Carrier 50PG20 User Manual

41
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 contac-
tor. The indoor fan may operate during cooling with compres-
sors 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 sensor fan configuration
(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 without
Humidi-MiZer device, the IGC control fan output is also moni-
tored by the MBB control. This can result in additional modifi-
cation 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:
• If fan request G in ON, the IDF will be ON.
• If cooling request Y1 or Y2 is ON, the IDF will be ON.
• 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.LO;
Configuration → 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. Facto-
ry 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),
the fan will stop after a configured delay (Configuration
→ COOL → FOD.C). Factory default value is 60 seconds.
THERMOSTAT CONTROL — To operate the unit in Ther-
mostat mode, the Unit Control Type (Configuration
→ UNIT → U.CTL) configuration must be set to 2 (Thermo-
stat). There are up to four types of thermostat control depend-
ing on model size. These are configured with the Thermostat
Control Type (Configuration
→ UNIT → T.CTL).
For economizer equipped units (Configuration
→ UNIT → EC.EN = Ye s ), the Adaptive control algorithm is
used whenever the economizer can provide cooling. This will
ensure proper time delays and SAT control when the econo-
mizer is cooling. Cooling begins when the Y1 input is ener-
gized. 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 Tem-
perature (Temper atures
→ AIR.T → SAT) is less than Minimum
Supply Air Temperature Lower Level (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 the Scrolling Marquee at
Configuration
→ COOL. Compressor minimum on-time
(Configuration
→ COOL → MRT.C) and compressor minimum
off-time (Configuration
→ COOL → MOT.C) do apply.
T.CT L
= 1 (1 Stage Y1) — When T.CTL = 1, no additional
compressor staging timers or supply air temperature limits
apply. Compressor staging will follow the thermostat inputs
directly. Y1 will turn on refrigerant circuit A. Y2 will add re-
frigerant circuit B. Compressor minimum on-time (MRT.C)
and compressor minimum off-time (MOT.C) do apply.
SPACE SENSOR CONTROL — To operate the unit in
Space Sensor mode, set the Unit Control Type to 3 (Configura-
tion
→ UNIT → U.CTL=3). To enable heating during space
temperature control, a jumper wire must be added between R
and W1 on the field connection terminal strip (see Major Sys-
tem Components section for wiring diagrams).
Because Space Sensor mode is an “Auto” mode, the control
will switch between cooling and heating to maintain space
temperature. However, to minimize unnecessary changes, there
is a 10-minute mode select timeguard (Operating Modes
→
COOL → MS.TG), after the last stage of heat turns off before
cooling is allowed.
The unit tries to maintain the space temperature at the Occu-
pied Cool Set Point (Setpoints
→ OCSP) or the Unoccupied
Cool Set Point (Setpoints
→ UCSP). See the Occupancy
Determination section for factors that affect the Occupied sta-
tus (Run Status
→ VIEW → OCC). The Cooling Demand (Op-
erating Modes
→ COOL → SPT → DMD.C) is equal to Space
Temperature (Operating Modes
→ COOL → SPT → SPT) minus
the occupied or unoccupied set point (DMD.C = SPT – set
point). See Table 37 for an example of reading and changing
the occupied set point (OCSP).
Table 37 — Reading and Changing Cooling Occupied Set Point
DISPLAY
MENU
KEYPAD
ENTRY
ITEM DISPLAY ITEM EXPANSION COMMENT
SETPOINTS
OCSP 78 Occupied Cool Set point Default: 78
78 Scrolling Stops
78 Value flashes
Select 75
75 Change accepted
OCSP 75 Occupied Cool Set point Item/Value/Units scroll again
ENTER
ENTER
ENTER
ENTER
ESCAPE

Carrier 50PG20 Specifications

General

Brand	Carrier
Model	50PG20
Category	Air Conditioner
Language	English