Carrier Comprehensive Guide for Air Conditioner Operation and Service
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Check Operation Ð Verify operation of all safety con- trols. Replace all service panels. Be sure that control panel cover is closed tightly.

OPERATING SEQUENCE

Cooling Ð When the ®rst stage (TC1) of the cooling ther- mostat closes, the timer starts. After approximately 3 sec- onds, the timer activates the compressor and fan motor no. 1 contactor. When the liquid pressure builds to approxi- mately 257 psig (1772 kPa), fan motor no. 2 is energized.

On demand for additional cooling capacity, the second stage (TC2) of the cooling thermostat closes, energizing a ®eld- supplied liquid line solenoid (LLS) valve, which opens. This increases the suction pressure, causing the compressor to op- erate at higher capacity.

When fan switch is set at AUTO, the indoor-air fan cycles with the compressor. When the switch is set at CONT, the indoor-air fan runs continuously.

At shutdown, the Time Guard II timer prevents the com- pressor from restarting for approximately 5 minutes.

When installed, a ®eld-supplied solenoid valve (wired in parallel with the compressor contactor coil), shuts off the liq- uid line to prevent refrigerant migration back to the com- pressor during the off cycle.

Heating Ð The heating thermostat (TH) energizes a ®eld- supplied relay which operates heating controls and ener- gizes the indoor-fan relay. When the fan switch is set at AUTO, the indoor-air fan cycles with the heating control. The indoor- air fan runs continuously when the fan switch is set at CONT.

Fan Cycling Ð Head pressure control is accomplished by cycling the fans. The no. 2 fan responds to liquid line pressure, cycling on at approximately 257 psig (1772 kPa) and off at approximately 126 psig (869 kPa).

Winter Start Control (If Installed) Ð When the com- pressor starts, the control's bypass timer contacts close for 150 seconds, thereby bypassing the low-pressure switch dur- ing start-up. After 150 seconds, the bypass timer contacts open and the low-pressure switch is restored to the safety circuit.

SERVICE

Capacity Control Ð A suction pressure-actuated un- loader controls 2 cylinders and provides capacity control. Un- loaders are factory set (see Tables 1A-1D), but can be ®eld adjusted as described in the 2 following sections.

CONTROL SET POINT (cylinder load point) is adjustable from 0 to 85 psig (586 kPa). To adjust, turn control set point adjustment nut (Fig. 12) clockwise to its bottom stop. In this position, set point is 85 psig (586 kPa). Next, turn adjust- ment counterclockwise to desired control set point. Every full turn counterclockwise decreases set point by 7.5 psig (51.7 kPa).

PRESSURE DIFFERENTIAL (difference between cylinder load and unload points) is adjustable from 6 to 22 psig (41.4 to 152 kPa). To adjust, turn pressure differential adjustment screw (Fig. 12) counterclockwise to its back stop position. In this position, differential is 6 psig (41.4 kPa). Next, turn adjustment clockwise to desired pressure differential setting. Every full turn clockwise increases differential by 1.5 psig (10.3 kPa).

Head Pressure Control Ð Fan cycling is a standard feature. The no. 2 fan cycles in response to changes in liquid pressure. The switch cycles the fan off at 126 ± 4 psig (869

±28 kPa) as pressure decreases, and cycles it back on at 257 (+5, −0) psig (1772 [+103, −0] kPa).

Fig. 12 Ð Compressor Capacity Control Unloader

Time Guard II Circuit Ð Prevents short-cycling by pro- viding a delay of approximately 5 minutes before restarting compressor after shutdown from safety device action.

On start-up, the Time Guard II timer causes a delay of approximately 3 seconds after thermostat closes.

On compressor shutdown, the timer recycles for approxi- mately 5 minutes. During this time, the compressor cannot restart.

Refer to Fig. 13 and to label diagram on unit.

Fig. 13 Ð Timer Sequence Chart

Winter-Start Control (If Required) Ð Install Ac- cessory Package 38AE900021.

Crankcase Heater Ð The heater prevents refrigerant migration and compressor oil dilution during shutdown when- ever compressor is not operating. It is wired into the control circuit, and cycles with the compressor; the heater is off when compressor is running, and on when compressor is off.

Both compressor service valves must be closed whenever the crankcase heater is deenergized for more than 6 hours. The crankcase heater is operable as long as the control cir- cuit is energized.

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Contents Safety Considerations ContentsInstallation Dimensions ft-in Component Locations Typical Ð 38AE Shown Ð Physical Data SI, 60 Hz Ð Physical Data English, 60 HzÐ Physical Data SI, 50 Hz Ð Physical Data English, 50 HzComplete Refrigerant Piping Connections Rig and Mount the UnitNEC Complete Electrical ConnectionsIFC Ð Electrical Data 3 Ph/50 HzLlsv Ð Before Starting Unit ensure the following PRE-START-UPSTART-UP Charging Data R-2238AE012 and 38AKS024 Charging Chart 38AE014 Charging Chart 38AE016 Charging Chart Operating Sequence ServiceOutdoor Fan LubricationProblem Solution TroubleshootingCompressor Running but Cooling Insufficient TroubleshootingPage Packaged Service Training Preliminary Information START-UP ChecklistPre-Start-Up Start-Up

38AE014, 38AE016, 38AE012 specifications

The Carrier 38AE012, 38AE016, and 38AE014 are part of the Carrier series of packaged rooftop air conditioning units, designed to deliver reliable and efficient cooling solutions for commercial and industrial applications. These units showcase advanced engineering and technology, addressing the diverse needs of modern HVAC systems.

One of the primary features of the Carrier 38AE series is their high-efficiency performance. They utilize advanced scroll compressor technology, which results in lower energy consumption while providing consistent cooling. With high SEER (Seasonal Energy Efficiency Ratio) ratings, these units help businesses reduce operational costs while maintaining comfortable indoor environments.

The construction of the Carrier 38AE units emphasizes durability and resilience. Built with high-quality materials, they are engineered to withstand harsh weather conditions and the rigors of daily use. The weatherized cabinets protect internal components from precipitation and corrosion, ensuring long-term reliability.

The 38AE series incorporates a sophisticated electronic control system that enhances performance monitoring and diagnostics. This feature allows facility managers to easily manage and optimize the unit's operations, improving efficiency and reducing potential downtime. Integrated with smart controls, these systems can be programmed for specific operating schedules, allowing for further energy savings.

Another standout technology in the Carrier 38AE series is the environmentally friendly refrigerant. By utilizing R-410A, these units contribute to reduced ozone depletion while still providing powerful cooling capabilities. This aligns with contemporary regulatory standards and climate initiatives to promote sustainable usage of HVAC systems.

The Carrier 38AE012, 38AE016, and 38AE014 models also excel in noise reduction technology, which is essential for commercial settings where ambient noise levels need to be minimized. The design includes low-noise fans and strategically placed insulation, resulting in quieter operation that enhances comfort for occupants.

In terms of installation, these units are versatile and can be easily mounted on building rooftops or on the ground. They feature a compact design, which facilitates seamless integration into existing structures without requiring extensive modifications.

Overall, the Carrier 38AE012, 38AE016, and 38AE014 models stand out for their combination of efficiency, durability, and advanced technology. They cater to a wide range of commercial needs, providing essential cooling while prioritizing sustainability and user comfort. With a commitment to innovation, Carrier continues to be a leader in the HVAC industry, ensuring that their products meet the evolving demands of energy efficiency and reliability.
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