Glow Worm Flexicom HX cuts out or runs on part load

[slimwallet]

I am perplexed by a problem with the boiler. Thermostat cuts in, boiler lights and water outlet temp rises quite rapidly to near the set point. After a period, sometimes a few minutes, sometimes 10+ minutes boiler will quieten right down and outlet temperature will start to decline and plateau at about 58 degC but will still be considerably higher than inlet temp. After 10 or maybe 20 minutes boiler will again pick up and heat rapidly again for a few minutes. This goes on continually but means house is not heating to thermostat set level. We are cold!

Using Glow Worm diagnostic codes there is always a heat request(d8) but boiler does not deliver. When heating rapidly (correctly) the state is S04 (burner on) but when in the not heating correctly mode it shows S03 (Ignition) although it clearly is alight as it is still heating to a limited extent.

I have been through all the diagnostic codes and nothing looks untoward, pump is on and working, ignition times are fine and no unsuccesful ignition attempts and no safety lockouts.

The only possible area of doubt is the ionisation current which flicks from 8-9 when in the low heat mode and sometimes is 7-8 when heating correctly.

Does anyone have any thoughts?


Thanks

 

[mickyg]

circulation. CHeck D40 and D41 if its greater than 23C at any point there lies your problem, not boiler

 

[slimwallet]

Sorry but I don't quite understand. D40 is flow temperature. My setpoint D5 is set to 82degC, the max cos were cold and very occasionally when boiler doesn't go into limp mode it will reach this but more usually when it does cut in properly it will reach 74degC and then revert to limp.

D41 is the return temp which is always lower, when house has warmed a bit it gets up to 50degC and sometimes higher if boiler doesn't go into limp mode.

Is any of that a problem as I'm sure that is how it used to be. Boiler is about 4 yrs old and not been a problem before last two weeeks

Thanks

 

[mickyg]

D40 and D41 are read only and show the current temp. You need to check them at the same time at various points in the heating cycle. As i said anyway, you have a circulation problem. pump, cold feed blockage etc......
Oh btw is it really necessary to run the boiler at 82C?? its very inefficient

 

[Aquilani]

I would agree that the problem is with Circulation. A difference between flow and return greater than 23 degrees will cause the boiler to modulate down to low flame.

 

[slimwallet]

Many Thanks,

I will investigate flow. The 82DegC setting is to try and get the house warm!!! If the house warmed up better then I wouldn't have it set so high.