Air rushing round hot water/heating system HELP :-)

[Mrmethane]

Hello

You say the system is working ok, radiators are getting hot and hot water ok, pump is on number two and all rads from your posts appear to have been bled numerous times. How long has this been happening and what controls do you have on your system, i.e trvs three way valve, etc etc.

 

[steveorules]

Hi mr methane
The controls i have, there is 1 trv on a downstairs rad (on max), a 3 way valve by the grundfos pump, air vent next to hw cylinder, F&E tank in loft, digital room stat and digital heating/hw timer unit The rushing noise has been there for a couple of years i would say, heating and hot water work fine, not much air in any rad when bled, dont hear noise going through rads, sounds like its going round in a loop pump to boiler and back ?? its finaly annoying me enough to try and sort it.
Any ideas that i could try ??
Cheers mate,
Steve.

 

[Whitworth]

Quote from automatic bypass valve manufacturer;
Should persistent water velocity noise occur in the system,
gradually turn the ABV to a lower setting until the noise is
eliminated.
Does your system have an automatic bypass valve?
Not in the trade BTW was looking at ABV's the other day for my own system.

 

[steveorules]

Hi Whitworth,
Im not sure what an ABV is , but i dont think i have one, thanks for joining in mate. Any ideas gratefuly received.

 

[JohnD]

automatic bypass valve?

Perhaps it means that the air is going round a short loop and not being pumped round the system (air which is pumped round with the water usually ends up getting trapped in a radiator)

sometimes it means automatic bleed valve.

Some systems have a bypass which enables pressure from the pump to escape back into the return pipe, especially when all the TRVs have closed down and cut off most circulation. This can be adjusted with a manual valve or with a spring-loaded one.

If your system is not well balanced, your room stat might leave the pump running when all the TRVs are fully shut, thus causing flow to go round the bypass.

have you noticed if the noise is still present when the boiler is heating the hot water cylinder?

Some photos of your pipework around the boiler, pump, motorised valve and cylinder might help.

 

[steveorules]

JohnD,

I've only got 1 TRV on the living room rad which is set on max, the noise is there when the boiler is heating the hot water or heating or both.
I dont understand why the air doesn't end up in the rads ?
Some times the pump gets really noisey when the air gets stuck in that area, I have to play around with the pump speed switch to get it to clear. I've checked the vent by the side of the HW cylinder again - not much air, and I let a fair amount of water out to be sure.
I've taken some photo's as requested.

Cheers mate,
Steve.

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• steveorules
• 21 Mar 2011
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• steveorules
• 21 Mar 2011
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• steveorules
• 21 Mar 2011
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• steveorules
• 21 Mar 2011
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[JohnD]

coming out of the motorised valve is a vertical copper pipe with a brass fitting on the end. Have you bled it?

I can't see a balancing valve on the pipes that go to and from the cylinder coil. Is there one? Do these pipes go cold once the cyl is up to temp?

have you looked in the loft to see if the F&E is pumping over or sucking air?

what speed is the pump set to?

 

[steveorules]

JohnD,

Yeh I bled the vent pipe, hardly any air came out, loads of water.
F&E tank - level ok, not much sediment in bottom (3mm) well below outlet, have not checked if pumping over or sucking (will check tomorrow).
No balance valve on pipes to cylinder coil, when cylinder is up to temp, the lower pipe starts to cool but not cold, the upper pipe stays hot.
I also noticed that the 'top up' pipe going up to the F&E tank gets warm (all the way up to the ceiling, not sure if its just heat conducting ?)
Pump speed set on No. 2 (4 bed house) Boiler has settings 1 to 6, its on No. 4

Cheers mate, I'll get back to you.
Steve.

 

[jimbob22]

What happened after you bled the air off at the AV ?
Was there still exactly the same noise at the pump when the boiler was running again ?

 

[steveorules]

Jimbo,

Very little air at AV, plenty of water. Made no difference after bleeding.

Any ideas ??

Cheers,
Steve.

 

[steveorules]

JohnD,
I checked the F&E tank, no pumping over or sucking air.
Whats next mate ??
Cheers
Steve.

 

[rojaca]

air is not being encourage to vent due to the orientation of the expansion pipe. velocity of water is carrying the lighter air along the pipe into the pump. ideally i would step up the horizontal pipe at the elbow to 28mm then teeing off for open vent followed by the cold feed. You may find possibly a blockage on cold feed is causing air to be drawn in through open vent pipe (poss unlikely though as you've done rad test described).
There is a tip on here somewhere about putting a cup of water over end of vent pipe when system is running and seeing if it draws up water out of cup

 

[JBPHS]

Combined feed and expansion usually corrects this.