Why does RCD trip when measuring voltage with LoZ function?

[nahuelparabere]

Why does RCD trip when measuring voltage with LoZ function?

 

[davesparks]

Could you clarify what you mean by a LoZ function?
Does that mean a low Z or low impedance function?

 

[mainline]

Could you clarify what you mean by a LoZ function?
Does that mean a low Z or low impedance function?

LoZ stands for Low Impedance (Z)

 

[buzzlightyear]

Why does RCD trip when measuring voltage with LoZ function

what testers have you got.

 

[davesparks]

Presumably you are testing from live to earth here?

As it is a low impedance test it will be allowing enough current to flow through the tester to exceed the tripping threshold of the RCD.

Does it always cause an RCD to trip or has it happened with one specific RCD or installation?

 

[nahuelparabere]

Presumably you are testing from live to earth here?

As it is a low impedance test it will be allowing enough current to flow through the tester to exceed the tripping threshold of the RCD.

Does it always cause an RCD to trip or has it happened with one specific RCD or installation?

Hi Dave, thanks for answering, it happened twice so far with rcbo's in different houses when measuring voltage between active and neutral with the low impedance function.
Probably just very sensitive rcbo's, I was wondering if someone else experienced the same and see if there's a guess why.
Cheers!

 

[davesparks]

Hi Dave, thanks for answering, it happened twice so far with rcbo's in different houses when measuring voltage between active and neutral with the low impedance function.
Probably just very sensitive rcbo's, I was wondering if someone else experienced the same and see if there's a guess why.
Cheers!

Why were you using the low impedance function to measure the voltage rather than a normal, high impedance, voltage measurement?

It may not be that the RCBO's are over-sensitive, it's more likely that there is already some leakage on those circuits and the additional current takes it over the tripping threshold.

 

[nahuelparabere]

Why were you using the low impedance function to measure the voltage rather than a normal, high impedance, voltage measurement?

It may not be that the RCBO's are over-sensitive, it's more likely that there is already some leakage on those circuits and the additional current takes it over the tripping threshold.

I was fault finding and at some stage used LoZ function to check ghost voltage, I looked for leakage with leakage clamp but there was none, I probably should have done a ramp test to check the sensitivity of the rcbo.

 

[mainline]

I'm assuming that you're using a multi meter such as Kline or fluke with a loZ function to do the measurement ?.

L to N should have been fine, L to E or N to E would probably cause the rcd to trip.

 

[cireland]

Is this any help?

 

[mainline]

Is this any help?

In reality, it should be fine according to the 117 specs the loZ is around 2k but the automatic selection that the meter does obviously can cause some rcds to trip.


Also, as Davesparks said.