High ze at spur?

[Mewff91]

Hi All just doing some testing in my friends house as he has just moved into a new home and wants some work done.

Whilst i was carrying out a ze test on the upstairs ring final circuit i found a spur which had a ze of 2.4 ohms seemed a bit high to me, i tried tightening the earth etc changing the socket as it was a cheap on still the same reading?

Anyone have any pointers or had this problem before?

Also whilst carry out a ze test i found that when reconecting the main earth i had a few small sparks emit from it. I left the main earth disconnected and testing on volts the main earth to the ground and had 55v

The supply is a tn-c-s system

Just wondered if any of you have come across this before?

Thanks in advance

- - - Updated - - -

Zs on ring final do apologise it is late!!!!!!

 

[daiplayer]

what was the Ze reading ?

 

[ackbarthestar]

Also whilst carry out a ze test i found that when reconecting the main earth i had a few small sparks emit from it. I left the main earth disconnected and testing on volts the main earth to the ground and had 55v

Read more: http://www.electriciansforums.net/i...lations/59917-high-ze-spur.html#ixzz1zhxQwaIH
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I assume that the installation was isolated before you commenced with the Ze test?

That apart, how did you measure the Suppliers 'earth' to real earth? Since the suppliers earth is the neutral and 55v is way too high. The DNO allow something in the region of 11V max.

 

[Thomas123]

what was the Ze reading ?

Yeah, you may have a ze of 2.3 ohms so a Zs of 2.4 ohms then would be low.

 

[telectrix]

need to start at the beginning. Zefirst, then Zs. a high reading for Zs could be caused by 1. main switch/isolator. 2. RCD. 3 MCB. 4. poor connections.

 

[AndyL]

Is it just high Zs on the one socket, if so check line and CPC connections at both ends i.e at the socket and at the point at which it connects to the ring ( if you can find it)

 

[telectrix]

and if in doubt, make sure the cure all ills is fitted. 30mA RCD.

 

[Mewff91]

Hi guys

I had a zs reading of 2.4 ohms at the spured socket
had a ze reading of 0.16 ohms

Ze is fine as for a tncs max is 0.35 ohms.

Max zs on 32a breaker type b is 1.16 ohms
not sure why its so high.
All othe sockets on the ring seem ok and within the 1.16 ohms?

 

[telectrix]

test at the back of the socket, on the terminals. could be a bit of resistance in the pin connections in the socket.

 

[Mewff91]

Just popped over there found that the socket feeding the spur is infact a spur itself.
I Think im going to add them both into the ring final Circuit will be easy too as all cables are in the loft dropping down stud walls.
couldnt get to the socket i think its fed from as there was loads of stuff in the way hate it when that happens!

Didnt get chance to test again will do some testing tommorrow.