Carrier 48/50PG C03-14 manual Indoor Air Quality IAQ, Air Baffles, IAQ Analog Input, 48/50PM16−28

48/50PG and PM

C08057

Fig. 17 − Humidi−MiZer System Valve Locations

48/50PM16−28

Air Baffles

The units with Humidi-MiZertoption are equipped with Motormaster control to maintain adequate discharge pressure for proper unit operation during low ambient operation. This becomes especially critical in the Reheat2 mode of operation. Wind could have a detrimental effect depending on the orientation and the expected design latent load of the space. If the unit is oriented with the vertical condenser coil toward the prevailing wind, then the field-fabricated wind baffles are required. If the unit is not oriented as described above, but there is expected long operational periods in the Reheat2 mode, then the field-fabricated wind baffles are recommended. See Fig. 18 or 19 for dimensions of the field-fabricated wind baffles.

Indoor Air Quality (IAQ)

The ComfortLink 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 indoor-outdoor differential demand ventilation control, or with other sensor types for the outdoor air lockout function. The factory-installed indoor air quality CO2 sensor is mounted in the return section. A field-installed indoor air quality CO2 sensor may be mounted in the return or directly in the occupied space, per job requirements. The indoor air quality modes of operation can be affected by configurations for indoor air quality sensor (Configuration→AIR.Q→IA.CF), indoor air quality switch (Configuration→AIR.Q→II.CF), outdoor air quality sensor (Configuration→AIR.Q→OA.CF) and other related fan and limit configurations as described below.

IAQ (Analog Input)

The ComfortLink control is configured for indoor air quality sensors which provide 4 to 20 mA for 0 to 2000 ppm. If a sensor has a different range, the ppm display range must be reconfigured by entering new values for Configuration→AIR.Q→I.4M and 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 Configuration→AIR.Q→EC.MN position 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 IAQ and the Outdoor Air Quality (OAQ). The lower of these two positions is referred to as the Minimum IAQ Damper Position (Configuration→AIR.Q→AQ.MN) while the higher is referred to as Economizer Minimum Position (EC.MN). The AQ.MN should be set to an economizer position that brings in enough fresh air to remove contaminants and CO2 generated by sources other than people. The EC.MN should be set to an economizer position that brings in enough fresh air to remove contaminants and CO2 generated by all sources including people. The EC.MN value is the design value for maximum occupancy.

The ComfortLink control will begin to open the damper from the 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 EC.MN. When the IAQ/OAQ differential is between AQD.L and AQD.H, the control will modulate the damper between AQ.MN and EC.MN in a linear manner as shown in Fig. 20. The damper position will never exceed the bounds specified by AQ.MN and EC.MN during IAQ control.

IA.CF = 2 (Override IAQ)

When IA.CF = 2, the IAQ algorithm maintains the damper at Configuration →AIR.Q→EC.MN until the override condition triggers. The override triggers when the IAQ/OAQ differential is greater than Configuration→AIR.Q→AQD.H. The override position is Configuration→AIR.Q→OVR.P (Economizer Override Position). The economizer position will return to EC.MN when the IAQ/OAQ differential is less than 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 configuration 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 exceed Configuration→AIR.→EC.MN or Configuration→AIR.Q→OVR.P to provide economizer cooling.

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