live metal switches and sockets

[paul b b]

Hello chaps, long time no see!

just been to a house to look at instaling some new lights and the customer told me after that all light switches gave him a buzz.

i went round and it seems all metal switches, sockets, lightfittings are live.

there is an rcd (30ma) it trips at 10.5 ms on 1x but not at all on 5x

the system is a tt, zs at socket was 188ohms.

live to earth at cu 240A

the house has been rewired anout 10 years ago, he has lived there for a year and it has been like that since he moved in, and he has kids!

any ideas?

thanks

Paul BB

 

[NozSpark]

Offer him a full PIR... there's got to be a dodgy earth or IR fault somewhere and if it's giving him a buzz it really needs finding

 

[steptoe]

RCD,

why would it work at 1X but not at 5 X more fault,?

like saying a 6A MCB throws at 7A but its fine at 40A and my shower works good....... :| strange .

deffo needs a good seeing to,

metalwork sitting live, NOT good,

 

[Manator]

I have a copy of the ERA 2007 report and of all the RCD's recorded as failure, none have passed a x1 test but failed a x5 test.

Did you get any error reports ? Did the manual test button fail after this test?

Have you tested the metal switch plates for voltage? If the carpets are nylon or similar, and the switch is earthed there could be static at the switch when touched, this needs to be investigated though. As for the RCD problem, I would try another RCD just to confirm any suspicions.

 

[gselectrical]

It may not be tripping on 5x because of the high zs. I have experienced this many times with my fluke. Excessive touch voltage during test if I remember correctly. GS

 

[Manator]

Thats why I asked if any error report was shown, it would also give some light (no pun intended) to the problem of a voltage perceptable at the light switches.

 

[steptoe]

It may not be tripping on 5x because of the high zs. I have experienced this many times with my fluke. Excessive touch voltage during test if I remember correctly. GS

good point GS,

>50v

that would show on the meter though as why the test was stopped,

not that the RCD failed.

perhaps just been missed by OP as not a normal occurence.

 

[NozSpark]

I recon he's got an N-E fault somewhere,,, they can play funny tricks with TT's

 

[tom1]

just thinking that noz i had problems with rcd and neutral earth fault a little while back, but i got a very low zs on a different circuit

 

[paul b b]

thanks chaps,

sorry megger says >25 on 5x, i'v never had it before so was not sure.

if i disconect live and earth from cu 1 at a time and test would i be able to tell what circuit it was on?

where is the best place to start testing to fault find?

thanks

 

[NozSpark]

Looks like your Megger is set up wrong..

it's not allowing over 25v touch voltage when it should be 50v

I've never had the need to alter this setting, so I don't know how to revert it

 

[tom1]

thanks chaps,sorry megger says >25 on 5x, i'v never had it before so was not sure.

if i disconect live and earth from cu 1 at a time and test would i be able to tell what circuit it was on? what do you mean mate

where is the best place to start testing to fault find?

thanks

have you tested rcd in compleat isolation, ir test and r2 test

has it really been like this for ten years

 

[Badger]

RCD,why would it work at 1X but not at 5 X more fault,?

like saying a 6A MCB throws at 7A but its fine at 40A and my shower works good....... :| strange .

deffo needs a good seeing to,

metalwork sitting live, NOT good,

you talking about his misses again steps :slap :coat

 

[steptoe]

you talking about his misses again steps :slap :coat

who's missus badger.?

not me,

:innocent

 

[ianmacd]

Looks like your Megger is set up wrong..it's not allowing over 25v touch voltage when it should be 50v

I've never had the need to alter this setting, so I don't know how to revert it

Assuming MFT15xx then this is from the manual:

RCD Touch voltage selection (to select either 25 V or 50 V) 1. With the instrument turned OFF, hold down the YELLOW test button

and turn the left hand rotary switch to any ON position.

2. Keep the button held down until the instrument displays the

 

[Adrian]

my robin tester some times wont trip on 5x on tt systems, all I do is set it to 150ma x1 , same thing and that works for me

 

[Dunx]

Chexk all the fittings have earth continuity with a flying lead back to MET. Check what voltage you get between live fitting and MET. Can't get any significant voltage if there is an earth...... !

Dunx