This sequence assumes the thermostat’s is configured for two (2) fan speeds.
Two speed fan sequencing during a heating cycle:
The room temperature is 1.1°F or more below the heat set point (High Demand):
At the start of the heating cycle the thermostat will enable the high speed fan. This will remain until the room’s temperature is within 1°F of the heat set point. At which point the thermostat will disable the high speed fan and, five seconds later, enable the low speed fan. The room will continue to heat with just the low speed fan until reaching the heat set point. If the room’s temperature drops back to below 1.0°F from the heat set point, the thermostat will disable the low speed fan and, five seconds later, re-enable the high speed fan and keep it enabled until the room reaches the heat set point.
The room temperature is 1.0°F or less below the heat set point (Low Demand):
At the start of a heating cycle the thermostat will enable the low speed fan and give it the opportunity to provide all the necessary heating to condition the room. This will remain until the room is at the heat set point, unless the room’s temperature drops below 1.0°F from the heat set point. At which point, the thermostat will disable the low speed fan and, five seconds later, enable the high speed fan and used it until the room reaches the heat set point.
Two speed fan sequencing during a cooling cycle:
The room temperature is 1.1°F or more above the cool set point (High Demand):
At the start of the cooling cycle the thermostat will enable the high speed fan. This will remain until the room’s temperature is within 1°F of the cool set point. At which point the thermostat will disable the high speed fan and, five seconds later, enable the low speed fan. The room will continue to cool with just the low speed fan until reaching the cool set point. If the room’s temperature rises back to above 1.0°F from the cool set point, the thermostat will disable the low speed fan and, five seconds later, re-enable the high speed fan and keep it enabled until the room reaches the cool set point.
The room temperature is 1.0°F or less above the cool set point (Low Demand):
At the start of a cooling cycle the thermostat will enable the low speed fan and give it the opportunity to provide all the necessary cooling to condition the room. This will remain until the room is at the cool set point, unless the room’s temperature raises above 1.0°F from the cool set point. At which point, the thermostat will disable the low speed fan and, five seconds later, enable the high speed fan and used it until the room reaches the cool set point.
Why this staging sequence?
This staging sequence accomplishes three agenda’s:
- It quickly brings the room to the desired temperature and then relaxes the fan speed to provide a more comfortable supply CFM when the room is being maintained.
- It utilizes the low speed fan more often, which is quieter for tenants.
- It allows for the greatest efficiency to comfort ratio. Note: this is only true if both fan stages are mechanically operating correctly.