Central Heating Pump Airlock ? DAB A55/130

[pgs0971]

Hi,
My central heating pump seems to have a mind of its own over the last few years when we start to use the heating in winter. I have a combi boiler and when the heating is turned on the pump whirls into action but after a while it will just stop. I recently flushed the system with Fernox and have bled all the rads which all seem to ok. I also removed the pump yesterday and noticed a bit of scale around the pump disc and cleaned off what I could. After refitting the pump it now runs more smoothly and quietly but still stops after 30 mins or so of running time. Its not the thermostat and i've noticed that once it stops, if I undo the pump "bleed screw" the pump kicks back into action. Can anybody tell me why it would appear that the pump keeps getting an airlock (if thats what it is) and if I should just replace the pump and would this solve the problem? I would estimate the pump has been on the system for at least 5 years.
Many thanks

 

[pgs0971]

Problem - The pump stops operating after a while but starts again as soon as the centre screw on the pump is undone just half a turn. Does anybody know if this is more likely to be a faulty pump or would it be air getting in the system (even though all rads have been bled and operate well).

Thanks

 

[advancedplumber]

hmmm. you stated " when we use the heating in the winter" , are you telling us that you don't use your heating though the summer / mild months????? if so pumps seize up after periods of not being used. it does't have to be very long. i've seen pumps seize after a month without use, depending on inital age. the berring clog up and i normally just replace cos you play about with it but i've been called back the next week after restarting the pump and have learnt to replace instead of fixing. wilo make a "smart" pump. it holds a charge enough to bring the pump on for a few seconds, just enough to keep the berring from seizing. this is brought on by a timer . it does this automatically once a month. it also has an inverter built in which adjusts your speed rate automatically so if the pump doesn't need to be flat out, it will slow down automatically thus increasing it's life span. and for about fifty sheets its better than a standard one which is about 35 quid. easy to change yourself too. a replaceent will do the trick. adding an inhibitor to your system will also help it from happening again .

 

[pgs0971]

Thanks for your comments "advancedplumber", I will look into the wilo pump as a possible replacement.

I'm just unsure if its a problem with the actual pump or not as when I took the housing off the impellor seemed to move very freely. When I turn the heating on the pump starts straight away. The pump then seems to stop after 25 mins or so before all the rads are completely hot. To resart the pump I just have to loosen the bleed screw which seems to release some pressure and a bit of water dribbles out. This does get the pump started again though and the rest of the rads heat up fully.

Does this sound like a common pump problem or could air be getting in ?
Thanks

 

[pgs0971]

I bought a replacement circulating pump today for my old floorstanding oil combi (Boulter Camray 90/130) but not yet fitted it.

The original pump has been getting an airlock after 20 mins or so of it running. I've noticed that the pump appears to be on the return pipe and is fitted with the arrow facing downwards to the floor. Whilst I have read this pumps can be fitted in either direction I have also read that pumps facing downwards can be the cause of air locks in the pump which I believe is what is happening here.
I have checked the boiler manual and although it would appear the pump is definately connected to the return on the boiler (which would seem to be ok for combis), it is this pipe that gets hot first when the boiler is on ???!!!!!????

Anyway, I have now tried rotating the pump 180 degrees (but not the pump casing where the arrow still faces downwards) and the pump is now working perfectly and we have consistent heating.


thanks.