UK Different test results after DB change

[Welsh_sparky_21]

Is it common to get different test results when upgrading a db? Basically I done an EICR in November and came back to upgrade the db and done live tests on all the circuits, but my results were quite different. Like 0.30 ohms out on one circuit

 

[buzzlightyear]

but my results were quite different. Like 0.30 ohms out on one circuit

my Chrystal ball saying different ,what was it before you tested some times there is a slit difference ,but how much .

 

[Petej999]

Is it common to get different test results when upgrading a db? Basically I done an EICR in November and came back to upgrade the db and done live tests on all the circuits, but my results were quite different. Like 0.30 ohms out on one circuit

Either you or the previous

 

[Petej999]

What tests were you engaged in to get this discrepancy??

 

[buzzlightyear]

Is it common to get different test results when upgrading a db? Basically I done an EICR in November and came back to upgrade the db and done live tests on all the circuits, but my results were quite different. Like 0.30 ohms out on one circuit

please clarify what where you testing at the time .

 

[timhoward]

If low current Zs tests - then maybe.
Otherwise somethings up. More info please.

 

[Welsh_sparky_21]

What tests were you engaged in to get this discrepancy??

Zs tests on the circuits

 

[123]

Are your tests after the board change?

 

[Welsh_sparky_21]

Are your tests after the board change?

Tested before, during initial EICR way last year. Then went back to upgrade DB this week and we live test after upgrading DB, the Zs readings on some circuits were a lot lower than they were. Meter tails were upgraded and the Ze went down by 0.11 but some circuits the Zs was 0.30 lower

 

[timhoward]

Tested before, during initial EICR way last year. Then went back to upgrade DB this week and we live test after upgrading DB, the Zs readings on some circuits were a lot lower than they were. Meter tails were upgraded and the Ze went down by 0.11 but some circuits the Zs was 0.30 lower

It might simply be a result of re-terminating all the CPC's properly.
Does it happen to be the case that the ring final circuits are closer to original readings? In theory these will have had the CPC disconnected for fig 8 tests, so should be more recently tightened.
For other circuits it's conceivable that the CPC's weren't touched during the EICR...depending on how the tests were carried out of course.

Then again live Zs tests are notoriously variable and can be affected by electrical 'noise' easily.

 

[Welsh_sparky_21]

It might simply be a result of re-terminating all the CPC's properly.
Does it happen to be the case that the ring final circuits are closer to original readings? In theory these will have had the CPC disconnected for fig 8 tests, so should be more recently tightened.
For other circuits it's conceivable that the CPC's weren't touched during the EICR...depending on how the tests were carried out of course.

Then again live Zs tests are notoriously variable and can be affected by electrical 'noise' easily.

Like you say could be a combination of that, and the fact the ze is went down by 0.11 since the tails have been upgraded etc

 

[Dustydazzler]

I have got different readings on ZS when using my mft and my dads mft on the same circuits

Not wildly out but certainly enough out to make me look twice at the read out

 

[LastManOnline]

It might simply be a result of re-terminating all the CPC's properly.

My money is on this possibility or something similar. For instance, we have recently had to carry out testing on premises that were dormant/vacant for 2 years (covid related). A number of FLi socket circuit tests were marginally higher than the regs allowed. I did wonder why the installation had been passed in the first place. However as the installation opened up for business again and sockets started to be regularly used we found on retesting some weeks later that Zs values had dropped significantly. Sometimes it can be as simple as a fine film of dust lying on the contacts

 

[Vortigern]

Of course if you get a high reading on a socket, the usual thing to do is to put the plug (tester plug top) in and out of the socket several times and switch the socket outlet on and off several times then the reading drops usually quite significantly.

 

[LastManOnline]

Of course if you get a high reading on a socket, the usual thing to do is to put the plug (tester plug top) in and out of the socket several times

Yes. That's what would normally be done on getting a high reading. And that's what we did on initial testing, but it did, nt bring the readings down. It was only after several weeks of the sockets been in continuous use that that there was an impact on the readings. I, m just speculating that the long dormant period led to this situation somehow

 

[UNG]

A lot can depend on the environment the MFT was kept / transported to site in prior to the testing being carried out and if it was given time to acclimatise to the conditions of the premises being tested

This is one of the reasons why I'm not a fan of wholesalers on the day calibration events as it is difficult to produce accurate calibration results without the lab conditions to give a baseline to qualify the results to the required standard