Lennox HS21 Series - User Manual

The Lennox HS21 Series Units are high-efficiency residential split-system condensing units featuring a two-speed compressor. These units are available in sizes ranging from 3 to 5 tons, in either single or three-phase configurations. They incorporate solid-state two-speed control, which regulates compressor speed based on thermostat demand. The HS21 is designed for use with an expansion valve at the indoor coil.

Function Description:

The HS21 units provide cooling by operating a two-speed compressor. The solid-state control system automatically switches between low and high speed operation based on thermostat demand. This allows for efficient cooling and dehumidification. The system includes various safety features such as high and low-pressure switches and compressor over-temperature sensing to protect the unit.

Important Technical Specifications:

Early Model Units (HS21-411, -511, -651):

Condenser Coil:
- Face Area: 21.64/20.81 sq.ft. (HS21-411/413, HS21-511/513), 23.92/23.01 sq.ft. (HS21-651/653)
- Tube Diameter: 3/8 in.
- No. of Rows: 2
- Fins per Inch: 20
Condenser Fan:
- Diameter: 24 in. (HS21-411/413, HS21-511/513), 24 in. (HS21-651/653)
- No. of Blades: 3 (HS21-411/413, HS21-511/513), 4 (HS21-651/653)
- Motor hp: 1/6 (HS21-411/413, HS21-511/513), 1/4 (HS21-651/653)
- Cfm: 3200 (HS21-411/413, HS21-511/513), 4200 (HS21-651/653)
- Rpm: 815 (HS21-411/413, HS21-511/513), 815 (HS21-651/653)
- Watts: 170 (HS21-411/413, HS21-511/513), 310 (HS21-651/653)
Refrigerant Charge (HCFC-22): 11 lbs. 6 oz. (HS21-411/413), 11 lbs. 14 oz. (HS21-511/513), 13 lbs. 14 oz. (HS21-651/653)
Liquid Line Connection (sweat): 3/8 in.
Suction Line Connection (sweat): 7/8 in. (HS21-411/413, HS21-511/513), 1-1/8 in. (HS21-651/653)
Electrical Data (208/230V, 60Hz):
- Rated Load Amps: 17.6 (HS21-411), 12.7 (HS21-413), 21.6 (HS21-511), 15.8 (HS21-513), 30.8 (HS21-651), 19.9 (HS21-653)
- Max Fuse or Circuit Breaker Size: 40A (HS21-411), 25A (HS21-413), 45A (HS21-511), 35A (HS21-513), 60A (HS21-651), 45A (HS21-653)
- Minimum Circuit Ampacity: 23.0 (HS21-411), 16.9 (HS21-413), 28.0 (HS21-511), 20.8 (HS21-513), 40.2 (HS21-651), 26.6 (HS21-653)

Late Model Units (HS21-036, -048, -060):

Nominal Tonnage: 3 (HS21-036), 4 (HS21-048), 5 (HS21-060)
Liquid Line Connection (sweat): 3/8 in. (9.5 mm)
Suction Line Connection (sweat): 7/8 in. (22.2 mm) (HS21-036, HS21-048), 1-1/8 in. (28.5 mm) (HS21-060)
Condenser Coil:
- Net Face Area (Outer/Inner): 21.77/21.11 sq.ft. (2.02/1.96 m²) (HS21-036, HS21-048), 24.06/23.33 sq.ft. (2.24/2.17 m²) (HS21-060)
- Tube Diameter & No. of Rows: 5/16 in. (7.9 mm) - 2
- Fins per Inch: 22 (866)
Condenser Fan:
- Diameter & No. of Blades: 24 in. (610 mm) - 3 (HS21-036, HS21-048), 24 in. (610 mm) - 4 (HS21-060)
- Motor hp: 1/6 (124) (HS21-036, HS21-048), 1/4 (187) (HS21-060)
- Cfm (L/s): 3200 (1510) (HS21-036, HS21-048), 4200 (1980) (HS21-060)
- Rpm: 815 (HS21-036, HS21-048), 815 (HS21-060)
- Watts: 170 (HS21-036, HS21-048), 310 (HS21-060)
Refrigerant Charge (HCFC-22): 10 lbs. 13 oz. (4.90 kg) (HS21-036), 11 lbs. 3 oz. (5.07 kg) (HS21-048), 12 lbs. 7 oz. (5.64 kg) (HS21-060)
Shipping Weight (1 package): 328 lbs. (149 kg) (HS21-036), 329 lbs. (149 kg) (HS21-048), 352 lbs. (160 kg) (HS21-060)
Electrical Data (208/230V, 60Hz):
- Rec. Max Fuse/Circuit Breaker Size: 40A (HS21-036 1ph), 25A (HS21-036 3ph), 45A (HS21-048 1ph), 35A (HS21-048 3ph), 60A (HS21-060 1ph), 45A (HS21-060 3ph)
- Minimum Circuit Ampacity: 23.0 (HS21-036 1ph), 16.9 (HS21-036 3ph), 28.0 (HS21-048 1ph), 20.8 (HS21-048 3ph), 40.2 (HS21-060 1ph), 26.6 (HS21-060 3ph)

Usage Features:

Two-Speed Control (TSC5 A14): This Lennox-built control provides automatic switching between low and high speed operation. It includes safety timed-off delays, compressor over-temperature sensing, and unit fault condition tracking. A manual override button allows bypassing the five-minute delay for servicing. Diagnostic LEDs (D1, D2, D4, D8) display problem codes.
Compressor: All compressors are rated at 208/230 VAC, single or three-phase, and equipped with internal pressure relief valves (450±50 psig).
Crankcase Heater (HR1): A self-regulating, well-mounted 40-watt heater is used on all models, operating only when demand is satisfied.
Outdoor Fan Motor (B4): Controlled by the compressor contactor K1 (single-phase) or relay K10 (three-phase).
Low Pressure Switch (S87): SPST N.C. switch on the compressor suction line, opens below 25±5 psig, automatically resets above 55±5 psig. Wired in series with high pressure switch S4.
High Pressure Limit Switch (S4): SPST N.C. switch on the compressor discharge line, opens above 410±10 psig, requires manual reset. Wired in series with low pressure switch S87.
Optional Equipment:
- CCB1 EfficiencyPlus™ Humidity Control (A20): Controls humidity by automatically adjusting compressor and indoor blower speed.
- EBR1 Blower Relay Kit (A51): Provides varying indoor blower speeds for multi-tap motors when used with EfficiencyPlus and a two-speed HS21, enhancing dehumidification.
- Room Thermostat (S1): Compatible with numerous types, 51H34 electromechanical thermostat recommended.
- Low Ambient Control Kit (LB-57113BC / 24H77): Enables operation down to 30°F (-1°C) when additional controls are needed (unit operates satisfactorily down to 45°F (7°C) without it).
Refrigerant System: Includes a discharge muffler to attenuate gas pulsations and a thermometer well for measuring liquid line temperature during charging. Full-service liquid and suction line valves are accessible for leak testing, evacuating, charging, and checking charge.
Charging: Units are factory-charged with HCFC-22. Charge adjustments are provided for varying line set lengths (up to 50 ft). The approach method (TXV systems) is used for charging, requiring accurate readings of ambient temperature, liquid temperature, and liquid pressure.

Maintenance Features:

Electrostatic Discharge (ESD) Precautions: Technicians are advised to take precautions to protect electronic controls during installation and service by neutralizing electrostatic charge.
Control Box: Located in the top front section of the unit, designed to be watertight with rubber washers on screws and foam-rubber weatherstrip along the top edge.
Seasonal Maintenance: At the beginning of each heating or cooling season, the system should be cleaned.
- Outdoor Unit: Clean and inspect condenser coil (can be flushed with water hose). Visually inspect all connecting lines, joints, and coils for oil leaks.
- Indoor Coil: Clean coil if necessary. Check connecting lines and coil for oil leaks. Check condensate line and clean if necessary.
- Indoor Unit: Clean or change filters. Adjust blower cooling speed. Check static pressure drop over coil. Check belt drive blowers (condition/tension). Check all wiring for loose connections. Check for correct voltage at unit. Check amp-draw on blower motor.
Evacuating the System: Critical for proper operation. Requires evacuation to absolute pressure of .92 inches of mercury (23 mm or 23,000 microns) initially, then to less than .0197 inches of mercury (.500 mm or 500 microns) after nitrogen purge. A temperature vacuum gauge, mercury vacuum (U-tube), or thermocouple gauge is recommended for accuracy.
Leak Testing: Involves pressurizing the line set and indoor coil to 150 psig (1034 kPa) with dry nitrogen and a small amount of refrigerant (if using an electronic leak detector) to check for leaks.