Oh dear, cavity wiring and new insulation.

[Click-Sure]

I hate cavity wiring at the best of times, but I've been out tonight to see a whole house using it, it looks like it may have gone in as the walls went up, Bricklayer Sparks?

Well, all was well until the current owners decided to get environmentally consious and decided to call a contractor with a tanker full of fast-foam to insulate their cavities. Got a call today from the confused resident regarding a few dead sockets on the downstairs ring (fuses checked etc).

Turned out this is quite a heavily loaded ring final and the extra heat genereated by the cable in the walls has caused them to pop out of the terminals, which I have fixed for them, tested, IR has fallen to below acceptable levels. I told them there and then that its re-wire time, no other option and if it isn't done then they need to hope they've got a direct line to the fire station.

Not interested, even when advised to get a few quotes from local competant registered sparks, said they didn't think it was as big of a risk as I said it was and didn't want the distruption of a rewire (expense not mentioned).

Now we work in a regulated (so-so) industry like the gas boys, why can't we stick condemed stickers on CU's?

I'm worred about this now, they've got 3 young daughters, should I be contacting the REC/DNO to explain the situation and get them to cut supply to the property until work is carried out?

 

[Pensdown]

Now we work in a regulated (so-so) industry like the gas boys, why can't we stick condemed stickers on CU's?

Nice idea! I'll start the wording for the label....

"On the 10th April 2008 this installation was tested and inspected to BS 7671 2007 and.........

 

[Chris.J]

If the circuit was derated by replacing the 32A MCB with a 20A one, this would make it safer.
Could this be an option for this house & what would the regs. have to say on this?

 

[SeanT]

Sounds dangerous and irresponsible to me, although probably within the regs to do it, would have trouble explaining it as more than a temporary measure - for one the op knows that the circuit is heavily loaded, for another he knows that it has actually been damaged to an unknown (despite being able to take measurements) extent...
Sounds a lot like the current owners need to call the insulation "installer" out and get them to look at their downstairs ring circuit.... they are supposed to check for these things before pumping their crap in....

 

[Click-Sure]

Had a call from the customer today, looks like thy've either come to their senses, or spoken to somebody in the know. They have asked me to quote for the cheapest option to get things safe for now while they persue things with the insulation cowboys.

Told them they will have to be very sparing with what electrical appliances they use, particularly downstairs but to change the wire in their rewirable fuse holders from 30 amp to 15 amp wire, this they understand and will do (he was looking for fuse wire whilst I was on the phone to them.

Told them cheapest option to get things running properly again was a rewire using PVC trunking throughout, otherwise a conventional rewire but with a less than recomended number of outlets. Either way the bulk of the work I will probably pass on.

 

[Kes]

<..they are supposed to check for these things before pumping their rubbish in....>

How are they supposed to do that? I mean, how, actually, do they do that?

 

[plugwash]

I imagine it would be quite easy to obtain a camera/light assembly that could be used to check what was going on in a cavity either from the top or from a small entry hole.

 

[SeanT]

I imagine that it'd be even easier to take a couple of socket fronts off upstairs and down, to see where the cables run.

 

[Lectrician]

Had a call from the customer today, looks like thy've either come to their senses, or spoken to somebody in the know. They have asked me to quote for the cheapest option to get things safe for now while they persue things with the insulation cowboys.

Told them they will have to be very sparing with what electrical appliances they use, particularly downstairs but to change the wire in their rewirable fuse holders from 30 amp to 15 amp wire, this they understand and will do (he was looking for fuse wire whilst I was on the phone to them.

Told them cheapest option to get things running properly again was a rewire using PVC trunking throughout, otherwise a conventional rewire but with a less than recomended number of outlets. Either way the bulk of the work I will probably pass on.

I would have recommended a 15amp retro fit MCB, 3036 will hold too long on a gentle overload.


In saying this, if the IR was as poor as you say, I would not have livened the circuit back up, I would let them do that - You don't want that on your shoulders.

 

[GaryMo]

I imagine that it'd be even easier to take a couple of socket fronts off upstairs and down, to see where the cables run.

Is that definitive? If cables exit through top, side or bottom knockouts (but not rear) does that mean no cables exist in the cavity?

I would say it would be practically impossible to check the cavity completely for cables before insulating. It's a shame the dodgy electrician who routed them in there in the first place didn't think of that.

 

[Lectrician]

It was common place on council rewires in the 60's/70's to surface clip cables to surface accessories, however, in the 'posher' installation, the cables where all fished down the cavities on external walls.

Not that I witnessed the original rewiring, but I have rewired many since!

 

[ban-all-sheds]

<..they are supposed to check for these things before pumping their rubbish in....>

How are they supposed to do that? I mean, how, actually, do they do that?

I don't know, but...

...if there are cables in the cavity, is it appropriate to put insulation in there, and would doing so be a workmanlike operation?

 

[plugwash]

I would say it would be practically impossible to check the cavity completely for cables before insulating.

I agree checks can never be perfect but IMO that does not excuse not doing reasonable due diligence. Also there are probablly things other than cables that you want to check for before undertaking the pracitcally irreversable process of filling a cavity with foam. For example I belive that cavity wall insulation done without appropriate care and attention can easilly cause serious and very difficult to correct damp problems.

It's a shame the dodgy electrician who routed them in there in the first place didn't think of that.

How long has adding cavity wall insulation been common? I think probablly only a couple of decades at most. There is a lot of wiring in service that is older than that.

 

[ban-all-sheds]

It's really incredibly simple.

1) As an installer you should know that there could be cables there. If you don't you are incompetent and should be fined/jailed if you carry on installing.

2) As an installer you should know that putting insulation over the cables could cause a fire. If you don't you are incompetent and should be fined/jailed if you carry on installing.

3) As an installer if you cannot establish that there are no cables there then you do not put insulation in. If you do you are incompetent and should be fined/jailed.

 

[Kes]

<..they are supposed to check for these things before pumping their rubbish in....>

How are they supposed to do that? I mean, how, actually, do they do that?

I don't know, but...

...if there are cables in the cavity, is it appropriate to put insulation in there, and would doing so be a workmanlike operation?

I agree entirely with your sentiments, but as there doesn't seem to be a practicable way of telling that there is cavity wiring then the conclusion must be that (foam) cavity wall insulation should be banned as a trade.

I asked as I don't really like to hear workmen, who may well be perfectly competent, called cowboys. It may be argued that they are by definition, but shouldn't the argumant be against using foam cav insulation? So...

How are they supposed to do that? I mean, how, actually, do they do that?