Tumble Dryer --------------

[Clive]

Hi Guys

Can someone out there put me straight, I’ve got an old Condenser Hotpoint TDC 60N Tumble Dryer and it keeps blowing the thermostats at the back of the machine where the heating elements are and I'm trying to find out what’s causing them to blow, they are the one shot type.

I'm only guessing here but could the cause be the heating elements themselves, I have seen on a website it said for a working heater the resistance should be between 20 and 50 ohms.
Can someone tell me how to perform this test using a multimeter, I’ve included a sketch of the wiring coming from the elements plus a photo of them but I'm uncertain where I should place the test leads in order to perform the test, if someone could mark on my photo where I should place them that would be great, well at least I will be able to eliminate the heating elements.

The problem may well be the heating control module itself but at a cost of £111.00 I want to eliminate anything else first.

There are no blockages within the condenser and the machine is clear of any fluff build up plus the door is not opened during the cycle as I know a rush of cold air into the machine can cause the stats to blow.


My thanks to anyone who can help.

 

[James]

the 1 shot stat you are on about is a safety device that is triggered when the temperature in the heating box rises above a certain limit.

there are several possible reasons it could be blowing.
in roughly the order of likelihood see reasons below.
1. insufficient airflow
check for blockages in filters, pipes and condenser chamber
check fan motor is turning freely and the fan is clean.
2. operational stat is failing and therefore heater is on when it should be off
3. heater control board as you have already mentioned
4. the replacement thermal overload (safety stat) you are fitting is not the correct electrical or temperature rating.

note, if the machine is being run from a circuit that is protected by an rcd then a faulty heating element is unlikely. they normally start to leak current to earth as the element starts to fail due to the moisture and therefore would be tripping the rcd.

 

[Charlie_]

Blower motor and fan blades all ok?

 

[telectrix]

is it a Creda? we had one that blew the thermal overloads a few times. replacement with a better quality type ( maybe resettable) is an idea. assuming all is well wrt. james the spark's post.

 

[The Ghost]

Maybe check your model on Electrical Safety First, for recalls on your machine.

 

[marconi]

I had a similar problem but on a vented dryer. The problem was my wife would open the door before the end of the cycle to see if the clothes were dry or not too dry for easy ironing. What happens if you open the door before the final cool cycle has completed is that hot water vapour is turned into high temperature steam when it touches the still hot element - the rapid rise in temperature is detected by the safety stats and they trip.

See: Tumble Dryer Thermostat Failures - https://www.ukwhitegoods.co.uk/help/fix-it-yourself/tumble-dryer-self-help/2761-tumble-dryer-thermostat-failures

Human Error
We will try to break it gently.

The single, commonest reason for the safety thermostat to trip is that people will open the door during the drying cycle.

After 20 minutes, the inside of the dryer is running at 100c plus. The clothes are starting to warm through, steam is coming off. By an hour, they're cooking nicely. The control panel will tell you to set cottons for 90-120 minutes.

If the door is opened after an hour (“To see how they're doing"), the airflow stops, the temperature at the element soars (briefly) and the safety will trip. It happens all the time.

If you have to open the door, set the timer to the propeller symbol and just wait a minute to take the heat off the element and will save you a repair bill. Best bet is to trust the machine to do its job; it will, if used correctly.

 

[Clive]

First off thank you guys for taking the time to reply,

James thanks for the list of possibilities,

1: I’m sure it’s not an air flow problem the machine is as clean as whistle inside because I had to completely strip it down because of another problem which was none electrical so took the opportunity of cleaning everything even the float chamber item 610 in the exploded view, which I believe if the condensate water bottle is not emptied it overflows into the chamber where there is a float mechanism which in turn operates a micro switch turning the machine off if actuated.
As you can see from some of the photos the fans are all clean and are running fine.
The door filter is also kept clean.


2: The operational stat, I’m assuming that’s not the one shot ones at the back of the machine just above the heating elements, if it isn’t I haven’t a clue where to find it any ideas??.

If it is the one shot ones, I had bought some which were about £6 a pair, but thinking maybe it’s because they are cheapos I bought the last pair from Whirlpool.uk.spares £26.80 a pair didn’t it blow one of them second time of using the machine.

3: I’ve a gut feeling it could be the heating module as you’ve suggested, I just wish I knew how to test it to make sure, as I said I don’t want to rush out and buy a new one only to find I’ve still got the problem.
Just a thought but I suppose it could be the selector switch at the front of the machine mind you I wouldn’t know how to test that either, again have you any ideas??

4: As far as fitting the correct stats, all I can say is the ones I’ve purchased are against the model number of the machine being A Hotpoint Ultima TDC60N.

Yes the machine is running on an RCD protected circuit, but could the heating element have too high or too low a resistance without causing the RCD to trip??, I think I saw a short video talking about the resistance of the elements being incorrect, although nothing was said about the RCD tripping the video was on E Spares, so it wasn’t Joe Blogs down the road.


Telectrix the machine is a Hotpoint Ultima TDC60N as far as better quality stats are concerned see my answer above to James.


Vortigern Recalls, I’m talking about an old machine here probably before they started making machines which need recalling LOL.


Marconi, I’ve told her indoors if she gets opening the door before the buzzer sounds to indicate the machine cycle as ended, then I’m going to buy her a set of electrical screwdrivers and a multimeter for next Christma


Human Error, If only it were that simple, I wouldn’t be on this forum trying to pick everybody’s brains .

 

[Clive]

 

[Charlie_]

To test the element you just need to use an ohm meter across the element terminals, with wires disconnected..
You sure the motor/fan is running at full speed?

 

[rapparee]

Those one shot thermostats are actually able to be reset.

 

[marconi]

I think Charlie's #9 a good idea to check out the fan - and also to see how easily the drum rotates to see if bearings are ok and it is not rubbing against anything.

Just a thought and probably unlikely as the root cause - what is your mains voltage V? The power dissipated by the element is P = Vsquared/R, so increases in V could be making a big difference to the elements heat output. Do your household lamps fail regularly?

PS1: For the avoidance of any upset, the mention of Human Error in my last post wasn't directed at you.
PS2: As a lad, to occupy you during the long summer holidays, did your dad give you items of electrical/mechanical equipment to disassemble and re-assemble without any parts left over! It is a talent you obviously have.

 

[marconi]

Have you check out the front thermostat to see if it switches or whether it is stuck closed/on?

Connect a multimeter on ohms across it and apply heat to it from a hair dryer.