RCD tripping

[Cymbeline]

Hi - last Friday evening one of my two rcd tripped. I reset it and all was fine. At the time I noticed it was at the same time as my central heating programmer switched off the central heating upstairs. This Friday (last night) it did exactly the same thing at the same time. At the time only the up stairs heating was on which is controlled by a Honeywell 2 port valve. My heating downstairs is completely separate underfloor heating system it's individual controls, so unrelated - at the time this was switched off.
When the timer switched off the zone valve was still open a thermostat calling for heat - so it appears that when the zone valve closed the fault occurred. At no other stage through out the week has this happened at it seems very odd that it was exactly the same time on a Friday . The seven day programmer is set the same for every day but maybe it's an intermittent fault and just a coincidence?
My guess is that there is a fault with the zone valve micro switch caused when the power switches off? I'm not electrically qualified but thought that an electrical fault like this would more likely to occur when the micro switch turned on the circuit rather than turn it off?
Some help on this would be appreciated

 

[EFLImpudence]

As it doesn't happen every time the valve switches off, is there anything else on on Fridays?

Is your seven day timer a manual one or electronic?

 

[Cymbeline]

Thank you for your reply. I have an electronic 7 day programmer. No nothing else specifically on related to Friday. The power tripped on both occasions at exactly the time the programmer turner off. At the time of switching off the valve was open and boiler running - in other words the thermostat had shut the valve prior to end of programme period.

 

[Cymbeline]

One typo - ‘the thermostat hadn’t shut the valve’

 

[EFLImpudence]

Sometimes RCDs do just do this.

It is very difficult to diagnose random faults although if it persists it may become more apparent.


Alter the timing slightly and see what happens and come back.

 

[ban-all-sheds]

One typo - ‘the thermostat hadn’t shut the valve’