Confused

[Bez]

Went to check an external light (bulkhead) light at a property today. Opened it up to find no inards at all. (no wonder it doesn't work said the customerBlushing).

Switched Live, Neutral & Earth sticking out of the wall in T&E. I stuck a multimeter on it and got the following voltage.

L-N 238V

L-E 120V

Didn't have time to dig any deeper. Really old property, TT but couldn't trace rod.

Any ideas as to odd voltage reading?

 

[Andy™]

what did you get N-E? sounds like a dodgy earth connection

 

[Lurch]

Dubious earth.

 

[revjames]

Possibly a fault due to damp in another fitting perhaps?

 

[Bez]

Should have taken a photo but there was a thin, almost spring like rusty cable exiting the house and going underground. Is this some sort of prehistoric earthing system?

 

[Andy™]

Should have taken a photo but there was a thin, almost spring like rusty cable exiting the house and going underground. Is this some sort of prehistoric earthing system?

bare copper going to rod with corroded connections maybe?

 

[Bez]

[quote name='Andy

 

[Andy™]

i wouldnt like to have to alter anything. especially with those rubber cables. insulation just falls off looking at it

 

[batty]

Quite often bare cable will be an old BT earth. I would start at mains see if you have an earth there if there is probably will find you have disconnected earth or possibly rest of circuit is twin with no cpc.

 

[Andy™]

Quite often bare cable will be an old BT earth. I would start at mains see if you have an earth there if there is probably will find you have disconnected earth or possibly rest of circuit is twin with no cpc.

or as i have found before.... old 3036 2 way board with no earthing to lighting, and earths for sockets conneted to earth terminal. on its own. with no main earth or bonding.

 

[Bez]

Have refused to fit new light anyway, unless he lets me do further investigations. Up to customer now.

 

[Megaohm7]

Lord only knows mate, the whole place needs re-wire and earthing properly I reckon. Still got those black rubber singles in the house with all sockets on timber backing. 2 White porcelin fuses protecting lights and sockets, in a nice little plywood box.

Did the little plywood box have dovetail joints and brass hinges ?????

 

[kme]

Prob`ly!

 

[steptoe]

Did the little plywood box have dovetail joints and brass hinges ?????

and lined with asbestos........

(well inside the little carriers anyways)

 

[paul b b]

just a quick Q here, sorry to sound thick...... you did a L-E, i take it there was no RCD or it would have tripped, so did you just do a reading out of intrest? and i take it, it should have been 0v on L-E.

thanks

 

[Lurch]

just a quick Q here, sorry to sound thick...... you did a L-E, i take it there was no RCD or it would have tripped, so did you just do a reading out of intrest? and i take it, it should have been 0v on L-E.

Should be 230V L-E, I'm sure that was a mistake on your part, think about it a bit.

An RCD won;t trip if you test across L and E with anything of a high enough impedance that it doesn;t draw more then the In of the RCD (so just about any meter).

 

[batty]

just a quick Q here, sorry to sound thick...... you did a L-E, i take it there was no RCD or it would have tripped, so did you just do a reading out of intrest? and i take it, it should have been 0v on L-E.thanks

L-N Should be 230-240v

L-E Should be 230-240v

N-E Should be 0v

 

[kme]

An RCD won;t trip if you test across L and E with anything of a high enough impedance that it doesn;t draw more then the In of the RCD (so just about any meter).

It is worth noting that a lot of the "voltage testers" WILL trip an RCD; although some have a "RCD-LOC" similar to a loop tester.

For instance, I have the di-log tester, as discussed in another thread recently. If I want to test line-earth, I connect it line-neutral for 5 seconds first, then it won`t trip on L-E. (capacitor charging on initial contact draws more than 30mA )

HTH

KME

 

[Lurch]

Worth knowing, I've never had a voltage indicator trip an RCD on L-E tests, I must have been lucky.

 

[ProDave]

I keep getting odd jobs on a house like that. All still wired in rubber cable, old round toggle light switches on wooden back boards, all sockets (now 13A) in wooden boxes.

I keep telling him it needs a complete rewire. But he just says, I'm 90 years old and don't want the upheaval of a rewire. Leave that for my son to have done when i'm gone.

So I just patch it up as best I can.