Method and apparatus for controlling fans in heating, ventilating, and air-conditioning systems

A method of calibrating an environmental maintenance module that controls a temperature of a zone of a building, the method comprising:

• (a) receiving, over a time period, a plurality of temperatures of the zone, each zone temperature being at a different time within the time period;
• (b) calculating a location parameter for the zone temperatures;
• (c) computing a scale parameter that quantifies a variation of the zone temperatures relative to the location parameter;
• (d) determining a first temperature setpoint for the zone, wherein the environmental maintenance module uses the first temperature setpoint in controlling the temperature of the zone.

An HVAC system, comprising:

• an environmental maintenance module including at least one variable-speed fan operatively coupled to a plurality of zones of a building;
• a controller operatively coupled to the environmental maintenance module for controlling the variable-speed fan, the controller including at least one processor configured to:
• (a) for each zone:
• receive a zone temperature corresponding to that zone;
• and
• compute a first zone temperature error by calculating a difference between that zone temperature and a first setpoint of that zone;
• (b) identify a first critical zone by analyzing the first zone temperature errors;
• and
• (c) use the first zone temperature error of the critical zone to determine a final speed setting of the variable-speed fan.

An HVAC system, comprising:

• an environmental maintenance module configured to control a temperature of a zone of a building;
• a controller operatively coupled to the environmental maintenance module for calibrating the environmental maintenance module, the controller including at least one processor configured to:
• (a) receive, over a time period, a plurality of temperatures of the zone, each zone temperature being at a different time within the time period;
• (b) calculate a location parameter for the zone temperatures;
• (c) compute a scale parameter that quantifies a variation of the zone temperatures relative to the location parameter;
• (d) determine a first temperature setpoint for the zone, wherein the environmental maintenance module uses the first temperature setpoint in controlling the temperature of the zone.

An HVAC system, comprising:

• an environmental maintenance module configured to control a temperature of a zone of a building;
• a controller operatively coupled to the environmental maintenance module for calibrating the environmental maintenance module, the controller including at least one processor configured to:
• periodically access a database which includes prior values for a fan speed and zone temperature information over a plurality of time intervals in a period of time;
• determine whether the fan speed was at or above a predetermined level over any time interval in the time period;
• set current low and high temperature setpoints according to the determination whether the fan speed was at or above a predetermined level over an interval of time, wherein the environmental maintenance module uses the low and high temperature setpoints in controlling the temperature of the zone.