Lennox HP21 User Manual

Page 19
FIGURE 14
TO PLACE CONTROL IN TEST MODE:
1− Make sure all control terminals are connected as shown
on unit wiring diagram before attempting to place control
in test mode. See NOTE.
2− Turn indoor thermostat to heat mode and adjust to high-
est temperature setting.
NOTE − Control will not go into test mode when discon-
nected from unit. Unit load must be applied to control termi-
nals before the control will go into test mode.
3− With unit operating, momentarily short across TEST"
pins as shown.
4− LED should light and unit should operate in defrost mode
for at least 30 seconds or until normal termination.
5− To leave test mode, momentarily short across TEST"
terminals again.
WARNING − AVOID CONTACT WITH OTHER CONTROL
TERMINALS OR CONTROL COMPONENTS.
8− TEST" Pins
Each board is equipped with a set of test pins for use in
troubleshooting the unit. When momentarily shorted
together, these pins initiate a conventional defrost peri-
od. Because the defrost period was initiated by
momentarily shorting the two TEST" pins, the defrost
period must last a minimum of 30 seconds (see fig-
ure 14).
A defrost initiated by shorting the defrost pins together
can be terminated by shorting the defrost pins again.
Otherwise, defrost will be terminated as in normal op-
eration.
The defrost control continually self-tests its internal cir-
cuits. If an internal failure occurs, test mode will not
function and defrost LED will not light.
IMPORTANT − CONTROL WILL BEGIN TEST MODE
ONLY IF NORMAL LOAD IS APPLIED TO CONTROL
TERMINALS. DO NOT ATTEMPT TO OPERATE OR
TEST CONTROL OUT OF UNIT.
HP21−3 Units
HP21−3 units are equipped with a demand defrost system
which initiates a defrost cycle based on temperature differ-
ential and compressor run time. The control board includes
two permanently attached sensors which monitor coil and
outdoor ambient temperatures. The coil temperature sen-
sor is equipped with a spring clip which allows proper
positioning on the outdoor coil return bend. The ambient
temperature sensor is installed in a sampling tube at the
base of the unit. These sensors must not be detached from
the control board and must be replaced as part of the con-
trol board. Do not attempt to cut or splice the temperature
sensor wires.
Figure 15
CCWY ORR
Yout
CC
RV
C
AMB
COIL
SENSOR
CONNECTIONS
TEST
PINS
TERMINATION
TEMPERATURE
PINS
HP21−3 DEFROST CONTROL
Operation
When the reversing valve is de−energized, the Y1 circuit is
energized, and the coil temperature is below 35°F (2°C),
the board logs the compressor run time. When the unit is
initially started and the control is not calibrated, a defrost
cycle will be initiated after 34 minutes of heating mode com-
pressor run time. The control will terminate the defrost
cycle when the coil temperature rises above the preset ter-
mination temperature or after 14 minutes of defrost
operation. The termination temperature is factory set at
70°F. This setting may be adjusted in the field to 50°F
(10°C), 60°F (16°C), 70°F (21°C), or 80°F (27°C). The con-
trol will attempt to self−calibrate after this (and all other)
defrost cycle(s). Calibration success depends on stable
system temperatures during the 20−minute calibration peri-
od. If the board fails to calibrate, another defrost cycle will
be initiated after 34 minutes of heating mode compressor
run time. Once the defrost board is calibrated, it will use de-
mand defrost logic to initiate a defrost cycle. A demand
defrost system initiates defrost when the difference be-
tween the clear coil and frosted coil temperatures exceeds
the maximum difference allowed by the control.
If the control determines an ambient temperature sensor
failure and the coil temperature is 35°F (2°C) or lower, the
control will repeatedly initiate a defrost cycle after 34 min-
utes of heating mode compressor run time. If the control
determines that the coil temperature sensor has failed, the
control will not initiate a defrost cycle.
Test Mode
When Y1 is energized and 24V power is being applied to
the board, a test cycle (approximately 12 seconds) can be
initiated by placing the termination temperature jumper
across the Test" pins. If the jumper is applied to the test
pins before power is applied, or if the jumper is left across
the Test" pins longer than 5 minutes, the control will ignore
the test jumper and will revert to normal operation. The test
jumper will initiate continuous defrost cycles until the test
jumper is removed or the 5−minute test period ends.

Lennox HP21 Specifications

General

Brand	Lennox
Model	HP21
Category	Heat Pump
Language	English

Summary

SPECIFICATIONS

ELECTRICAL DATA

Presents detailed electrical specifications for various HP21 models.

I-APPLICATION

II-UNIT COMPONENTS

A-Control Transformer T19

Details the function of the control transformer in supplying 24VAC to unit controls.

B-Contactors K1 and K69

Explains the role of contactors K1 and K69 in energizing the compressor.

C-Defrost Relay K4

Describes the defrost relay's function in controlling defrost cycles.

D-Hard Start Relay K31 (single-phase only)

Explains the hard start relay's role in the compressor starting circuit.

E-Terminal Strip TB15

Details the low voltage terminal strip for thermostat wiring connections.

F-Compressor B1

Refers to compressor specifications and terminal box details.

G-Outdoor Fan Motor B4

Provides specifications for outdoor fans used in HP21 units.

H-High Pressure Limit S4

Describes the high pressure limit switch that interrupts unit operation.

I-Crankcase Thermostat S40

Explains the crankcase thermostat's role in monitoring compressor temperature.

J-Service Light Thermostat S54

Details the service light thermostat mounted on the compressor discharge line.

K-Start Capacitor C7

Explains the start capacitor's function in single-phase compressor startup.

L-Bleed Resistor R21

Describes the bleed resistor's purpose in discharging the start capacitor.

M-Run Capacitor C5

Details the run capacitor's role in maximizing motor efficiency.

N-Fan Capacitor C1

Explains the fan capacitor's requirement for single-phase PSC outdoor fan motors.

O-Dual Capacitor C12

Describes the dual capacitor used in late model single-phase units for motor efficiency.

P- Two-Speed Controls

Introduces two-speed controls, ESD precautions, and TSC-2.

III-REFRIGERANT SYSTEM

A-Field Piping

Details liquid and vapor line requirements for field refrigerant piping.

B-Unit Circuitry

Describes the conventional heat pump circuitry with check and expansion valves.

C-Reversing Valve

Explains the function of the reversing valve in directing refrigerant flow.

D-Strainer

Details the liquid line strainer's role in protecting the expansion valve.

E-Filter/Drier

Details the filter/drier's location and function in the system.

F-Expansion Valve

Explains the externally equalized thermal expansion valve used as the primary device.

G-Discharge Muffler

Locates the discharge muffler between the compressor and reversing valve.

H-Accumulator

Explains the suction line accumulator's location and purpose.

I-Thermometer Well

Describes the thermometer well for measuring liquid line temperature.

IV-CHARGING

C-Charging

Outlines procedures for charging the system with refrigerant.

V-MAINTENANCE

A-Heat Pump Unit

Details cleaning and inspection of the outdoor coil and fan.

B-Indoor Coil

Covers cleaning and inspection of indoor coils and lines.

C-Indoor Unit

Explains cleaning filters, inspecting coils, and checking blower.

VI-MISCELLANEOUS

HP21 CONTROL BOX WEATHERPROOFING

Details components and procedures for ensuring control box watertightness.

VII-WIRING DIAGRAMS AND OPERATION SEQUENCE

A-Field Wiring

Covers field wiring requirements and connection diagrams.

B-Operation Sequence - Compressor

Explains compressor startup sequences for single and three-phase motors.

C-SINGLE-PHASE STARTING SEQUENCE

Details the step-by-step starting sequence for single-phase compressors.

D-SINGLE-PHASE COMPRESSOR STARTUP

Describes single-phase compressor startup for low and high speed operation.

E-SINGLE-PHASE COOLING SEQUENCE

Outlines the sequence of operations during single-phase cooling mode.

F-SINGLE-PHASE HEATING SEQUENCE

Outlines the sequence of operations during single-phase heating mode.

G-SINGLE-PHASE DEFROST SEQUENCE

Details the defrost sequence for single-phase units.

H-THREE-PHASE STARTING SEQUENCE

Explains the starting sequence for three-phase compressors.

I-THREE-PHASE COMPRESSOR STARTUP

Describes three-phase compressor startup for low and high speed.

J-THREE-PHASE COOLING SEQUENCE

Outlines the sequence of operations during three-phase cooling mode.

K-THREE-PHASE HEATING SEQUENCE

Outlines the sequence of operations during three-phase heating mode.

L-THREE-PHASE DEFROST SEQUENCE

Details the defrost sequence for three-phase units.

HP21-2/-3 Wiring (Single Phase Units Shown)

HP21-2/-3 Wiring (Three Phase Units Shown)

HP21-4/-5 Wiring (Single Phase Units Shown)

HP21-4/-5 Wiring (Three Phase Units Shown)

HP21-36-230/60-230 Wiring SINGLE PHASE

HP21-36-233/60-233 Wiring

HP21-36-230 / 60-230-3 UNITS SINGLE PHASE OPERATION SEQUENCE

SINGLE-PHASE COOLING SEQUENCE

Details the cooling sequence for single-phase units with TSC control.

SINGLE-PHASE HEATING SEQUENCE

Details the heating sequence for single-phase units with TSC control.

DEFROST SEQUENCE

Explains the defrost sequence for single-phase units.

HP21-36-230 / 60-230-3 UNITS THREE PHASE OPERATION SEQUENCE

THREE-PHASE COOLING SEQUENCE

Details the cooling sequence for three-phase units with TSC control.

THREE-PHASE HEATING SEQUENCE

Details the heating sequence for three-phase units with TSC control.

DEFROST SEQUENCE

Explains the defrost sequence for three-phase units.

VIII-TROUBLESHOOTING FLOWCHARTS

TWO-SPEED CONTROL TROUBLESHOOTING FLOWCHART

Provides a flowchart to diagnose problems with the TSC control.

HP21 UNIT CONTROLS DIAGNOSTICS

Presents a diagnostic procedure for HP21 unit controls.

SERVICE NOTES