Heat Pump Controls; Commercial Defrost Board; Crankcase Heater; Compressor Protection - Carrier 38AUQ Installation, Start-Up And Service Instructions Manual

Heat Pump Controls

Compressor Protection

Compressor Overcurrent
The compressor has internal limbered motor protection.
Compressor Overtemperature
The compressor has an internal protector to protect it against
excessively high discharge gas temperatures.
High Pressure Switch
The system is provided with a high pressure switch mount-
ed on the discharge line. The switch is stem-mounted and
brazed into the discharge tube. Trip setting is 630 ± 10 psig
(4344 ± 69 kPa) when hot. Reset is automatic at 505 ± 20
psig (3482 ± 140 kPa).
Loss of Charge Switch
The system is protected against a loss of charge and low
evaporator coil loading condition by a loss of charge switch
located on the liquid line and a freeze protection thermostat on
the indoor coil. The switch is stem-mounted. Loss of Charge
Switch trip setting is 27 psig ± 3 psig (186 ±21 kPa). Reset is
automatic at 44 ±5 psig (303 ± 35 kPa).
Outdoor Fan Motor Protection
The outdoor fan motor is internally protected against overtem-
perature.
Inputs
Point Name
G Fan
Y1 Cool 1
Wi Heat 1
R Power
C Common
DFT1 Defrost Switch
Outputs
Point Name
OF OD Fan
RVS1
RVS2
COMP 1
HEAT 2
Configuration
Point Name
Select Jumper
1 Compressor
Speed-Up Configuration
Point Name
Speed-Up Jumper
Speed-Up Jumper
Jumper for 1-3 secs: Factory Test, defrost runs for 12 seconds or less
Jumper for 5-20 secs: Forced Defrost, defrost runs for 30 secs if DFT2 is open
Table 12 —38AUQ Defrost Board I/O and Jumper Configurations
Type of I/O Connection Pin Number
DI, 24-vac
DI, 24-vac
DI, 24-vac
24-vac
24-vac, ground
DI, 24-vac
Type of I/O Connection Pin Number
DO, 24-vac
DO, 24-vac
DO, 24-vac
DO, 24-vac
DO, 24-vac
Type of I/O Connection Pin Number
24-vac
24-vac
Type of I/O Connection Pin Number
Control Circuit, 24-V
The control circuit is protected against overcurrent conditions
by a circuit breaker mounted on control transformer TRAN.
Reset is manual.

Crankcase Heater

The heater prevents refrigerant migration and compressor oil
dilution during shutdown whenever compressor is not operat-
ing. The heater is wired to cycle with the compressor; the heat-
er is off when compressor is running, and on when compressor
is off.
The crankcase heater will operate as long as the power circuit
is energized.
IMPORTANT: Never open any switch or disconnect that
energizes the crankcase heater unless unit is being serviced
or is to be shut down for a prolonged period. After a pro-
longed shutdown on a service job, energize the crankcase
heater for 24 hours before starting the compressor.
Commercial Defrost Control
The Commercial Defrost Control Board (DFB) coordinates
thermostat demands for supply fan control, 1 or 2 stage
cooling, 1 or 2 stage heating, emergency heating and defrost
control with unit operating sequences. See Fig. 22 for board
arrangement.
The DFB is located in the 38AUQ's main control box (see
Fig. 21). All connections are factory-wired. Refer to Table 12
for details of DFB Inputs and Outputs.
Unit Connection
P2-3
P2-5
P2-7
P3-1
P3-3
DFT-1 to DFT-1
Unit Connection
OF
P3-7 to P3-5
P3-6 to P3-4
P3-10
E-HEAT HC-1 (TB4-1)
Unit Connection
P1-1
P1-2
Unit Connection
JMP17
JMP18
22
Note
Not used
TB-Y1
TB-W1
TRAN2
TRAN2
DFB
Note
OFR
RVS1 Energize in COOL
RVS2 Energize in COOL
CADM1-Y
Note
Note