In the loft all day ! dirty, dusty and full of fibreglass. can any body help with an high Zs ? Mines a megger1553, it was showing 10.8v so hopefully not the meter playing up. It's TNCS was TT, It has 2 boards, looks like the rear extension is al on the new board, anyway come to test my downlights in the bathroom and it's reading is > 1.47k ohms. On RCD test auto it reads > 25v so it didn't operate the RCD. Had a look at most of the switches and fittings i could get to and the same readings, all except the extension and a small room above the fuse boards which are seperate, they have good readings, the one i may take my suupply to reads 0.70 ohms. The meter also flashed 255v for a few seconds then went to 228v then i did the Zs test to reveal > 1.47 k ohms, any help would be appreciated tonight before i go back tomorrow for a better look, what is annoying is all the diy lights that are up ! no certs anywhere and it's all free at the moment, i could just take my feed from the good circuit and mention the problem !!

Ze is 0.23 and the RCD works fine at source.

You say it's a TT converted to TN-C-S - it is actually connected to the means of earthing I take it (the board from which these high Zs circuits emanate from)

Failing that you've lost an earth somewhere along the way.

What does an earthed wander lead for continuity show up ?

Regards

OMS

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Failure is always an option

It's got to be a broken or no cpc in the lighting circuit from the old board hasn't it ?

Stu

I'm getting 230v at the fitting between L & E

Is there any bonding ?

Have you checked IR N-E

Regards

OMS

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Failure is always an option

I'll take the wonder lead tomorrow, but with getting 230v L & E at the last fitting ,it's thrown me. I found loads of bad earth connections around the house but not one of them made a difference. Quite alot of fittings are made up of a bit of flex coming from the ceiling !! I'll tell the customer tomorrow i cant certify it from this circuit and see what they say.

It went thru my mind about N-E but would that not pull the RCD ? No more checks than Zs, because the paid for work was going backwards ; )

Brian,

Just a thought, if you were measuring at the fitting with the megger it probably will read 230 L&E even with 1.4k Zs.

Try either the screwdriver in the garden trick and measure the cpc to that or with it all dead, take the Live out of the mcb and stick it in the earth bar and measure L-E at the fitting on ohms range.


Stu

With no current flowing, you'd get that even if the c.p.c. has a resistance of several meg ohms to earth (provided the L-c.p.c. resistance was still significantly higher). My first guess is a very bad (but not perfectly insulating) joint in the c.p.c..
- Andy.

I remember in the 80's an electrical distributor when they found out electricians were going to the local auto stockist to buy a screwdriver for this purpose ordered a box full from Draper or somewhere and they went in two days, it was called the 'Mini bottom-hose' screwdriver at about a metre long in both flat and crosshead. LOL

I bet BOD has still got one!!!

regards

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"Take nothing but a picture,
leave nothing but footprints!"
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"Oh! The drama of it all."
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"You can throw all the philosophy you like at the problem, but at the end of the day it's just basic electrical theory!"
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Edited: 17 January 2013 at 11:51 PM by rocknroll

Thanks for the replies, i will try again next week. never tried the screwdriver trick, will give that a try ! I told her all this on the phone last night and asked her what she wanted to do. I will put my new feed to the downlights on the good circuit and fill out the certificate with the fault on for her and anybody else to see. It needs a EICR doing, i'm sick of working for nothing ! half a day yesturday taking switches and pendants down, she tells me now it's had lots of different sparks over the years and i am the first to talk about certificates !! I have learnt one thing thou 230v L -E even thou it's a bad earth, i must admit i took that for granted as ok ,years ago.

You should charge the customer extra Brian, i know its difficult sometimes but these are faults that need rectifying and the customer should pay for that half day at least! Its not your fault.

"I bet BOD has still got one!!!"

No, believe it or not, it was the heater bypass hose on the cylinder head that caused me issues during 1976 on my Mini van

But, I feel I've let you down, so I'll have to get on a popular internet auction site to buy one..................

Regards

BOD

regards

-------------------------
"Take nothing but a picture,
leave nothing but footprints!"
-------------------------
"Oh! The drama of it all."
-------------------------
"You can throw all the philosophy you like at the problem, but at the end of the day it's just basic electrical theory!"
-------------------------