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Discuss Worcester boiler pump runs for hours in the Central Heating Forum area at PlumbersForums.net

Worcester Bosch Greenstar 30CDI (2010) - same problem (Pump runs constantly after mains power interruption).

First noticed - approx. 6 years? after installation.
Problem - pump runs continuously after power-cut (no weather compensating controller, no room thermostat).
Issue - if a power cut occurs during period when house is empty, the Pump will run continuously until "workaround" is applied.
Attempted fix(s) - "power off" (of varying length up to 12hrs) or "reset" or adding HW/CH will not solve the problem.

WORKAROUND - Create Boiler demand (Ie HW) during or prior to boiler power up sequence (this is the only thing that works for us).

SOLUTION - Worcester Bosch need to publish better/actionable advice to support this known issue for the installed base.

Thank you to this forum and George4321G for adding a clear workaround.
Concern - I was going to arrange the PCB replacement, but reading that this didn't help in earlier post?
 
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have the same problem. Every time the boiler is turned off at the mains or there is a power cut, after about a min or so, the pump runs, and it runs forever (the burners are not on in this time). During this time if i run a tap or turn on heating it works but afterwards the pump continues to run... forever.
However, I have discovered if a hot tap is running or if the heating is on (and thermostat set to on) before the boiler is turned on at the mains and then turned off a few seconds after the burners start then the pump will stop after its normal over run of a min or so and then stay off. They boiler will then function as normal.
I would still like to find a cause/proper fix to this as I am concerned if we have a power cut when out/away then it will run its pump forever until we return to "reset it".
I have tried resetting the service settings on the PCB to defaults but that makes no difference. I also tried turning off the syphon pre-fill cycle at startup (again in the service settings) that didn't help. I even had our gas engineer change the PCB at it's service and that also didn't make any difference and the engineer had no other ideas as everything else appearked ok at its service.
I have the same problem with my W-B Greenstar 30 cdi. My plumber was mystified by it and phoned up WB to ask their advice, which suggested it was either a faulty pump or PCB, so he has quoted me for replacement of both and labour, but willing to refund cost of one of the parts (pump or PCB) once he has tested the repair and which is the problem part. I am sceptical of this! The problem seemed to sort itself for no apparent reason about 3 months ago after the standard service but then started again after we experienced a power cut about 3 weeks ago. Having just read your thread I tried your remedy above and in fact it seems to work as the pump is now mysteriously working properly again, trning itself off after the usual couple of minutes. Rather than a faulty part I wonder if this is a design fault and WB either dont know about it or are not owning up to it. Thanks for your comment anyway.
 
I have the same problem. Every time the boiler is turned off at the mains or there is a power cut, after about a min or so, the pump runs, and it runs forever (the burners are not on in this time). During this time if i run a tap or turn on heating it works but afterwards the pump continues to run... forever.
However, I have discovered if a hot tap is running or if the heating is on (and thermostat set to on) before the boiler is turned on at the mains and then turned off a few seconds after the burners start then the pump will stop after its normal over run of a min or so and then stay off. They boiler will then function as normal.
I would still like to find a cause/proper fix to this as I am concerned if we have a power cut when out/away then it will run its pump forever until we return to "reset it".
I have tried resetting the service settings on the PCB to defaults but that makes no difference. I also tried turning off the syphon pre-fill cycle at startup (again in the service settings) that didn't help. I even had our gas engineer change the PCB at it's service and that also didn't make any difference and the engineer had no other ideas as everything else appearked ok at its service.
Anyone have any ideas?
George, I have the same problem and your workaround fixes it. Did you ever find out the actual problem. Thanks in advance
 
Very glad the workaround I found by fiddling is so helpful! To answer the question did I ever work out the real cause- no, no idea, had it serviced by two different engineers who (apart from this wierd constant running issue) can see nothing wrong and have no idea of the cause. I am just living with it, and since weston power have replaced some local overhead cables we seem to have stopped getting power cuts. However when we moved in I'm certain the boiler didn't do this. It has never broken down and I can't think of anything that may have occured for this fault to start. As so many people have exactly the same fault I don't understand why there isn't a definate cause & repair identified by WB.
I just can't understand it - I can't see how it's a wiring fault becuase when it is started up using my workaround it is then perfect and stays perfect, if it were wiring wouldn't it recurr every time the affected switch/wiring is live? I guess it has to be to do with something specific that it does during it's startup procedure, some sort of signal/sensor failing to send a signal back to the PCB to tell it to turn the pump off but also something that must work fine the rest of the time as it is completely normal if started in the workaround. Even if turn on without my workaround (so the pump is running constantly) the actual heat output/function for both hot water and heating works fine and turns on & off correctly so it doesn't stop the boiler working.
 
No, never fixed it still living with my workaround that I found by chance fiddling.
2 gas engineers have no clue either, fond nothing wrong generally.
It's not the PCB as had that changed, all that's left to change would be the pump & it's associated control module?
Assume must be some signal that the PCB is expecting during the startup that it doesn't receive - some sensor? But it is odd that the boiler works completely fine if started using the workaround so it can't be something that is completely faulty.
Don't see how it can be wiring as again boiler works perfectly after starting by workaround, if it were wiring it would be faulty every time that circuit is activated.
As it is clearly quite a commmon fault how on earth can WB not know what the cause is?
 
Thats the confusion! My gas enginner who serviced it last week put a new PCB on it and was rather lost by the problem. "the pump can only run if the PCB tells it to" was how it was left but the PCB is new. No fault codes or anything. WB are also lost and can only suggest get engineer to phone them when the boiler is opened up to test each component - maybe I will do that next year at its service. It would make sense being frost protection but if it was a sensor or something then I don't get why it only does this if unit is turned on from the mains without a "demand" but if there is a "demand" at time of turning on its all ok and functions normally and its pump turnes off as expected, i would expect the fault all the time. Looks something i will just have to live with, thanks for your help.
Has there been any resolution to this please, as my boiler has the same problem.
 

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