Worcester boiler pump runs for hours

[Geraint Thomas]

Hi all,

We've bought a property that has a Worcester Greenstar 37CDi boiler installed, with an old British Gas RS2 Thermostat linked to it. I'm not clued up on boilers in any way, though I'm quite handy with mechanics and always like to learn how things work.

The problem: The internal Bosch pump will run for hours, even when the heating and water are set to 'off'. If I switch the boiler off and on, it's quiet for around 60 seconds, to which the pump will fire back up. The boiler isn't heating, it's just the pump. Sometimes the boiler will go days without making a sound, other times it's on all night and all the next day before I turn it off out of concern. It's running as I type this now.

A few things to note:

• The black plastic flow manifold had a tiny leak in the seam of the plastic. Multiple layers of super glue left to dry had fixed this issue with no leaks since, although the boiler has had this behavious before the leak.
• The internal condenser pipe (I think) was full of gunk. It's the grey plastic device that has a clear flexi tube attached to it. I've taken this out, cleaned it out and re-installed it.
• I've checked the wires that control the pump speed (purple, white and black wires), but these don't look damaged.
• The boiler was installed in 2007.

Is this normal operation? If not, is there anything I can do or check? I'm happy to try and repair most things, but if gas is involved in any process I'll stay away.

Many thanks!

 

[Geraint Thomas]

Update:

I've taken a video:


It shows 24°C in the video before I stepped into the shower earlier. After the shower it was around 55°C, but now 30 minutes later it's only dropped to 53°C, which doesn't seem to be dropping that fast.

I turned the Eco mode off, then back on again, then held the reset button to reset the boiler. It then started to short cycle, and the temperature has now dropped. The boiler is now quiet and remains silent.

What on earth is causing this?

 

[ShaunCorbs]

No not normal please put the case / cover back on

Try turning the heating dial eg left hand knob to frost does the pump still run ?

Might take 5-10 mins to turn off once dial turned

 

[Geraint Thomas]

No not normal please put the case / cover back on

Try turning the heating dial eg left hand knob to frost does the pump still run ?

Might take 5-10 mins to turn off once dial turned

Well it's still silent, as mentioned earlier on... if it happens again I'll certainly give it a go. Since it short cycled we've been using the hot taps in the house and all is well at the moment.

I'll give it a go if it happens again, although I did turn the heating and water both to 'off', so I presumed that would override the dials?

 

[George4321]

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?

 

[Knappers]

Hi, not on all boilers but definitely on that one.
The case is part of the gasway and by taking it off your putting the safe operation of the boiler and yourself at risk.
Your entitled to do your own gaswork but if you don't want to take the risk then it's important you know that by taking case off you are doing gas work!

 

[George4321]

Personally I haven't taken the case of mine at all, only my gas engineer has done so at it's service. But any ideas on why the boiler is running it's pump like this - mine is exactly the same as in the video above. I have worked out a work around on how to stop it (see my post above) but it's still not supposed to do this? It doesn't seem to be the main PCB but what on earth could it be? Geraint, have you worked it out? It seems to be a common probem so sombody must know the answer?

 

[George4321]

PS - does the pump itself have it's own PCB in that box/connection bit on the side of the pump or is it simply connectors etc? Is there any way it could be running independantly of the main boiler PCB control board? I believe along with a control wire from the main PCB the pump has it's own permanant live feed.

 

[John.g]

I read somewhere that weather compensation, if fitted, will cause the above, if you have weather compensation installed can you disable it to see if the pump stops?.

 

[George4321]

It doesn't have any weather compensation systems/settings set. Any other ideas anyone?