Method for providing variable output gas-fired furnace with a constant temperature rise and efficiency

A method for providing a variable output gas-fired furnace means with a constant temperature rise and efficiency where the furnace means includes burners, a blower, a thermostat and a delay timer, the method comprising the steps of:

• sensing the temperature in an area to be conditioned;
• comparing the sensed temperature to a predetermined set point;
• if the sensed temperature deviates from the predetermined set point by more than a predetermined amount, gas is supplied to the burners and the blower is started;
• determining the reference revolution per minute of the blower;
• determining the reference cubic feet per minute delivered by the blower;
• determining the manifold pressure;
• determining whether the furnace is in a high heat or a low heat mode of operation;
• determining the desired cubic feet per minute delivered by the blower for the current mode of operation;
• reading the actual revolution per minute of the blower;
• adjusting the speed of the blower motor if the actual and desired revolution per minute of the blower are not the same;
• determining whether the thermostat is satisfied;
• if the thermostat is not satisfied, returning to the step of determining the manifold pressure;
• and
• if the thermostat is satisfied, shutting off the gas and starting the delay timer.