Are you sure the boiler is not modulating down (perhaps the DHW flowrate is slow)?
Often you need to run cooler water from the rads through the boiler with the gas off to cool down the main heat exchanger and then open the hot tap to cool the plate exchanger. Then when you check maximum burner pressure you have sufficient time before it modulates down
Have you followed section 10.5 to set the minimum and maximum pressures on the gas valve itself before adjusting the board pots?
Remember to disconnect the sense and setup the ignition pressure.
Otherwise perhaps the sensors are iffy or the plate is blocked - how hot do the flow/returns to the plate get.
Otherwise the board could be suspect - I had a similar fault wherby no amount of adjustment would get the pressure above 8 mbar (that however affected the heating as well).
Be aware that with a brand new board you may struggle to get the full 15 mbar bp. I suspect Honeywell have modified the boards as the bp's can drift upwards.
Have a word with Phoenix about the sulphide - perhaps they will install a filter - in the old town gas days filters were often fitted before the gov.
Often you need to run cooler water from the rads through the boiler with the gas off to cool down the main heat exchanger and then open the hot tap to cool the plate exchanger. Then when you check maximum burner pressure you have sufficient time before it modulates down
Have you followed section 10.5 to set the minimum and maximum pressures on the gas valve itself before adjusting the board pots?
Remember to disconnect the sense and setup the ignition pressure.
Otherwise perhaps the sensors are iffy or the plate is blocked - how hot do the flow/returns to the plate get.
Otherwise the board could be suspect - I had a similar fault wherby no amount of adjustment would get the pressure above 8 mbar (that however affected the heating as well).
Be aware that with a brand new board you may struggle to get the full 15 mbar bp. I suspect Honeywell have modified the boards as the bp's can drift upwards.
Have a word with Phoenix about the sulphide - perhaps they will install a filter - in the old town gas days filters were often fitted before the gov.
it doesn't get easier, with new boiler models being launched as fast as they currently are experience is becoming difficult to aquire. A particular boiler model used to be sold for 10 years before the next model is launched now its perhaps every year.
