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high zs

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  1. D

    High zs

    Hi Guys. Testing domestic rewire today. ZE = 0.14 OHMS. But when tested on the load side of the rcd it was 0.57 ohms. I was using a megger 1552 multitester. The zs readings where much higher than they should have been. Is there a problem with this meter and rcd . No trip function seemed to...
  2. G

    high zs reading

    Testing a new terrapin buliding at a primary school today. The supply to the terapin is 90metres of 35mm 4core. Swa as CPC. At the terapin db i get 0.59 ohms as Zs. All the circuits in the terapin are 30ma RCD protected. Is this acceptable as the zs of the individual circuits does not meet the...
  3. M

    High Zs readings

    Hi all, some advise please... I have a building full of type 4 3871 FE breakers, that have recently undergone a PIR. Many of the ring circuits have come back as having high Zs readings and have thus failed, with each only failing by like 0.04 of an ohm. There are no earths in the circuits, with...
  4. F

    high zs readings

    what causes high zs readings on a ring socket circuit and when testing end to end l=0.60 n=0.68 e=over 200 help what could this be
  5. P

    Slightly high Zs on large ring circuit

    Hi all, I did a PIR yesterday at a largeish house (150m2). there is only 1 ring final circuit for all house sockets. Zs was 1.25ohms, vs 1.16 permitted maximum value. there is an RCD so additional protection in theory although the RCD did not disconnect at 5x 30 ma test. I will obviously...
  6. S

    High zs reading on ring

    Hi all did a zs reading on a ring circuit today and got a high reading of 1.26 on a 32 amp bs en 60898. I looked in the on site guide and it states the max is 1.16 but in the regs it says 1.44 so I don't no which one is correct? When doing the zs by calculation zs= ze which is 0.18 tncs + r1...
  7. M

    High Zs readings

    I have read a bit on here about getting high Zs readings compared to (R1 + R2) + Ze tests. I have just replaced an old fuseboard with a Contactum dual RCD CU. Ze is 0.2 on a TNCS system On the ring circuit I have an (R1 + R2) of .54 but a measured Zs of 1.39 -- PSCC of 384, PFC of 158 On the...
  8. T

    High Zs on 800A MCCB

    High looking for a bit of advice might be picking this up incorrect. A main supply panel board with an 800a and 400a mccb feeding a factory an office block respectively. Tested Ze 0.07 ohms Production Building Zs 0.04 ohms Office Block Zs 0.07 ohms Length of runs from panel board to both...
  9. M

    ANOTHER WEIRD ONE!!!!High ZS readings

    Hi There, We have just been testing a job that is coming to a close. The job is a detached bungalow out in the sticks. The supply comes down overhead lines then down the column, then underground into the property. Im pretty sure its a PME system. My end to end readings on the ring mains are...
  10. S

    high ZS what would you do?

    Was having this discussion today with the guy i was working with. You went and did an PIR and found several of the ZS current over the max ZS alloud by the regs so wont disconnect in 0.4s. I was told on the 2392 tesing course that it would be okay to put these circuits on an rcd, as this will...
  11. S

    Question regarding high Zs on 3-phase motor circuit using BS88 fuses

    Industrial installation (non-domestic). Here's the scenario: A large (150kW) 3-phase motor circuit where the supply is taken from a starter fitted with 315A BS88 HRC fuses. From calculation using the cable data, the Zs value exceeds the manufacturers requirement for 5s disconnection time...
  12. R

    reasons for high zs?

    Tnc-s install. with a ze of 0.31. Im gettin a high zs of 44.1 on kitchen lights. All lights have earth conected. Does this sound like a loose earth or faulty jb buried somewhere?? Iv repalced fuseboard and all bonding and earthing meet regs. I understand its RCD protected so ok but id like...
  13. Dean Williams

    High Zs with RCBO

    Hi folks Just tested a convent/nursing home for nuns found some long ring circuits frotected by 32A Type C RCBOs, the max Zs allowable is 0.72, but i was getting readings between 0.83 and 0.98. Are these readings acceptable because of the use of RCBOs, i.e. does it matter what the reading is...
  14. G

    PIR Test high Zs on 32 Amp RCBO

    Hi people I had an high Zs of 0.85 on a 32 Amp type C ring circuit, which was on an RCBO. My first thought was to give it a code 2 'requires improvement', and then change it to a type 'B' so it would conform. Then I thought it is on an 30mA RCBO, where the max Zs in theory can be 1667 ohms...
  15. E

    high ZS and not tripping out RCD problem

    I have just finished a job on a house that has not been altered electrically for 40 years, my job was to rewire kitchen, upgrade earthing to current spec and fit new distribution board to 17th edition. All well and good but when I tested it, the old existing ring was giving me high resistance...
  16. J

    high Zs results

    hello i am wondering all the ways of how to fiz a high Zs reading as i no this mean internal earth reading including bonding?? befor u all start im only asking
  17. W

    does anyone could help,high Zs value

    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...
  18. J

    Zdb = high Zs???

    benn putting in a new lighting circuit in a flat lately, all done and came to testing, tested the Ze at the board having isolated it and removed incoming earth so as to get no paralell paths, reading was 2.66 !!! so went to the mains cupboard to look at getting the Ze of the whole building, but...
  19. I

    High Zs readings on ring main

    Hi Guys, I have recently changed the CU in my home in order to have a Napit inspection (not yet a member).I have done a Zs check on all the sockets. Most of the readings are ok but a couple are reading in the region of 1.30 to 1.39 ohms.The MCB is a 32 amp B type.The max allowed from...
  20. T

    High ZS but R1+R2 and Ze ok

    Just extended a ring to include 4 more sockets. Arangement =T-N-C-S ZE of .27 and R1 + R2 of the ring is .67 ohms max So by calc Zs should be .94 ohms. Im getting 1.3 ohms on zs test at sockets. anything from 0.7 to 1.3 ohms around the ring. :confused:

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