No zs????

leestaf · Oct 7, 2011

Hi all
I have tested a small house and have continuity of ring conductors at the CU, I have tried to gain a measurement at the kitchen sockets for Zs but my meter says >200 suggesting open circuit however if i plug my Martindale in it says all is ok and no dropped earths?????? There is only one ring maion for the small power in the house as its a tiny 2 up 2 down. Any Help/Ideas guys???
Thanks in advance

Sparky Ninja · Oct 7, 2011

>200 doesn't necessary mean open circuit, it could be that the Zs is beyond the range of the instrument. Have you obtained a value of Ze?

Does your martindale given values of EFLI or just indicate polarity?

leestaf · Oct 7, 2011

Hi Widdler
Fluke meter used 1552b and fluke plug in tester showed no loss of polarity and Ze was 0.14ohms

Sparky Ninja · Oct 7, 2011

Have you tried the tester on another socket outlet circuit?

leestaf · Oct 7, 2011

Tester tried before and after on other points and all fine, meters came back from calibration week before, plug in tester tried the same way and working fine. Cant understand why PIT is sensitive enough to pick up earth but meters arent? or could it be im barking??

telectrix · Oct 7, 2011

are yo saying that the >200 is just on the kitchen sockets? if so, sounds like a polarity reversal somewhere.

scotsparky · Oct 7, 2011

Are there junction boxes?

MarkieSparkie · Oct 7, 2011

Hi Lee, What are your continuity readings for the ring? I presume the ring is RCD additionally protected and you are attempting to perform a no-trip loop test? Others have reported sometimes the RCD introducing an apparent additional impedance when testing in no-trip with some testers. To check this disconnect the final circuits from the RCD and no-trip loop test directly at RCD output terminals, if the reading is significantly different to your recorded Ze you have confirmed an apparent RCD impedance cause by the particular test method and/or instrument used. If this is the case reconnect the final circuits and record the calculated Zs from Zs=Ze +(R1+R2).

leestaf · Oct 8, 2011

Hi Guys
Thanks for help so far
The continuity readings are fine 0.7 0.7 and 1.25, the polarity is ok and this woulld have been picked up by the tester as it wont perform if polarity is wrong. Ins Res is 11.24 on L-E but wouldnt think this would result in >200 measurement.
Junction box could be a possibillity but i hope not as the kitchen has a flat roof and no access so unless YeeeHaaa Joe has been at work i would'nt expect JB's
BS3036 fuseboard at present so no RCD but im due to upgrade to 17th CU as part of remedials of a dom PIR.
Think a little further investigation required to fix this.
Many Thanks to you all

telectrix · Oct 8, 2011

check for a N-E reversal. the martindale won't pick this up.

leestaf · Oct 8, 2011

Will try plug in tester again but the meter wouldn't test if polarity wrong.
Had sockets off and they seemed ok. Weird

malcolmsanford · Oct 8, 2011

Lee how many sockets are not allowing you to test for the Zs? Was wondering if for some abstract reason the BS 1363 leads was not making contacts in the socket properly?

Are any other sockets in the house giving you the same problem. If not then I think the best way to do this is with a wander lead one end attached to one end of the ring cable at the CU and with a socket adapter go around testing continuity at each socket just to make sure everything is as it should

leestaf · Oct 8, 2011

Good idea Malcolm will do,there are 4 x 2g sockets in the small galley kitchen however as the house is a 2 up 2 down the kitchen is extended to the rear of the property and this'd It's where the problem is. I doubt its a coincidence bit will give the ****** lead a go cheers.