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.

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.

Table 12 —38AUQ Defrost Board I/O and Jumper Configurations

Inputs

Point Name

Type of I/O

Connection Pin Number

Unit Connection

Note

G Fan

DI, 24-vac

P2-3

 

Not used

Y1 Cool 1

DI, 24-vac

P2-5

TB-Y1

 

Wi Heat 1

DI, 24-vac

P2-7

TB-W1

 

R Power

24-vac

P3-1

TRAN2

 

C Common

24-vac, ground

P3-3

TRAN2

 

DFT1 Defrost Switch

DI, 24-vac

DFT-1 to DFT-1

DFB

 

Outputs

Point Name

Type of I/O

Connection Pin Number

Unit Connection

Note

OF OD Fan

DO, 24-vac

OF

OFR

 

RVS1

DO, 24-vac

P3-7 to P3-5

RVS1

Energize in COOL

RVS2

DO, 24-vac

P3-6 to P3-4

RVS2

Energize in COOL

COMP 1

DO, 24-vac

P3-10

CADM1-Y

 

HEAT 2

DO, 24-vac

E-HEAT

HC-1 (TB4-1)

 

Configuration

Point Name

Type of I/O

Connection Pin Number

Unit Connection

Note

Select Jumper

24-vac

P1-1

 

 

1 Compressor

24-vac

P1-2

 

 

Speed-Up Configuration

Point Name

Type of I/O

Connection Pin Number

Unit Connection

Note

Speed-Up Jumper

 

JMP17

 

 

Speed-Up Jumper

 

JMP18

 

 

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

22

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Carrier 38AUQ appendix Heat Pump Controls, Compressor Protection, Crankcase Heater, Commercial Defrost Control
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38AUQ specifications

The Carrier 38AUQ is a versatile and efficient air conditioning unit designed to meet a variety of residential and light commercial cooling needs. Known for its advanced technology and robust performance, the 38AUQ model showcases Carrier's commitment to sustainability and energy efficiency.

One of the standout features of the Carrier 38AUQ is its use of variable-speed inverter technology. This allows the unit to adjust its cooling output in response to the temperature demands of the environment. By operating at multiple speed levels, it minimizes energy consumption and maximizes comfort, ensuring a consistent, quiet cooling experience.

The 38AUQ is equipped with a high-efficiency compressor, which helps to further enhance its energy performance. This component plays a critical role in ensuring that the unit operates smoothly, reducing both electricity bills and the environmental impact. Efficiency ratings often exceed industry standards, making the 38AUQ a suitable choice for those looking to reduce their carbon footprint while enjoying a comfortable indoor climate.

In terms of design, the Carrier 38AUQ boasts a compact and sleek profile that allows for easy installation in a variety of settings. Its durable construction is built to withstand harsh weather conditions, ensuring longevity and reliability. Additionally, an advanced air purification system is integrated, featuring filters that capture airborne particles, improving indoor air quality.

The unit also offers a range of smart features, including compatibility with smart home systems. Users can remotely control their air conditioning via smartphone apps, allowing for customizable settings and energy management from anywhere. This connectivity aligns with modern living preferences, enhancing convenience and control.

Furthermore, the Carrier 38AUQ is designed with noise reduction in mind. The advanced sound-absorbing materials and quiet operation of its fan and compressor make it one of the quieter air conditioning options on the market. This is particularly beneficial for residential applications, where noise can be a significant concern.

Overall, the Carrier 38AUQ combines cutting-edge technology, energy efficiency, and user-friendly features, making it a top choice for both homeowners and small business operators seeking reliable cooling solutions. Its commitment to performance and efficiency makes it a standout model in the Carrier air conditioning lineup.
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