Carrier 25TPA7 - User Manual

The 25TPA7 Performance™ Series 2-Stage Heat Pump with Puron Refrigerant is designed for residential heating and cooling applications, available in 2 to 5 tons capacity. This unit is engineered for efficiency and reliability, utilizing Puron (R-410A) refrigerant, which is an environmentally friendly alternative.

Function Description:

This heat pump operates in two stages for both heating and cooling, allowing for more precise temperature control and enhanced energy efficiency compared to single-stage units. In cooling mode, it extracts heat from the indoor air and transfers it outdoors. In heating mode, it reverses the process, extracting heat from the outdoor air and transferring it indoors. The 2-stage operation means the compressor can run at a lower capacity (approximately 67%) during mild conditions and switch to full capacity (100%) during more extreme temperatures, optimizing comfort and reducing energy consumption.

The unit is equipped with a defrost control system that prevents ice buildup on the outdoor coil during heating operation in cold weather. This control is time/temperature based, with field-selectable settings for defrost intervals (30, 60, 90, or 120 minutes, factory set to 60 minutes). The defrost cycle is initiated when the coil temperature reaches approximately 32°F (0°C) and terminates when the defrost thermostat opens or automatically after 10 minutes. A "Quiet Shift-2" feature, which is field-selectable, reduces noise during defrost and heating cycle restarts by temporarily de-energizing the compressor and reversing valve.

The 25TPA7 is designed to be connected to a factory-approved indoor unit, such as an ECM furnace or variable speed furnace, to form a complete HVAC system. The indoor unit's blower operation is matched to the compressor's capacity stages, allowing for optimal airflow during high and low-stage cooling.

Important Technical Specifications:

Refrigerant: Puron (R-410A)
Capacity: 2 to 5 tons
Compressor: 2-stage scroll compressor with an internal unloading mechanism.
Compressor Protection: Internal pressure relief (IPR) and internal overload attached to motor windings.
Low Pressure Switch: Included for system protection.
Liquid Line Size: Maximum 3/8-in. OD for all residential applications.
Filter Drier: Factory-supplied liquid-line filter drier is required for installation.
Crankcase Heater: All sizes are equipped with a crankcase heater; required for refrigerant tubing longer than 80 ft (24.4 m) or when the outdoor unit is 20 ft (6.1 m) below the indoor unit.
Control Voltage: 24v AC, minimum 40va transformer capacity.
Winding Resistance (at 70°F +/- 20°F):
- 024 Unit: Start (S-C) 1.652 ohms, Run (R-C) 1.065 ohms
- 036 Unit: Start (S-C) 1.587 ohms, Run (R-C) 0.751 ohms
- 048 Unit: Start (S-C) 1.299 ohms, Run (R-C) 0.477 ohms
- 060 Unit: Start (S-C) 1.203 ohms, Run (R-C) 0.383 ohms
Compressor Solenoid: 24v DC, with an internal rectifier in the plug harness.

Usage Features:

2-Stage Operation: Provides enhanced comfort and energy efficiency by operating at partial capacity during mild conditions and full capacity during peak demand.
Thermidistat Compatibility: Designed to integrate with Thermidistat controls for advanced temperature and humidity management.
Quiet Operation: Installation recommendations emphasize locating the unit away from windows and patios to minimize sound disturbance. The "Quiet Shift-2" feature further reduces operational noise during defrost cycles.
Flexible Installation: Can be installed on a solid, level mounting pad or on a rooftop platform. Clearances for airflow, wiring, and service must be maintained.
Long-Line Applications: Specific accessories (e.g., Liquid-Line Solenoid Valve) and guidelines are provided for installations with long refrigerant tubing runs (greater than 80 ft or 24.38 m) or significant elevation differences (greater than ±20 ft or ±6.10 m).
Low Ambient Cooling: Requires specific accessories (e.g., compressor start assist, crankcase heater, evaporator freeze thermostat, hard shutoff TXV, isolation relay, low-ambient pressure switch) for cooling applications below 55°F (12.8°C).
Sea Coast Applications: Requires a hard shutoff TXV for installations within 2 miles (3.2 km) of the sea coast.

Maintenance Features:

Refrigerant Charge Check: The unit is factory charged for operation with 15 ft (4.57 m) of field-supplied or factory accessory tubing. Proper refrigerant charge is crucial for maximum efficiency and should be checked using the subcooling method under favorable conditions (outdoor temperature 70-100°F / 21.11-37.78°C, indoor temperature 70-80°F / 21.11-26.67°C).
Evacuation Procedure: Refrigerant tubes and indoor coil must be evacuated to 500 microns using the deep vacuum method to eliminate contamination and moisture.
Service Valves: Equipped with Schrader valves for easy access during service. Piston metering device in the liquid service valve is critical for proper heating operation.
Defrost Thermostat Check: Ensure the defrost thermostat is properly located and securely attached to the stub tube on the liquid header.
Periodic Maintenance: To ensure continuing high performance and minimize equipment failure, periodic maintenance is required. Frequency may vary based on geographic areas and should follow the guidelines in the User's Manual.
Troubleshooting: Winding resistance values are provided to diagnose compressor motor issues. The unit also features a 5-minute lockout timer on the defrost control board, initiated upon any power interruption, to protect the compressor.