Worcester 240 Combi BF problems.

[brk1]

Need help from an expert here please. Just lately my boiler has been performing strangely, the heating side of it works just fine ,but the hot water side lets us down badly .It used to give hot water if you reduced the flow while the central heating was on ,if no heating was on ,it runs warm for a few moments then runs cold again . The boiler appears to be running correctly , if you turn the hot tap on , the burner lights and stays on until you close the tap but the hot water doesn't come from the tap ,no idea if the water is actually sent up to the "water to heat" unit or not or whether something is broken and its leaking through somewhere else . When we experienced the hot water by using a decreased flow of water I just thought it was a perished/split diaphragm so bought a new kit to replace it ,when I stripped the diverter valve down ,it was badly perished but not split ,so that wasn't the problem so now I'm lost , hot water was misty when it first came out so somebody suggested cleaning the water to water heat exchanger ,that's been done and now runs crystal clear from the central heating side and the DHW side so that unit is clean and not blocked , the DHW sensor has been changed ,that didn't cure it .I started this renovation/clean up job last night and worked till about 2 in the morning ,at 7 this morning I started the rebuild ,popped out to get a few new fibre washers and I'm pretty well asleep on my feet now ,trying to strip down and rebuild while everybody else was asleep so as to cause no disruption to family life , I've replaced the diverter valve before and last time replaced the rubber diaphragm with a kit without problems ,now for the life of me I can't guarantee I've put the diverter valve back together properly or not (I'm tired and my brain is virtually asleep without me) at the moment , it doesn't seem to reach the micro switch when hot water is demanded ,and when the system gets re-pressurised ,the valve doesn't seem to stop, the pressure gauge goes up to max and the relief valve ejects the extra water, so there's a good chance I have put it back together wrong ,I'm sure I haven't and the logical method of working it out seems right ,but it's not working correctly so I must have made a boo boo somewhere .So if anybody changes these diaphragm regularly please let me know if I've rebuilt it in the correct order.it seems to fit together best that way but it doesn't want to work that way. So far I have gone to rebuild as from opened up valve
1. Opened up diverter valve fixed to main boiler
2. Diaphragm into open valve with large silver dish type washer and small spring assembly to the front .
3. Large spring onto this plate followed by front of valve casing.
4. Rebuild final pipework with water restricter inside
5.Turn water on and re-pressurise

This seems to fit together the best way but doesn't seem to work ,I just wish I wasn't so tired when I took it apart last night and remembered how it came apart. Maybe I am rebuilding it correctly and the actual diverter valve has gone/broken . Can't find any pics as to rebuilding the diverter valve and have nearly run out of fibre washers for today and still can't get it working correctly ,I've already changes the diverter valve once when the diaphragm kits weren't available ,and also previously renewed just the diaphragm kit when the old one perished ,obviously I wasn't quite so tired then and all went fine and without problems . This time I'm extremely tired and it's really bugging me .I think I've rebuilt it correctly but it's not working so something is wrong somewhere , was much better paying out for the new kit than £100 or so for a complete new valve . So if anybody can help, firstly with the valve rebuild ,then what the hot water failure might be, I'd be extremely greatful .

 

[Gasguru]

From your description it would appear you have rebuilt the front end of the diverter correctly. Where did you obtain the kit...there are some cheap non-genuine kits (Banico) available...they appear to work but quality is poor.

Giannoni (the diverter manufacturer) actually make different diaphragms (the spring rates etc differ)...perhaps you have been unlucky and have the wrong one although I have never had problems with the "standard" replacements.

Have you sufficient pressure and flow? Is the small black plastic disc fitted to the end of the pin? Have you checked the contact resistance of the microswitches? Have you checked the boiler heating flow pipe does not get hot during DHW demand? Be aware the "slip" coupling piece between the front diverter cover and the domestic heat exchanger contains an O ring that often leaks after being disturbed..ie I find it you always need to replace the ring.

 

[brk1]

Thanks for answering ,I actually changed the diaphragm a couple of weeks back but that didn't cure the problem, valve was working fine then ,but it didn't solve the problem , that's the first thing that I thought had gone when I was having to dribble the hot water flow to achieve hot water ,instead of a full pressure blast sending the split wide open and not pressing the micro switch. The black plastic cap was replaced onto the pin end ,I always get problems with that "O" ring as well , will have to get a replacement for that. . When I rebuilt it doesn't seem to shoot out as fast as it used to ,and doesn't seem to push the micro switch any more, that's why I thought I may have rebuilt it wrong. The micro switch seems O.K , light pressure still pushes both contacts in .I can't see why the central heating flow continues round the system once the filling loop is switched off ,again I wondered if that was down to a wrongly built valve. The kit came from a proper heating components shop and I belive he said they are made by Ariston , I know last time I had one it was the Giannoni make ,but this one has been working already before yesterdays clean up anyway. Going through the fault finder doesn't pinpoint the no hot water problem, if the PCB was at fault, I wouldn't have thought all the burners would have come on and off when hot water demand was present then switched off .I can't check to see if the Central heating flow pipe until I can fully fill up and pressurise again , there certainly didn't seem to be a breach in the water to water heat exchange until ,I had to fluch each channel separately to clear them so shouldn't be a breach in there.

 

[superdupergasman]

is your little grey knob turning the valve off tightly enough?? sometimes it spins and needs nipping up with some pliers!

 

[brk1]

Little grey knob ? Don't know that I've got one of them ,where is this situated please ?

 

[Gasguru]

is your little grey knob turning the valve off tightly enough?? sometimes it spins and needs nipping up with some pliers!

You thinking of the CDi instead?


For the OP

I don't know why you de-presurised the boiler to change the diaphragm. The front water section is not cconnected to the rear section waterwise. If the presure is going up you probably have a faulty filling loop valve. The loop should be disconnected after filling. If the pressure still rises the domestic heat exchanger has a fault but that would be highly unusual.

When you replaced the diaphragm did you use silicon grease on the central pin? Perhaps it is binding on the O rings in each casing half. Is the flowrate sufficient?

 

[brk1]

I had taken the diverter valve completely off for a clean up when I cleaned out the water to water heat exchanger ,while boiler was stripped apart ,thought I'd clean as much as possible to eliminate dirty/broken parts of the boiler as I went along , will try some fresh silicon grease on the spindle , water pressure is very high in my house ,I usually have to restrict the main stopcock a little ,just to decrease the mains pressure into the boiler. Sticking pin might be the reason ,I didn't even re-pressurise on one attempt ,I just open the flow and return on the CH circuit and the gauge started to climb to high without topping up the pressure at all. I think the filling loop is still alright as you can physically here it shut off when you close it after topping up the pressure, will try fresh grease as soon as I'm fully awake and got myself a fresh supply of fibre washers, used all my 1/2" up trying to get this thing running again..

 

[Gasguru]

....I think the filling loop is still alright as you can physically here it shut off when you close it

Forget thinking and disconnect it....you will not hear water flowing through the valve at a drop per second and that's all it may take to raise the pressure.

Bleed the air from all the radiators and re-charge the expansion vessel to 0.8 Bar...see FAQs.

 

[brk1]

Large idiot reporting back now , my filling loop is virtually the same as the one in the FAQ but some idiot had left the bloody thing open while in a brain dead state of mind (it's hidden behind the washing machine and didn't look at it again) so every time I opened the CH circuit the loop was refilling the system, greased the spindle up, that now works a treat ,system is sealed up and flowing properly again .I'm just going to run it for a while ,get people bathed ,then I'll bleed the rads and sort the expansion chamber again, hot water still not very hot though ,fairly hot while central heating is on but still struggles when it's off. Would pressurizing the expansion vessel cure this or have I got to look deeper. Need to get people washed and dressed before I can check whether the hot water is coming out of Heating flow as soon as the coast is clear again . Thanks for all this help, I'm finally back to where I started now ,with a nice internally clean boiler, whether it gives me hot water is a different thing

 

[brk1]

Latest update , now had a chance to get everything tested ,Expansion vessel is going to need to be re-pressurised properly ,it has air in it but is probably too full of water as well .Gasguru ,when the hot water supply is turned on, the burner ignites and heats the water but it flows into the boiler flow pipe and doesn't come out of the hot water pipe or maybe just a trickle of it does ,it's being sent round the heating system ,you can feel the hot water going straight down the CH flow pipe and the DHW pipe remains cold ,what part is at fault now please .

 

[Gasguru]

It's a diverter problem...when you open the hot tap the diaphragm comes towards you operating the microswitch to fire up the boiler. As the pin moves forwards it also retracts from the rear half casing of the front section. This allows the rear section inards to come forward and divert water from the primary heat exchanger flow pipe to the domestic heat exchanger.

Should be similar to this //www.diynot.com/forums/viewtopic.php?t=23327

I hope when you last replaced the valve it was a genuine part since problems have been reported with the cheaper copies.

 

[brk1]

Thanks for answering again gasguru ,I've just been looking for the receipt but reckon that's one I finally threw away , being self employed I keep virtually every receipt I get ,but periodically I have a clean up ,I can still picture it sitting on the floor, however long ago that was , it's been working probably 9 yrs since I actually changed the complete Valve assembly ,the last time I just replaced the diaphragm kit ,is there a good chance that the rear pin has become dried out and I can disassemble the rear of the valve ,grease it up and rebuild it similar to greasing the front pin , that made a big difference or would I be better off buying a complete new valve , found what looks like a genuine one on ebay for £62 delivered ,I know when I bought the first one ,it was something like £69 + vat ,I'm sure it was an original, it came with all the necessary washers but never had a schematic/manual with it like the link you sent me above .The one inside the boiler is marked up E4439DDH4 ,not a valid part number , was probably an original seeing the boilers were still fairly new then .

 

[Gasguru]

Unless you can knock up a suitable tool to remove the inserts (to get at the O rings) I would change the whole valve. 9 years is good going. Normally it's just crud on the centre pin that causes the valve to jam.

 

[brk1]

Thanks again for all this help, be easier (especially on my ears nag nag) to send off for a new complete valve and just replace the lot in one go ,rather than trying to repair the old one ,only to find out it didn't work properly and have to strip down again .Thankyou .