For Space Heating Applications, a room thermostat is used to control outlet temperature. On a call for heat, the unit will provide air heated to the maximum allowed temperature until the room thermostat is satisfied. Once satisfied, the unit will either turn off or will continue to operate at a reduced outlet temperature. An override option may also be supplied. In this case a room thermostat is supplied in addition to the basic system. The unit is set to full-fire when room temperature falls too low. Direct Spark units are supplied with an ignition transformer for the igniter. Piloted Units are supplied with a solenoid-operated Automatic Pilot Valve and a small pressure regulator – around 20,000 BTU – as well as an ignition transformer for the pilot spark igniter.
The fan efficiency is defined as the ratio of air power (output) to shaft power requirement (input). An optimally designed fan impeller with improved aerodynamics requires less shaft input power for desired delivery of air volume with total pressure rise as per the system requirement. With reduced shaft power requirement, there is a commensurate reduction in energy consumption.