Washing machine trips RCD but only on program 3 !

Alanp

Section62 said:

Alanp said:

The m/c will fill with water,and at some point it will bring on the heating element, if the fuse trips then it’s a fair sign the element is tripping, it may show a fault code...

The point I made is that the heating element will be used on other programmes (except cold/'no heat' ones) and therefore if the element is faulty then the machine would cause the tripping problem with more than the one programme.

Barring something very unusual about the design of the OP's machine, the possibility of a faulty element can be ruled out just from the symptoms - there's no need to carry out a potentially dangerous (and quite likely inconclusive) test to work this out.

Alanp said:

...but your only testing it , your not going to leave it like that, of course it could be anything causing it to trip, you could, take the back and top off and ( unplugged of course) have a good look around to see if there are any signs of burning on any wiring or component, if you are in doubt, then call a professional...

Likewise the "PCB-burning smell" is not something which would point towards a faulty element. 

The smell, in conjunction with the fault only happening with one programme, would suggest a fault within the control circuitry - and on a machine of that age the chances of being able to carry out an economical repair are slim.  For safety reasons it would be better to leave it to a professional, or just replace the machine.

Elements can go faulty but not trip the fuse straight away, indeed I have one doing this at work albeit in a hot water cylinder, the burning smell could be the wiring to the element, I’m not sure that you can distinguish a burning smell between a pcb or something else

Bendy_House

Alanp said:

Elements can go faulty but not trip the fuse straight away, indeed I have one doing this at work albeit in a hot water cylinder, the burning smell could be the wiring to the element, I’m not sure that you can distinguish a burning smell between a pcb or something else

It was the OP who seemingly did! :-) To anyone familiar with it, the smell is very distinctive (and very evocative of childhood hobbies...) Mind you, other hard insulators - such as you'd find around wire terminals - can also smell the same.

Fair do's, it isn't at all conclusive. For such a recognisable smell, along with an accompanying 'pop' (classic exploding Leccy-Caps), the PCB would be the first place to suspect. But, why would an exploding Cap trigger an earth-leakage issue? And why only on one setting?

Oooh, I do hope the OP takes his W/M apart - even if they're throwing it out!

Section62

Alanp said:

Elements can go faulty but not trip the fuse straight away, indeed I have one doing this at work albeit in a hot water cylinder....

Still glossing over the point that the fault only happens on one specific program, and not one in which the heating element would normally be expected to be working harder than in other programmes.

Alanp said:

...the burning smell could be the wiring to the element, I’m not sure that you can distinguish a burning smell between a pcb or something else

What failure mode could cause the wiring to the element to burn?

I agree with Bendy - the smell from overheated electronic components/circuit boards is quite distinctive from other burning smells, and if the OP is confident that it what the smell is then we have to take that information at face value.

The point, again, is that given the risks with white goods starting household fires, an appliance which has produced the symptoms of a burning smell (whatever the source) and a 'pop' is one which needs professional attention, or being replaced.

Money saving is great, but not at the risk of burning your house down, or of electrocuting yourself.

GDB2222

Bendy_House said:

Annemos said:

Until I read this post, I hadn't even thought about this. If one does predominately 30 degree washes, does the element last much longer compared to if one was to do more regular hotter washes?  

(Is that a daft question? Sorry if it is!) 

Not at all daft. And almost certainly the element will last longer on cooler washes.

Regardless of the wash temp set, the element almost certainly still comes on 'full' for however long it takes to get the water to that temp. But to get to a 30oC wash will obviously occur much more quickly than a 90oC one. So the element will be used for a much shorter period of time.

I suspect the cooler water temp, as it gets to only 30oC, will also cushion the stress on the element a bit more too, so even the element's 'core' temp (from the actual heating wire) will be conducted away more quickly by the cooler water. Whereas, with the water at 90oC, the whole element is likely to be much hotter throughout.

"I suspect the cooler water temp, as it gets to only 30oC, will also cushion the stress on the element a bit more too, so even the element's 'core' temp (from the actual heating wire) will be conducted away more quickly by the cooler water. Whereas, with the water at 90oC, the whole element is likely to be much hotter throughout."

Water is very complicated stuff, because of the hydrogen bonding between molecules. There's an awful lot going on. For example, most of the heat conduction is through convection, so you need to consider how that changes with temperature. There may be localised boiling near the element. And so on.

You are probably right in your assumption, but it's not a certainty. 

Bendy_House

GDB2222 said:

For example, most of the heat conduction is through convection, so you need to consider how that changes with temperature. There may be localised boiling near the element. And so on.

First there's conduction, and then there's convection

Probably...