Air in radiators and boiler stat

Hi all,

I have a couple of problems with my CH. The first is that I'm constantly needing to bleed off air from the top radiator in the house - at least once a day. The trouble is, I can't find where the air is getting in - there's no obvious sign of water getting out when the pump is off. I've already got the pump on its lowest speed (I'd wondered if it was that pulling air through the overflow; if I run the pump on a higher speed, more air seems to come in). Anyone got any useful tricks to track down where it's coming from?

The second problem is that some of the rads (especially the downstairs ones) aren't all that hot. It seems to me that the thermostat in the boiler (an Ideal WRS 450) is turning the boiler off even when it's perishing cold out and the rads themselves aren't all that warm. I've never known a stat to 'sort-of' fail, though - I'd expect it to either run all the time or not at all. Is it likely to be a faulty stat...?

Thanks for any advice!

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OK, here goes :



1.) It's an Ideal WRS 450 gas boiler
2.) Two things are happening - one is that air is being drawn into the system, the other is that the boiler appears to stop running even though the radiators aren't all that hot (hot at the tops of the rads, cool at the bottoms).

3, 4) The air bleeding problem is long standing, and dates back several years before I had to deal with the heating. I guess I was just after any suggestions as to where air frequently gets into heating systems - just to give me an idea as to where to start looking.

The boiler cutting out problem is probably more recent - I can only remember noticing it this winter. I think the problem may be due to the thermostat in the boiler 'thinking' the water is already hot enough - again, I was just after suggestions as to whether it's feasible that the thermostat in the boiler could fail in this manner, or whether it's likely to be something else.

5.) Doesn't really happen at a definite time. The heating works, it just doesn't work as well as I think it ought to!

6.) Anything else of relevance? Hmm. The valves for the CH and HW seem to be opening and closing OK, though I'll perhaps take the motor units off and confirm that they open and close fully. Pump also appears to be running OK. At times when boiler isn't on and I think it should be, the room stat is calling for heat, and the programmer is in the on position. Rotating the boiler stat does not produce a 'click'. When the boiler IS running, rotating the stat DOES produce a 'click', as expected, and the boiler goes out.

I don't really expect someone to tell me exactly what's wrong! I was just after any 'pointers' as to what might be worth looking at (I don't really want to go and buy a new boiler stat if it's unlikely to be the problem!).

Cheers!

IS IT AIR ? if you can vent gas from the rads it does not have to be air .if you have sludge deposits in the system tis will give of a flammable gas (helium or hydrogen, can never remember ) yous your own common sense to test it..also have you observed your vent pipe to the tank when the pump starts up and shuts down to see if it pumps over or draws in.

sorry COG, helium is NOT flamable

That's a thought; I'd just assumed it was air, but there probably is a fair bit of sludge in the system. I'll test the gas to see what it is (takes me back to testing for hydrogen at school!).

Thanks also for the tip about the header - I'll try immersing the end of it in a tub of water and see if it sucks that through or chucks more out...

Cheers!