Rcd problems

[sidekick]

Just fitted dual RCD consumer unit. Wiring old and no earth on light circuits. Customer does not want me to disturb newly decorated and new carpeted house so new consumer unit with testing is as far as i can go.
However, on fitting consumer unit, at least four circuits trip the RCD. I tested insulation values before i started the change and all were ok. Even though wiring old it still looks in good condition.
With the suspect circuits off RCD stays on but test button in effective. Circuits on and it trips.
If I put all circuits on same RCD it still trips.
Any ideas on best way to find the problem. Currently left without RCDs connected ( not good but at least MCB board better than old rewireable board removed)

 

[sidekick]

What state is the insulation in on the VIR (rubber) cables.

No telling what the state of the cables are under the boards and your IR reading hint at the rubber insulation starting to perish.

I'd start to split the circuits down and IR test to find the fault, checking for the hidden FCU with a neon that's probably stashed being a cupboard.

All visible looks in good condition still and customer wants no carpets disturbed. Already checked sockets and all cables twisted together at connections so very worried about seperating them for fear of breaking up.

 

[spark 68]

I know it is a bit late now, but I would likely have knocked back a CU change alone on this (can of worms), VIR cable and all that, I would probably have recommended a rewire as well as the CU change, and it is not very often that I find I have to recommend a full rewire (usually just a partial at most), unless the installation really is that bad, got at or otherwise.

 

[Octopus]

Last job I looked at like this, I refused to quote for a CU change without doing a "partial" inspection. IR's were terrible so my estimate became a full rewire, and did the job too.

 

[sidekick]

This may be useful info for you re. the unearthed metal fittings.

http://www.esc.org.uk/fileadmin/user_upload/documents/industry/best_practice/BPG1v2_web.pdf

Page 5 does recommend you decline to replace the consumer unit if they won't change the fittings.......bit late for that I guess!

Good luck anyway

Many thanks for that. very imformative. Wish I'd read this before.

 

[ian.goddard57]

Sidekick, fare play to you.
You've overcome a hell of a lot so far. Sounds like a house of horror to me. Just started doing this with the testing and board changes. Very interesting to hear all the advice given by you guys.
Thanks might help me on a job like this one day.

 

[wildgoose]

No defo no other loads so thinking must be that RCD spur. Calling Monday to look again.

If you are testing from the CCU with any rcd spurs left on the installation, then there is a high probability that the N/E IR test will fail - especially with
some of the cheaper rcd spurs. Take them out of circuit and repeat the test.

 

[sidekick]

Could someone please clarify the following.

1. Is it acceptable to carry out work (ie Change a consumer unit) as long as the installation is left in no worse condition than before the work started. (mcb trip switches better than rewirable fuses and some circuits, lights now on RCD)
2. Best practice guides state that if rewire or other remedial work not agreed by customer for light circuits without cpc then consumer unit should not be changed.

Are both point above correct and do they conflict. Or is one regulation and the other only a guide and why.

 

[Spazz]

Could someone please clarify the following.

1. Is it acceptable to carry out work (ie Change a consumer unit) as long as the installation is left in no worse condition than before the work started. (mcb trip switches better than rewirable fuses and some circuits, lights now on RCD)
2. Best practice guides state that if rewire or other remedial work not agreed by customer for light circuits without cpc then consumer unit should not be changed.

Are both point above correct and do they conflict. Or is one regulation and the other only a guide and why.

1 - The point of doing the work in the first place is to make it better than it currently is
2 - RCDs for lighting is standard (and in BS7671) but if there is no CPC and the consumer does not want to do the work then what is the point in doing the CU, and putting the RCD on the lights as it wont work if a fault occurs???

You can then issue a EDN if you believe it creates a high enough risk to life - if not just tell the customer to find someone else!

 

[sidekick]

1 - The point of doing the work in the first place is to make it better than it currently is
2 - RCDs for lighting is standard (and in BS7671) but if there is no CPC and the consumer does not want to do the work then what is the point in doing the CU, and putting the RCD on the lights as it wont work if a fault occurs???

You can then issue a EDN if you believe it creates a high enough risk to life - if not just tell the customer to find someone else!

Would the RCD not trip if a fault occured and someone touched a live fitting. Thought RCD picked up the imbalance of current going out line and returning neutral and assume going elsewhere trips off.
Also as bathroom shower in good twin and earth now on RCD and garage with sockets now on RCD, thats an improvement.
The idea of CU change was to put sockets and garage on RCD and MCB's avoiding need to rewire fuses if need arose and to give extra capacity for other plans (now on hold untill current mess sorted)

 

[Strima]

Would the RCD not trip if a fault occured and someone touched a live fitting.

It should and will however the disconnection times required may not be achieved.

 

[sidekick]

It should and will however the disconnection times required may not be achieved.

No. But at the very least there is some additional protection where before the work there was none. Risk assessment now to be done on all class 1 fittings.

 

[Spazz]

Would the RCD not trip if a fault occured and someone touched a live fitting. Thought RCD picked up the imbalance of current going out line and returning neutral and assume going elsewhere trips off.
Also as bathroom shower in good twin and earth now on RCD and garage with sockets now on RCD, thats an improvement.
The idea of CU change was to put sockets and garage on RCD and MCB's avoiding need to rewire fuses if need arose and to give extra capacity for other plans (now on hold untill current mess sorted)

It would operate but why on earth would anyone be coming into contact with the lighting circuit, unless they are changing the bulb?
lighting circuits really needs a CPC for their protection from faults. - out of interest the property you are talking about has it got metal light holders, frames, etc?

These must be earthed as to manufacture instructions.

ceiling roses dont make much difference as the earth is not used (apart from to act as fault protection if a wire came lose and happened to come into contact).

 

[Ponty Massive]

Would the RCD not trip if a fault occured and someone touched a live fitting.

Possibly, depends on the path through the person to earth, however you normally want the fault to be detected before someone touches it !!!!

 

[spark 68]

Hmm!,

A difficult one SK, I doubt you will find anyone to categorically state "ignore" the ESC etc.

IMO it is still better that the CU change is done by a Pro, rather than a 'Jack the lad' from the pub, and I agree the RCD protection and MCB's proper earthing and bonding et al. is much safer than it was before.

What you have to remember is that BS7671 the ESC etc. are just guides and recommendations, but, and it is a big but, they can be used to beat you to death in a court of law should the poo hit the fan.

We live in the real world and have to earn a crust, and if you don't do it, then someone else will (Jack the lad from the pub again), I think you just have to do a risk assessment (God I hate that word), and take each case on it's merits.
It is all very well the IET and ESC in their ivory towers saying it should not be done, but if the client is going to do something then they will still go ahead regardless of what you or I say or do.
I think you just have to do the best you can (rectum protectum), and try to balance it up, and try to persuade the client to do things the correct way Difficult).

Please take note Iam not suggesting for anybody to do this or do that, at the end of the day it is your paw print on the EIC, and it is entirely down to you, and you have to take responsibility for your own actions.
Nothing is black and white apart from reconnecting obviously dangerous circuits, and earthing/bonding issues should not be ignored, all I will say is follow the regs, and you will not go far wrong.

 

[Octopus]

Could someone please clarify the following.

1. Is it acceptable to carry out work (ie Change a consumer unit) as long as the installation is left in no worse condition than before the work started. (mcb trip switches better than rewirable fuses and some circuits, lights now on RCD)
2. Best practice guides state that if rewire or other remedial work not agreed by customer for light circuits without cpc then consumer unit should not be changed.

Are both point above correct and do they conflict. Or is one regulation and the other only a guide and why.

I'm going to stick my tin hat on and dissappear down into my bunker but....

There are hundreds of thousands (if not more) of houses in the UK that don't have a cpc on the lighting circuits. Changing the CU for one with dual RCD's or RCBO's, coupled with installing bonding WILL make them safer. A note on the EIC stating that class 1 light fittings is a must.

Taking a position that means you decline to change a CU unless the homeowner won't agree to a lighting rewire is plain daft.