Zs

[cliffed]

Recently been to test new build,everything fine except for one area,lighting circuit should be reasonably low reading,like other circuits,but Zs is 2.20 ohms,other reading much lower,.66 ohms,1.2 ohms.This is a new build ,& would expect lower,at this stage, I'm just testing,would you be prepared to be happy on this reading.All protected by rcbo's 30 ma 10 amp.

 

[telectrix]

what's your R1+R2? for the lighting and your Ze? could just be a long cable run.

 

[cliffed]

what's your R1+R2? for the lighting and your Ze? could just be a long cable run.

It's 0.63, so things don't add up,I personally did not 2nd fix,may get orig sparkie back,but I have been told by my gaffer it's ok.

 

[Pete999]

Recently been to test new build,everything fine except for one area,lighting circuit should be reasonably low reading,like other circuits,but Zs is 2.20 ohms,other reading much lower,.66 ohms,1.2 ohms.This is a new build ,& would expect lower,at this stage, I'm just testing,would you be prepared to be happy on this reading.All protected by rcbo's 30 ma 10 amp.

BS and type of rcbo?

 

[Octopus]

Recently been to test new build,everything fine except for one area,lighting circuit should be reasonably low reading,like other circuits,but Zs is 2.20 ohms,other reading much lower,.66 ohms,1.2 ohms.This is a new build ,& would expect lower,at this stage, I'm just testing,would you be prepared to be happy on this reading.All protected by rcbo's 30 ma 10 amp.

Swap the 2 lighting circuits between the RCBO's and see if the "variance" moves with them or not. RCD's and RCBO's can do odd things to Zs readings.....

 

[cliffed]

Swap the 2 lighting circuits between the RCBO's and see if the "variance" moves with them or not. RCD's and RCBO's can do odd things to Zs readings.....

Maybe,the rcbo's is c type 61009 10 amp 30 ma

 

[Leesparkykent]

It's 0.63, so things don't add up,I personally did not 2nd fix,may get orig sparkie back,but I have been told by my gaffer it's ok.

0.63 Ze or R1+R2?

 

[Octopus]

Maybe,the rcbo's is c type 61009 10 amp 30 ma

would you expect this to affect the Zs?

 

[cliffed]

0.63 is the R1+R2

 

[tony mc]

Have you tried a ZS test without it going through the RCBO ?

 

[cliffed]

No,all other circuits test fine,with rcbo's in place.

 

[Leesparkykent]

0.63 is the R1+R2

So if wired in 1mm that would indicate the circuits roughly 17 meters. Try doing an EFLI test on the supply and load side of the RCBO. The RCBO could be adding the additional unexpected resistance. Or the RCBO isn't tight on the busbar but this would usually give a higher reading.

 

[cliffed]

Cabled in 1.5mm length of circuit approx 25 metres,the rcbo's are fine

 

[Octopus]

Cabled in 1.5mm length of circuit approx 25 metres,the rcbo's are fine

How have you determined this?

 

[Leesparkykent]

R1+R2 works out about right then for the estimated length of circuit. All other circuits are giving readings that are expected and your confident the RCBO's tight on the busbar and the line conductors in the RCBO terminal tight with no trapped insulation then it can only be the RCBO. I would probably swap it for a 6A C type or 10A B type depending on the characteristics of the load. As it stands ATM the circuit still comply as the RCD part of the RCBO is providing fault protection.

 

[cliffed]

R1+R2 works out about right then for the estimated length of circuit. All other circuits are giving readings that are expected and your confident the RCBO's tight on the busbar and the line conductors in the RCBO terminal tight with no trapped insulation then it can only be the RCBO. I would probably swap it for a 6A C type or 10A B type depending on the characteristics of the load. As it stands ATM the circuit still comply as the RCD part of the RCBO is providing fault protection.

Thanks,yes my thinking too,6 amp rcbo's,in place of 10 amp.
lenght of cable estimated by measuring.

 

[David M]

Just swap the RCBO for one that is known to be fine and test again, start by eliminating the simple things. As Lee said if everything else tests out fine then maybe the RCBO is suspect.

 

[Octopus]

Just swap the RCBO for one that is known to be fine and test again, start by eliminating the simple things. As Lee said if everything else tests out fine then maybe the RCBO is suspect.

Which is what I suggested in post #5 and the OP seems to have ignored!

 

[David M]

Which is what I suggested in post #5 and the OP seems to have ignored!

Yes, just seen your post, I'd just skipped through quick and not noticed your suggestion. I apologise for repeating what you had already put forward.

 

[TJ Anderson]

Yes, just seen your post, I'd just skipped through quick and not noticed your suggestion. I apologise for repeating what you had already put forward.

Take 3 lead Zs on the busbar terminal and then on the load terminals of RCBO and you will see what it is adding to your reading.