DIYbanter - View Single Post - Electrical advice: Washing machine tripping RCD

tony sayer

In article ,
scribeth thus
Out of the blue, my faithfull old Hoover washer tripped the RCD on my consumer
unit.

After reset, it'll stay untripped when the machine is powered on at the socket,
but as soon as I turn the control to anything other than 'off' the RCD trips.

The strange thing is that I've left the washing machine unplugged and yet the
RCD still tripped a couple more times, but seems to have settled now and been ok
for a few hours.

So, two questions:-
1. Any idea why the RCD might be tripping when machine is not plugged in (I'm
assuming it is the machine that is faulty)

2. Assuming the machine is faulty, anyone know where to start looking for what
could be causing the imbalance? Don't want to invest in a new machine if this
one could be fixed easily/cheaply.

Note that the ring main MCB is not tripping, just the RCD for all the downstairs
breakers.

I have electrical knowledge and multimeters etc. Just seeking opionions on what
might be most likely.

Thanks, as always, for sharing your knowledge and experience.

Some appliances around the house have a bit of earth leakage thats when
the Live line supply is going back to the neutral at the substation end
via a path other then the neutral supply.

The principal of the RCD is to monitor the current IN on the live
incomer and then OUT on the neutral no matter what the overall actual
current is, its the balance between them, current flowing in MUST be the
same as that going OUT on the neutral line any that's not the same i.e.
leaking to Earth and NOT returning via the Neutral line it will if it
exceeds the trips rated tripping level then the trip will just go on a
trip;!

So in your instance there is likely to be a bit of equipment thats got
some leakage, it might be say around 20 milliamps now thats below a 30
milliamp RCD so all's well.

Now add in something else thats got some leakage say its a bit of gear
like a washing machine thats got say 15 milliamps "ma" for short! Then
you can see that added 20 and 15 makes 35 which is now in excess of the
trips rated current - not good!..

Some PC gear can and does have a small amount of leakage many PC's all
on the same circuit can cause tripping. However in a domestic situation
Cooker hotplates, Immersion heaters, heating elements in washing
machines, same in dishwashers, motors in washers anywhere where water
can get into the electric's will cause leakage.

One other real PITA with trips is the Earth Neutral short this doesn't
immeaditly cause a trip its the same principal live in must equal
neutral out here the neutral is connected to earth so some current is
leaking away Via earth instead of the neutral.

If nothing is switched on then the trip will remain OK but if something
is switched on and it DOES NOT have to have any leakage at all in it at
all, it can be earth free if the current now rises so that more than the
nominal 30 ma is going away via the earth short then out will go the
trip.

This can be a sod to find and cause a lot of confusion needs someone
with a multimeter to test for that there should be infinite resistance
between earth and BOTH the live and Neutral conductors in the wiring.

HTH...

--
Tony Sayer