Control; Indoor Fan; Cooling - Carrier 50PG20-28 Controls, Start-Up, Operation, Service And Troubleshooting Instructions

Indoor Fan -- The indoor thn is controlled by the indoor
tan relay output (Outputs--->FA?_i9--->IDF) o n the MBB (main
base board) control, wNch then operates the indoor tan contac-
tor. The indoor fan may operate during cooling with compres-
sors mode, fiee cooling with outdoor air mode, heating mode,
or for ventilation with outdoor air mode.
The indoor tan operation can be affected by configurations
for thermostat control type (Configuration---_UNIr---_T.CrL),
the occupancy thn configuration (Configuration---_UNIT---_
OC.FN), the indoor air quality sensor tan configuration
(Configuration--+AIR.Q---_IA.F?€), the indoor air quality
switch tan configuration ((bnfiguration---_AIILQ---_ILF?€),
and the tan status switch configuration ((bnfiguration---_
UNIT--+ F?V:SW). For 48PG gas heating units without
Humidi-MiZer device, the IGC control tan 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 ha thermostat mode, the IDF
relay will be on in the following situations:
• If tan request G in ON, the IDF wilt be ON.
• If cooling request Y1 or Y2 is ON, the IDFwill be ON.
• If heating request W1 or W2 is ON, the IDFwill be ON.
SPACE SENSOR CONTROL In Space Sensor Control
mode, the IDF (indoor tan) 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 ((bnfiguration-->
UNIT _'OC.FN= YES), the indoor l_aal wilt be ON. If OCFN
equals NO or the unit is unoccupied, the indoor tan will operate
only when heating or cooling is necessary.
Coo[in 0 -- Compressors will not operate if the outdoor
temperature is less than the value configured for the circuit
lockout temperatures ((bnfiguration_DOL_'A.LO;
Configuration _'OOL _B.LO; and Configuration
COOL _,CC.LO;). The Mthilnmn On Time (Configuration
(DOL ---_IR T.. O, and Minhnum Off Time (Configuration --+
COOL---_MOT.0 time guards apply to all compressors. Facto-
131default values are 3 minutes for Minilnum On Time and
5 minutes for Minilnuln OffTime.
If the indoor tan control is configured to cycle with the
cooling demand (Configumtion---_UNIT_OC.FN= No),
the tan will stop after a configured delay (Configuration
_DOL---_FOD.C). Factory default value is 60 seconds.
THERMOSTAT CONTROL To operate the unit in The>
mostat mode, the Unit Control Type (Configuration
_UNIT--+U.(TL) configuration must be set to 2 (Thermo-
stat). There are up to fore 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--+ECEN = Yes), the Adaptive control atgorithln is
used whenever the economizer can provide cooling. TNs 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% tbr 5 minutes,
compressor staging will beNn.
Con[iguration---_UNIT---_T.CTL = 0 (Adaptive) When
T.(TL = 0, additional timers mad supply air temperature limits
apply to control the compressor staNng. In Adaptive mode, a
stage of colnpression wilt be turned off if the Supply-Air Tem-
perature ( Temperatures --+AIR. T---a7AI) is less than Minilnum
Supply Air Temperature Lower Level (Setpoints--_AT.L). In
addition, a stage of compression will be turned on if the SATis
greater than the Minhnum Supply Air Temperature Upper
Level (Setpoin ts ---_qA T.U). If SA T.L and SAT. U are con figured
so that they axe close together, the last stage of compressor
might cycle rapidly, slowed only by its minimum on and
off-tilne requirements. Configurable time delays also apply
when adding stages (Configuration_'COOL_.INO or
removing stages (Configuration_DOL _.DE O. C.INC
aald C.DEC are accessible via the Scrolling Marquee at
Configuration_'OOL. Compressor minilnmn on-time
(Configuration _,COOL ---_MRT.0 and compressor minimmn
oil'-time (Configuration _'OOL--_AIOT. 0 do apply.
T..CTL 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-
fiigerant circuit B. Compressor minimuln on-tilne (MRT. 0
mad compressor minilnmn off-time (MOT.O do apply.
SPACE SENSOR CONTROL To operate the unit in
Space Sensor mode, set the Unit Control Type to 3 (Configum-
tion--+UNIT---_U.CTL=3). To enable heating during space
telnperamre control, a jumper wire must be added bewveen R
mad W1 on the field connection terminal strip (see Major Sys-
tem Components section for wiring diagrams).
Because Space Sensor mode is ml "Auto" 1node, the control
will switch bewveen cooling and heating to maintain space
temperature. However, to lninimize unnecessary changes, there
is a 10-1ninute 1node select tilnegumd (Operating Modes---_
COOL---_MS. TG), after the last stage of heat rams off before
cooling is allowed.
The unit tries to maintain the space temperature at the Occu-
pied Cool Set Point (Setpoints_O(SP) or the Unoccupied
Coot Set Point (Setpoints--+UCSP). See the Occupancy
Determination section for factors that affect the Occupied sta-
res (Run Stams---_VIEW_OC O. The Cooling Demmld (Op-
erating Modes_DOL---A7PT---_DMD. 0 is equal to Space
Temperature (Operating Modes _'OOL ---AqPT---_qP1) minus
the occupied or unoccupied set point (DMD.C SPY set
point). See Table 37 for ml example of reading and chmlging
the occupied set point (OCSP).
Table 37 -- Reading and Changing Cooling Occupied Set Point
DISPLAY KEYPAD ITEM DISPLAY ITEM EXPANSION COMMENT
MENU ENTRY
] OCSP 78 Occupied CooI Set point Default: 78
] 78 Scrolling Stops
] 78 Value flashes
SETPOINTS
] Select 75
] 75 Change accepted
OCSP 75 Occupied CooI Set point Item/Value/Units scroll again
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