Zs reading help?

[Roger]

Ok I understand how it been calculated as the maths could not be easier.Blimey i've spent time getting worried when my Zs is 2 ohms higher than the required 1.44 on a 32amp RCD protected ring.
The table 41.5 is listed under the TT system and that is what I have always worked to.
Reading the small print Note
The circuit loop impedances given in the table should not be exceeded when the conductors are at there normal operating temperature.
Like the previous post RCD/RCBo's are the 'magic bullet' or get out of jail card.

Never stop learning,now to play with my new Megger 1720 on the house.

 

[Blowcat]

Hi guys,
I had a job this morning to change a faulty shower unit in a flat with a direct replacment. when I had fitted the replacment unit I started the minor works cert. Tested the insulation resistance on the 10mm T+E cable all fine. But when I did then Zs I had a reading of 595 ohm? Having messed about checking the conections on the probes on the meter and what not I just thought I would test another circuit to compare,and sure enough same round about reading. Did a Ze on the board to make sure the incoming earthing was up to scratch and got a reading of 0.12 ohm (TNS Supply). What could cause this kind of reading on the Zs??:thinking:

Assuming all connections are good and your R1+R2 is roughly what you expected, I would do a Zs reading at your incoming supply using the tester on the RCD range, to see if your incoming supply is getting a good Zs on the RCD Zs range.