air trapped in combi boiler

I had to drain the water from my central heating system and since refilling, I cannot get the combi boiler to work. I think the noise I can hear is air preventing the pump from circulating the water. Consequently, the boiler does not light.
The combi boiler is installed higher than the radiators on the first floor. I've tried venting the pump but only a tiny amount of air is expelled and not enough to fix the problem. All radiators have been blead as well.
It's pretty cold in here right now so would appreciate any help/suggestions people can offer.
Thanks Stuart http://www.radox.freeserve.co.uk/home.htm
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Stuart Dalby wrote:

The newer combis I've come across had automatic air bleed valves but they delivered shut. Chck the install/user manual for yours. Even if it has one it may be shut or blocked by crud. Alt. there may be a manual bleed valve or access cap on the end of the pump.
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The combi boliers I have come across tend to have an air vent in them at the highest point to release air. Does this exists and is it working?
On Tue, 7 Oct 2003 11:08:26 +0100, "Stuart Dalby"

Lawrence
usenet at lklyne dt co dt uk
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them
Thanks for the info. I have found the automatic air vent but it did look to be blocked. I've now bled the air from there (not much came out). I'm now starting to wonder if it's not the pump spinning in air but something else that has gone. It's an old boiler. I'm considering replacing it.
Thanks again, Stuart http://www.radox.freeserve.co.uk/home.htm
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I drained and refilled just last week to try and improve circulation around the downstairs radiators. The water looked remarkably clean despite dire warnings here about black sludge. Have to redrain etc today to replace the cleaning chemical with inhibitor. Water circulation has improved noticeably. Hmm, should really start now rather than catching up on News....
Anyway, the commisioning instructions for my boiler (a Vokera Flowmatic combi) require venting the dhw heat exchanger during filling. This is different from the automatic air vent (which should be left open), more like a radiator bleed valve. The boiler made a lot of gurgling noises but didn't work at all until after I had bled this.
So could there be another bit you need to bleed?
David
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Flowmatic
is
more
noises
Got a professional coming tonight to take a look. I've had enough bleeding the damm thing ;-)
Stuart http://www.radox.freeserve.co.uk/home.htm
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Sounds like an airlock. Is it a pressurized system or open? If open, try forcing mains pressure water back up the drain point, but be careful not to overfill the header tank.
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try
not
It's a closed system. I've tried draining the system and then refilling, hopefully so as I drain the radiators, the air in the pump would be dislodged but no success. I think I've had it - new boiler required.
Stuart http://www.radox.freeserve.co.uk/home.htm
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If there is air in the system, I'm not sure how a new boiler will help?
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Thanks to all who tried to help me with my combi problem.
Turns out the problem was air in the system had caused one of the thermostatic switches in the boiler to trip - thereby preventing it firing up until it was manually reset (by pressing a switch on the back of the sensor). That was it!
It would appear I did get all of the air out of the system so the pump was switching on but the lack of action from the burner made me think nothing was happening.
Oh well - you live and learn. So glad I didn't give up on the boiler and buy a new one.
Thanks again, Stuart http://www.radox.freeserve.co.uk/home.htm
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