Zs to high!

[roboze]

hi all ,

i just got round to testing a new build i've done, and seem to getting unusually high Zs readings.

the incoming supply is 3phase (its a big house) and ze is 0.23

all other tests are fine.

the board is wylex with individuall c-type rcbo`s

all fittings are chrome.

all circuits other than the garage (white plastic fittings) zre showing abnormally high Zs readings.

So...... could it be the rcbo`s ?
could the amount of earthed chrome contribute to it?
anyone any ideas? would much appreciate your input.

my tester is a robin multi tester on the zs test it trips the rcbo but still gets a reading.

thanks people

Rob

ps its a PME system

 

[JulianC]

the zs test it trips the rcbo but still gets a reading.

That sounds like your problem - it's not getting to the correct reading before the RCBO trips.

 

[Deleted member 9648]

Calculate the zs...Ze + R1 R2. Or temporarily swap the RCBO for an mcb.......I'd calculate.

 

[bugsy]

By pass the rcd first then double check by calculation

 

[roboze]

yeah think i`ll check a couple of circuits with an mcb and if ok i`ll calculate the rest, thx chaps

 

[pevvers]

You will also find that some RCD modules put an impedance in line with the circuit as well... I remember doing a load of domestic PIR's, and finding that if I measured the earth fault loop impedance on both sides the RCD main switch I could get anything up to 0.40 ohms difference, so always worth having a look at that.

But with your Robin I don't think you'll get a decent reading anyway... (Get a Megger MFT 15 series if you can, mine have never let me down!!)