Help - Glow worm ultracom 18hxi short cycling/kettling/air trapped?

[kally195]

Evening,

Our system: glow worm ultracom 18hxi boiler, unvented under pressure hot water tank (possibly aquasystem?), a mix of microbore copper pipes and modern copper pipes. 10 radiators.

We have had issues for the past year, British Gas have said it is because there is restricted flow. Husband got the system working by down rating to 9kW so that it fires up, drops to one flame, runs at one flame for about 13 minutes then fires at 3 flames up to 70°C, where is sits happily.

Hot water does similar, fires up slowly and runs at 70° until the return gets to a certain temp, then it short cycles for the rest of the hot water programme time.

Today we had the heating drained down for a new radiator install (involving moving pipes). On first fire up, the boiler was unhappy and started banging loudly, going past 70° then shutting off. It now fires up and shuts off, then comes back on at one flame. It sits at one flame, currently at 54° and not getting any hotter.

If I turn the heating off and put it to hot water, it just short cycles continuously, firing up and switching off and continue to shoot up to 85° before falling back down.

If I put the heating and hot water on together, it fires up and runs at 3 flames happily, but only at about 64°.

I've been doing lots of looking and I am not sure if it is air in the system, sludge, a knackered heat exchange or what!

Any advice?

 

[ianmcd]

you have an airlock, your system will have motorised valves (Zone valves) these should have been latched open to maual during draining and re-filling, that is what that lever is there for

 

[kally195]

Thank you! Next daft question - how do I shift it?

 

[ianmcd]

post some pics of your valves and boiler and pump and HW cyl so we can see exactly what setup you have

 

[kally195]

Will do later on, thanks again

 

[kally195]

post some pics of your valves and boiler and pump and HW cyl so we can see exactly what setup you have

Here you are. My plumber (who by his own admission is not a heating engineer and did not realise that we had motorised valves that needed opening - this all started last year when he first drained the system...) went up into the loft just now and bled the left hand pipe on the third photo - loads of air came out.

Suspect more air in system still though, so any advice would be greatly appreciated.

 

[kally195]

Letting the air out hasn't made the heating any happier - it fired up at 5 flames, got to 70° quickly then shut off. It then came back on at 3 flames, ran there for a couple of minutes getting to around 64° then dropped down to one flame where it is now sitting. It occasionally tries to run at 3 flames but then drops back down to one flame and the temp on the boiler display drops quite significantly.

 

[kally195]

The boiler is giving fairly consistent s53 codes, so there's a blockage somewhere restricting flow.