Measuring ZE - Am I getting too high a measurement? - what is 'normal range'?

[lewismogwai]

Hi all, I've just put in a new 32amp ring main in a domestic Crabtree Starbreaker box , I've tested for R1 + R2 at all of the 12 sockets in the ring (a loft conversion) and I'm getting 0.36 as the highest reading.

When I test for ZE I'm getting 1.28 which when I add this to R1 + R2 I'm getting a reading of 1.64 for ZE, which of course is too high to make the maximum earth fault loop impedence in ohms against BS7671:2008 (2011), which specifies a value of 1.16, which of course needs to be adjusted down to 0.92 to comply.

Any ideas as to how I can put this right? Is my ZE abnormally high and would you say that my R1 + R2 is on the high side?

Any help much appreciated.

 

[Andy78]

What earthing system do you have ? What's the max ZE for your system ?
There's your answer.

 

[Sintra]

What type of system is it? Are there any RCD's or RCBO's protecting the circuit?

 

[telectrix]

32A MCB type B is 1.44 adjusted to 1.16. your Ze is excessive both for TNC-S and TN-S. if it's a TN system, call DNO.

 

[lewismogwai]

What earthing system do you have ? What's the max ZE for your system ?
There's your answer.

You know what, as I didn't put the board in I didn't think there was a standard for this, as it was all down the measurement on the circuits coming off it - I'l have a look thanks.

 

[lewismogwai]

Its a Crabtree Starbreaker - lts got a 63A 30mA RCCB on it for earth leakage protection, to go with the MCB's - Type B BS EN 60898 - with the load split between upstairs and downstairs.

 

[Octopus]

Its a Crabtree Starbreaker - lts got a 63A 30mA RCCB on it for earth leakage protection, to go with the MCB's - Type B BS EN 60898 - with the load split between upstairs and downstairs.

And the supply type is?

 

[Engineer54]

Is he talking about Ze or Zs?? ....He's as confused as me!! lol!!

 

[Geordie Spark]

Is he talking about Ze or Zs?? ....He's as confused me!! lol!!

Does he even know?

 

[monkeyelectric]

Hi all, I've just put in a new 32amp ring main in a domestic Crabtree Starbreaker box , I've tested for R1 + R2 at all of the 12 sockets in the ring (a loft conversion) and I'm getting 0.36 as the highest reading.

When I test for ZE I'm getting 1.28 which when I add this to R1 + R2 I'm getting a reading of 1.64 for ZE, which of course is too high to make the maximum earth fault loop impedence in ohms against BS7671:2008 (2011), which specifies a value of 1.16, which of course needs to be adjusted down to 0.92 to comply.

Any ideas as to how I can put this right? Is my ZE abnormally high and would you say that my R1 + R2 is on the high side?

Any help much appreciated.

Have you nulled the leads? As everyone else has asked what is the earthing arrangement?

 

[chrish_1977]

Sounds like its a user error, what do you think you should be getting and are you testing correctly?

 

[xbeazt]

think he is after max Zs for the circuit.

 

[telectrix]

i told him that in post #4.

 

[Octopus]

7 hours and no feedback from the OP.

Maybe he's realised his mistake, or killed himself?

 

[pencilpusher]

If its a TT, then the jobs a bloody good 'en! :hurray: