In message , Neil
writes
Swiftflow 100 died today. Main burner not firing on either DHW or CH. Pilot
+ fan + pump running fine. I havent got the installers instructions that
would allow me to work through the flowchart that Hepworth thoughtfully
include. Before shelling out 115 for a new Gas Valve are there any overheat
or flow sensors that would prevent the gas valve operating on both HW & CH ?

Is there 24V at the gas valve?

I.e. the question is whether the pcb is delivering the volts to the gas
valve or not. It is a common pcb fault, although it could be caused by a
sensor failure. You'll find an indication on the pcb as to which
connectors they are on.

If it's the pcb, phone me on 01923 229224, you can't look at my website
atm as the server is down
--
geoff