Hi Robert, if your puma is the permanent pilot version the fan has to run all the time to provide ventilation for the pilot but on a slow speed. You dont usually notice it unless the fan is on its way out and making more noise than usual. If it is an electronic ignition model (80e)the microswitch on the hot water flow sensor could be stuck on. This would also cause the boiler to fire up intermittantly.
Ian.
February 2007