air in system after draining down

[patagonia]

On Friday we paid an awful lot of money to have our system drained, a motorised valve and a gate valve replaced, the boiler and kickspace power flushed and new hoses on the latter and the boiler serviced. I noticed that the plumber's assistant was bleeding the rads while the pump was running which I always understood one should not do but perhaps it's different when you are filling up. However, we now have a lot of sloshing and sqelching noises, despite my having bled the whole system twice when the system was cold - a lot of air came out of some rads. The boiler is not kettling now but at times it sounds more like a washing machine than a boiler and I note that when a zone cuts out there is a massive squelching noise round the main flow and return pipes; also at that point, i.e. when all zones are satisfied, there is a clicking noise in the boiler and the pump light goes on and off, which has never happened before. Strangely, if I turn the boiler stat down (even though the boiler is not running) the pump then runs continuously, as it should on pump over-run till all the heat has dissipated. When the boiler has been running for a while and has got to the set temperature, it goes off but immediately goes on and off several times till it gets away again. Has anybody any suggestions as to what might be wrong? How long should it take to eliminate air from the system after a drain down? We are moving house on May l5 and wanted to leave everything in order for the next people. So this query is URGENT.

 

[ChrisR]

A bit hard to guess without being there, knowing what the boiler and system is etc, but give it a couple of days to settle. Keep bleeding rads and any other bleed point like in an airing cupd.
If no better call them back. There's often something needing a quick call back after a flush.

 

[patagonia]

Thanks, Chris. It's a Kingfisher MF, fully pumped system, with expansion tank in loft (boiler in cellar) and combined feed and vent, but no vent over top of tank. Will carry on bleeding but could air be responsible for the clicking etc. or cd this be a wiring problem or, heaven forfend, a faulty pcb? What does a pcb cost these days?

Patagonia

 

[patagonia]

I've started bleeding again and found in two of the rads there seems to be a mixture of air and water, i.e. water comes out but with a hissing noise. Does one carry on till the noise stops, ending up with a very wet towel, or leave it?

 

[patagonia]

Well, I've been round the whole house and most of the rads had no air in at all. The towel rail had a small amount of air and 4 of the rads had the mix of air and water. I decided I'd carry on bleeding till only water came out. The bleed valve in the airing cupboard had no air in it at all and neither had the one near the boiler in the cellar. I believe our Grundfos Alpha is self-venting. So I can't understand why we should have all this sqelching in the pipes. Needless to say, I'm not running the CH in this mild weather and we won't need any more hot water till this evening so the boiler will be off till then. I presume there is no point in bleeding if the boiler hasn't been on since the last bleed?