radiators a lot of air ?

[nismohks]

Hi i have a central heating system. Ill try my best to explain what type it is so bear with me. It has a water tank at the top and a boiler below it with a pump next to it. The radiators have valves on both sides.

Recently the radiators were removed and flushed out to clean the sludge inside them, thought the pipes were not cleaned (dont know how to do that if it is possible). The radiators do get hot but after a few hours they fill up with air. After bleeding they fill up with lots of air again after a few hours. I dont know where the air is coming from ??
Also when is the best time to bleed the radiators with the system on or off? cold or hot ?

thanks very much

 

[oilman]

1. Put some corrosion inhibitor in, if not done already.
2. Turn off pump before bleeding.
3. Be patient, air is difficult to get out sometimes, and it lurks anywhere.

 

[Haggy]

Hi

I had a smiliar problem when we first moved. The radiators would be bled and then seem to fill back up with air very quickly. The problem was a sticking ball valve in the header tank, which instead of being full of water was empty. Wiggling the arm around a bit freed it back up and everything works fine.

Worth keeping a close eye on it if this is the problem just in case it sticks when filling and floods the place out.

 

[oilman]

If it's a ball cock problem, change it. They don't cost anything like the cost of a cleanup

 

[corgiman]

oilman is right change it!!

 

[ChrisR]

Back to the air problem - the air!! Could be the pump was turned right up when the flushing was done and it's now sucking air down the vent pipe. To test this you can (only sometimes get close enough to ) hold a glass of water up under the vent pipe to see if it draws the water in.

Try the pump on speed 1 out of the usual max 3. 1 will usually do for a small flat, 2 for a semi. Bit rough though, that!

 

[corgiman]

Back to the air problem - the air!! Could be the pump was turned right up when the flushing was done and it's now sucking air down the vent pipe. To test this you can (only sometimes get close enough to ) hold a glass of water up under the vent pipe to see if it draws the water in.

Try the pump on speed 1 out of the usual max 3. 1 will usually do for a small flat, 2 for a semi. Bit rough though, that!

dont think this is worth doing chris as it appears the ball valve stuck and the system has just run dry no more than that