Could not get any hot water as boiler would not fire up.
No flame nothing.
However if i turn hot water tap on first and then switch boiler on as long as it is set to hot water or hot water/radiator it works when i switch on mains
However if dial is set to off and i switch boiler on and then switch it to either hot water or hot water and raditors it doesn't work.
three main things to watch out for first flow switch on hot water has continuity when switching.
next check three way diverter valve.
thirdremove secondry DHW exchanger check for blockage.
