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Heating modes – Carrier 48/50PD05 User Manual

Page 20

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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
CO

2

Sensor Only

When the CO

2

sensor detects a CO

2

level or IAQ Level

(InputsAIR.QIAQ) below the AQ Differential Low

(ConfigurationAIR.QAQD.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

(ConfigurationAIR.QAQ.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 (ConfigurationAIR.QAQ.MN). This will

happen

when

the

Commanded

Fan

Speed

(OutputsFANSF.SPD) is at the Supply Fan Maximum Speed

(ConfigurationUNITFS.MX). When the Commanded Fan

Speed (OutputsFANSF.SPD) is between Supply Fan

Maximum Speed (ConfigurationUNITFS.MX) and the

Supply Fan Minimum Speed (ConfigurationUNITFS.MN)

the damper will operate in the shaded area of Figure 8 based on the

IAQ Level (InputsAIR.QIAQ).
Economizer Operation for Units Equipped with Return Air
CO

2

Sensor and outside air CO

2

Sensor

The Economizer will operate similar to Economizer Operation for

Units Equipped with Return Air CO

2

Sensor Only but the IAQ

Level (InputsAIR.QIAQ) will be determined by actual

outside air CO

2

measurements instead of the 400 ppm CO

2

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 (ConfigurationUNITRH.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 StatusCOOLSA.CP) by

one degree F lower than the Supply Air Set Point

(SetpointSASP) or the current control point if the Supply Air

Set Point (SetpointSASP) 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 StatusCOOLSA.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 StatusCOOLSA.CP) is equal to the Supply Air Set

Point (SetpointSASP) + SASP Maximum Reset Down

(ConfigurationCOOLSATSA.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 StatusCOOLSA.CP)

higher by one more degree F. This reset cycle will continue to
raise the Supply Air Control Point (Run StatusCOOLSA.CP)

every 3 minutes until the Supply Air Control Point (Run

StatusCOOLSA.CP) is equal to the Supply Air Set Point

(SetpointSASP) or the supply air control point if reset was being

applied due to cooling requirements that reset the Supply Air Set
Point (SetpointSASP). 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 (SetpointSASP)

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 (ConfigurationUNITRH.S) is set to

YES

and

Space

Humidity

Switch

(ConfigurationUNITRH.SW) configuration variable is set to

0. Relative humidity set point is set by changing the value of

Space RH Set point (SetpointRH.SP).

When the relative

humidity in the space is above the Space RH Set point

(SetpointRH.SP) the PD unit controls will reset the supply air

temperature by one degree F lower than the Supply Air Set Point

(SetpointSASP) or the current control point if the Supply Air

Set Point (SetpointSASP) has already been modified. After 5

minutes the PD unit will reset the Supply Air Control Point (Run

StatusCOOLSA.CP) lower by one more degree F. This reset

cycle will continue to lower the Supply Air Control Point (Run

StatusCOOLSA.CP) every 5 minutes until the Supply Air

Control Point (Run StatusCOOLSA.CP) is equal to the

Supply Air Set Point (SetpointSASP) + SASP Maximum Reset

Down (ConfigurationCOOLSATSA.MD).

When the

relative humidity in the space goes below the Space RH Set Point

(SetpointRH.SP)

--

the

Space

RH

Deadband

(SetpointRH.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 (SetpointRH.SP) --

the Space RH Deadband (SetpointRH.DB), the PD unit will

reset

the

Supply

Air

Control

Point

(Run

StatusCOOLSA.CP) higher by one more degree F. This reset

cycle will continue to raise the Supply Air Control Point (Run

StatusCOOLSA.CP) every 3 minutes until the supply air

temperature control point is equal to the Supply Air Set Point

(SetpointSASP) or the supply air control point if reset was being

applied due to cooling requirements that reset the Supply Air Set
Point (SetpointSASP).

Heating Modes

Gas Heating Mode Using Space Temperature Sensor

T55, T56, or T58 (48PD Units Only)

For

gas

units,

the

Type

of

Heat

Installed

(ConfigurationHEATHT.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

(ConfigurationHEATHT.LO), Heat Minimum On Time

(ConfigurationHEATMRT.H) and Heat Minimum Off Time

(ConfigurationHEATMOT.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 (ConfigurationHEATMRT.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 (ConfigurationUNITOC.FN) to NO, the fan will stop

after a delay configured by Fan--off Delay, Gas Heat

(ConfigurationHEATFOD.G). The factory default for

Fan--off Delay, Gas Heat (ConfigurationHEATFOD.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/

50P

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