Worcester Bosch Greenstar 30 CDi circulating pump always on

2 Jun 2009
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United Kingdom
I have a Worcester Bosch Greenstar 30 CDi boiler, about four years old.

I've noticed that it is giving out an almost constant hum. I think it's the circulating pump. This is even the case when, as now, the central heating has been turned off for the summer (I did this on the boiler console, not just at the room stat).

Is this normal? If not, any ideas what might be going on?
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had same problem with this boiler was the main board. pump anti sieze. but no it aint normal best get an rgi. theres a few from your area on here
If its a combi as I expect, does anyone know the PCB part number?

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It's a combi boiler. The temperature gauge on the console also seems a bit high at times - 38, say, even if it's been idle for some time. I wonder whether perhaps it's overheating and the pump is drawing heat of the system?
These boilers retain the heat for a very long time, if the pump does not run. Maybe there is another fault causing the pump to run. Could also be the preheat.
The interesting question is: are you SURE the hum comes from the pump being on permanently?
I'm not certain that it's the pump. I'm not a boiler engineer myself. But when I feel the pipes below the boiler they're vibrating when there is the hum, which is why I think it's the pump. Also, the bathroom rad is sometimes slightly warm (even though the central heating is off), which also suggest to me that water is circulating in the central heating system.

I'm trying to get in an RGI at the mo to have a look at it. So thanks for all the thoughts guys. Any futher thoughts would be great.
Very odd, these boilers are so quiet that I had a client calling me that the new boiler didn't work; only when I asked if she could see a green control light did she realise it was on.
I reckon something causes a blockage which stops the heat from dissipating and keeps the pump running on max.
You could try turning the boiler off at the mains for an hour to cool it down and then repower and see if its still apparently running the pump.

If so it could think that it needs to provide pump over run.

Some of the earlier Worcester PCBs did often get time constant faults particularly affecting the anticycle delay.


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