Help -DHW but no CH Help and information on all topics relating to your central heating, air conditioning and ventilation issues.

[Miketm]

Can anyone give advice on Heatline S24 Compact. Boiler did not fire checked the gas valve - its OK. Changed the PCB it now fires up but it fires up ok only when DHW is called but cannot get it to fire when CH demand. Checked out by manually overridding divertor and leaving on the hot water tap running - this allowed water to be pumped around the radiators so pump works. Unsure where problem lies , think it is something about triggering the CH - is ther a way to check how this is triggered?- any suggestions much appreciated. Mike

[htg engineer]

Room thermostat ? is the CH demand light on ?

htg

[Miketm]

Thanks htg engineer - I have now solved the puzzle - there was a brown wire connector missing on the new pcb - i took the one off old pcb and now the system works on CH. I admit I am not a heating engineer , but am a qualified mech engineer - so combi 's are an unknown to me.

Incidentally I would still like to know what actually triggers a signal to the pum/gas valve to operate when CH is demanded. I noticed there is a flow sensor that does this on the DWH supply. Does the thermostat signal the pump to start - guessing there may be a flow sensor in the CH circuit pipe?