Cooling Modes

exceed Econ Min at Max Fan Speed (Configuration→ECON→MP.MX) or IAQ Override Position (Configuration→AIR.Q→OVR.P) to provide economizer cooling.

IA.CF = 3 (Control Minimum Position)

When IA.CF = 3, an external 4 to 20 mA source is used to set the minimum position. The 4mA signal corresponds to 0% and the 20 mA signal corresponds to 100%. In this mode, configuration such

as Econ Min at Max Fan Speed (Configuration→ECON→MP.MX), Econo Min IAQ Position (Configuration→AIR.Q→AQ.MN) and the economizer minimum position and DCV minimum position curves in figure 3 are not used.

If the indoor fan is not operating, the economizer position will be zero. The damper position may exceed the economizer minimum position to provide economizer cooling.

IAQ (Switch Input)

Indoor air quality can also be measured using a switch input. For the purpose of specifying the type of switch input, low CO2 levels are considered normal. The IAQ switch input is defined by the IAQ Switch Input Config (Configuration→AIR.Q→II.CF). Enthalpy and IAQ are controlled by the same switch input and therefore cannot be used simultaneously.

II.CF = 0 (NO IAQ)

The II.CF = 0, configuration signifies that there is no IAQ switch input. The damper will operate at the Econ Min at Max Fan Speed (Configuration→ECON→MP.MX) and corresponding damper position curve based on indoor fan speed when the space is occupied and the indoor fan is on.

II.CF = 1 (DCV Normally Open)

II.CF = 2 (DCV Normally Closed)

The Demand Control Ventilation (DCV) allows the economizer minimum position to be decreased when there is no IAQ problem. If IAQ is low, the economizer minimum position is Econo Min IAQ Position (Configuration→AIR.Q→AQ.MN) when the indoor fan is operating at Supply Fan Maximum Speed (Configuration→UNIT→FS.MX). If IAQ is high, the economizer minimum position is Econ Min at Max Fan Speed (Configuration→ECON→MP.MX) when the indoor fan is

operating at Supply Fan Maximum Speed (Configuration→UNIT→FS.MX).

II.CF = 3 (Override Normally Open)

II.CF = 4 (Override Normally Closed)

The damper override function permits absolute positioning of the economizer damper for ventilation purposes. The override is active when IAQ is high and inactive when IAQ is low. The override position is configured by the IAQ Override Position (Configuration→AIR.Q→OVR.P).

Outdoor Air Quality (Analog Input)

The ComfortLink TM control is configured for outdoor air quality sensors which provide a 4 to 20 mA signal corresponding to 0 to 2000 ppm CO2. If a field supplied sensor has a different range, the ppm display range must be reconfigured by entering new values

for the OAQ Sensor Value at 4mA (Configuration→AIR.Q→O.4M) and OAQ Sensor Value at 20mA (Configuration→AIR.Q→O.20M).

OA.CF = 0 (NO OAQ)

This signifies that there is no outdoor air sensor installed. The default value of OAQ is 400 ppm CO2.

OA.CF = 1 (DCV)

The outdoor air quality sensor analog input is the value of OAQ.

OA.CF = 2 (OAQ Lockout)

The outdoor air quality analog input is only used to lock out the outdoor ventilation. The economizer commanded position is set to 0% when the CO2 ppm exceeds the OAQ lockout value

configured for the OAQ Lockout Limit (Configuration→AIR.Q→AQ.L). The default value for OAQ

Lockout Limit (Configuration→AIR.Q→OAQ.L) is 600 ppm CO2.

Fan Enable (Analog IAQ Sensor)

The DCV 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. The damper position may exceed Econ Min at Max Fan Speed (Configuration→ECON→MP.MX) and corresponding damper position curve to provide economizer cooling.

IA.FN = 0 (Never)

When IA.FN =0, the IAQ algorithm can never turn on the fan.

IA.FN = 1 (Occupied)

When IA.FN =1, the IAQ algorithm will turn on the indoor fan whenever the building is occupied and IAQ/OAQ differential is

greater than the Fan On AQ Differential (Configuration→AIR.Q→DF.ON). The indoor fan will turn off when the IAQ/OAQ differential is less than the Fan Off AQ Differential (Configuration→AIR.Q→DF.OF).

IA.FN = 2 (Always)

The indoor fan operation for IA.FN =2, is the same as the operation when IA.FN =1, except the algorithm is not limited to the occupied periods only. The fan can be triggered on when the space is occupied or unoccupied.

Fan Enable (Analog Switch Input)

The DCV 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 Switch Fan Config (Configuration→AIR.Q→II.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. The damper position may exceed Econ Min at Max Fan Speed (Configuration→ECON→MP.MX) and corresponding damper position curve to provide economizer cooling.

II.FN = 0 (Never)

When II.FN =0, the IAQ algorithm can never turn on the fan.

II.FN = 1 (Occupied)

When II.FN =1, the IAQ algorithm will turn on the indoor fan whenever the building is occupied and IAQ is high. The indoor fan will turn off when the IAQ returns to normal.

II.FN = 2 (Always)

The indoor fan operation for II.FN =2, is the same as the operation when IA.FN =1, except the algorithm is not limited to the occupied periods only. The fan can be triggered on when the space is occupied or unoccupied.

Cooling Mode Using Space Temperature Sensor T55, T56, T58 or T59

In cooling mode the PD control will maintain the Occupied Cool Set Point (Setpoint→OCSP) or the Unoccupied Cool Set Point (Setpoints→UCSP) by modulating the indoor fan speed to supply more or less airflow to the conditioned space at the Supply Air Temperature (Temperatures→AIR.T→SAT).

Cooling Supply Air Set Point

The Cool Supply Air Set Point (Setpoint→SASP)can be configured between 45F and 75F. The compressor modulates to

maintain a Supply Air Temperature (Temperatures→AIR.T→SAT)at the Cool Supply Air Set Point (Setpoint→SASP).

Cooling Speed Demand Window

When the temperature in the conditioned space is higher than the Occupied Cool Set Point (Setpoints→OCSP) plus the Fan Speed Control Demand (Configuration→COOL?FS.CD) configuration

48/50PD

48/50PD05 specifications

The Carrier 48/50PD05 is a remarkable addition to Carrier's lineup of rooftop units, offering advanced cooling and heating solutions for commercial applications. Designed for medium-sized buildings, this unit is well-suited for both new installations and as a replacement for older systems, thanks to its versatile features and efficient performance.

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