Heating Modes

48/50PD

Quality (IAQ) section of the Economizer Operation section above for more details on Demand Control Ventilation (DCV).

Economizer Operation for Units Equipped with Return Air CO2 Sensor Only

When the CO2 sensor detects a CO2 level or IAQ Level (Inputs→AIR.Q→IAQ) below the AQ Differential Low (Configuration→AIR.Q→AQD.L) value the MP.25, MP.50, MP.75 and MP.MX points will be recalculated to new values for MP.25, MP.50, MP.75 based on the Econ Min IAQ Position (Configuration→AIR.Q→AQ.MN). The economizer outside air damper will close and reduce the amount of outside air CFM to the conditioned space based on the lower IAQ sensor readings and indoor fan speed. The economizer outside air damper will continue to close and reduce the amount of outside air CFM to the conditioned space until the damper reaches user configurable Econ Min IAQ Position (Configuration→AIR.Q→AQ.MN). This will

happen when the Commanded Fan Speed (Outputs→FANS→F.SPD) is at the Supply Fan Maximum Speed (Configuration→UNIT→FS.MX). When the Commanded Fan Speed (Outputs→FANS→F.SPD) is between Supply Fan Maximum Speed (Configuration→UNIT→FS.MX) and the Supply Fan Minimum Speed (Configuration→UNIT→FS.MN) the damper will operate in the shaded area of Figure 8 based on the IAQ Level (Inputs→AIR.Q→IAQ).

Economizer Operation for Units Equipped with Return Air CO2 Sensor and outside air CO2 Sensor

The Economizer will operate similar to Economizer Operation for Units Equipped with Return Air CO2 Sensor Only but the IAQ Level (Inputs→AIR.Q→IAQ) will be determined by actual outside air CO2 measurements instead of the 400 ppm CO2 default value for OAQ.

Cooling Mode Using Space Temperature Sensor T55, T56, T58 or T59 and Humidistat (HL38MG029 or TSTATCCPLH01-B)

Enhanced dehumidifying will be provided when a humidistat (HL38MG029 or TSTATCCPLH01-B) is connected the PD unit terminal strip across the R and W2 terminals (since the PD unit does not support the use of conventional thermostat inputs the W2 terminal is reconfigured for humidity input) and Space Humidity Switch (Configuration→UNIT→RH.SW) configuration variable is set to 1 (Normally Open-no call to dehumidify). Relative humidity set point is set by adjusting the dial on the HL38MG029 or TSTATCCPLH01-B device. When the humidistat contacts close and provide 24VAC to the W2 terminal the PD unit will reset the Supply Air Control Point (Run Status→COOL→SA.CP) by one degree F lower than the Supply Air Set Point (Setpoint→SASP) or the current control point if the Supply Air Set Point (Setpoint→SASP) has already been modified. After 5 minutes if the humidistat contacts are still closed and 24 VAC is being supplied to the W2 terminal the PD unit will reset the Supply Air Control Point (Run Status→COOL→SA.CP) lower by one more degree F. This reset cycle will continue to lower the supply air temperature every 5 minutes until the Supply Air Control Point (Run Status→COOL→SA.CP) is equal to the Supply Air Set Point (Setpoint→SASP) + SASP Maximum Reset Down (Configuration→COOL→SAT→SA.MD). The unit will continue to operate at this reduced supply air temperature control point until the humidistat contacts open and 24VAC is no longer supplied to the W2 terminal. When 24VAC is no longer supplied to the W2 terminal the supply air control point will be reset higher by one degree F. After 3 minutes if the humidistat contacts are still open and 24VAC is not being supplied to the W2 terminal PD unit will reset the Supply Air Control Point (Run Status→COOL→SA.CP) higher by one more degree F. This reset cycle will continue to raise the Supply Air Control Point (Run Status→COOL→SA.CP) every 3 minutes until the Supply Air Control Point (Run Status→COOL→SA.CP) is equal to the Supply Air Set Point (Setpoint→SASP) or the supply air control point if reset was being

applied due to cooling requirements that reset the Supply Air Set Point (Setpoint→SASP). Whenever Relative Humidity Reset is applied the space temperature is controlled by modulating the fan speed even if the fan was locked at 100% due to (Setpoint→SASP) reset.

Cooling Mode Using Space Temperature Sensor T55, T56, or T58 and Humidity Sensor (HL39ZZ007 or 33ZCSENRH-01)

Enhanced dehumidifying will be provided when a humidly sensor (HL39ZZ007 or 33ZCSENRH-01) 4 to 20 ma control is connected the PD unit terminal strip across the TB1-J10 pin 3 and 4, power to humidity sensor is connected to R and C, the RH Sensor on OAQ Input (Configuration→UNIT→RH.S) is set to

YES and Space Humidity Switch (Configuration→UNIT→RH.SW) configuration variable is set to

0.Relative humidity set point is set by changing the value of Space RH Set point (Setpoint→RH.SP). When the relative humidity in the space is above the Space RH Set point (Setpoint→RH.SP) the PD unit controls will reset the supply air temperature by one degree F lower than the Supply Air Set Point (Setpoint→SASP) or the current control point if the Supply Air Set Point (Setpoint→SASP) has already been modified. After 5 minutes the PD unit will reset the Supply Air Control Point (Run Status→COOL→SA.CP) lower by one more degree F. This reset cycle will continue to lower the Supply Air Control Point (Run Status→COOL→SA.CP) every 5 minutes until the Supply Air Control Point (Run Status→COOL→SA.CP) is equal to the Supply Air Set Point (Setpoint→SASP) + SASP Maximum Reset Down (Configuration→COOL→ SAT→SA.MD). When the relative humidity in the space goes below the Space RH Set Point (Setpoint→RH.SP) - the Space RH Deadband (Setpoint→RH.DB) the supply air control point will be reset higher by one degree F. After 3 minutes if the humidity sensor reading is still below the Space RH Set Point (Setpoint→RH.SP) - the Space RH Deadband (Setpoint→RH.DB), the PD unit will

reset the Supply Air Control Point (Run Status→COOL→SA.CP) higher by one more degree F. This reset cycle will continue to raise the Supply Air Control Point (Run Status→COOL→SA.CP) every 3 minutes until the supply air temperature control point is equal to the Supply Air Set Point (Setpoint→SASP) or the supply air control point if reset was being applied due to cooling requirements that reset the Supply Air Set Point (Setpoint→SASP).

Gas Heating Mode Using Space Temperature Sensor T55, T56, or T58 (48PD Units Only)

For gas units, the Type of Heat Installed (Configuration→HEAT→HT.TY) will be factory set to a value of 1.

Heat will not operate if the outdoor temperature is greater than the value configured for the Heating Lockout Temperature (Configuration→HEAT→HT.LO), Heat Minimum On Time (Configuration→HEAT→MRT.H) and Heat Minimum Off Time (Configuration→HEAT→MOT.H). Timeguards apply to both stages of heating. Factory defaults values are 2 minute s ON and 2 minutes OFF. The Integrated Gas Controller (IGC) minimum on-time of 1 minute will be followed even if Heat Minimum On Time (Configuration→HEAT→MRT.H) is lower and during Service Test.

If the indoor fan control is configured to cycle with the heating demand by setting Fan ON When Occupied Heat Minimum On Time (Configuration→UNIT→OC.FN) to NO, the fan will stop after a delay configured by Fan-off Delay, Gas Heat (Configuration→HEAT→FOD.G). The factory default for Fan-off Delay, Gas Heat (Configuration→HEAT→FOD.G) is 45 seconds. If the IGC temperature limit switch opens within 10 minutes of the end of the gas heat cycle, the next fan off delay will

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.

One of the standout features of the 48/50PD05 is its energy efficiency. It incorporates state-of-the-art technology to achieve high Seasonal Energy Efficiency Ratios (SEER) and EER ratings, reducing operational costs while delivering superior comfort. The unit is also compliant with the latest energy regulations, making it an environmentally friendly choice for building owners concerned about sustainability.

The 48/50PD05 is equipped with a highly efficient scroll compressor, which not only enhances performance but also contributes to quiet operation. This is a significant advantage in commercial spaces where noise levels need to be kept in check for comfort and productivity. Additionally, the unit includes advanced airflow design, ensuring even distribution of conditioned air throughout the space.

Technologically, the Carrier 48/50PD05 features Carrier's Infinity Control system, which allows for precise control of indoor climate. This intelligent control mechanism can be integrated with smart building management systems, enabling users to monitor and manage energy use effectively. Wi-Fi connectivity is also available, providing remote access for real-time adjustments and diagnostics.

Durability is another characteristic of the 48/50PD05. Constructed with high-quality materials, the unit withstands various environmental conditions, ensuring longevity and reliability. Moreover, the modular design facilitates easy maintenance, making service procedures efficient and cost-effective.

In addition to cooling, the Carrier 48/50PD05 offers heating capabilities, often utilizing gas or electric heating options that can be tailored to the specific needs of a building. The unit can also be equipped with integrated economizers, allowing for free cooling during suitable outdoor conditions, further enhancing energy savings.

Overall, the Carrier 48/50PD05 stands out as a high-performance HVAC solution that combines efficiency, technology, and durability. It provides building owners with a versatile tool to ensure comfort while minimizing their environmental footprint. With a strong emphasis on energy savings and advanced control features, this rooftop unit is a smart investment for any commercial property.