Worcester 9.24 boiler problems

[timsy]

Hi, I have had ongoing problems with this boiler for the last 2 months and am trying this forum before I give up with it and buy a new boiler! During this time, various engineers have replaced:

- gas valve
- expansion vessel
- over ride valve
- pump
- circuit board
- thermal coupler

My central heating fires up for about 10-20 minutes before the pilot goes out. I am wondering if it is the Heat Exchanger, altho the British Gas engineer hasnt said so yet. I've been told an obvious symptom of a dodgy HE is poor water flow from the tap, but it seems to be OK. Could it be anything else, or do I need a new HE - if so, where can I get one from? How much should it cost in total (labour/part) to fit?

The best alternative I have found is a new Worcester-Bosch Greenstar 28i condenser boiler fitted by BG as part of their Combi Xpress deal. Price if I do before Xmas is £1,550 - money I don't have at the moment!


thanks
Tim

(PS. all work has been covered under BG's breakdown service so this hasnt cost me anything so far, just loads of inconvenience and cold mornings!)

 

[compheat]

I installed a 9.24 in my last house in 1989 and it was still working fine in 2004. It's possible that the main HE is partially blocked this would cause the overheat stat to cut off the pilot light. The easiest way to check is to disconnect this stat and see if the boiler stays on longer. It could also be a faulty stat. By the sound of it you've nearly got a new boiler
Do you have the same problem in hot water mode or is it just on the heating??

 

[timsy]

well the water HAD been OK and it was just when the CH kicked in - until the latest set of repairs! (gas valve)

Every time something is repaired, a new fault springs up. The fuse kept blowing last week (new pump fixed that), now its the pilot light (new thermal coupler didnt solve the problem).

Today it cut out when I ran a bath. I suspect it would last me while I had a shower ie. whenever the boiler is in use for greater than 10 mins or so whether CH or HW, it cuts out. The overheat stat (which I incorrectly referred to previously as an override valve) is new so I dont think its that. Is it wise to disable a safety feature by the way?! How do I unblock my HE ?

Yes you're right my boiler has had more new parts fitted than the Bionic Man hence my reluctance having come this far to give up and get a new one!!

 

[compheat]

has long as you stay with the boiler when you disconnect overheat stat so you can turn off when it starts to make a noise you'll be ok. You need to drain the boiler to remove the HE or you could just put a good sludge remover into the system and see if that works. Taking out the HE is not covered by BG. Its not difficult to do just awkward depending on location of boiler

 

[mark333]

hi ,
will the boiler temperature control knob control the boiler temp (if you lower , and higher the temp does' it control the boiler the temp by lighting and extingushing the boiler )?

 

[andsam]

Try reducing the dhw flow rate either at the tap or at the cold water isolation valve under the boiler. This will make the dhw temp increase quicker allowing the dhw themister kick in quicker allowing the boiler to modulate before it gets too hot. I had a similar prob , it was the dhw heat exchanger at fault but by doing the above it gave some hot water while i ordered a replacement. Because you are getting poor heat transfer the boiler is over heating before the dhw thermister has a chance to start modulating the burner.

 

[compheat]

Yes thats exactly what it does Its called a Variable Potentionometer.(i think thats how you spell it)

 

[HarrogateGas]

A common fault on these is the pump over-run stat........at a set temp the switching switches over on the stat fo the pump over-run .....if this fails your pump might be stoping and thus overheating. Ive changed a few of these for this fault over the years.

 

[timsy]

Since my last post in December, I have flushed some of the rads, run a de-sludger through the system, and replaced the thermal coupler again. The pilot no longer cuts out after the HW/CH has run for a period of time like it did before. In fact, the heating will now stay on for upto 3 hours or so, before the pilot light returns to the sedentary position.

The problem now is that the CH seems to come on as and when it wants. I leave the heating on all day, with the thermostat set at 21 degrees. The boiler fires up on demand for HW no problem, but doesn't always do so when the therm drops below 21 degrees and should trigger the boiler to fire up again. The pump is new and is constantly running. I can sometimes encourage the CH to kick in by running the domestic HW tap in the kitchen for a minute or so, to get the pilot to flame up. Then when I switch off the tap, the pilot stays alight and I start to get CH again. Sometimes the boiler won't fire up all day even tho the heating is in switched on and its sub zero in the living room where the stat is. Then all of a sudden it will decide to start and I'll have CH for a few hours. It's an intermittent fault, its as though there is a switch or something that is sticking that wont send the sigal through to the boiler to fire up.

Any thoughts on what it might be?

For the record, in the last few months the following parts have been replaced:

pump
expansion vessel
circuit board
overheat stat
gas valve
thermal coupler

 

[fitz1]

could be flame-lift

 

[ChrisR]

SOunds a bit like the switches on the end of the diverter valve are sticking. See if water has got to them.
WHich model, by the way?

If you need a secondary (domestic hw) heat exchanger for it I have one, by the way, which I doubt I'll ever install!

 

[timsy]

I did ask the BG engineer more than once if he thought it could be a fault with the diverter valve but he said he didn't think so because it was responding fine to the HW tap being switched on. They are due back today or Monday when they've got the thermistors so I will mention it again.

I'd be interested in your secondary heat exchanger, depending on how much you want for it, as mine has definitely furred up a bit. I have been put off by the cost (£160+VAT) plus 3 hours' labour (another £160 or so), esp as I probably need a primary HE too, which another £160 (Giannoni PR20/321), another 1 hour's labour if both are done at same time, making a total of around £600. Hardly worth it, may as well get a new combi. But if it's sitting there gathering dust and you don't mind donating it to a good cause.... !

(I have a Worcester 9.24 Electronic RSF Econ which last rolled off the production line about 13 years ago)

 

[timsy]

BG visited again today and it appears that I need a new plug-in relay switch, Worcester part no. 871646118. Unfortunately the manufacturer has none in stock and the boiler is obselete. Have tried HRPC but so far no luck. Anyone got any ideas?

 

[ChrisR]

You might get one from a boiler-breaker. There's one I get near every few days or so. Would need good description of part and where it fits - part number may not help. Also precise boiler model , there were about 3 9-24's. GC number should be on it.
No sign of relay switch on parts list I have.

h/e - half new price inc vat.

 

[timsy]

Worcester 9.24 Electronic RSF-E combi (GC number 47 311 07)

plug-in 24v relay switch: Manufacturers part number 8716146118

Will consider H/E if I get this part first
cheers