Faulty RCD tripping on the button but not via the tester

[tony9i9i9i]

Have a thorough read through the thread I've linked below Tony. I had a similar problem to you (ignore the fact I wrote that the RCD was faulty in my first post in the linked thread, I was wrong as I suspect you may be) and this thread helped me to understand why a perfectly good RCD will not trip when tested from a socket or light rather than at the RCD itself (with outgoing terminals disconnected).

It is always unlikely that the RCD is faulty, not impossible, just unlikely. I have only come across a handful of faulty RCD's in the last 10 years.

Here is the link/thread Why isnt the RCD tripping? - https://www.electriciansforums.net/threads/why-isnt-the-rcd-tripping.176881/#gsc.tab=0

Will do thanks.

 

[OLDBOY]

RCD's sometimes seemingly dont operate within the specfied time when tested with loads in circuit because of an appliance with a capacitor. Fridges and freezers in particular are prime candidates. This is because for a split second after the supply is disconnected the appliance capacitor holds on to a charge, so the tester still sees a voltage even though the RCD has operated.

 

[tony9i9i9i]

Thanks everyone for your help on this one, I've bookmarked the other thread.

Turns out on this one it was a faulty RCD, I went back with a new one, tested the original as advised and it would not operate. Swapped it out and it's all tickety.