Indoor Fan; Cooling - Carrier 48PG03-16 Controls, Start-Up, Operation, Service And Troubleshooting Instructions

c. SCH.N = 65-99: Follow the global programmed
schedule. If the 48/50PG unit is configured as a Global
Schedule broadcaster
BROD→B.GS = YES), the unit will follow the unit's
programmed schedule and broadcast the schedule so that
other devices programmed to follow this schedule
number can receive the schedule. If the 48/50PG unit is
not programmed as a Global Schedule broadcaster
(Configuration →CCN→BROD→B.GS = NO), the
unit will receive its information from the unit
programmed to broadcast this schedule number.
While using a programmed schedule, occupancy can be
temporarily switched from unoccupied to occupied by
pressing the override button for approximately 3 seconds
on a T-55, T-56, or T-58 device. Override will only occur
if Configuration →CCN→SCH.O→OV.SP is set to
YES. The length of the override period is determined by
the setting of Configuration→CCN→SCH.O→OV.EX.

Indoor Fan

The indoor fan is controlled by the indoor fan relay output
(Outputs→FANS→IDF) on the MBB (main base board) control,
which then operates the indoor fan contactor. The indoor fan may
operate during cooling with compressors mode, free cooling with
outdoor air mode, heating mode, or for ventilation with outdoor
air mode.
The indoor fan operation can be affected by configurations for
thermostat control type (Configuration→UNIT→T.CTL), the
occupancy fan configuration (Configuration→UNIT→ OC.FN),
the indoor air quality
(Configuration→AIR.Q→IA.FN), the indoor air quality switch
fan configuration (Configuration→AIR.Q→II.FN), and the fan
status switch configuration (Configuration→ UNIT→ FN.SW).
For 48PG gas heating units, the IGC control fan output is also
monitored by the MBB control. This can result in additional
modification of fan delays or other operation due to safety
functions of the IGC control. See the Indoor Air Quality section if
using IAQ (indoor air quality) accessory sensors.
Thermostat Control
In thermostat mode, the IDF relay will be on in the following
situations:
S If fan request G in ON, the IDF will be ON.
S If cooling request Y1 or Y2 is ON, the IDF will be
ON.
S If heating request W1 or W2 is ON, the IDF will be
ON.
Space Sensor Control
In Space Sensor Control mode, the IDF (indoor fan) relay will be
on in the following situations. If the unit is in Occupied mode
and the indoor fan is configured to always run while occupied
(Configuration→ UNIT →OC.FN = YES), the indoor fan will
be ON. If OC.FN equals NO or the unit is unoccupied, the indoor
fan will operate only when heating or cooling is necessary.

Cooling

Compressors will not operate if the outdoor temperature is less
than the value configured for the circuit lockout temperatures
(Configuration→COOL→CA.LOConfiguration→COOL→CB.
LO;and Configuration→COOL→CC.LO;). The Minimum On
Time (Configuration→COOL→MRT.C), and Minimum Off
Time (Configuration→COOL→MOT.C) time guards apply to
all compressors. Factory default values are 3 minutes for
Minimum On Time and 5 minutes for Minimum Off Time.
If the indoor fan control is configured to cycle with the cooling
demand (Configuration→UNIT→OC.FN = No),
stop after a configured
→COOL→FOD.C). Factory default value is 60 seconds.
(Configuration→ CCN→
sensor fan configuration
the fan will
delay (Configuration
Thermosat Control
To operate the unit in Thermostat mode, the Unit Control Type
(Configuration →UNIT→U.CTL) configuration must be set to 2
(Thermostat). There are up to four types of thermostat control
depending on model size. These are configured with the
Thermostat Control Type (Configuration→UNIT→T.CTL).
For economizer equipped
→UNIT→EC.EN = Yes), the Adaptive control algorithm is used
whenever the economizer can provide cooling. This will ensure
proper time delays and SAT control when the economizer is
cooling. Cooling begins when the Y1 input is energized. The
economizer will try to provide cooling as described in the
Economizer section. If the economizer is not available for cooling
or the economizer has been at 100% for 5 minutes, compressor
staging will begin.
Configuration→UNIT→T.CTL = 0 (Adaptive)
When T.CTL = 0, additional timers and supply air temperature
limits apply to control the compressor staging. In Adaptive mode,
a stage of compression will be turned off if the Supply-Air
Temperature (Temperatures→AIR.T→SAT)
Minimum Supply Air
(Setpoints→SAT.L). In addition, a stage of compression will be
turned on if the SAT is greater than the Minimum Supply Air
Temperature Upper Level (Setpoints→SAT.U). If SAT.L and
SAT.U are configured so that they are close together, the last stage
of compressor might cycle rapidly, slowed only by its minimum
on and off-time requirements. Configurable time delays also
apply when adding stages (Configuration→COOL→C.INC) or
removing stages (Configuration→COOL→C.DEC). C.INC and
C.DEC are accessible via
Configuration→COOL.
Compressor
(Configuration→COOL→MRT.C) and compressor minimum
off-time (Configuration→COOL→MOT.C) do apply.
For size 16 units, the algorithm must decide how to map a
two-stage thermostat to three stages of compression. The
staging algorithm uses information from Y1, Y2, and the
supply-air temperature to determine the number of stages. If Y1 =
OFF, then no compressors will operate unless they are
forced to run in order to satisfy their minimum on-time. If Y1 =
ON, then either 1 or 2 stages will operate. Finally, if Y2 = ON,
then after the C.INC delay times, the maximum number of stages
will operate. When only Y1 is ON, the unit will decide to operate
1 or 2 stages of compression using the following logic. When Y1
turns ON, the first stage of compressor will turn on immediately.
The algorithms begin to count the number of seconds since the
last change in the number of
to 1). After the
(Configuration→UNIT→SAT.T) is reached, a
for SAT is stored. If, while operating with only one compressor
on, the return temperature begins to rise, and therefore the SAT
temperature rises also, the second compressor will be added when
SAT is greater the SAT reference plus SAT positive demand
(Configuration→COOL→SAT→SA.PD). After the second
compressor has been added, another SAT reference value will be
taken. The second stage will be turned off when SAT is less
than SAT reference plus
(Configuration→COOL→SAT→SA.ND). If at any time Y2 is
turned ON, then the algorithm would immediately try to reach 3
stages following the C.INC requirement. If Y1 turns OFF, then all
the compressors will turn off after their minimum ontime has
been met.
62
units (Configuration
is less than
Temperature Lower Level
the Scrolling Marquee
minimum on-time
being
compressors (in this case, from 0
compressor settling time
reference value
SAT negative demand
at