Rubber Wiring - Safe or Unsafe?

[Harry]

I recently had an electrical problem where a short on a lighting circuit in the loft caused my radiators and water taps to become live.

Obviously the plumbing is inadequately earthed, which I will remedy. Additionally, a short-circuit tripped my (very old) trip switch. I called an electrician, who sucked air through his teeth and told me that all of the old rubber-insulated wiring in my house (both lighting circuits and one ring main) would need to be rewired. He also took out the fuses from the lighting circuits (which he said were reading very low insulation levels), and fitted a 30mA RCB for the entire house.

I am wondering whether he took the best course of action. Might my old rubber-insulated wiring still be serviceable? If so, could I simply rewire the shorted/failing sections (which are in the loft and easily accessible)? I'm worried that if I try to do this, my old lighting circuit will not work with the newly fitted 30 mA RCB.

Will such a repair be possible, and if so, what are the risks associated with it? Will it be safe?

Will a qualified electrician undertake repairs like I've described, or will they require me to rewire the whole house!?

Will a house with (functional) rubber insulated wiring pass an electrical safety inspection for e.g. renting?

Thanks for any help or advice.

Best wishes

Harry

[Nigel Molesworth]

Absolutely, categorically, no.

[Owain]

Unsafe.

Yes. It was very nice of him to leave you with some electricity working. He oculd have pulled the main fuse and phoned the electric co to advise them of a dangerous installation. The electric co can refuse to supply electricity to a consumer whose installation falls below minimum requirements.

Nay, Nay and thrice Nay.

No.

If the insulation of the remaining sections is low - which it will be - then it is not a safe repair. Also, rubber insulation becomes brittle. It will fall apart as soon as you touch it.

No. It will not be safe. The risks include destruction of your home by fire, destruction of you or any other occupant by fire, and destruction of you or any other occupant by electrocution.

They should not undertake such repairs.

No. You have been told your lighting circuits have an unacceptably low insulation reading. Disconnecting them, and fitting the whole-house 30mA RCD to the remaining wiring, should be regarded as a temporary measure only until ALL the wiring is replaced and a proper split-load consumer unit fitted.

Owain

[John Rumm]

Sounds like an understatement!

Not quite sure if I follow the bit about removing fuses... The RCD ought to save your life should something similar happen in the near future. I would make sure you heve plenty of smoke alarms as well.

Not a chance - you are living on borrowed time.

*You may not get another warning*

might be

Your house bursts into flames or you get eletrocuted.

Nope

yes

In your case no - you have already said that it is failing insulation resistance checks.

[Harry]

Thank you both for your feedback. I will get on the case urgently (by removing the fuses, I meant that I have cut off both lighting circuits until I can resolve the issue - I am however still running power through one rubber insulated circuit - see below).

The one ring main circuit which has rubber insulated wiring passed the insulation resistance checks easily (the electrician said three times the suggested minimum), and has caused no problems. In spite of this, should I still be seeking to replace it, and how urgently?

Thanks again for the advice Harry

[Ian Stirling]

Yes. Rubber not only degrades in terms of insulation resistance, it also becomes crumbly, and degrades physically to the extent that any disturbance at all can cause it to fail. This could be as little as a mouse walking over it, causing a failure.

This probably has a fairly small chance (under 10%) of actually causing a fire, if the circuit is properly designed.

If it's not, and the wire is a bit small, then a fire is more likely. It will probably fail some time in the next couple of decades.

[Harry Bloomfield]

Harry formulated on Thursday :

1st warning bell!

I'm surprised he was willing to even touch it at all. He could well have decided the whole lot was such a risk it needed to be disconnected from the supply without further delay.

Not a chance.

You could, but it would be a complete waste of time.

Safe? absolutely not. The risks... The place going up in smoke possibly your insurance refusing to pay out. Risks of death and/or serious injury.

An odd job man might do it, but certainly not someone with a reputation and qualifications to guard.

Highly unlikely. The safety should be taken even more seriously if your intention is to put someone elses life at risk, than your own.

[Andy Dingley]

I'm surprised he left you any fuses at all.

What part of "NO" are you having the trouble with?

[Andy Cap]

Whilst I agree that the rubber has to go and that without any doubt, the lighting circuits WILL be in an extemely dangerous state, I removed the last two rubber insulated rings from my house last spring, admittedly the kitchen load had already been removed and so they were both lightly loaded but they were in a perfectly serviceable condition, with no sign whatsoever of brittleness, even after 50 years since the house was built, and so I would suggest that condition very much depends on location.

Having said all that, you should get it replaced ASAP.

Andy

[nightjar]

Rubber insulated wire has a service life of 20 years, but has not been installed for at least twice that long. Any rubber insulated cable should be replaced immediately and it would be very advisable to pull the fuses on any circuit using it until it has been replaced.

Colin Bignell

[Richard A Downing]

IANAE (I am not an electrician)

Some 20 years ago I moved into a 1930's semi. I knew when I bought it that it would need rewiring as it had just two 15 Amp (round pin) power sockets, plus the cooker point and lighting. The fuseboard didn't even have a 'consumer unit', just a couple of Steel and Ceramic fuse boxes - I wish I had taken a photo.

Well, on the morning of moving in, I checked the insulation resistance with a megger and immediately condemned the lot - pulled the fuses and went down to the local Electrical Dealer to buy a consumer unit and lots of cable and so on. I tacked 2.5 T&E to the skirting to wire up a couple of double 13Amp sockets, and put in two lights over the stairs and in the kitchen. Then, illegally and probably foolishly, I moved the meter tails to the new CU - I even had SWMBO standing by to stop anyone making a loud noise while I did it. But I could sleep at night until the full rewire was done.

When I started the rewire proper I found rubber dust in steel conduit buried in the hair plaster - the wires were just hanging there - bare! Where the conduits ended there were rubber 'boots' on the end to prevent chafing of the isulation on the sharp metal - hard and crumbly. Now I assume that the rubber was intact until I disturbed it, but a passing truck could have done that. I stood and shivered for some time after the discovery.

Don't mess with Rubber Insulation.

R.

[Ian Stirling]

And maybe even batch of rubber, or age. Then there's the issue of - if you've got 1950s wiring in, did the electrician completely rip out all the 1940s stuff, or is there some going through that hard to drill wall.

[John Rumm]

I would not take too much comfort from that. The minimum is 250K ohms - with decent insulation you would expect a reading of at least tens of meg ohms with modern PVC insulated wire. Rubber when new would have probably been higher still.

Yes, within the month.

[meow2222]

20 years ago it was not uncommon to find old rubber installations. As often as not, removing a fitting would reveal what Richard describes, bare L&N wires twisting around each other with only air and the remaining lumps of broken down rubber for spacers. And that was 20 years ago.

NT

[meow2222]

Given the overall condition of the install, which is evidently terrible, yes it all needs replacing. If youre getting bit by the radiators, you quite likely have no earth on the system, which is a relatively serious risk. If so, connecting rads and taps to what you think is earth wont make the least difference.

There are also risks not yet mentioned. If you rent this property, jail time would be a very real risk, following the death of your tenant. You also run the risk of being prosecuted on less dramatic grounds.

If it were mine I'd disconnect the lot at the CU, fit a few sockets on new wire, and use extension leads taped out of the way until it was all done. And that would be an ideal time to replace the CU too, with a split job. (note if your supply is TT then both CU halves will need an RCD)

If perchance its round pin, which I doubt, I know someone who would make a sensible use of the old plugs and sockets.

NT

[Andy Cap]

they were in a perfectly serviceable

In my particular case, it was a new build at that time and I know there is now no rubber left anywhere in the house.

Andy

[Ian Stirling]

True, I was more using the generic 'you', rather than just referring to your case.

[nightjar]

In the early 1970s, I was taken to check the lift installation at an Electricity Board area office, by the senior engineer in charge of the engineering department at that office. The rules required two people to be present, for safety. I lightly touched the woven cloth sheath of the flexible cable that dropped down the length of the shaft and connected the lift to the control gear and heard a sound like dry leaves rustling. The senior engineer decided that we would not investigate that cable any further.

Colin Bignell

[Andrew Gabriel]

In my university hall of residence, we had to put up with the best part of a year with no lifts whilst they were being reconditioned (which did include complete replacement of the motors and lifting gear, so it was quite substantial). The lifts, although in appearence unchanged, same cars, etc, were much faster. However, it only lasted about 2 months before the trailing cable to a lift cage caught fire. That was apparently about the only item which hadn't been replaced. The fire pretty much wrote off the lift cars, and left the top two floors of the building completely black and smelling of burning car tires. It was a few weeks before the top floors were cleaned up to the point people could use them, and another year before the lifts were working again.

[Stephen Dawson]

I think you will find the minimum is 500K at 500V.

Steve Dawson