When demand for h/w , boiler kicks in and off again after about 30 secs , then back on then off and so on . C/H loop works ok but overpressurises and opens up relief v/v , so i run it at a lower pressure to compensate. H/W temperature is adequate when c/h is on as heat in boiler warms cold water up (when boiler not fired up with tap open ,I think) But now that Spring is here c/h not on as much and cannot get a decent bath out of it now !!!!!
Alpha 240p H/W
- Thread starter gr8nty
- Start date
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sludged secondary heat ex
expansion vessel needs recharging
When boiler is in H/W mode the boiler still is in its mode i.e. pump , switches etc. its the burner that goes out and then re-ignites and then out etc .I do not think the exchanger is blocked as the flow of water is fine unless its on the loop side .Even though i fail to see how that would interlock out the burners.
because you can't get the heat transfer
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Does the boiler fire up with the mode selector switch set to hot water only?
Does the water go warm/hot then cold every 30 seconds?
With the heating on do the radiators get really hot with the heating temperature set to maximum?
Does the water go warm/hot then cold every 30 seconds?
With the heating on do the radiators get really hot with the heating temperature set to maximum?
The boiler works fine in all settings h/w only or ch/hw . everything kicks in no interlocks from fan ,microswitches all activated . 30 secs was just a figure its different each time . when opening hot tap boiler operation starts off fine but then flame goes out and then on again after maybe 20 secs ? Nothing visible takes flame out all switches , fan look fine.
radiators are fine nice and toasty . Just looses pressure if I charge system up to recommended pressure and it looks like its overpressure when running.
radiators are fine nice and toasty . Just looses pressure if I charge system up to recommended pressure and it looks like its overpressure when running.
As kev said sounds like plate heat exchanger could be blocked on the primary side.
Easy to check by feeling flow and return pipework on main heat exchanger - if blocked you will feel a large temperature difference.
Easy to check by feeling flow and return pipework on main heat exchanger - if blocked you will feel a large temperature difference.
I am capable of removing exchanger and have time to spare to work on it. What is best product/way of unblocking it . Could this also be the reason why the system is pressurising so much because of resistance to flow in primary loop ?
Depends whats bocking it - sometimes just backflowing it with high pressure hose will do the job.
This has nothing to do with the overpressure.
The expansion vessel is probably flat - it should have about 0.8 Bar (a tyre valve will be found on it). Check pressure when boiler is drained down. Relief valve will need cleaning out. Re-presurise to 1 Bar.
This has nothing to do with the overpressure.
The expansion vessel is probably flat - it should have about 0.8 Bar (a tyre valve will be found on it). Check pressure when boiler is drained down. Relief valve will need cleaning out. Re-presurise to 1 Bar.
I do have access to the expasion vessel and just need to lend a pump.
still confused about blocked second heat exchanger why would that cause the boiler to go out and on etc. I have felt the inlet and outlet pipes and there is not much temperature difference ( too hot to touch for long both sides ) when the burners are on ,and the obviously they cool when the burners go out and then they heat up again when burners fire up again.
still confused about blocked second heat exchanger why would that cause the boiler to go out and on etc. I have felt the inlet and outlet pipes and there is not much temperature difference ( too hot to touch for long both sides ) when the burners are on ,and the obviously they cool when the burners go out and then they heat up again when burners fire up again.
Cycle pump available from cycle shop.
If plate exchanger is blocked water can't be circulated from the main heat exchanger at the top and therefore the burner cycles on and off - however if the flow return pipes feel similar the plate exchanger is possibly OK.
Only other sensor to check would be the DHW thermister
If plate exchanger is blocked water can't be circulated from the main heat exchanger at the top and therefore the burner cycles on and off - however if the flow return pipes feel similar the plate exchanger is possibly OK.
Only other sensor to check would be the DHW thermister
I have charged the expansion vessel , no water came out of valve which is a good thing right ?
I have removed the secondary heat exchanger and it was as clean as a whistle . I have removed and cleaned the dhw temp sensor . Do not know how to test it though , should i just buy a replacement ?
I have removed the secondary heat exchanger and it was as clean as a whistle . I have removed and cleaned the dhw temp sensor . Do not know how to test it though , should i just buy a replacement ?
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