Vented heating system - trapped air / pipe vibration

[lazyade]

Hi,

I'm helping a mate out, trying to fix a problem with his vented heating system. He had to drain the system last week to replace some downstairs rads, since refilling there's a bubbling noise around the pump and downstairs by the boiler you can hear air in the system. The boiler runs and heats the water and central heating circuit (each has its own 2-port valve). We've bled all the rads and the bleed screw in the centre of the pump but this hasn't fixed the problem. When the system is set to just pump to the central heating circuit there is a vibration in the pipes, not a banging but more like a light tap.

I've done quite a bit of reading up and there seems to be a consensus to check the F&E cold fill pipe and the system vent. I've moved a magnet around these today (just above the pump) but there was nothing magnetic there.

I've attached a couple of photos of the vent and cold F&E fill pipe. Do these look correct? Someone has suggested that the vent pipe (the one on the right in the photo) should go straight up, so the the air can escape, and the flow fed through a tee to the pump.

Any thoughts on how to remove the air around the pump?

Vent and F&E cold fill

• lazyade
• 14 Mar 2014
• 1

F&E cold fill on left, vent on right

Pump

• lazyade
• 14 Mar 2014
• 1

Pump (under the F&E cold feed and vent), 2-port valves underneath.

Vent and F&E cold fill

• lazyade
• 14 Mar 2014
• 1

F&E cold fill on left, vent on right

Pump

• lazyade
• 14 Mar 2014
• 1

Pump (under the F&E cold feed and vent), 2-port valves underneath.

Vent and F&E cold fill

• lazyade
• 14 Mar 2014
• 1

F&E cold fill on left, vent on right

Pump

• lazyade
• 14 Mar 2014
• 1

Pump (under the F&E cold feed and vent), 2-port valves underneath.

Pump

• lazyade
• 14 Mar 2014
• 1

Pump (under the F&E cold feed and vent), 2-port valves underneath.

Pump

• lazyade
• 14 Mar 2014
• 1

Pump (under the F&E cold feed and vent), 2-port valves underneath.

Pump

• lazyade
• 14 Mar 2014
• 1

Pump (under the F&E cold feed and vent), 2-port valves underneath.

 

[Whitespirit66]

edit

 

[Blagard]

When you filled the system did you move the levers on the motorised valves to the venting position?

If not you trapped air in the system when you filled it and now when you start up the system air is rising against the flow from the pump.

 

[lazyade]

When you filled the system did you move the levers on the motorised valves to the venting position?

If not you trapped air in the system when you filled it and now when you start up the system air is rising against the flow from the pump.

No I don't think he opened the 2-ports, we'll drain it down in the morning and try again with the 2-ports open.

 

[lazyade]

Well this morning we drained down the system (with the 2-ports open), re-filled (again with the 2-ports open), drained all the rads but there's still a gurgling round the pump and a ticking noise from the central heating loop (if you turn on just the hot water circuit you don't get the noise in the pipes).

Any suggestions? I should have added to the original post that he also added a TF1 cleaner on the return pipe above the boiler when the problem started - this couldn't be causing the problem could it?

Also on the pics on my original post, is it right that the vent pipe isn't straight to the flow pipe coming from the boiler? (it comes off after the tee)

Cheers
Adrian

 

[Blagard]

Well at least you have eliminated one source of trapped air. I would be inclined to turn the pump up to maximum to see if it can clear out any other trapped air pockets.

While I would agree the vent pipe going straight up would be better, what you have is not strictly speaking wrong. However one of these air separators instead of your tee would be better: You can get cheaper on ebay search for Tower Air Separator.

http://www.toolstation.com/shop/p75473?

This version even has the connection for cold feed, but not really needed in your case. It does show the arrangement though!
http://www.heatingcontrolsonline.co...-22mm-air-separator-with-cold-feed-p-269.html

 

[lazyade]

Well at least you have eliminated one source of trapped air. I would be inclined to turn the pump up to maximum to see if it can clear out any other trapped air pockets.

While I would agree the vent pipe going straight up would be better, what you have is not strictly speaking wrong. However one of these air separators instead of your tee would be better: You can get cheaper on ebay search for Tower Air Separator.

http://www.toolstation.com/shop/p75473?

This version even has the connection for cold feed, but not really needed in your case. It does show the arrangement though!
http://www.heatingcontrolsonline.co...r-separator-with-cold-feed-p-269.html[/QUOTE]

We fitted an air separator this weekend (to the pipe section just before the pump) but unfortunately it hasn't improved the sound of air around the pump (the pump sounds like it has trickling water going through it when it's running)! The system does get hot but there is a vibration on the heating circuit that is annoying. Even though the pump was only replaced about 12 months ago could it be that? Or could it be because it's only a cheap Wilo pump?

Thanks for the help so far but any other suggestions?

 

[lazyade]

Any thoughts on the above? Should I be looking to cut my losses with Wilo pump? If so how do you calculate the correct rated pump for your house (I'd probably go for a Grundfos)?