48/50PD
a.(Configuration→ECON→UEFC = 0) - Disabled When UEFC = 0, unoccupied free cooling is disabled. Cooling will only occur if the space exceeds the unoccupied setpoints.
b.(Configuration→ECON→UEFC = 1) - Unoccupied When UEFC is set to 1, unoccupied free cooling can occur throughout the entire unoccupied period. The space temperature must be higher then the
c.(Configuration→ECON→UEFC = 2) - Preoccupancy When UEFC is set to 2, unoccupied free cooling can only occur when the time until the next occupied period is less than the Free Cool PreOcc Time (FC.TM) in minutes.
2.Free Cool PreOcc Time (Configuration→ECON→FC.TM)
FC.TM is the configuration that determines how many minutes before occupancy that free cooling can occur when set for Preoccupancy (UEFC = 2).
3.1.Free Cool Low Temp Limit (Configuration→ECON→FC.LO)
Unoccupied free cooling cannot occur if the Outdoor Air Temperature (Temperature→ AIR.T→ OAT) is less than FC.LO.
Power Exhaust
To enable power exhaust set Power Exhaust Installed (Configuration→ECON→PE.EN) to YES. On the
damper position and Commanded Fan Speed (Outputs→FANS→F.SPD) to turn on the power exhaust when the calculated outside air CFM reaches Power Exhaust Stage1 CFM (Configuration→ECON→PE1.C). The power exhaust will turn off when the calculated outside air CFM falls below Power Exhaust Stage1 CFM (Configuration→ECON→PE1.C). The Power Exhaust Stage2 CFM (Configuration→ECON→PE2.C) is not currently used on the
Indoor Air Quality (IAQ)
The ComfortLink TM control has the capability for several methods of demand ventilation control. Indoor air quality is typically measured using a CO2 sensor whose measurements are displayed in parts per million (ppm). Outdoor air quality may be measured with a CO2 sensor for
IAQ (Analog Input)
The ComfortLink TM control is configured for indoor air quality sensors which provide 4 to 20 mA signal for 0 to 2000 ppm CO2. If the sensor being used has a different range, the ppm display range must be reconfigured by entering new values for the IAQ Sensor Value at 4mA (Configuration→AIR.Q→I.4M) and IAQ Sensor Value at 20mA (Configuration→AIR.Q→I.20M).
IA.CF = 0 (No IAQ)
IA.CF = 0 signifies that there is no IAQ sensor installed. The damper will operate at the Econ Min at Max Fan Speed
(Configuration→ECON→MP.MX) when the fan is at Supply Fan Maximum Speed (Configuration→UNIT→FS.MX) and the damper position will vary at other fan speeds as described in the Cooling Mode with Economizer section below when the space is occupied and the indoor fan is on.
IA.CF = 1 (DCV)
When IA.CF = 1 the IAQ algorithm is set for Demand Control Ventilation (DCV). During DCV, the damper modulates between two user configurations depending upon the relationship between the Indoor Air Quality (IAQ) and the Outdoor Air Quality (OAQ). The lower of these two positions is referred to as the Econo Min IAQ Position (Configuration→AIR.Q→AQ.MN) while the higher is referred to as the Econ Min at Max Fan Speed (Configuration→ECON→MP.MX). The Econo Min IAQ Position (Configuration→AIR.Q→AQ.MN) should be set to an economizer position that brings in enough fresh air to remove contaminates and CO2 generated by sources other than people.
The Econ Min at Max Fan Speed (Configuration→ECON→MP.MX) should be set to an economizer position that brings in fresh air to remove contaminates and CO2 generated by all sources including people when the indoor fan is operating at the Supply Fan Maximum Speed (Configuration→UNIT→FS.MX). The Econ Min at Max Fan Speed (Configuration→ECON→MP.MX) value is the design value for maximum occupancy.
The ComfortLink TM control will begin to open the damper from the Econo Min IAQ Position (Configuration→AIR.Q→AQ.MN) position when the IAQ level begins to exceed the Outdoor Air Quality (OAQ) level by a configurable amount. This amount is
referred to as AQ Differential Low
(Configuration→AIR.Q→AQD.L). When the differential between IAQ and OAQ reaches AQ Differential High (Configuration→AIR.Q→AQD.H), the economizer position will be at the Econ Min at Max Fan Speed (Configuration→ECON→MP.MX) when the indoor fan speed is
at Supply Fan Maximum Speed
(Configuration→UNIT→FS.MX). When the IAQ/OAQ
differential is between AQ Differential Low (Configuration→AIR.Q→AQD.L) and AQ Differential High (Configuration→AIR.Q→AQD.H), the control will modulate the damper between Econ Min at Max Fan Speed (Configuration→ECON→MP.MX) and Econo Min IAQ Position (Configuration→AIR.Q→AQ.MN) in a linear manner as shown in Figure 3. At other fan speeds the economizer damper will operate in the shaded area between the two economizer position curves but at the actual fan speed as indicated by Commanded Fan Speed (Outputs→FANS→F.SPD).
IA.CF = 2 (Override IAQ)
When IA.CF = 2, the IAQ algorithm maintains the damper at Econ Min at Max Fan Speed (Configuration→ECON→MP.MX) when the indoor fan speed is at Supply Fan Maximum Speed (Configuration→UNIT→FS.MX) or in the shaded area of Figure 3 when the indoor fan speed is at the Commanded Fan Speed (Outputs→FANS→F.SPD) until the override condition triggers. The override triggers when the IAQ/OAQ differential is greater than AQ Differential High (Configuration→AIR.Q→AQD.H). The IAQ Override Position (Configuration→AIR.Q→OVR.P). The economizer damper will return to the Econ Min at Max Fan Speed (Configuration→ECON→MP.MX) or MP.MX curve at other fan speeds when the IAQ/OAQ differential is less than the AQ Differential Low (Configuration→AIR.Q→AQD.L).
The override algorithm will operate whenever the building is occupied and the indoor fan is operating or whenever the IAQ algorithm has caused the indoor fan to operate. The IAQ Analog Fan Config (Configuration→AIR.Q→IA.FN) determines whether or not the IAQ algorithm can turn on the indoor fan.
If the indoor fan is not operating, the economizer position will be zero. If the override is not active and the building is unoccupied, the economizer position will be zero. The damper position may
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