Sequence of Operation
Fan Coil CARRIER CORPORATION ©2020
Integration Guide All rights reserved
24
Indoor air quality
The Fan Coil controls either 2-position or Demand Controlled Ventilation (DCV) to provide the necessary
ventilation to the occupied space. To meet any ventilation requirement, the fan must always be configured for the
Continuous or Always On mode of operation. If the fan is configured for Automatic operation, the fan is started
during occupied periods, if required, but ASHRAE base ventilation requirements will NOT be met using Automatic
fan operation.
Demand Control Ventilation (DCV)
If the optional indoor air quality sensor (CO
2
) is installed, the Fan Coil maintains indoor air quality, via a
modulating OA damper providing demand-controlled ventilation. The control operates the modulating OA damper
during occupied periods. The control monitors the CO
2
level and compares it to the configured setpoints and
adjusts the ventilation rate as required.
The control provides proportional ventilation to meet the requirements of ASHRAE specifications by providing a
base ventilation rate and then increasing the rate as the CO
2
level increases. The control begins to proportionally
increase ventilation when the CO
2
level rises above the start ventilation setpoint and reaches the full ventilation
rate when the CO
2
level is at or above the maximum setpoint.
A user-configurable minimum damper position insures that proper base ventilation is delivered when occupants
are not present. If the additional outdoor air being introduced for ventilation causes an unacceptable drop in the
supply air temperature, or could cause a coil freeze-up condition, then the control can be set to temper the supply
air during DCV control. Reheat Enable must be set to Enable and 2-Pipe Changeover must be set to No. Heating
must be available. The control uses heating to prevent the supply air from falling below the user-configured
Temper/Reheat SAT setpoint. Access the IAQ configurations on the Properties page > Equipment tab >
Configuration.
The following conditions must be true for this algorithm to run:
• Damper Control is configured for DCV
• The unit is in an occupied mode
• The fan is on
• If enabled, the fan status must be On
• IAQ sensor reading is greater than the DCV Start Control Setpoint
The control has 4 adjustable setpoints:
• DCV Start Control setpoint
• DCV Maximum Control setpoint
• Minimum damper position
• DCV Maximum damper position
2-Position OA Ventilation Damper Type - The control can be configured to operate an OA ventilation damper in a
2-position mode to provide ventilation during occupied periods. The damper opens 100% during any occupied or
override period to insure proper ventilation is delivered to the occupied space. If the fan is off or the space is
unoccupied, the damper closes.
The following conditions must be true in order for this algorithm to run:
• Damper Control is configured for 2-position
• The unit is in an occupied mode
• Fan is on
• If enabled, the fan status must be on
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