Re-wiring needed?

[F]

A relative has had a few light bulbs fail recently. They've also had the fuse on the lighting circuit blow a couple of times, though not when a bulb has failed.

I can't see how a fault on a circuit can increase the load on a light bulb sufficient to make it fail, but do the bulb failures indicate a problem?

On the other hand, I can see that a fuse letting go more than once over a few days may tell a different story.

The wiring is at least 45 years old. Is a rewire on the cards? Is it possible/desirable/cost effective to rewire just the lighting circuit: the house may well be sold in the next two or three years and, although recently redecorated, really needs a complete refurbishment which we would rather leave for a purchaser to undertake.

[JimK]

probably

doubt it's possible if doing "by the book"..

I'd get some quotes for doing it "properly" and maybe get the sparky to investigate that lighting circuit?

- then decide if you want to do it or just accept the bulb and agro costs and possible further risks of failures in that and other circuits for 2 or 3 more years and accept that the future purchasers will/ should haggle the cost of doing it off the sale price of the house......

tough call really... depends how crap it is??

Cheers JimK

[Peter Crosland]

At that age it will almost certainly be lethal or close to it. In the event of a fire caused by the wiring the insurer might be reluctant to pay out. Doing part of the job is a non starter.

Peter Crosland

[cynic]

The wiring will certainly not comply with current requirements but this does not necessarily mean it is actively dangerous (it might or it might not be) If it is PVC its general condition should not be that bad. How much load is runing from the fuse which is failing? Often with systems of that vintage circuits were added to on an ad hoc basis and especially with things such as bathroom wall radiant heaters on top of the expected lighting load. Also are there any outside lights which may be suffering ingress of water or rodent damage? Light pendant cord drops may be deteriorating and cause short circuits with vibration etc. To do a thorough job you could rewire the premises but equally you could trace the real problem and carry out adequate repairs to restore safe working, which in the circumstances you describe may be the economic solution

[ARWadsworth]

Try a short circuit behind a bedroom light switch that sometimes short circuits when the bedroom door is closed and sometimes doesn't short circuit when the bedroom door is closed. Depending how hard the door was closed was the clue. Teenage daughter pissed up going to bed and the lights tripped. Mother closing the door after cleaning her room and the lights were fine. A short circuit is a very large increased load and WILL blow a fuse or MCB

Probably not.

There is probably only one fault on the lighting circuit.You need to find it.

45 years ago is just about when new lighting circuits were required by the IEE to have an earth conductor. (1966 anyone?) If the lights have no earth then the lighting circuit really does need a rewire.

If you can find the fault and are happy to fix it and sell the house in 3 years time without a rewire then do so.

Adam

[Andrew Gabriel]

You cannot infer simply from that age and a couple of blown fuses that a rewire is required. The wiring could all be basically sound, with just one fault blowing the fuse. It might be that the circuit loading has been increased above what it was originally designed for. On the other hand, it might all be in a really dangerous state and about to set light to the house. It needs to be inspected, and the cause of the blown fuses identified.

If the fuse carrier is hot just after the fuse blew, then the circuit was overloaded. If the fuse carrier is cold, then the fuse was blown by a fault current (short circuit).

[Tim Downie]

A bit of an exageration surely? My uncle's house had lead coated wiring and it worked fine. Wiring from the 60s would probably be PVC covered and whilst perhaps not ideal, I would guess that it's safe enough.

Do you know this or are you just scaremongering?

That much is probably true.

Tim

[Harry Bloomfield]

F brought next idea :

Probably not, but their life can be shortened if there is a poor intermitant contact somewhere.

That could indicate a fault, or it could indicate an overloaded circuit.

Is this a fuse, or an MCB? If an MCB, then the MCB could be over sensitive, but MCB's do often trip when a lamp blows.

Find the cause of the problem first. 45 years old would probably mean it is modern PVC, but it may or may not include an earth. If there is no earth then yes, it really could use a rewire for safety.

Possible, yes.

Desirable, probably not.

Cost effective - that would depend upon the condition of the other circuits. It causes a lot of disruption and is not really a process you would want to go through twice if it can be helped. Doing it separately would also cost much more.

[F]

It's not been extended since being installed so, though I don't know what the actual load is, it's going to be within the original spec.

Which is what I would prefer, but another member of the family, who knows nothing but how to throw money at a problem, is involved. The type who gets British Gas in to replace a boiler...

[F]

I think you may have misunderstood, the failure I was referring to was that of the bulb, not the fuse.

[F]

I've not seen any flickering.

Fuse. We have MCBs and yes, they do trip when a bulb goes. GU10s seem to be particularly good at that trick.

[Peter Crosland]

Insurance companies expect a property to be kept in a good state of repair. If they find it has not been then it gives them the opportun ity not to pay a claim. What the OP really needs to do is get it inspected by a professional.

Peter Crosland

[Mike Clarke]

But wouldn't that depend on the type of fittings. If all the switches and light fittings are plastic then the lack of a CPC isn't much of a risk.

[js.b1]

At 45yrs old means quite possibly:

- Power - TRS rubber with earth (CPC)

- Fixed Radial - TRS without earth radials, separate bare earth in plaster

- Light - PVC sheathed, polyethylene insulated without earth

The problem with TRS is the insulation ends rot out of sight. It will even pass an IR test - because air is a perfect insulator, usually there is significant visible black tracking from past "events" and it is a fire risk.

The problem with lighting without earth is all fittings must be Class- II (no earth required). It is possible to leave them untouched if IR passes current regulations AND a visible inspection of every fitting confirms all ok, just add RCBO protection (there is a PDF document covering exactly this, NICEIC).

The slight problem with polyethylene insulated is heat - it tends to split circumferentially and the red insulation will appear brown (somewhat surreal). This is easily spotted at light fittings with bad terminal connections.

45yr old cable will be out of modern BS7671 zone incidentally, everything will be diagonal to the shortest route to save cable (that means diagonal falls or rises wrapping around internal and external corners). Also 45yr old may well have borrowed neutral on the hall lights which will require a 3C+E cable to be dropped upstairs-hall to downstairs-hall light switch, otherwise it will show up when the up/ down lighting circuits are split across RCD/RCBO.

In general - if ever a room is redecorated, even if the wiring is ok, expose the cables carefully and fit PVC oval. That way future cable replacements are just a few minutes per room, minimal disruption to the extent of no wall disruption required. SI2006 does permit addition of mechanical protection even in a "special location" or "connected with a special location" without notification (it also permits replacement of a circuit if you screwup anywhere, garden, kitchen, bathroom, house).

The OP needs someone to examine what they have, hour wise it is nearly always cheaper to replace the upstairs lighting circuit than fault hunt. Realise however that piecemeal replacement can cost significantly more than all in one go. Electricians like to paid at electrician hourly rate for the whole job, when 97% of a rewire is basic labouring rate.

[Invisible Man]

Unlikely an insurer would refuse a claim unless it was known to be in dangerous condition. Our fuse wire used to go everytime a halogen spot failed. We now have a split load CU all RCD protected (TT suppply), no halogen bulbs and no problems.

1965 built, probably original wiring, PVC, lights do have earths. System had never had an earth spike but has now. PVC lasts a long time.

[John Rumm]

Indeed this is true. The risk comes from the fact that many folks will swap switches and light fittings to suit fashion / taste and not restrict themselves (or for that matter even appreciate the need to) to class II equipment.

[js.b1]

... and backboxes.

Without a CPC the backbox should be class-II.

MK do some under the EGA tube range. Moss Electrical or such like carry them - not cheap.

[Old Git]

More than likely not. When I started my apprenticeship in 1960 (50yrs back), we were using PVC on all circuits and this was general in most parts of the country.

True.

-- Snip

[<me9]

That certainly wasn't universal. I've recently surveyed a friend's wiring from the mid 60s. It was evident theat no proper testing had been done, the one ring circuit that was supposed to be present was two radials, with the wires neatly curled up in a plastered over back box part way round the ring.

Wall lights (May have been an early addition) had the wires diagonally down from the nearest access point.

[Old Git]

Yes, I agree and I didn't say it was universal, I was just pointing out that the assertion that "45yr old cable will be out of modern BS7671 zone incidentally, everything will be diagonal to the shortest route to save cable (that means diagonal falls or rises wrapping around internal and external corners)" was an incorrect assumption.