Trip Testing RCBO

[mikeymoo]

Whilst testing a RCBO for trip current on 5x i'm getting a result of >40ma.
Changed the Rcbo but still get the same result with is outside what the regs say..
Any suggestions?

 

[Moog]

Whilst testing a RCBO for trip current on 5x i'm getting a result of >40ma.
Changed the Rcbo but still get the same result with is outside what the regs say..
Any suggestions?

1. Meter lost calibration
2. Meter's Batteries not supplying 150mA due to being flat or drained


Hope this helps

 

[mikeymoo]

checked with another meter and same reading. Batterys changed also??

 

[platty1005]

How far from the RCBO are you testing Try to test as close to the RCBO as possible
If you are far away the resistance of the cable may affect the current output
Also What make and model are you using My Old robin RCD tester does not need batteries
I assume you are using a new multifunctuion tester If yes which one ?
What Is the Voltage at the test instrument?
What are the full set of test results ? IE 2 x 1/2 , 2 x 1 and 2 x 5
What make of RCBO is it ?
What is the mA rating ( 30mA )
There are a lot of cheap rcbo's on the market that don't comply with BSEN 61009

 

[mikeymoo]

How far from the RCBO are you testing Try to test as close to the RCBO as possible
If you are far away the resistance of the cable may affect the current output
Also What make and model are you using My Old robin RCD tester does not need batteries
I assume you are using a new multifunctuion tester If yes which one ?
What Is the Voltage at the test instrument?
What are the full set of test results ? IE 2 x 1/2 , 2 x 1 and 2 x 5
What make of RCBO is it ?
What is the mA rating ( 30mA )
There are a lot of cheap rcbo's on the market that don't comply with BSEN 61009

Sorry guys the readings were 40ms not 40ma... Tried it at the closest socket on the ring. Approx 9 mts from cu. Its a megger 1557, also tried with a fluke and get the same reading. Its a Chint RCBO. Changed with 2 others and just the same. Just on the one downstairs ring. Others are coming back at around 17ms
Also put the one from the ground on the upstairs and its testing at 15ms.
All other reading at well within what the should be..

 

[MikeK]

Hi mate

Whats the ZS on tthe down ring?

Does the TEST Button trip the RCD?



MikeK


PS

Many RCBO cannt detect earth leakage without good incoming Neutral (without earth fly lead.)

check the lenghth of wire strip on incoming Neutral.
If to short and part insulation under terminal, may be enough to give voltage but may not trip RCBO.

MikeK

 

[platty1005]

Hi Mikeymoo

It looks like a fault on the downstairs ring circuit if the same RCBO trips correctly when connected to upstairs ring

I would start by treating this down ring as a new circuit and carry out a full inspection and test

Continuity of ring final circuit conductors
Insulation Resistance
Polarity
Loop impedance

It is most likely you will find a fault and then will need to rectify in order to get correct reading for the RCBO

 

[mikeymoo]

Thanks for your imput guys..

And yeah RCD does trip with the test button.
Insulation resistance is >299
Polarity is fine
Zs 0.44

rcd trips at 17.6ms -100%
and 50ms -500%

trip current is 23ma

Its really got me puzzled

 

[Spudnik]

Have you tried testing the RCBO direct with no cables connected to it????????

At least that way you'll know if it is the RCBO or not.

 

[mikeymoo]

No will try that thanks..