High Ze...

Spearmint · Feb 21, 2015

Had the DNO out last week to remove old three phase overhead lines to a property undergoing refurbishment as they were sagging really low (within 2m from the ground!), had been for years and the new owner didn't like the look of them! Anyway the DNO agreed to remove and joint a new underground supply from the existing pole to a new location at the other end of the property. After all the work was done they mentioned that they dropped the fuses from 80A to 60A due to high EFLI.

Firm I work for only have Metrel MFTs, can't remember model off top of my head but all the same model. Went to test the new board before energising and I'm getting a Ze of 0.44... on a TN-C-S. Now these MFTs can only do no trip, and I'm aware of that higher readings no trip can give but the only way of getting a lower reading is to reduce the test current. Reducing to 30ma for example gives 0.34, even that's not ideal! I feel uncomfortable with these readings but we don't have a high current tester.

So... should I push for a new tester to verify the reading or just recommend getting the DNO out?

davesparks · Feb 21, 2015

They have already reduced the size of the fuses to compensate for the increased EFLI, so why are you now questioning a slightly higher than usual EFLI?

Leesparkykent · Feb 21, 2015

Is it this metrel?

telectrix · Feb 21, 2015

if my mft looked like that, i'd be considering suicide.

Leesparkykent · Feb 21, 2015

telectrix said:
if my mft looked like that, i'd be considering suicide.

Hahaha

Spearmint · Feb 21, 2015

davesparks said:
They have already reduced the size of the fuses to compensate for the increased EFLI, so why are you now questioning a slightly higher than usual EFLI?

Probably me just being over cautious! I've only been told that that's what has been done, I personally wasn't onsite when the work was finalised. If I went by the fuse holder ratings I'd still be thinking there's 100A fuses in each one!

Leesparkykent said:
Is it this metrel?

No, it's got a rotary dial for a start.

Leesparkykent · Feb 21, 2015

This one?

Spearmint · Feb 21, 2015

Leesparkykent said:
This one?

Near as damnit! Those colours as a bit trippy though, ours are more blue and grey.

Leesparkykent · Feb 21, 2015

These both do high limit, you just have to flick across.

Spearmint · Feb 21, 2015

Leesparkykent said:
These both do high limit, you just have to flick across.

Looks almost identical to this apart from it isn't just an insulation tester.

trev · Feb 21, 2015

That one isn't just an IR tester nate. It looks very much like my 61557 which is sadly no longer with us

Leesparkykent · Feb 21, 2015

Spearmint said:
Looks almost identical to this apart from it isn't just an insulation tester.
View attachment 28068

looks like its off the ark lol

Spearmint · Feb 21, 2015

trev said:
That one isn't just an IR tester nate. It looks very much like my 61557 which is sadly no longer with us

Yeah you're right, didn't look at the picture properly. The ones we use do the full lot apart from earth electrodes.

Leesparkykent said:
looks like its off the ark lol

Sometimes feels like it's from the bloody ark!!!

trev · Feb 21, 2015

Spearmint said:
Yeah you're right, didn't look at the picture properly. The ones we use do the full lot apart from earth electrodes.

Sometimes feels like it's from the bloody ark!!!

Damn good testers though