RCD failing ramp test. x1 and x5 both OK

[Soulcraft Electric]

Testing an Ashley & Rock BS4293 RCD Type AC (CU dated 1989, property built c. 1990-91) this morning with a Metrel 3152 on RCD Auto; x1 and x5 were both satisfactory, but the ramp test failed to trip. I tested a few times at both a socket outlet and the RCD terminals with the same outcome. Any suggestions other than replacement or is that my only option?

 

[plugsandsparks]

RCD or tester ?

 

[Soulcraft Electric]

RCD or tester ?

Haha, RCD... Tester is fine.

 

[GBDamo]

Genuine earth leakage from one or more circuits giving a false baseline, try testing at the RCD terminals with all circuits isolated then flick them on one ate a time until the culprit is found.

 

[timhoward]

I've had it once where the 4 tests that did trip each shook the device a little and by the time of the ramp test the connection was loose on the bus bar. The tester would probably fail to test if that were the case though.

As above, confirming that a ramp test at the terminals with no load also fails would be good.
Does test button work? Do x1 tests still trip it?

I'm idly wondering about DC leakage even though that apparently didn't affect x1 and x5 tests.

 

[Soulcraft Electric]

Genuine earth leakage from one or more circuits giving a false baseline, try testing at the RCD terminals with all circuits isolated then flick them on one ate a time until the culprit is found.

Tests were carried out with at both a socket and then again at the terminals with all MCBs off - same result

 

[Soulcraft Electric]

I've had it once where the 4 tests that did trip each shook the device a little and by the time of the ramp test the connection was loose on the bus bar. The tester would probably fail to test if that were the case though.

As above, confirming that a ramp test at the terminals with no load also fails would be good.
Does test button work? Do x1 tests still trip it?

I'm idly wondering about DC leakage even though that apparently didn't affect x1 and x5 tests.

Tests were carried out with at both a socket and then again at the terminals with all MCBs off - same result

 

[GBDamo]

Only because I've done it myself, have you checked the MFT is on the right setting?

I've had it on 10mA before now, in that case the 1x and ramp 'failed.

If so it's looking at a new RCD..