21 
1 
2 Why does my old washing machine trip rcd at random times RESOLVED
My 1992 Zanussi washing machine FJ1040 has been tripping the RCD every few months for several years which was a slight nuisance. But now it trips the RCD every wash or maybe 2 or 3 times per wash. I reset it after 10 minutes and it carries on where it left off.
I've removed the heater and the emi filter as well as changing the brushes (one looked distressed), but it still trips. It all looks good inside with no leaks. If I put a cheap multimeter across the plug's live and earth, just after a trip, it gives a resistance of about 0.5Mohm which increases to >2Mohm over a few minutes, which is why I leave it for about 10 minutes before I reset the RCD trip switch to continue the wash cycle.
I presume sometime is getting hot over about 20 minutes and causing a short to earth.
Any ideas?
Update (10/30/23)
That should be 30mA not 250mA!
Update: the washing machine can now run a full wash program without tripping. Took a few runs to get there. I assume the brushes were settling in.
Это хороший вопрос?
Hi @dce,
Breakdown of wire insulation due to rubbing caused by vibration of machine perhaps.
Any heat/scorch marks on the body inside the machine?
Try and isolate it if possible by disconnecting components one at a time e.g. motor, pump etc to hopefully get some idea of where it may be located.
If you have one or access to one an infra red thermometer might point out a heat source in the wiring
Just what I'd try.
из jayeff
Thanks @jayeff . All wiring inspection was ok, but easy to miss something I guess. My infrared camera didn’t find any unexpected hot spots.
After running just a 1 minute fast spin, the commutator got to 40C. (Normal?) maybe the new brushes bedding in.
Also on immediately unpluging the power plug and measuring the live (hot) to earth resistance, found it was about 100kohms. ( didn’t trip rcd). But when I pulled off the earth lead off the motor, the resistance measured >2Mohms. I think this confirms that the earth leak is in the motor, I suspect at the commutator.
Next plan is to clean commutator and have a better profile on the brushes to reduce the commutator temperature and so keep the earth leakage down to a non trippable level ( <250mA)
из Dave Empson