That would make 4 round dials
All clearly marked from left to right as
Preheat
Hot water
Heating
On/off switch
The 5th large dial you are referring to is probably a wireless receiver unit linked to your wireless room thermostat
If its flashing red it probably needs rebinding
The procedure to rebind it will be with the boiler book
Or you can ring up the manufacturer helpline to guide you
Q, August 2015
