C.typ=3 (Tstat Multi) Required Configuration - Carrier 38APS025 Manual

As the capacity requirement begins to decrease, the ma-
chine controls will reduce the unit's capacity to maintain the
Control Point. If the unit is equipped with Minimum Load
Control, it will not be active until the unit is on its last stage of
capacity.
C.TYP = 3 (TSTAT MULTI) — This
allow the MBB to monitor the thermostat inputs to make a
determination of supply air temperature. Unlike traditional
2-stage thermostat control, the unit is allowed to perform VAV
style operation using multiple stages of cooling capacity to
attempt to meet the current Control Point (Run Sta-
tus VIEW CTPT).
Recommended Applications — This control scheme is rec-
ommended for constant volume or 100% outdoor air applica-
tions. It can be used with or without digital compressors. This
control method is recommended for 38APD,APS025-030 units
with digital scroll option and 38APD,APS040-130 units with
two-stage thermostat control. Minimum Load Control is sup-
ported by this control scheme. Minimum Load Control and
digital compressor operation are not supported simultaneously.
Hardware Requirements
• supply air sensor
• return air sensor or mixed air sensor
• 2-stage thermostat
This control scheme requires a supply air sensor and a return
air sensor or mixed air sensor. In lieu of wiring sensors to the
38AP unit, both values can be communicated via CCN to the
38AP. For information on broadcasting values, see the section
Thermistors on page 28. Configuration OPT1 RAT.T
(RAT Thermistor Type) and Configuration OPT1 SAT.T
(SAT Thermistor Type) must be configured for either 0 (5 k )
or 1 (10 k ) type sensors whether they are hard wired or their
values are communicated to the controller.
SUBMODE
OPT1
OPT2
COOL
configuration will
Table 27 — C.TYP=3 (Tstat Multi) Required Configuration
CONFIGURATION MODE
ITEM DISPLAY
RAT.T X
SAT.T X
C.TYP X
SETPOINTS MODE
CSP.1 XX.X
CSP.2 XX.X
Required Configurations — Table 27 lists the configurations
required for proper operation.
Recommended Settings — With this Control Type, CSP.2
should be set to the design Supply Air Temperature. CSP.1
will depend on the application. The difference between the
default values for CSP.1 and CSP.2 is 5° F (2.8° C). In most
cases, the default differential is acceptable, but the application
may require a smaller or larger difference. For example, a face
split coil may a larger differential. CSP.1 should be set to a
value that allows the unit to operate without rapid cycling.
CSP.1 should be greater than CSP.2 to allow the unit to
produce a lower supply air temperature when Y2 is made, if
the unit has the available capacity.
Wiring— See Fig. 81.
Sequence of Operation — The MBB monitors the thermostat
inputs to make a determination of Active Set Point (Run Sta-
tus VIEW SETP). The control will vary the Active Set
Point based on Y1 and Y2 inputs. When Y1 is closed Cooling
Setpoint 1 (Setpoints COOL CSP.1) will be used and when
Y2 is closed Cooling Setpoint 2 (Setpoints COOL CSP.2)
will be used as the basis for the Active Set Point, SETP. Ther-
mostat inputs can be monitored at the unit's interface device,
Y1Thermostat Input (Inputs GEN.I Y.1) and Y2 Thermo-
stat Input (Inputs GEN.I Y.2). With this type of control,
the MBB capacity control routine stages compressor capacity
to attempt to meet the current Control Point (Run Sta-
tus VIEW CTPT).
tus VIEW CTPT) is the Active Set Point (SETP) adjusted
for any temperature reset that is applied. See Temperature
Reset on page 129 for additional information.
For mechanical cooling, the unit's Control Method (Con-
figuration OPT2 CTRL) and inputs must allow the ma-
chine to run. See Control Methods on page 60 for additional
information.
ITEM DESCRIPTION
RAT Thermistor Type
SAT Thermistor Type
Machine Control Type
Cooling Setpoint 1
Cooling Setpoint 2
67
The Control Point (Run
COMMENT
Default: 0
Range: 0 to 2
Must be set for appropriate value:
0 = 5 k
1 = 10 k
2 = None
Default: 0
Range: 0-2
Must be set for appropriate value:
0 = 5 k
1 = 10 k
2 = None
Default: 4
Range: 1 to 9
Set Item to 3 (Tstat Multi)
Range: 40.0 to 80.0 F (4.4 to 26.7 C)
Default: 60.0 F (15.6 C)
Set for desired Supply Air Temperature
with Y1 input.
Range: 40.0 to 80.0 F (4.4 to 26.7 C)
Default: 55.0 F (12.8 C)
Set for desired Supply Air Temperature
with Y2 input. Should be lower than
CSP.1
Sta-