RCBO tests

[TheReturnOfHightower]

Anyone an idea why an RCBO measures >40ms on a 5x test on the second half of the sine wave but all other tests are within requirements? Sorry, it's not a single RCBO, there's 2 RCBOs in this board and both have similar results leading me to think not a faulty RCBO but an issue further upstream somewhere. Continuity, IR, Zs all textbook.

Trip times are something like 48ms on 1x, 28ms 5x on first half and >40ms second half 5 for both devices. No other RCBOs in the board but a different, adjacent board's RCBO tests fine.

 

[Strima]

What make of RCBO? fivebloodywords...

 

[static zap]

Nothing for certain but a technical thought ,since DC
sensitive RCBO's have been mentioned !
Are there any DC powered appliances - PC Power supplies,inverter washing machines present.
(Wacky idea, each half cycle has a polarity , Are we looking at a pulsed DC leak de sensitizing 1 polarity ?)...
I may just be a rabied dog barking up a theoretic tree ... Faults do come in batches .
(though does feel like a feature of install / or test gear brand mix)
-----
rolyberkin was having similar problems with a 32A
Lewden.
RCBO Test data - 40 milliseconds
I Have my doubts at times with MFT
software -"recognising test results" that are not common yet !

 

[Andy78]

My first thoughts would be to check all loads were removed and the tester was on the right setting for the rcbo type.

 

[TheReturnOfHightower]

All loads removed, tested with this the only breaker turned on. Settings checked and double checked, and used on another board no issues.

RCBO is the mem2 pod snap in type, both on c32.

 

[Ian1981]

With the pods the manufacturer advises that You have to remove the wire from the terminal and just insert the probe into the terminal.
The only probe I’ve managed to inert are the very fine ones that screw or insert onto the tests lead

Unsure if this is 100% correct

 

[Ian1981]

@westward10 might be the man to help regarding mem pods?

 

[westward10]

The latter pods generally read 38/28, ×1/×5. Earlier devices can be random and can be 38 or even 39 ×5. They do fail ×5 so you can assume if you are testing them correctly to be duff.