Boiler airlock

[bodgeitandsee]

Hi
Further to my other post I have a specific question about an airlock.
My rads are all fully bled but the boiler flow and return pipes sound empty. I have had the pump running for several hours (boiler off) what should I do now.
I can't seem to find anywhere else in the loft to bleed the system.
I have an old Ideal W 450 boiler on a fully pumped, vented system.
For info I live in a bungalow if that makes any difference to the bleeding procedure and the pump and valves are in the loft (on horizontal pipework) with pipes dropping to wall mounted boiler.
Thanks for any help.

 

[chrishutt]

the boiler flow and return pipes sound empty

And what does that sound like?

 

[bodgeitandsee]

sounds "ringing and hollow". As comparison I went tapping 22mm pipes in airing cupboard and they sounded solid.
If I do fire the boiler it hisses (is this kettling) so turned off after few seconds again.

 

[chrishutt]

Sounds like the boiler's still air locked. Can't you work out where the high points are and look for places to vent air?

 

[bodgeitandsee]

Been up in the loft and can't see any vents up there, will go for another look now. Is there normally a vent in the loft?
Just fired the boiler up and could hear whooshing in the pipework but it wouldn't clear and with the boiler stat on low the pipes were getting very hot so thought it best to shut off.
The pump has been running all this while but these noises in the boiler pipes were only once the boiler was fired up.
Funny thing is it almost sounded like the water went the other way once I turned boiler off although this is a gut feeling type observation with no factual basis.
Thanks for taking an interest in my prob. Other half went to bed ages ago because she was so cold and I'm in the dog house.

 

[chrishutt]

Very difficult to guess what's happening without being there, hands on pipes as it were. I'm worried about your pump. If it's been running dry for a long time, it's not going to do it any good.

If the pump is still working, you might try fitting it pointing the wrong way just to try to clear the air (don't run boiler at same time). There might be other side effects so do it a bit gingerly, and don't blame me if something unexpected happens, but I think it's what I would try. Remember to put it back the right way!

 

[bodgeitandsee]

Chris,
Thanks for advice so far.
Just been up there again and under a dirty great mound of loft lagging found 2 lttle stand pipes with drain tails soldered on top. Chased these back and sure enough they go into the flow and return pipes.
Put a length of hose on each and..... nowt.
They are a foot higher than the pipe runs and about 2 feet below the f&e tank, I'd have thought the gravity from F&E would bleed them or would they just be a vent with no air because they are above the pipe runs?
Gets me! Getting late now for this lark.

Thanks for the ongoing.

 

[chrishutt]

The drain valves must be the means of venting air. Quite likely that they or their pipes are blocked. To clear, drain down to that level, cut off drain cocks and push rod down pipes to clear, then replace with manual air vents, or even automatic ones! Flush out any debris from blockages.

 

[bodgeitandsee]

Answers why I also found a strong bit of wire nearby too then, must be a usual problem. I inherited this system a few months back so it's all new to me.
So just need to drain the F&E below the drain tails effectively, not the system?
Auto vents sound great but will probably leave the drain tails on. At least I can unscrew the ends right out and poke straight down the pipe. If I fit vent valves I'd have to take them off if it did this again in the future.
Am I likely to find another one somewhere for the dhw side or will it all vent off these? The vents are actually on the CH circuit.
Thanks.

 

[bodgeitandsee]

Chris,
Thanks for the help last night.
Went to the loft standpipe vents this morning and they bled straight through and the system is now ticking alog with boiler on low for another couple of hours. Why it wouldn't bleed last night I don't know but there we go.