wiring type

[markymark2406]

Just been round a mates to look at a electrical job he has standard grey twin and earth cableing underneath his floor boards but he also has old black coloured twin and earth i have never seen black before was this common place years back?

Also is it permisible to have a back up immersion heater on a switch fused spur on a ring circuit?

 

[stephenf8542]

What do you mean by ''back up'' immersion heater,what heats his water now?

 

[ericmark]

I seem to remember the Black twin often did not include an earth and likely a rubber cable with by now is likely to have de-graded to a dangerous point.

As to Back-Up immersion heater I can see how when only used when central heating has failed that one could stretch a point and connect to ring main.

But if it is set to lower temperature than central heating so it auto switches on if demand is higher than what central heating can supply then no I would say it needs its own dedicated supply.

 

[wingcoax]

Black cable defo sounds like TRS. check with power off as outer sheath can crumble when handled.

 

[markymark2406]

Yes the immersion heater is just a back up for heating water in the failure of the gas central heating.

The black cable has an earth.

 

[Jackthebiscuit]

The black cable has an earth.

Can you safely see if the conductors are 'tinned'? This will confirm that it is not a PVC cable but TRS (Tough Rubber Sheath) who's sheath will not be so tough now an should be replaced as it is well passed it's sell by date.

 

[Click-Sure]

TRS will feel a bit slippery, similar to a candle (in my mind anyway) when touched, pvc will just feel like normal modern cable. Never seen black PVC cable.

 

[markymark2406]

yes i see how you mean slippery like wax so its rubber?

 

[RF Lighting]

Sounds like it.

Any live rubber wiring should be replaced ASAP

 

[Spark123]

Lead can also a bit darker than normal twin and earth, needless to say if it is lead then it needs replaced.