strange problem with MCB tripping

[juians]

One of the MCB's in the house started to trip out, so I went round unplugging everything one by one until it stopped tripping, it turned out it was the dishwasher that was causing the trip, so a new dishwasher was bought and is now working fine. However this morning the MCB started tripping again, so I went round unplugging everything one by one and eventually found out that the washing machine was tripping the MCB.

This is far too much of a coincidence, I cant beleive that the washing machine has developed a fault that trips the circuit breaker in the same way as the dishwasher in a matter of days.

Any ideas what could be the cause? Do the MCB's themselves go faulty?

 

[JohnD]

Do you know the difference between an MCB and an RCD?

What letters and numbers are printed on it?

 

[juians]

I'm not at home so cant read whats written on it, but can report back later on tonight when I get home.

I dont really know what the difference is, I was assuming this was the MCB that was tripping, but maybe its the RCD.

The switch that is tripping controls the electrical sockets for the whole house (both floors), ie when it trips no sockets work, but lights etc still work fine.

 

[JohnD]

An MCB trips when there is excessive current draw. For example if you have a 32A MCB controlling all the sockets, and you have a 13A dishwasher + a 13A tumbledrier + a 13A washing machine + 13A fan heater + a 13A kettle + a 13A toaster + a 13A combi microwave all going at the same time, and the total load exceeds the capacity of the circuit.

An RCD trips when there is a leakage of current to earth, for example you cut through the flex of your lawnmower, or you drop your electric curling tongs in the bath, or your washing machine has a water leak that drips in the motor, or you put a nail through the wall into a cable, or the heating element in your oven is old and defective, or the rain gets into an outdoor light, or you hang wet washing over radiators and the steam causes condensation in a light switch. An RCD can trip if there is a single fault, or if there are several small faults which are each insignificant, but together add up to the specified current. An RCD is an important safety device and always has a button on it marked "T" or "Test" and a label that tells you to test it monthly or six-monthly or something.

 

[juians]

Thanks for the info, I'll have a look and work out what it is when I get home.

I dont think its overall current draw related, as I turned on a few high draw devices that are on the same circuit at the same time (cooker, dishwasher, iron, fridge, freezer, toaster) and it didnt trip, but as soon as I plug the washing machine in without any of these devices running (note I dont need to start a wash, just plug it in and switch it on so that the electronics are powered), it trips.

 

[JohnD]

it is a watery appliance (and presumably in a kitchen) so it may have a leak inside or nearby, or it might be condensation if room is very humid

examine the plug, flex and socket for any signs of damage. Also look for signs of mice which gnaw insulation in appliances and under the floor.

You can get a plug-in RCD adaptor as used with lawnmowers at an electrical or gardening counter, it is worth using one with any suspect appliance

 

[juians]

Its just odd that a few days ago it was my dishwasher tripping the switch, and now its my washing machine, so I think its too much of a coincedence for it to be an actual fault on both machines.

What else could it be?

 

[holmslaw]

..

 

[rebuke]

It might be worth checking all your plumbing around the dishwasher and washing machine - if you have a small leak somewhere then perhaps it's what has caused the trips?

 

[juians]

The dishwasher and washing machine are in different rooms.

I will be checking for water/dodgy wiring etc, but it all just seems too coincedental to me.

 

[JohnD]

...An RCD can trip if there is a single fault, or if there are several small faults which are each insignificant, but together add up to the specified current...

so it might be that you have a background leakage which is nearly, but not quite, enough to cause the trip, and plugging in one watery appliance is enough.

apart from the plug in ones, watery appliances with leakage include immersion heaters and boilers.

 

[juians]

Well I got to the bottom of it.

It was tripping an RCD.

And it was a complete coincedence, the water supply had leaked water into the extension socket that the washing machine was plugged into.

All dried out and working fine now, thanks all

 

[Chri5]

the water supply had leaked water into the extension socket that the washing machine was plugged into.

Extension leads are used on portable devices as temporary measures. Please sort out a more permanent option.

Next time maybe the cat walks acrosss a puddle with the extension lead socket float upside down. It dangerous, sort it out the correct way