CU change: incomplete CPCs in lighting circuits

harrymonkfish · Sep 2, 2009

Hi all.

I've almost completed my first CU change for my assesment and would like some feedback on my choices.

First point is the cpcs in the lighting circuits x2 are incomplete. It is a PME supply.

I've change the board to an insulated, duel RCD, so every circuit is covered.
I have a single ring (32a) for the whole house on one side (all tests work out fine) along with a cooker circuit (32a), and a shower circuit (40a) to be added later, although the shower is installed but is not connected.

The two lighting circuits (10a) are on the second RCD.

Upgraded main bonding to 10mm for gas, water and included central heating pipework with water.
Upgraded main earth to 16mm

I used some 4mm green and yellow to connect the pipework for the taps to the bathroom sink and under the bath. I havn't gone any further than this as far as supplementary bonding in the bathroom is concerned.

All light fittings are of the insulated type for the whole property.

I'm a bit confused as to what to put down on the cert for R1+R2 and Zs for the lighting circuits.

There is also a an old cable that was connected to the old CU 15a. I couldn't find anything that this circuit powered so did not reinstate it. Turned out to be an old immersion heater cable. Thing is, the owner did some digging around with a voltage indicator and discovered a voltage along the cable. I tested today and it has a an intermittent votage of 2V. It is run in the ceiling with other cables that are in use?

Any help, advice, comments or suggestions greatly appreciated.

Many thanks
Harry

zupos40 · Sep 3, 2009

harrymonkfish said:
Hi all.

I've almost completed my first CU change for my assesment and would like some feedback on my choices.

First point is the cpcs in the lighting circuits x2 are incomplete. It is a PME supply.

I've change the board to an insulated, duel RCD, so every circuit is covered.
I have a single ring (32a) for the whole house on one side (all tests work out fine) along with a cooker circuit (32a), and a shower circuit (40a) to be added later, although the shower is installed but is not connected.

The two lighting circuits (10a) are on the second RCD.

Upgraded main bonding to 10mm for gas, water and included central heating pipework with water.
Upgraded main earth to 16mm

I used some 4mm green and yellow to connect the pipework for the taps to the bathroom sink and under the bath. I havn't gone any further than this as far as supplementary bonding in the bathroom is concerned.

All light fittings are of the insulated type for the whole property.

I'm a bit confused as to what to put down on the cert for R1+R2 and Zs for the lighting circuits.

There is also a an old cable that was connected to the old CU 15a. I couldn't find anything that this circuit powered so did not reinstate it. Turned out to be an old immersion heater cable. Thing is, the owner did some digging around with a voltage indicator and discovered a voltage along the cable. I tested today and it has a an intermittent votage of 2V. It is run in the ceiling with other cables that are in use?

Any help, advice, comments or suggestions greatly appreciated.

Many thanks
Harry

Lighting circuits, your have two choices, either rewire the light and ensure whole circuit is earthed
or
inform client in writing that as lighting is not earthed that no metal light fitting or switches can be installed on these circuit (class I) if you take this option then installation will be class II and not ADS, you can now my sticky labels, that must be posted on CCU informing everyone that lighting is not earthed, the fact the installation is protected by 30mA RCD will reduce the risk of fire if fault occured.

100 Swift WAR7273 Warning no provision for earthing metal equipment Labels NICEI

Personnelly I would not put both lighting circuits on the same RCD may be lighting and shower on one, lighting and socket on other, but again not lighting circuit that in shower room or bath room, so that if shower trips RCD, you do not increase risk, by client also having no lights.

Socket outlets - Hope you do not mind personelly I like more than 1 ring final circuit, not knowing how many socket etc, its had to say if 1 ring is satisfactorary, but now it RCD protected a fault on any piece of equipment and client has not power and from experience, washing machines, dishwashers etc are prone to trip RCD if filters etc are not cleaned out, I resently had problem with nuisance tripping as a result of number of appliance plugged into ring causing RCD to trip.

I alway inspect installation and would have advised client that it would be a good idea to split ring into 2, some say yes other say no, but you advised them.

Otherwise every thing sound ok

Had8Lives · Sep 4, 2009

In answer to your question about R1 and R2 for lighting circuits with no CPCs, you will just have to put No earth in the box, but you could note down the line impeadance( L to N) if your meter can measure this. If the client does not want their ring circuit seperating, I would advise that the lights be put on RCBOs as one lighting circuit could trip the RCD for both if a bulb blows a bit heavily. Do I take it that there may be some borrowed neutrals in the 2 way switching of the lighting circuits?

Regarding the old immersion circuit, if it is bundled with other cbles, it could be getting voltage induced into it.

harrymonkfish · Sep 4, 2009

Well all went well. Had my assesment with nic this morning and passed with flying colours

.

Spent the last 3 days in an absolute panic.

Should't have worried so much.

Lovely bloke. Very helpful. And it was not the heavy investigation I was expecting.

Chuffed to bits.

leekemp85 · Sep 4, 2009

well done passing. I was worried until the day had gone. but I think I will be as bad next year

have a look at this its really useful
Best Practice Guides | Electrical Safety Council

chocolate · Sep 4, 2009

How did you get away with issuing a full electrical installation cert with lighting circuits that did not have complete CPCs ?????? Without an R1+R2 value, you also couldn't measure a Zs at those fittings either !!!!n Also, RCDs would be useless for those fittings !!!!

Well done with your assessment !!!

TPES · Sep 5, 2009

well done,

I'm interested to know what your assesor said about the issues of no cpc's on lighting, was he happy with the configuration of the board and everything else..? Well must have been..

Congrats on passing, good feeling hey.

harrymonkfish · Sep 5, 2009

Hi.

The assessor was quite happy with the work I have carried out. I followed the guidelines from the Electrical Safety Councils guide on changing a CU with lighting with no cpcs.

He said i covered all the bases. I didnt install the lighting circuits or any other circuit for that matter. It was a CU change along with upgrading of earthing and bonding.

Thanks for the thanks
Harry

zupos40 · Sep 7, 2009

chocolate said:
How did you get away with issuing a full electrical installation cert with lighting circuits that did not have complete CPCs ?????? Without an R1+R2 value, you also couldn't measure a Zs at those fittings either !!!!n Also, RCDs would be useless for those fittings !!!!

Well done with your assessment !!!

Chocolate the RCD will still work on class II (no earth or double insulation circuits) and is a must in this case where some of the installation is earthed too reduce the risk of fire.

Why the RCD will work because it detect the diference between the current going down the LINE and returning through the neutral any damage to the insulation would result in some current flow through the body of the appliance or fitting (leakage) and not returning through the neutral. I have known for GLS lamp to trip the RCD with the blow.

chocolate · Sep 7, 2009

Help me out here !!!!!

So the current enters the appliance via the L conductor, and normally and equal amount of current leaves it again through the N conductor. So an RCD wouldn't trip.

Your now saying that some current is leaking away from the L and through the appliance / fitting. But where's it going to ? I thought the appliance was double insulated or class 2 ? For the current to leak somewhere else other than back through the N, then that path must be conductive. In which case, where does it conduct to, inorder to create a closed loop for current to flow ? Surely that's what we call earth leakage ? But without a cpc present . . . .

To trip an RCD, leakage current must have an alternative conductive path away from the fitting other than the Neutral.

It still begs the question how without a cpc, you were able to complete a full electrical installation certificate for that circuit.

pushrod · Sep 7, 2009

An rcd is an earth fault device and the easiest way for any current to leak would be through the cpc, but that doesn't mean to say that there aren't other higher resistance paths that might allow enough leakage to trip the rcd .
A consumer unit can be changed where there is no cpc as long as a risk assessment is carried out, Jason originally posted this really useful link http://www.esc.org.uk/pdfs/business-and-community/electrical-industry/BPG1_08.pdf

harrymonkfish · Sep 8, 2009

chocolate said:
Help me out here !!!!!
It still begs the question how without a cpc, you were able to complete a full electrical installation certificate for that circuit.

The installation cert was for the change of CU. I did not install the lighting circuit. That was installed some 40 odd years ago.

I made the installation safer as a whole. All sockets and the cooker are now rcd protected.

I DID NOT make the lighting circuits any less safer than before I started!

I used the information in this guide http://www.niceic.com/inc/file-get.asp?FILE=BPG1_aug07.pdf&RURL=/en/contractor/section.asp%7C%7C13 to show me the way.

pushrod · Sep 8, 2009

harrymonkfish said:
I used the information in this guide http://www.niceic.com/inc/file-get.asp?FILE=BPG1_aug07.pdf&RURL=/en/contractor/section.asp%7C%7C13 to show me the way.

Hey, that's the link i just posted

Spudnik · Sep 8, 2009

harrymonkfish said:
The installation cert was for the change of CU. I did not install the lighting circuit. That was installed some 40 odd years ago.

I made the installation safer as a whole. All sockets and the cooker are now rcd protected.

I DID NOT make the lighting circuits any less safer than before I started!

I used the information in this guide http://www.niceic.com/inc/file-get.asp?FILE=BPG1_aug07.pdf&RURL=/en/contractor/section.asp%7C%7C13 to show me the way.

Indeed, however, and i quote:

"Where it is proposed to replace a consumer unit, but the customer is unable, or not prepared, to accept either the cost or disruption of re-wiring the circuit(s) or installing separate protective conductors, a risk assessment should be undertaken for the purpose of advising the customer as to the level of risk that would exist on completion of the proposed work. A disclaimer does not absolve the installer from responsibility"

Its the last bit you need to pay particular attention to.

You need to ensure that all Class I fittings are removed and replaced with Class II etc.

harrymonkfish · Sep 8, 2009

Jason.S said:
Indeed, however, and i quote:

"Where it is proposed to replace a consumer unit, but the customer is unable, or not prepared, to accept either the cost or disruption of re-wiring the circuit(s) or installing separate protective conductors, a risk assessment should be undertaken for the purpose of advising the customer as to the level of risk that would exist on completion of the proposed work. A disclaimer does not absolve the installer from responsibility"

Its the last bit you need to pay particular attention to.

You need to ensure that all Class I fittings are removed and replaced with Class II etc.