This document describes the installation, start-up, and service procedures for Carrier 50DPE014, 50DP016, and 50DP020 Single-Package Cooling Units.
Function Description:
These units are single-package cooling units designed for commercial and industrial applications. They are capable of providing cooling, heating (with optional electric heat), and ventilation air circulation. Some models are equipped with economizers for modulating outdoor air control, allowing for "free cooling" when outdoor air conditions are favorable. Certain units also feature variable volume air handling systems with electric unloaders on the compressor, controlled by a step controller, proportional thermostat, and 7-day timer to maintain desired temperatures and optimize energy usage.
Important Technical Specifications:
The units come in various sizes (50DPE014, 50DP016, 50DP020) with different operating weights, refrigerant charges, and electrical configurations.
- Refrigerant: R-22, with charges varying by system (e.g., 20.8 lb for 50DPE014, 21.2 lb for 50DP016, 17.0 lb for 50DP020).
- Compressor: Semi-hermetic, 6 cylinders. 50DPE014 and 50DP016 have 1 compressor, while 50DP020 has 2.
- Refrigerant Metering Device: Capillary tubes, with varying quantities and dimensions depending on the unit and circuit (upper/lower).
- Outdoor Coil: Copper tube, aluminum or copper plate fins, with 3 or 4 rows.
- Outdoor Air Fan: Propeller type, direct drive, with nominal Cfms ranging from 11,400 to 12,000.
- Indoor Coil: Copper tube, aluminum or copper plate fins, with 3 or 4 rows.
- Indoor Air Fan: Centrifugal, belt drive. Sizes vary (e.g., 2-10x10 for 50DPE014/50DP016, 2-12x12 for 50DP020). Nominal Cfms range from 5000 to 7200. Some units (50DPE014, 50DP016) have adjustable standard and alternate drives, while 50DP020 has fixed pulleys.
- High-Pressure Switch: Cutout at 428 psig, reset at 320 psig.
- Low-Pressure Switch (Liquid Line): Cutout at 27 psig, reset at 60 psig.
- Air Inlet Screens: Economizer models include 20x25x1 or 20x20x1 screens.
- Indoor Air Filters: 10% efficient disposable fiberglass filters, with various sizes and quantities (e.g., 2x20x20x2, 3x16x20x2, 2x16x25x2 for 50DPE014).
- Electrical Data: Units are available in 208/230-3-60, 460-3-60, and 575-3-60 voltage configurations. Minimum Circuit Amps (MCA) and Maximum Overcurrent Protection (MOCP) values are provided for each model and voltage.
- Air Quantity Limits: Minimum and maximum CFM values are specified for each unit model (e.g., 3750-6250 CFM for 50DPE014, 5400-9000 CFM for 50DP020).
Usage Features:
- Installation: Units can be supported by an accessory roof curb or alternate unit supports (sleepers or pads). Proper leveling (±1/16 in. per linear ft) is crucial for drain function. Ductwork can be connected through-the-bottom or concentrically.
- Condensate Drain: Requires a 3/4-in. connection and a trap at least 4 in. deep, protected against freeze-up.
- Electrical Connections: Field power supply and control wiring must comply with NEC and local codes. Voltage imbalance should not exceed 2% to avoid damage and warranty invalidation.
- Outdoor Air Inlet: Manual outdoor air dampers allow for up to 25% ventilation air. Optional economizers provide modulating outdoor air control based on enthalpy settings.
- Start-Up: Requires checking all installations, ensuring compressor hold-down bolts are secure, electrical connections are tight, and refrigerant service valves are open. Crankcase heaters must be energized for 24 hours prior to start-up.
- Operating Modes: Supports Cooling, Heating (with electric heat), Continuous Fan, and Automatic Changeover.
- Head Pressure Control: Fan cycling thermostats shut off one outdoor fan motor at 55°F, allowing operation down to 40°F outdoor air.
- Economizer Operation: In cooling mode, the economizer damper modulates based on outdoor air enthalpy and mixed air thermostat settings. A freeze protection thermostat (FPT) prevents ice buildup on the indoor coil.
- Variable Volume Units: These units feature a step controller with a 7-day timer and proportional thermostat for precise temperature control and compressor unloading. The 7-day timer allows for scheduled ON/OFF times.
Maintenance Features:
- General Cleaning: Inspect unit interior at the start of each heating and cooling season. Remove top and side panels for access.
- Coil Cleaning: Indoor coils should be cleaned with a commercial coil cleaner. Outdoor coils should be cleaned annually or as required, and inspected monthly.
- Condensate Drains: Check and clean annually at the start of the cooling season. Keep drains and traps dry in winter.
- Filters: Replace or clean indoor air filters at the start of each heating and cooling season, or more often as needed. Outdoor air inlet screens should be cleaned with steam or hot water and mild detergent.
- Lubrication: Compressors are factory-charged with oil. Fan shaft bearings are permanently lubricated. Fan motor bearings and indoor blower motors require cleaning and repacking with suitable grease annually after the first 5 years.
- Fan Adjustment: Indoor air fan speed can be adjusted by manipulating the movable pulley flange (for 50DPE014 and 50DP016). Belt tension should be checked and adjusted. Outdoor air fan height can be adjusted by loosening hub screws.
- Refrigerant Charge: Refer to unit nameplate and charging charts (Fig. 24, 25) for correct refrigerant amounts. Charging procedures involve evacuating the system and weighing in the specified amount, or adding refrigerant based on suction pressure and temperature readings.
- Economizer Adjustment: Involves setting enthalpy control, mixed air thermostat, and adjusting mechanical linkage for correct damper positioning.
- 50DP020 Indoor Air Fan Motor Removal: Detailed steps are provided for removing the motor and pulley assembly for maintenance.
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