Earthing Reading

[paul_sut]

Hi all i did a fuse board change the other day and when testing i got a ZE reading of 0.43 and a KA of 5.93 why would the KA be so high, also zs failed on all circuits for breakers. This is TNS. what would any one recommend??

 

[Snapester]

over 200ohms for a TT? This is a TNS so anything over 0.8 would have me checking it out. As for relying solely on the RCD and leaving the installation in that state i think is unacceptable. What were the readings on the RCD testing, did they satisfy?

 

[Octopus]

With additional proTection by rcd is in place then 1667 ohms is the highest zs, we have 6ohms here, that's 1661 ohms less that the maxium.....although that is totally unrealistic zs and should be investigated but even then the regs states anything over 200ohms. So he has done everything to bs7671 here.

Yes, but....... the OP, to his credit is questioning the live test results and isn't happy with the, I'd be investigating them too, if it was me. With a Ze of 0.43 and high Zs on all circuits it shouldn't take too long to track down the issue.

Relying on the 1667 value is not ideal, especially when the calculated values indicate that the live tests should be within normal readings........

 

[Octopus]

You're too diplomatic today Murdoch

Being careful.

The mods are probably watching this thread and input is subdued and generally constructive as yet, it wouldn't take much for one or two posters to stir up trouble and for the OP retaliate.........

 

[trev]

Being careful.

The mods are probably watching this thread and input is subdued and generally constructive as yet, it wouldn't take much for one or two posters to stir up trouble and for the OP retaliate.........

Hmmmm, with hindsight maybe I should edit my last contribution

 

[p11jor]

That's not my attitude to leave it, I have suggested many things to test for but untill he gets back there he can't just turn & lock off the customers electric,

I wouldn't use the 1667 myself if I had a good Ze like he does but what I am saying is lets not panic and start telling them kids will burn, the zs's are withing a figure stated in bs7671 for disc times there is now additional protection via rcd do a improvement had been made, then as stated by OP he will return to investigate with so e guidance of our selfs on here who may of experienced the same problems....let's not be booking them into a hotel for the week due to a slightly high zs that If it was a tt system would problem be much greater than that and not even flinched at.

 

[Snapester]

No we aren't having ago and i think its even good he came on here for advice, we are mainly saying from my point of view that his Ze which he states was 0.43 which is a respectable reading on a TNS which i think he has read the PFC wrong as if you do the math 230/0.43 = 534.8 which looks close to what he had only decimal in wrong place?
So therefore the fault obviously lies within the installation loose connection with earthing system?

 

[trev]

Snapester, there is no problem with his reading. He has written the result down wrong, he's said somewhere in here that his tester read 543A which obviously is .543KA not 5.43
He's probably looked at this for so long and got himself going round and round in circles till he's ended up disappearing up his own back end.
It's easily done, we've all been there

 

[Snapester]

No you misunderstand his Ze is fine thats what im saying but his Zs test results are coming in high hence must be within the installation?

 

[trev]

Yeah mate but one of the confusions is over his pfc, and I reckon he's got himself screwed up somewhere. I did it once using a mate's meter, he came in while I was tearing my hair out and said "It'll help if you set the range properly"
2 minutes later job done and we're in the van having a smoke.
I'd bet if he goes back with a clear head it'll be jobs a goodun

 

[p11jor]

Zs = Ze + (r1+r2) so the r1+r2 are low so I don't think it's within the installation I'm defo going for something at the intake.....sheathing of armoured or Somthing on the lines of that ..... Looking forward to finding out now

 

[trev]

Zs = Ze + (r1+r2) so the r1+r2 are low so I don't think it's within the installation I'm defo going for something at the intake.....sheathing of armoured or Somthing on the lines of that ..... Looking forward to finding out now

Ze = .43+(R1+R2).23=.66 so we should be looking at something around that (disregarding parallel paths for now) but often an RCD will introduce a huge increase in the measured value hence the allowance of 1667 ohms. Maybe that's where he should be looking

 

[Rauer]

How have you tested r1+r2 on the ring? Have you tested the resistance through the meter?