central heating trips the RCD switch.

[griffo7]

Hi, Im having this anoying problem with my central heating. I have a gloworm micron 50ff boiler, when the central heating comes on from cold it will heat up the water for a while but when it starts to get hot the RCD trips on the main fusebox. I cant get my head round this! could it be the pcb in the boiler (are these prone to going?), could it be the pump? could it be the motorised valve? there is a thermostat on the water tank could this be faulty? i bought a new room thermostat and tried it but still have the same problem. usually when i turn the room thermostat down to a low temp this usually switches the central heating off, (but this doesn't turn it off when it does work for the short time). if anyones got any ideas please let me know as im pulling my hair out with it.
Thanks Ian

 

[keego]

Unlikely to be the PCB, check the pump & 3 port first to make sure there's no leaks from the valves shorting one of them out. If that's OK you will need to get a test meter on all the components.

 

[griffo7]

ive checked the pump and theres no leaks inside the wiring casing, and no leakes in the motorised valve. how do i know if theres a problem with these twc components with a test meter (what am i looking out for on the readings?). If this helps i cant manually move the adjustments switch on the motorised valve, with being just a very basic diy'er not sure if its meant to move.
cheers ian

 

[diverdee]

if it trips the rcd and not the breaker is most likely earth leakage.most likely culprit will be pump insulation breaking down when hot.very hard to test without special equipment get a sparky in

 

[griffo7]

if it trips the rcd and not the breaker is most likely earth leakage.most likely culprit will be pump insulation breaking down when hot.very hard to test without special equipment get a sparky in

Thanks for your help, i think i will just buy a new pump and try it.
Ian