Cold weather airlocks in CH pump

[Keith Hawkins]

Hi all,

I keep getting airlocks in my CH pump on very cold mornings and consequently poor circulation when I need it most. Bleeding the pump fixes the problem but obviously, I'd like to stop it happening. The pump (grundfos UPS2) is high in the system below a 22mm combined vent & feed pipe. The water level in the feed tank, about 2m above the pump, is 3 - 4 inches above the feed & vent pipe inlet/outlet. I have lowered the pump speed from highest to medium and have just switched it to lowest. There is no apparent air build-up anywhere else in the system.

Any suggestion welcome.

 

[JohnD]

can we see a photo showing the orientation of the pump and its pipes, please, and the direction it pumps.

 

[Keith Hawkins]

Hi JohnD,
Picture attached. The pump is 2 years old and has been installed with the text on it upside down. I assume that the flow is downwards into the white Drayton Mid-Position motorised Valve below. The combined F/V pipe is shown top right in the picture.

 

[JohnD]

the pump is made in two parts. The "barrel" is mostly motor, and can be rotated, but should be horizontal on its axis. On the far end is the actual pump, there should be an arrow in the casting showing direction of flow. You can also tell from the shape of the casting, you can see (but in your case you may need a mirror) that one of the pipes is directed to the centre (inlet) and one to the edge (outlet).

I was thinking that if it pumped upwards, it would be more likely to blow any stray bubbles out so they can rise away and escape. I am not a plumber. Some of the pros might know if this would be suitable, seeing you have a combined feed and vent.

 

[Keith Hawkins]

Thanks for your comments John. I'm not a plumber either, but I believe that I read somewhere that the pump should be positioned to pump away from the feed and vent. I am wondering whether a separate vent pipe might fix it. I also wonder what static pressure is necessary for the pump.