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I used 2 lead on high setting when I bypassed RCBO.It's plausible that the non-trip Zs is being affected by interference/noise, but the high current should be fine
Discuss I am getting very high zs readings in the UK Electrical Forum area at ElectriciansForums.net
I used 2 lead on high setting when I bypassed RCBO.It's plausible that the non-trip Zs is being affected by interference/noise, but the high current should be fine
Fair enough, although you should be testing for zs using main earth only, removing parallel paths.I am teasting ze with main earth disconnected, zdb with earth connected.
I didn't know that. I thought zs db/circuit should be tested with all parallel path connected.you should be testing for zs using main earth only, removing parallel paths
I will do this when I go back there. I have another mft (1553) which I will be also using . My concern is how to proceed if It also gives same results.I was about to suggest similar to @Julie -
Another thought - if you have a long wander lead with you, measure it's resistance on the continuity range.
Then do Zs@DB again normally. Then Zs@DB with the wander lead between the tester and the CPC bar. It should increase by the resistance first measured.
There are two reasons to measure ze/zdb , the first is with everything connected I.e. all parallel paths - this will give the maximum fault level, you can then check the protective devices are suitable for that fault level; the second which applies to ze/zdb and zs is with the minimum fault level likely to occur - so at the furthest point with all the parallel earth paths removed, in this case it is to ensure that the protection will operate in the required time in the worst caseI didn't know that. I thought zs db/circuit should be tested with all parallel path connected.
There are two reasons to measure ze/zdb , the first is with everything connected I.e. all parallel paths - this will give the maximum fault level, you can then check the protective devices are suitable for that fault level; the second which applies to ze/zdb and zs is with the minimum fault level likely to occur - so at the furthest point with all the parallel earth paths removed, in this case it is to ensure that the protection will operate in the required time in the worst case
by disconnecing main bonding conductors to water and Gas?so at the furthest point with all the parallel earth paths removed
That's actually how I was taught and what GN3 appears to say; Julie's logic and reasoning is spot on, and in this case I might have done it anyway to help build a picture of what is going on.I didn't know that. I thought zs db/circuit should be tested with all parallel path connected.
No argument about the logic/reasoning. I'm also mindful that GN3 implies that in all circumstances where you have live final circuits (required for these tests) you should have the bonding connected. But it also doesn't specifically describe the Zdb test as far as I can tell.There are two reasons to measure ze/zdb , the first is with everything connected I.e. all parallel paths - this will give the maximum fault level, you can then check the protective devices are suitable for that fault level; the second which applies to ze/zdb and zs is with the minimum fault level likely to occur - so at the furthest point with all the parallel earth paths removed, in this case it is to ensure that the protection will operate in the required time in the worst case
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