32a RCBO Failing 5x with >50v showing

[HOWIES]

Hi

Circuit Info

32a B RCBO Feeding a Combi Boiler through a FCU in the airing cupboard of the bathroom.

Tested at 1/2 Passed tested at 1 > passed reading Oo 20.5 and 180o at 21.3

When testing at x5 the RCBO is tripping but my meter (kewtech KT63) is showing fail >50v

Im assuming that this is because it it requiring greater than 50v to operate

I have tested:-
at the terminals
FCU
At the terminals with live disconnected
" " " " " " " neutral disconnected

all other RCDs (2 in total) in the CU have passed with x1 29.6 & 31.4 and x5 26.8 & 22.3

It is a TT system and the Ze is 81.9
Zs of all other circuits are between 82.1 and 84.7

Have i missed something? or is the RCBO Faulty

 

[marcusone]

Try testing at the RCBO terminals with loads off. If it fails then, change it.

 

[HOWIES]

thank you

 

[chrish_1977]

32a RCBO Failing 5x with >50v showing

Is it just me or are the zs' a bit low once you take into account the ze of 81.9, either that or very good readings, that's makes the R1+R2's really really low

 

[telectrix]

Re: 32a RCBO Failing 5x with >50v showing

Is it just me or are the zs' a bit low once you take into account the ze of 81.9, either that or very good readings, that's makes the R1+R2's really really low

parallel paths through bonding and extrraneous metal pipes.

 

[HOWIES]

yea , its a brand new install and the readings are superb. for instance the R1+R2 on the boiler feed is 0.13

 

[tony mc]

No the meter is telling you that the touch voltage in the premises is more than 50 volts when you are putting 150mA INTO THE CCT so it is aborting the test. What is the ZS reading for this circuit as it sounds like a failure of the CPC so a high EFLI ! !

Hi

Circuit Info

32a B RCBO Feeding a Combi Boiler through a FCU in the airing cupboard of the bathroom.

Tested at 1/2 Passed tested at 1 > passed reading Oo 20.5 and 180o at 21.3

When testing at x5 the RCBO is tripping but my meter (kewtech KT63) is showing fail >50v

Im assuming that this is because it it requiring greater than 50v to operate

I have tested:-
at the terminals
FCU
At the terminals with live disconnected
" " " " " " " neutral disconnected

all other RCDs (2 in total) in the CU have passed with x1 29.6 & 31.4 and x5 26.8 & 22.3

It is a TT system and the Ze is 81.9
Zs of all other circuits are between 82.1 and 84.7

Have i missed something? or is the RCBO Faulty

 

[HOWIES]

Zs is 81.17 tried the RCBO with every other circuit isolated still showing same error

 

[tony mc]

Have you tried another RCBO on that cct & if so did that trip in 40 ms or under ?

For touch voltage to attain 50 volts or over on 150 mA you would need a ZS of 333 ohms or more ! 50/0.15 !

 

[HOWIES]

Not another rcbo no. However there are two RCD'S in the CU which passed with flying colours. I've sorted out a replacement for the rcbo will be collecting it tomorrow so il check back then.

I've disconnected everything from the CU now except from that rcbo and the main switch and it's still failing so it must be the rcbo

 

[tony mc]

Disconnect both the line and neutral from the RCBO and test again, just out of interest what make of RCBO is it?

 

[HOWIES]

Did that. It's a British general and so is the CU RCD'S & MCB'S (supplied by landlord)

 

[HOWIES]

Update

Changed the RCBO this morning. All working fine.

Thanks for the help gents