Lower Ze reading than expected

[Wilko]

Sorry, I'm a bit lost here - what measures at 0.12 ? And then you get impedance dropping to 0.03 when you go further from the cut out into a flat? Can you explain again, cheers.

 

[Gavin John Hyde]

Sorry, I'm a bit lost here - what measures at 0.12 ? And then you get impedance dropping to 0.03 when you go further from the cut out into a flat? Can you explain again, cheers.

sorry .. 0.03 ohms is Ze measured at both the switched fuse and again in the flat , each time having the earth disconnected, the first time at Switched Fuse and the Second at the earth bar so really Ze@db. the 0.12 ohms is Zsdb in the flat... which i would expect to be higher given the large metal pipes that feed the heating system across the development which are linked into the earth bar with a 10mm earth cable.

 

[buzzlightyear]

However the variance Kewtech claim raises ones eyebrow a little...

it is no good if you can not trust your mft giving you false reading.

 

[buzzlightyear]

bin the kewtech.

 

[Strima]

In work we have nearly 20 MFTs so could justify buying the Megger test box, cracking bit of kit that gives us the option to test loop impedance. I have to say all the Meggers and Metrels we have are always within range. The Flukes can be a little more temperamental.

I don't think we'll be buying Kewtech in the near future...

 

[Wilko]

Keep in mind I've now started pain killing rituals here, but I'm lost again. I got 0.03 as Ze measuring L-E with the earth dis from the board, but why does it rise to 0.12 when the other bonding is included?

In work we have nearly 20 MFTs so could justify buying the Megger test box, cracking bit of kit that gives us the option to test loop impedance. I have to say all the Meggers and Metrels we have are always within range. The Flukes can be a little more temperamental.

I don't think we'll be buying Kewtech in the near future...

Mine works perfect, always has, always will . Hang on, just gotta go sacrifice a fatted lamb or summat.

 

[Strima]

Keep in mind I've now started pain killing rituals here, but I'm lost again. I got 0.03 as Ze measuring L-E with the earth dis from the board, but why does it rise to 0.12 when the other bonding is included?

Mine works perfect, always has, always will . Hang on, just gotta go sacrifice a fatted lamb or summat.

I thought the 0.12 was the Zdb not the Ze???

 

[Wilko]

I was harf way thru that post when this joyous IT device posted it. B thing has a mind of its own, maybe that's a good thing ..

 

[suffolkspark]

are your leads okay? might sound stupid but I got in a right muddle with my KT63 last week! was testing sockets in a house and getting 0.73 zs on one socket, then on others on the same ring stupidly low readings like 0.03 and massive kA!!!! I would have thought dodgy leads should have increased the reading but for some reason it didn't! cracked out some fresh leads and everything stabilised and all sockets tested near enough the same at 0.73....

with the substation so close though its entirely possible that it isn't reading too far off!

 

[Gavin John Hyde]

okay 0.03 ohms is the Ze i get whether i test Ze at CU or the switched fuse as its technically origin... the 0.12 ohms is ZSdb which given the flat is serviced by huge metal pipes for the district heating which are bonded its got a parallel path of some substance! the heating system has a boiler type thing which is fed by the pipes and if i run a continuity test on the boiler pipes i can connect to one next door in their cupboard and get a beep.
If it helps anybody understand i have had copies emailed to me from the original install certificates by the owner. back then they only got a Ze of a 0.11 and the Zs values for circuits are pretty much what i got today, maybe a fraction out in some cases. if you look at the Zs values they are all quite low. so i suspect the flat has never had much of a Ze to begin with.if i do a PFC or PSCC pluged in at the sockets i get more sensible readings but at the CU they are all over.
i have blocked out the cert number to stop cowboys copying for fakes...

View attachment cert1.jpeg

View attachment cert2.jpeg