24 Package AC

Updated on 01/04/26 by Mananjay MahatoShare on WhatsApp

Package Air Conditioners (PAC) are high-capacity systems where all major components (compressor, condenser, and evaporator) are housed within a single casing. These are commonly used for commercial spaces like banks, offices, and small halls.

1. Core Characteristics

  • Capacity Range: Generally available from 3 TR to 15 TR (Tons of Refrigeration).

  • All-in-One Design: Unlike split ACs, the entire refrigeration cycle happens inside one unit.

  • Factory Assembled: Built and tested in the factory; requires minimal field piping, reducing refrigerant leakage risks.

  • Mounting: Can be floor-mounted (vertical) or ceiling-suspended (horizontal).

2. Major Components & Operation

  • Compressor: Usually high-capacity Hermetic or Semi-hermetic reciprocating types; modern units use Scroll compressors for better efficiency.

  • Condenser Types:

    • Air-Cooled: Uses a propeller fan to discharge heat. Common in 3, 5, and 7.5 TR units.

    • Water-Cooled: Uses a Shell and Tube or Shell and Coil heat exchanger. Requires a cooling tower and pump. More efficient than air-cooled.

  • Expansion Device: Primarily uses a Thermostatic Expansion Valve (TEV) for precise refrigerant flow control.

  • Evaporator: Finned-tube cooling coil with a high-static centrifugal blower to push air through ductwork.

3. Working Principle

  1. Suction: The compressor pulls low-pressure refrigerant vapor from the evaporator.

  2. Compression: Vapor is compressed to high pressure/temperature.

  3. Condensation: Heat is rejected to the outside air (Air-cooled) or water (Water-cooled), turning refrigerant into liquid.

  4. Expansion: TEV reduces pressure, causing a temperature drop.

  5. Cooling: The evaporator coil absorbs heat from the room air. The Centrifugal Blower circulates this treated air through ducts.

4. Key Technical Facts for DRDO/ISRO

Feature Detail
Refrigerants Commonly R-22 (older), R-410A, or R-32.
Air Distribution Uses Ducting to distribute air to multiple points or a single large hall.
Blower Type Centrifugal (Didw/Sisw) to overcome static pressure of ducts.
Control Uses a LP/HP Cut-out switch and a solenoid valve for safety.
Power Supply Usually requires 3-Phase, 415V supply due to high motor loads.

5. Advantages & Disadvantages

  • Pros: * Easy installation (Plug and Play).

    • No long refrigerant piping needed.

    • Lower initial cost compared to Central Plants.

  • Cons: * Noisy (compressor is inside or near the conditioned space).

    • If the unit fails, the entire area loses cooling.

    • Limited duct length compared to AHUs.

6. Maintenance Checklist

  • Filter Cleaning: Washable HDPE filters should be cleaned every 15 days.

  • Belt Tension: Check the blower V-belt tension to avoid slipping or bearing wear.

  • Refrigerant Charge: Check “Sight Glass” for bubbles (indicates low charge).

  • Condenser Descaling: Essential for water-cooled units to maintain heat transfer.

24 Package AC