WORCESTER 240 CENTRAL HEATING DROPPING OUT AND RE IGNITING.

[jockskinner]

Hi folks,
I have a worcester 240 combi boiler and it has started doing strange things. The hot water side if fine its just the central heating side that has started playing up.
When the heating is switched on it can run fine then for no apparent reason the burners drop out and a loud clicking sound can be heard. The heating then goes into a dropping out and quickly re igniting itself for a while. Then it appears to settle down after about 15 minutes.. also sometimes it will not fire up when demanded.
The hot water switches on and off ok and does not seam to have any prople so I assume that the fault is purely on the ch side of the unit.
It is regularly serviced and we have had no proplems up till now.
I called a service engineer out after its last grop out and when he switched it on it came on ok but the next day when I switched it on it wouldnt start.

 

[picasso]

if your confident enough to work on your boiler put the link back between 1 and 2 on x4 of the pcb , this will eliminate the room stat and/or programmer and you will then know if its a boiler fault or something else.

 

[jockskinner]

Hi Picasso,
Thanks for the prompt reply. I worked as a service engineer in various comanies for many years and I am sure it is a simple fault. The service engineer came back this afternoon and I explained exactly what was happening. He is sure it is a sticky thermistor. I am sure it is something like that as it only effects the ch but I do not have any drawings to check things out.

 

[picasso]

a sticky thermistor should be interesting

 

[davebgas]

A 'sticky' thermistor????????????

This bloke who came out does realise a thermistor has NO moving parts to stick???!!!

 

[jockskinner]

Hi again,

I think he meant that sometimes it was working and other times it wasn't....he just didn't explain it very well. So is there anybody out there with any diagrams for my system. This should be a fairly easy fault to find as I don't suppose there is much component parts that are unique to the central heating side and not to the hot water side. There is no external thermostats or any room controllers as far I know.

 

[bengasman]

I doubt it is the ch sensor, I hope you agreed a no-cure, no-pay with the engineer?

 

[jockskinner]

Hi Again Folks,

So no drawings out there then for my worcester 240 then ?

The enginer comes out and tries to fix it under a maintainance insurace scheme. I am sure that these above mentioned symtoms must be ringing bells in someones head so anybody want to have a stab at what it is likely to be???

 

[bengasman]

The enginer comes out and tries to fix it under a maintainance insurace scheme.

So let the guy get on with it, or are you planning to tell him how to repair your boiler based on a long distance diagnostic?
Grannies........ eggs..........

 

[jockskinner]

Hi again and my thanks to bengasman for taking an interest. I was a electronic/service engineer for most off my working life before my heart decided it had had enought of a service engineers lifestyle and shut down. I have worked on everything from Space and Defence Systems...domestic appliances and ultrasonic welding and cleaners. I wouldn't try to second guess the boiler engineer or tell him how to repair my boiler. The reason I asked was purely my engineering curiousity on how these systems work. Had I had the necessary drawings and had been well enough I would have probably have fixed it myself. Combi boilers are not rocket science. Thanks to all who tried to help.
John.

 

[bengasman]

You might be able to download the whole engineer's manual from the WB website, or failing that, email them and they will send it to you.

 

[holty]

Hi again and my thanks to bengasman for taking an interest. I was a electronic/service engineer for most off my working life before my heart decided it had had enought of a service engineers lifestyle and shut down. I have worked on everything from Space and Defence Systems...domestic appliances and ultrasonic welding and cleaners. I wouldn't try to second guess the boiler engineer or tell him how to repair my boiler. The reason I asked was purely my engineering curiousity on how these systems work. Had I had the necessary drawings and had been well enough I would have probably have fixed it myself. Combi boilers are not rocket science. Thanks to all who tried to help.

surely then you would know a thermistor would not stick,are u sure he didnt mean air pressure switch.thats if yours is the rsf version.

 

[jockskinner]

Hi Holty,

Yes...I did know that but as bengasman was quick to tell me and I quote...

Let the man get on with it and don't try to tell the engineer how to repair my boiler.

Unfortunately since the engineers visit where he is going to order the faulty part....the ch system is running a dream and the original problem has gone. I am sure it will return sometime in the future as it feels like one of those faults that are difficult to pin down due to it being intermittent.

 

[jockskinner]

Hi again,

There was another symptom that I didn't mention and that was a loss of pressure from somewhere in the system (nothing obvious)
The pressure drops over a period of three to four weeks and I have to charge up the pressre. It does not appear to have any effect on the working of the ch as it has been like this for years???

John.

 

[bengasman]

Most boilers have some sort of safety device that checks for water in the pump/hex; as long as that sensor is satisfied, the boiler will run.
There is a long term effect in the form of corrosion that is caused by this which will slowly but surely kill the boiler, rads and valves. I strongly recommend you find the leak.