Hello, My worcetser combi was having temperature fluctuation problems. A qualified heating engineer rightly diagnosed the problem as a perished membrane. The screws on the diverter were corroded together and it would not open. He fitted a refurbished diverter form the same type of boiler with a new membrane. The system now works, however when the hot tap is turned off the boiler pilot light shuts down. We suspect that the membrane is not dropping quickly enough and the boiler is shutting down as it is overheating on the over-run. My question if anybody has encountered this problem before is WHY!
WORCESTER 9.24 COMBI DIVERTER PROBLEMS
- Thread starter frustrated boiler owner
- Start date
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He has probably not 'refurbished' the diverter properly, just re-used an old one he took out from somewhere and put a new diaphragm on it. If the passages in it are all bunged up and scaled then the moving parts may not be able to respond quick enough to the demand.
Ask him where he got the valve, and if he refurbished it himself, if he did, ask what the procedure was.
Is the pump OK by the way?
Ask him where he got the valve, and if he refurbished it himself, if he did, ask what the procedure was.
Is the pump OK by the way?
Thanks for the reply, you are right about the valve comming out an old boiler, the engineer is a friend of mine and he was trying his best to keep my old boiler going late in the day when spares were not available. I appreciate I may have to get a new valve if he cannot open up my old valve, which he is trying to do. I don't know about the pump though - HOW DO I TELL IF IT IS WORKING CORRECTLY?
Depending on which type it has do the following:
If it has a black plastic nut in the centre: Turn the boiler off, unscrew the nut by hand, once fully unscrewed pull the shaft towards you to locate the impeller on the shaft, then turn the impeller clockwise & anticlockwise to check its free rotation. If it feels stuck or tight then the pump head needs replaced.
Or
If it has a flathead screw in the middle (which I think this boiler has): Remove the screw with the boiler turned off, put a small flathead screwdriver into the hole and locate the shaft inside, turn the shaft wth the screwdriver clockwise & anti-clockwise to check its free rotation. You can also with this one, turn the boiler on, and gently stick the screwdriver in when the pump is turning to ensure that the shaft & impeller are turning.
If it has a black plastic nut in the centre: Turn the boiler off, unscrew the nut by hand, once fully unscrewed pull the shaft towards you to locate the impeller on the shaft, then turn the impeller clockwise & anticlockwise to check its free rotation. If it feels stuck or tight then the pump head needs replaced.
Or
If it has a flathead screw in the middle (which I think this boiler has): Remove the screw with the boiler turned off, put a small flathead screwdriver into the hole and locate the shaft inside, turn the shaft wth the screwdriver clockwise & anti-clockwise to check its free rotation. You can also with this one, turn the boiler on, and gently stick the screwdriver in when the pump is turning to ensure that the shaft & impeller are turning.
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fluctuation of dhw temp on these boilers is also a sign of scaling in the dhw H/x
Limescale is not a problem in my part of Scotland, for example kettles live very long and happy lives without any limescale on the elements. I dont know if he has manually reset the boiler, I will ask him tonight. He is pretty sure the problem is caused by the stand in diverter, and is trying to unseize the screws on the old diverter and refit it to see if this cures the probelm. Does anybody know if a post 1994 diverter will fit a pre 1994 boiler (if the old part cannot be fixed) as his supplier only has the latter part available (I know you can buy the pre 94 parts on ezypart.co.uk)
Its not limescale like we get here in the south east which I'm talking about. Its scale on the primary side of the plate heat exchanger which could be the problem.
Over the years which a heating system is in operation, if the system was not cleaned initially, or not maintained to remain clean, metal oxides and flux residues can collect inside radiators and on the inside of the heat exchanger (not the side that the mains water goes through). These collect around the heat exchanger as the concentration of heat there, coupled with the very small waterways makes it an ideal place for blockages to occur. I'm not that great at describing the science behind the formation of scale in heating systems so excuse the basic explanation. Agile or someone can do this better than I.
When the plate heat exchanger is blocked, the 'scale' which I refered to earlier can trap latent heat, and act as an insulator. This causes both the mains water not to be heated right (as heat can't transfer through the insulating scale), and also cause the boiler to overheat (as heat can't escape anywhere, i.e to mains water like it should).
I doubt that its the diverter as normally when its to blame you have a situation where the radiators heat up on DHW call, or where the hot water doesn't heat up at all.
Over the years which a heating system is in operation, if the system was not cleaned initially, or not maintained to remain clean, metal oxides and flux residues can collect inside radiators and on the inside of the heat exchanger (not the side that the mains water goes through). These collect around the heat exchanger as the concentration of heat there, coupled with the very small waterways makes it an ideal place for blockages to occur. I'm not that great at describing the science behind the formation of scale in heating systems so excuse the basic explanation. Agile or someone can do this better than I.
When the plate heat exchanger is blocked, the 'scale' which I refered to earlier can trap latent heat, and act as an insulator. This causes both the mains water not to be heated right (as heat can't transfer through the insulating scale), and also cause the boiler to overheat (as heat can't escape anywhere, i.e to mains water like it should).
I doubt that its the diverter as normally when its to blame you have a situation where the radiators heat up on DHW call, or where the hot water doesn't heat up at all.
Thanks for the explanation I will mention this tonight, your last point about radiators heating up on DHW call, the boiler came with my house 18 months ago and my radiators have always heated up when the hot tap is on, I assumed this was normal, am I correct?
No this is not correct, and is probably the reason why your man identified the diverter as being a problem.
Some boilers open the diverter AFTER a DHW call as a way of losing heat from the boiler, but normally only 1 radiator will get slightly warm because of this.
Combi's are only ever supposed to be working on heating OR hot water, and they have a hot water priority. When the hot ater is being taken, the diverter
should close off the radiator circuit and send all heat to hot water.
It sounds like your diverter valve is not moving correctly to the hot water position. This could be due to small deposits on the valve seating, or due to a perished diaphragm. Either way it probably needs replaced or at least a proper clean and new diaphragm. Also you may as well check the heat exchanger while your man is there.
Some boilers open the diverter AFTER a DHW call as a way of losing heat from the boiler, but normally only 1 radiator will get slightly warm because of this.
Combi's are only ever supposed to be working on heating OR hot water, and they have a hot water priority. When the hot ater is being taken, the diverter
should close off the radiator circuit and send all heat to hot water.
It sounds like your diverter valve is not moving correctly to the hot water position. This could be due to small deposits on the valve seating, or due to a perished diaphragm. Either way it probably needs replaced or at least a proper clean and new diaphragm. Also you may as well check the heat exchanger while your man is there.
It sounds as if the lower part of the diverter is not moving properly.
This part "follows" the diaphragm under its own spring pressure.
Check that when hot water flow stops the pin on the top of the diverter retracts promptly and that you can hear the microswitches click off.
It can be taken apart and cleaned out or boiled in citric acid solution but that can be dangerous.
Tony
This part "follows" the diaphragm under its own spring pressure.
Check that when hot water flow stops the pin on the top of the diverter retracts promptly and that you can hear the microswitches click off.
It can be taken apart and cleaned out or boiled in citric acid solution but that can be dangerous.
Tony
Tony, thanks for your advice, the diaphram was slow to fall before and after the change of diaphram and diverter, the diverter was checked and cleaned out fully. We are now wondering if a dead leg in the system where the old hw cylinder was removed could be causing this problem.
Has anybody encountered dead leg problems before. Also there is some confusion about the pre and post 94 spec diverters sold by ezypart does anybody know what the difference is?
Has anybody encountered dead leg problems before. Also there is some confusion about the pre and post 94 spec diverters sold by ezypart does anybody know what the difference is?
Be aware that Ezepart do not sell GENUINE Worcester spare parts. They sell generic diverter valves although they may or may not be apparently exactly the same as the original.
However I dont expect that that is the problem.
A dead leg full of air could well cause your problem!
Tony
However I dont expect that that is the problem.
A dead leg full of air could well cause your problem!
Tony
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