Problems venting air

[mgbgt2]

A friend has just moved house and has a conventional gas boiler (on the ground floor) and indirect HWC (22mm feed & return) with 4 radiators fed with microbore pipes. (probably about 10 years old)

The HWC and radiators are only just getting warm and I can hear lots of air rushing through the pump every 90 seconds or so but there is no air released from the radiator vents (just water) and none from a manual vent situated on a short "T" near the pump.

The radiators are evenly warm from top to bottom so I don't think there's any air trapped in them and the room and boiler stats are set to high. There's plenty of water in the header tank. The boiler cycles every 3-4 minutes so I think the problem may be due to air in the system somewhere. (I can't see any other vents)

I've tried the pump on various settings, fully opened the rad valves, and leaving the system off for 24 hours to let the air settle then venting but I can't get any more air out.

Any ideas on how I can purge the air from this system? Is there normally a vent on the boiler iteslf as that's the only place I have not looked as I can't see how to remove the case. Or is there something else that I could try?

 

[justlead1]

Hi There are so many permutations of systems / boilers it difficult to be precise. There may be air valves on boiler and cylinder cupboard area of pipework. But often leaving the system running (turning the pump on and off at say one minuet intervals)will push the air somewhere that it can be bleed from. However its nice to know how it got in there in the first place. Many systems gather air in one particular area/rad and are vented on a regular basis, it dont make them right but its a fact. Good Luck