Another Worcester 240 BF problem

[brk1]

After last weeks exploits of no hot water unless the heating was on, was finally tracked down to the valve stuck at the back of the diverter valve so hot water was going straight out the boiler flow , instead of the valve shutting and the water coming out of the HW flow. This week I've fitted new valve ,all went well ,no leaks ,not even on the front slip fitting sealed with the "O" ring .Pressurised the Expansion vessel , filled up the system to 1.0 bar , run water through the system ,then bled the pump, everything looked all systems go but still something is stuck or malfunctioning . When hot water or CH is turned on gas burner fires up ,then after a few seconds ,the pump makes a struggling sound ,starts clunking and the gas valve shuts off , sounds like the water is not getting through to the water to water heat exchanger ,then the pump just stays on and won't go off , can reset gas shortly afterwards and light pilot again ,but the circle repeats itself . The water to water heat exchanger doesn't get the slightest bit warm ,but does have water in it if you drain it so must be getting through to it somehow .The diverter valve was "AS New" and came from a recently scrapped boiler and looks great and all valves look like they are working/opening fine ,but if the valve is at fault I can get money back (7 Day warranty) and get a brand new one instead. So quick help if you can so I can return if need be ,I would have bought a straight new one had not some suspicious character have handed my debit card into the shop I last used it. Card got cancelled about 5 mins before I phoned the bank to do so myself, just after I had phoned the shop to be told it wasn't there at all ,starnge the timing on that one hey? Got a new card yesterday but new pin hasn't arrived so don't have access to my own money till the pin gets here , so here goes folks :

1. Is the diverter valve not working properly still ?
2. Or is there some other reason the gas valve trips constantly (obviously a safety feature) but being caused by what.

I believe it was the "gasguru" who was spot on for me last week and sorted my problems ,so if your out there m8 or any other kind soul who can help please feel free to leave me some good advice .

Or there was an option 3.

Anybody got a spare stick of dynamite

 

[ollski]

sounds like its full of air, is the auto air vent open?

 

[brk1]

Can't say I tried that ,it's got one of those auto vents up in the combustion chamber ,didn't think you could open them or close them either,hence the term auto vent ,I'll open up the chamber and see ,could well be corroded shut by now and not working properly !

 

[ollski]

Yes you can shut the cap, many boiler engineers do just that when they are leaking to prevent the need for replacement, doesn't really come to light until the system has had a bit of water drained out.

 

[brk1]

Just opened up the chamber ,AAV still had the black plastic cap on it and at some time its been leaking quite well (air coming out with trace of water) and its all green crusty solution, anything I can do to it to clean up for emergency weekend use , de-scaler etc and then leave the black cap off ? or am I doomed to no hot water for the weekend ,good job the weather's warm until I can get a new one, or is there another way of bleeding that top section?

 

[fazedup71]

have you thought about taking it apart and cleaning it? i did that the other week just to get everything back on over weekend but still changed it come Monday morning, did you fully check operation of valve before fitting? As in take the head of and manually push the pin and blow through valve to check it is closing and opening correctly

try tesco's for dynamite! they sell everything else!

 

[ollski]

Open it until all the air comes out, then screw it back down again.

 

[brk1]

If your talking about the diverter valve ,I'm as sure as I can be that it's working O.K ,all valves open/shut ,all pin ends are greased and slide through the valve very easily, the diaphragm easily switches the micro valve switch on ,water flows through O.K until it gets to the burner ,then that's where it seems to get blocked, ollski suggested the Auto air vent and it does sound like an air blockage after the gas valve has shut off ,as if the water is trying to go into the water to water heat exchanger ,you can here what sounds like a drip going into the water to water exchanger, but that's only what it sounds like physically , that's not my answer to what's wrong .I'm hoping to find out if I can clean out the AAVent or another way to bleed that top section . I've run plenty of water through the hot water system to try and flush out any air without turning the power on ,as that's when it shuts down ,due the water heating but probably not going where it should .

 

[fazedup71]

you can clean out the AAV that is what I was saying to do, simple enough job to do, take it off the boiler, take the top off sometimes it's easy to get off other times not so easy, take it all apart and give it a good clean

 

[Gasguru]

Turn the gas OFF at the meter.

Check the auto air vent top plastic screw is loosened a few turns but be aware they often leak.

Turn the heating on (with combustion cover off so you can check the aav is not ****ing water everywhere).

Cycle the hot tap on/off. Run the hot tap for a few seconds then off until the pump goes quiet as it expels air into the radiator circuit. Keep repeating until the pump is silent.

If you're lucky this will get rid of the air but don't persist for more than a miniute or so as you risk damaging the pump.

Taking off the combsution chamber cover is not something normally advised on the forum (since it forms part of the boiler safety system) but since you have done so a few checks need to be made. Make sure the seal around the edge is in good condition, make sure the "spire" clips are in place and not broken, make sure the screws tighten properly and the cover seals properly and the "rubber" washers are still intact. A cover that doesn't seal properly often "whistles".

If the boiler appears quiet and the ccombustion cover has been replaced turn on the gas and try the boiler.

I suggest the auto air vent is replaced..if it leaks it can cause serious damage.....it's a standard 3/8 Caleffi...easily obtainable from merchants. It is sealed with PTFE wound to a slight taper.[/b]

 

[brk1]

Thanks guys for all the help ,AAV actually still worked when I took the cap off it , took the whole vent out first just to make sure and cleaned it as best as possible for now ,put it back in and gave a slight tighten then toppeed up the system again ,bled it by the whole AAV being loosened until the water flowed ,then shut it up , carefully tried short bursts of hot water round the system so as not to get a shut off again just in case, nothing shut down ,could actually here the AAV working by this time ,few more short bursts and all was well, let the heating run for about 15 mins, no problems there .Seals are actually still alright as well as rubber washers around the screws ,no whistling from the case .After last weeks fiasco sorted by "Gasguru" (thanks) ,I've actually now got hot water coming out of the hot tap, without the need for the central heating being on ,instead of it going round the central heating circuit. Will pick a new AAV up next week and get it changed over , the old one is working for now but does dribble a bit when the air comes out ,they're not expensive and by then I should even be able to spend my own money ,instead of the wife's.