does anyone could help,high Zs value

[wiktor1072]

Hi evryone!!!just have a question regarding testing,today i have tested an installation,and the values r quite unexpected to me as i have done many tests so far but i can not explain why is like that?
i have got PFC measured 8,6kA which is high , i have measured Ze it comes to 0,04 ohm.
And now I have shower circuit 10mm cable R1+R2=0.05 ohm and Zs comes quite high 0,54 ohm,another lighting circuit R1+R2=0,57 Zs=1,25 ohm all the rest circuits is similar about Zs-0,5 ohm higher than R1+R2,I can not understand why is like that ,if anyone could help please!Many thanx.Wiktor
Just to know main incoming supply is in piro cable(do not know how is writing)
Thanx

 

[johnboy6083]

is this theinnaccurate readings that some of the fella's on here have reported with anti trip features on their testers?

 

[telectrix]

areyou sure you dissed the main earth from the board when testing Ze.

 

[BigBreakfast]

Hi Wiktor,

Is there an rcd covering the shower and if so are you taking into account the internal resistance of the rcd which can raise the value of Zs?

 

[wiktor1072]

areyou sure you dissed the main earth from the board when testing Ze.

Yes i did,I have disconnected the main earth and tested sevral times the value was the same ,I have put a spring clamp on the main cable and the reading is the same even if i test directly to the piro cooper..tnx

 

[wiktor1072]

Hi Wiktor,

Is there an rcd covering the shower and if so are you taking into account the internal resistance of the rcd which can raise the value of Zs?

Yes i have installed new dual rcd CU,vell so far i have normally installed wylex ,this CU is a new manufacturer i even do not know ebout it before,so You recon that could be the rcd's?thanx mate

 

[Red Devil]

What earth fault loop impedance tester were you using? Can you repeat the results on another brand of test intrument?

 

[Sparky Ninja]

Are you carrying out the test with ant-trip on?

 

[wiktor1072]

What earth fault loop impedance tester were you using? Can you repeat the results on another brand of test intrument?

i have got megger only at the moment ,and I did test on another property with i have tested sevral days ago and the resaults were good..

 

[wiktor1072]

Are you carrying out the test with ant-trip on?

No ! is off.that'right i am here,for the past three years i did not get so confused.tnx

 

[Johno]

I agree with an earlier post, for the Ze your tester is set to high and for Zs it would be set to no trip, try testing Ze on no trip and see if that matches.
Are you using the same leads?

 

[Sparky Ninja]

I'd carry out a zs test at the main switch at the DB, then on the MCB's to see if the RCD's or MCB's are giving any additional impedance.

No ! is off.that'right i am here,for the past three years i did not get so confused.tnx

huh?

 

[wiktor1072]

I agree with an earlier post, for the Ze your tester is set to high and for Zs it would be set to no trip, try testing Ze on no trip and see if that matches.
Are you using the same leads?

Yes !i am using the same lids,Ze tested on high (disconnected from MET)and Zs tested at non trip.That is the results I have got mate tnx

 

[Johno]

Have you tried Ze on no trip?

 

[wiktor1072]

Have you tried Ze on no trip?

yes that is what I normally do . I do measure Ze on a high,i have not tried on non trip.shall I?

 

[telectrix]

Or---- get a joiner to band a nail through a cable. that should bring it down

 

[Johno]

I only suggested it to see if it was a fault on one of the settings on your testers

 

[Johno]

if you were testing Ze on high and Zs on no trip, then I just thought that it was possible that this was the reason for the difference. Testing Ze on no trip would rule this out.

 

[wiktor1072]

if you were testing Ze on high and Zs on no trip, then I just thought that it was possible that this was the reason for the difference. Testing Ze on no trip would rule this out.

well,I can not test Zs on high because rcd would trip obviously,but Ze why i should test on non trip if there is no Rcd protection?tnx

 

[wiktor1072]

I only suggested it to see if it was a fault on one of the settings on your testers

oh I see!no mate I thought the same ,that is only the one installation I can not understand .the procedures I'am keeping the same.

 

[Johno]

Can you read? If so, read my posts again. What I am trying to say is that you need a common denominator to rule out a fault in the testers (not that this would totally rule this out), but if I were you I would try it.

 

[wiktor1072]

Can you read? If so, read my posts again. What I am trying to say is that you need a common denominator to rule out a fault in the testers (not that this would totally rule this out), but if I were you I would try it.

Right!

 

[Benny_Boy]

Just read this thread and having had a think about the current path am wondering if the main switch might have a high resistance contact in it. Could explain the uniformly high direct Zs readings you're getting. If you've got a spare, try swapping the main isolator and retest. Also if you have an isolator fitted after the meter but before the CU this is also a possible fault location.

Just have a think about where those electrons are flowing and elliminate every switch and union one by one. You'll get it!

 

[wiktor1072]

Just read this thread and having had a think about the current path am wondering if the main switch might have a high resistance contact in it. Could explain the uniformly high direct Zs readings you're getting. If you've got a spare, try swapping the main isolator and retest. Also if you have an isolator fitted after the meter but before the CU this is also a possible fault location.

Just have a think about where those electrons are flowing and elliminate every switch and union one by one. You'll get it!

HI Benny!!!that is the point!!!Thanks a lot,Today I have done the test
again as You and other guy suggest to get do Zs at Cu and there is a problem I got the new make of Cu I have not use before,but when I measured at the bass bar one Rcd showing 0,53 other 0,64 ohm at Ze=0,04.
Yes I am going to do the test once more at Main Isolator and see,unless now I know what is the problem.Thanx a lot mate,very helpfull!great job!

 

[wiktor1072]

I'd carry out a zs test at the main switch at the DB, then on the MCB's to see if the RCD's or MCB's are giving any additional impedance.






huh?

sorry mate just notice I have post a wrong message to You!
But thank You very much for an advise,I did the test as You sed and You are right the problem is with the rsd,s or with the main isolator,i will have to do just another test at the isolator on its own.But I got the answer,where is the problem,thank's a lot mate!!

 

[Benny_Boy]

sorry mate just notice I have post a wrong message to You!
But thank You very much for an advise,I did the test as You sed and You are right the problem is with the rsd,s or with the main isolator,i will have to do just another test at the isolator on its own.But I got the answer,where is the problem,thank's a lot mate!!

Glad to help.