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© 1994 Lennox Industries Inc.
Corp. 9434−L12
HP21
Service Literature
EARLY/LATE MODEL
Revised 07−2007
HP21 SERIES UNITS INCLUDING TSC−2, TSC−3 AND TSC-6
The HP21 is a high efficiency residential split-system heat
pump with a two-speed compressor. Early models include
HP21−411, −511 and −651. Late models built after March 1,
2000 include HP21−36, −48 and −60. All models are avail-
able in sizes ranging from 3 through 5 tons in either single
or three-phase configuration. Early and late models feature
solid-state two-speed control and new solid-state demand
defrost control. The two-speed control regulates compres-
sor speed in response to thermostat demand during
cooling mode. Compressor speed is regulated by outdoor
air temperature during heating mode. The defrost control
monitors outdoor air temperature and liquid line tempera-
ture to determine when defrost is needed. The series uses
conventional heat pump circuitry with expansion valves in
the outdoor and indoor units.
This manual is divided into sections which discuss the com-
ponents, refrigerant system, charging procedures,
maintenance and operation sequences. All specifications
in this manual are subject to change.
DANGER
Electric Shock Hazard.
May cause injury or death.
Line voltage is present at all compo-
nents when unit is not in operation on
units with single pole contactors.
Disconnect all remote electrical power
supplies before opening unit panel.
Unit may have multiple power supplies.
WARNING
Improper installation, adjustment, alteration, service
or maintenance can cause property damage, person-
al injury or loss of life. Installation and service must
be performed by a qualified installer or service
agency.
WARNING
Refrigerant can be harmful if it is inhaled. Refrigerant
must be used and recovered responsibly.
Failure to follow this warning may result in person-
al injury or death.
TABLE OF CONTENTS
General 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Specifications / Electrical 2. . . . . . . . . . . . . . . . . . . . . .
I Application 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
II Unit Components 3. . . . . . . . . . . . . . . . . . . . . . . . . . .
TSC−2 Control 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
TSC−3 Control 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
TSC−6 Control 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
III Refrigerant System 20. . . . . . . . . . . . . . . . . . . . . . . . .
IV Charging 23. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
V Maintenance 25. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
VI Miscellaneous 26. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
VII Wiring Diagrams and Operating Sequence 27. . . .
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