Re-wiring needed?

[js.b1]

Zones only came in 1987 with 15th revision.

Prior to that date diagonal was common - less material cost.

- Some electricians ran diagonal if they oversized cables re grouping to reduce material cost

- Other electricians did not run diagonal but grouping was handled by "60A fuse, grouping negated by diversity in domestic"

1951s - strict shortest route diagonal (shortages post WWII) 1970 - diagonal but not strict shortest route 1983 1984 1985 1987 - all slight diagonal, different electrician each time 1994 1995 2000 2002 - diagonal roofline prevented horizontal zone so assumed ceiling line became a diagonal zone and used doorframes as zones (under architrave)

NorthWest, Cumbria, Midlands, London.

Additionally PVC in the 1950-1960 period can be affected by green exudate, this is only an immediate issue where it enters wiring accessories and can cause tracking, but should be replaced.

The OP needs to check what the cables are, "at least 45 years old" may mean PVC/PVC or PVC/Polyethylene or some TRS for certain high current fixed circuits (washing machine). Rubber has the best insulation, tinned for corrosion protection, but a shorter life than PVC which can range from 200yrs from temperature data.

[John Rumm]

Most early 60's installs seem to have metal back boxes, so its probably too late on that score. Still the risk from these is small compared to that of metal light fittings etc.

[Harry Bloomfield]

You can pretty well guarantee that any house you walk into will have some sort of lighting or fitting installed which requires a CPC.

[Harry Bloomfield]

It happens that js.b1 formulated :

All very unlikely, though not impossible.

[NT]

I think a good answer is that it depends on exactly what you've got now. Wiring from '65 could be all basically sound, with satisfactory earthing measures, or it could be a dangerous mess, eg with rubber or even reused 1930s lead wiring on a 60A circuit, and ineffective earthing.

It would help to tell us

- what type of cables you've got from the fusebox, or a good pciture

- a picture of the fusebox so we can see the fuses

- a good pic of the lightswitches That should give some useful info.

I'd take any official requirements and redommendations with a pinch of salt, IME such recommendations for old installs are too often inappropriate or unhelpful.

NT

[F]

The house is some distance away but I'll see what I can do in the next few weeks.

My basic query was whether or not a fault in the wiring could cause bulbs to blow. It just seems very unlikely that any fault could increase the current at the bulb sufficient to blow it.

[The Natural Philosopher]

not a fault in the wiring, but a fault in the supply could. Typically a crap transformer feeding you whose voltage regulation is very poor.

[F]

Wouldn't that mean that neighbours would also be replacing bulbs?

[John Rumm]

If its a subset of bulbs that keep going (rather than all (in which case an overvoltage supply would be more likely), then one possibility that has been discussed here in the past, is a dodgy switch. I had an incident a many years back where I was called in by an elderly next door neighbour to replace a hall lamp that would routinely blow every 4 to 6 weeks. Having looked for and exhausted any possible causes I could think of, I replaced the switch. After that it lasted as expected.

[John Rumm]

Depends on if they are on the same phase - often the immediate neighbours aren't - that might mean one phase is a little less heavily loaded and running at a higher voltage.

[The Natural Philosopher]

depends if they sharee a transformer. Your drop wire might also be dodgy., but that's less likely to see voltage SURGES. Just DROPS.