Help With Tumble Dryer

[Nigel Heather]

I need help with my White Knight 447 tumble dryer.

Basically, the drum was turning but there was no heat. I quickly discovered that the element was dead (open circuit) so bought a replacement.

Disassembly was easy and I carefully (I thought) noted the wires that I removed to get at the element.

I replaced the element and switched on - the machine started and quickly started to heat (great job I thought).

I switched in on and off a few times and then the RCCB tripped. Disconnected the dryer and the RCCB could be reset. Powered on again and it tripped. Left for a while and I could start the dryer again but it soon went through exactly the same cycle.

The bit that is bugging me is that when I reassembled, I noticed that my careful drawing was missing one of the wires that I had removed.

Its a black one that comes from an oval device (possibly a fuse). From its length I guessed it must connect to the element, so I connected it to the same element in common with a black wire coming from the depths of the machine.

This means that the contact of my element are connected as follows

Common Return - Blue wire that goes to neutral via circuit breaker (100% sure this is correct) Feed 1a - Red wire from depths of machine (100% sure this is right) Feed 1b - not connected (100% sure this is right) Feed 2a - Black wire from depths of machine (95% sure this is right) Feed 2b - Black wire from oval device connected to back of machine (not convinced about this)

I've had a look at spade contacts on the old element and from the scratches I sure this only had three wires connected to it which bears out my theory.

But I can't imagine where the extra black wire goes.

I would be really grateful to hear your ideas and suggestions.

Thanks,

Nigel

[Nigel Heather]

Update ....

Still not working but I'm now pretty sure I have got the wiring correct. I've had a close look at the old element and the spade terminal does show that Feed 2 did have two wires connected to it. So I'm pretty convinced I do have it wired correctly.

Symptoms are that when turned on, the dryer will run for about 5 minutes and will then trip out the RCCB. Icannot reset the RCCB with the dryer still switched on. If I switch off the dryer I can reset the RRCB but as soon as I switch the dryer back on the RCCB trips.

If I leave the dryer to stand for 10 minutes or so, I can start the dryer but it will trip shortly after.

Sounds like something is overheating (or thinks it is overheating). The circuit breaker isn't tripping so this brings me back to the other sensor/fuse (the oval device screwed to the back).

Could this be the cause?

Anyone know what it is?

Cheers,

Nigel

[powerstation]

Its the inlet thermostat.

Wire as below:

double element connector is blue outer element connector a is black (from stat in back plate) outer element connector b is black (from heat switch at front) inner element is red (from switch at front) other black wire from stat at rear goes to black/white wire on terminal block other blue wire from cut-out with red button goes with the other blue neutral wires on terminal block

Peter

[Nigel Heather]

Thanks Peter,

Your description confirms that I have wired the element correctly.

Do you have any idea what could be causing the dryer to trip my RCCB?

I can only think it is heat related as it doesn't happen straight away and then if I let the dryer stand for a while it will be okay for another 5 minutes.

My thoughts are:

(i) Getting too hot so thermostat tripping - but I wouldn't have thought that would have tripped my consumer unit - or am I mistaken.

(ii) Faulty element - could it be that it is shorting out when it gets hot. Thing is, when cold both elements read 50ohms. When it has tripped and still in a state to trip if turned on, both elements still read 50ohms.

Tomorrow I will try and check that none of the plumbing is blocked. We keep the lint filter clean and I have checked the external vent hose - but I guess it's worth checking inside. I assume I need to take the lower back panel off.

Thanks again for the help.

Cheers,

Nigel

[powerstation]

If it is tripping the RCD then the element is faulty, metal sheathed elements do this when they have absorbed moisture. Confirm its not the motor etc by running the 10min cool down period on the timer, if it does not trip it confirms the heater.

Peter

[Nigel Heather]

It's not the motor.

The element is brand new, purchased today. Is there any way to test it?

I shall try taking it back to the dealer, but I fear they will just claim it is something else or that I damaged it myself.

Cheers,

Nigel

[powerstation]

To test correctly you need a insulation tester at 500v but your multimeter should show infinty Mohms between each of the terminals of the element and the metal sheath/mountning plate any less its faulty. If you have a socket outlet not connected to the RCB protection you could leave it on to dry out.

Peter

[Nigel Heather]

Did a test with a multimeter - did look like an earth fault as you suggest.

So I took it back to the shop and got them to test it with a megger. They confirmed an earth fault and are getting a replacement for me.

So on the whole looks promising.

The only niggle remaining is whether another fault could have caused the insulation breakdown and the same will happen again tomorrow.

What does the Inlet Thermostat do?

Is it a saftey cut designed to come on in abnormal conditions? Or is it a there to regulate the temperature?

If it were faulty could it cause the element to overheat and breakdown?

However bearing in mind that the element was on less than 5 minutes I doubt that this could have been the case.

Thanks for the help,

Nigel

[powerstation]

good

no its not the machine probably an old stock element that has absorbed moisture

it regulates the temperature of the element

no the insulation breakdown in your case is moisture, there is another cut-out to protect the machine from overheating on the rear panel the black one with two blue wires on it.

correct

[Nigel Heather]

Really appeciate the help - much indebted to you.

Thanks,

Nigel