Air in DHW

[cluelessmalc]

Hi can anyone help. I can't get any hot water from my Worcester 24CDi combi. Whenever I try and draw hot water there is terrible water hammer and air gurgling. The boiler lights but goes out after a few seconds and the automatic air vent continues to release air for about 30 seconds after?

Anybody any ideas please i'm a bit baffled as to how you get air in a sealed hot water system?

 

[gasafengineer]

Has the system/boiler any pressure in it.

 

[cluelessmalc]

Hi Yes the Heating is charged and maintaining it's pressure?

 

[tryitandsee]

Sounds like the pump has either got stuck or broken.
Try seeing if the pump can be turned, see wiki.

Don't forget I'm just an end user, not a Gas safe etc.

 

[cluelessmalc]

You just got me thinking cos we've not had the heating on for a few weeks. The system is charged and there was no air in it but when I try and fire up the heating it's doing the same thing? Does this still sound like the pump?

 

[tryitandsee]

To me the lay person, yes.

Carefully take out the silver screw to the pump, making sure you have towels to soak up leaking water.
Turn on central heating and feel the impeller spinning inside where you have removed screw with a small screw driver (small electrical one I use) you will know if it's spinning by it rattling the end of the screw driver. If not try and turn it with the screw driver to see if it wasn't stuck!

 

[cluelessmalc]

Many Thanks for your advice it was the pump. The impellor must have been stuck cos a couple of knocks with the old 2lb hammer freed it and now everything is fine. I think I'll get a replacement pump though just to be ready for next time.
Still a bit baffled as to how air was getting into the system. If anybody can explain it might save me a couple of restless nights thinking about it.

Thanks again for your advice. Much appreciated

 

[tryitandsee]

As the pump was not circulating water when gas came on, the heat generated was not being dispersed into the water, in effect boiling the standing still water. Not a good thing to be happening, luckily boiler shuts off as it should do, preventing further problems. I would have thought the safety cut out switch would/should have tripped.

Perhaps not a new pump needed, but a good service and drain down/flush would be better, as crap in the system is probably sticking the pump and a gas safe person would check out the trip/over heat switch for correct operation (just in case faulty).