Very high Zs reading

[mspms]

Good evening all. I wonder if anyone could give me a steer as to why I am getting very high Zs readings. I have been testin a circuit that has a R1+R2 of 0.23 ohms but I seem to be getting Zs reading on L-E of + 40ohms. L-N is coming in at 0.2ohms. The incoming fuse is a 63amp BS1361 an RCD main switch protecting all circuits. All other tests are fine. I am wondering whether it could be my meter not reading correctly on the Zs test. Any ideas?

Thanks all.

 

[Richard Burns]

What is your Ze?

 

[trev]

What's your Ze mate? When was your meter last calibrated? It could be a few things what earthing system is it?

 

[telectrix]

try taking as reading on the L busbar. if that is high, then it's due to internal resistance of RCD and/or MCB. flick them on and off a couple of times. if that reading is OK, try at the terminals of the socket, not the front. try flicking the socket switch/es on/off.

 

[Rauer]

try taking as reading on the L busbar. if that is high, then it's due to internal resistance of RCD and/or MCB. flick them on and off a couple of times. if that reading is OK, try at the terminals of the socket, not the front. try flicking the socket switch/es on/off.

Never considered that but will remember it for future reference!!

 

[mspms]

TN-C-S. Ze seems very good at 0.09ohms

 

[telectrix]

what was the pefc at socket?

 

[mspms]

Thanks for your suggestion I will give it a go. Just to add more pain, I thought I would try a reading from a socket in my own home and again I'm getting +40ohms. Just coincedence?

 

[telectrix]

mft leads. ????

 

[Strima]

What are you using to test the socket? Have you tried testing at the terminals on the back?

 

[mspms]

Sorry teletrix. It was a long day. I gave up and came home. The house is empty at the moment so no chance of any mishaps!

 

[mspms]

My Ze was really low at 0.09ohms. My meter has just been calibrated and it is a TN-C-S.

- - - Updated - - -

I'm using my 3pin plug and leads.

 

[trev]

Sounds like the RCD

 

[mspms]

Yes, MFT leads.

 

[Rauer]

Have you zero'd your leads on eloop?

 

[mspms]

Brand new RCD main switch today. I even tried with the old 2 pole main switch. still high.

 

[Rauer]

What tester is it?

 

[mspms]

Leads have been zeroed.

 

[stef]

Batteries going down? Bad contacts on the three pin plug? Dodgy terminations, any load on the circuit? (mainly an inductive might cause a false reading) What make of RCD is it?

 

[mspms]

Just a quick note I have just tried a socket in my place and I;m getting 48.1ohms with a pefc of ony 4.78amps.