi for the minute, - then the same detail but the earth from the earth tab on the boiler?

If doing the Insulation test ( bearing in mind its usually a spur on a ring main) would u need to unplug sensitive equipment to 500vdc? or would 250 v dc sufficed or Join L&N & just do the one 500v option?

 

[JohnW2]

Since we are talking about the 'accuracy' of terminology...

CPC's are the circuit protective conductors. This is the proper name for what is often miscalled an 'earth wire' with in the installation. A disconnected / broken CPC is still there in the installation but it is not connected to earth so 'earth wire' is not an accurate term.

There is obviously no disagreement that CPC is now the correct and accepted term. However, in terms of your explanation as to why we now use this terminology, is "CPC" actually any less inaccurate (i.e.any more accurate) than "earth wire" when it is 'disconnected / broken', given that a disconnected/broken conductor is not going to 'Protect' anything?

I must say that I had always assumed that the reason for the change in terminology was that 'earth wire' was not necessarily accurate because, particularly with the proliferation of TN-C-S supplies, the conductors in question are not necessarily at true earth potential.

Kind Regards, John

 

[RF Lighting]

Quite possibly that or a combination of both our statements. It might even relate to the CPC not being at earth potenial whilst clearing a fault condition.

 

[JohnW2]

This is a quenuine and serious question ...

The bath (because it is in the concrete floor) should be tested for continuity with the met (your connection removed, obviously). ... If less than 23kΩ it should be bonded as above. If >23kΩ it should NOT be bonded.

Would you be happy to make a decision not to bond (should conditions for omission of bonding not be satisfied) on the basis of a 'acceptably high' resistance obtained during a long dry spell of weather and when there was no recent history of the floor having been frequently drenched with water from above?

Kind Regards, John

 

[JohnW2]

Quite possibly that or a combination of both our statements. It might even relate to the CPC not being at earth potenial whilst clearing a fault condition.

Indeed - any of those things (or any combination thereof) may have been the reason. However, they are all, IMO, fairly weak arguments - after all, one could similarly suggest that, say, Line and Neutral conductors should not be termed at such, since they may not bear the potentials which those names suggest if broken/disconnected (or in the case of supply failure!) or during some fault conditions!

Kind Regards, John