Lennox HPXA19 Unit Information

Corp. 0302−L2

Service Literature

Revised 07−2006

HPXA19 SERIES UNITS

The HPXA19 is a high efficiency residential split−system
heat pump unit, which features a two−step scroll compres­sor and R410A refrigerant. HPXA19 units are available in
2, 3 (−036 and −038 models), 4 and 5 ton sizes. The series
includes the HPXA19−038, a 3 ton unit equipped with a vari­able speed condenser fan motor. The series is designed for
use with an expansion valve only (approved for use with
R410A) in the indoor unit.This manual is divided into sec­tions which discuss the major components, refrigerant sys­tem, charging procedure, maintenance and operation se­quence.
Information contained in this manual is intended for use by
qualified service technicians only. All specifications are
subject to change.

IMPORTANT

Operating pressures of this R410A unit are higher
than pressures in R22 units. Always use service
equipment rated for R410A.

HPXA19

WARNING

Improper installation, adjustment, alteration, service
or maintenance can cause property damage, person­al injury or loss of life. Installation and service must
be performed by a qualified installer or service
agency.

IMPORTANT

The Clean Air Act of 1990 bans the intentional vent­ing of (CFC’s and HFC’s) as of July 1, 1992. Approved
methods of recovery, recycling or reclaiming must
be followed. Fines and/or incarceration my be levied
for noncompliance.

Table of Contents

General 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Specifications / Electrical Data 2. . . . . . . . . . . . . . . . . .

I Application 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

II Unit Components 3. . . . . . . . . . . . . . . . . . . . . . . . . . . .

III Refrigerant System 16. . . . . . . . . . . . . . . . . . . . . . . . . .

DANGER

Shock Hazard
Remove all power at disconnect be-

fore removing access panel.
HPXA19 units use single-pole con­tactors. Potential exists for electrical
shock resulting in injury or death.
Line voltage exists at all components
(even when unit is not in operation).

IV Charging 18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

V Service and Recovery 22. . . . . . . . . . . . . . . . . . . . . . . .

VI Maintenance 22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

VII Diagrams and Operating Sequence 23. . . . . . . . . . .

Page 1

© 2003 Lennox Industries Inc.

SPECIFICATIONS

p

g

Kit

g

General
Data

Connections
(sweat)

Refrigerant

Outdoor

Netfacearea sq. ft. (m2) − Outer Coil 16.04 (1.49) 16.04 (1.49) 24.06 (2.24) 24.06 (2.24) 24.06 (2.24)

Nominal Tonnage (kW) 2 (7.0)

Liquid line o.d. − in. (mm) 3/8 (9.5) 3/8 (9.5) 3/8 (9.5) 3/8 (9.5) 3/8 (9.5)

Vapor line o.d. − in. (mm) 7/8 (22.2)

1

Coil

Tubediameter − in. (mm) 5/16 (0.52) 5/16 (0.52) 5/16 (0.52) 5/16 (0.52) 5/16 (0.52)

Outdoor

Diameter in.(mm) and no. of blades 24 (610) − 3 24 (610) − 3 24 (610) − 4 24 (610) − 4 24 (610) − 4

Fan

Shipping Data − lbs. (kg) 1 package 261 (118) 262 (119) 316 (143) 318 (144) 340 (154)

Model No. HPXA19−024 HPXA19−036 HPXA19−038 HPXA19−048 HPXA19−060

3 (10.6) 3 (10.6) 4 (14.1) 5 (17.6)

7/8 (22.2) 7/8 (22.2) 7/8 (22.2) 1−1/8 (28.5)

R−410A furnished 10 lbs. 4 oz.

(4.65 kg)

Inner Coil 15.56 (1.45)

11 lbs. 0 oz.

(5.00 kg)

13 lbs. 15 oz.

(6.32 kg)

12 lbs. 14 oz.

(5.84 kg)

14 lbs. 6 oz.

(6.52 kg)

15.56 (1.45) 23.33 (2.17) 23.33 (2.17) 23.33 (2.17)

Number of rows 2 2 2 2 2

Fins per inch (m) 22 22 22 22 22

Motor hp (W) 1/10 (74.8)

Cfm (L/s) 3159 (1485) 3159 (1485) 3135 (1480) first−stage

Rpm 825 825 700 first−stage

Watts 170 170 105 first−stage

1/10 (74.8) 1/3 (249) 1/4 (187) 1/4 (187)

3600 (1700) second−stage

820 second−stage

150 second−stage

3900 (1840) 4200 (1980)

820 820

300 350

ELECTRICAL DATA

Electrical
Data

Compressor

Outdoor Coil
Fan Motor

3

Maximum overcurrent protection (amps) 20 35 40 45 60

Line voltage data − 60hz 208/230V−1ph 208/230V−1ph 208/230V−1ph 208/230V−1ph 208/230V−1ph

2

Minimum circuit ampacity 13.7 22.1 23.7 28.2 33.8

Rated load amps 10.3 16.7 16.7 21.2 25.7

Locked rotor amps 52 82 82 96 118

Power factor 0.99 0.98 0.98 0.99 0.99

Full load amps 0.8 0.8 2.8 1.7 1.7

Locked rotor amps 2

2 Not Applicable 3.1 3.1

OPTIONAL ACCESSORIES − MUST BE ORDERED EXTRA

Compressor Hard Start Kit Factory

Installed

Compressor Low Ambient Cut−off 45F08 45F08 45F08 45F08 45F08

Freezestat

3/8 in. tubing 93G35 93G35 93G35 93G35 93G35

1/2 in. tubing 39H29 39H29 39H29 39H29 39H29

5/8 in. tubing 50A93 50A93 50A93 50A93 50A93

3

Indoor Blower Speed Relay Kit 40K58 40K58 40K58 40K58 40K58

Low Ambient Kit 54M89 54M89 68M04 54M89 54M89

Mild Weather Kit 33M07 33M07 33M07 33M07 33M07

Monitor Kit − Service Light 76F53 76F53 76F53 76F53 76F53

Mounting
Base

Outdoor
Thermostat
Kit

Part No. − Catalog No. MB2−L (69J07) MB2−L (69J07) MB2−L (69J07) MB2−L (69J07) MB2−L (69J07)

Net Weight 15 lbs. (7 kg)

Thermostat 56A87 56A87 56A87 56A87 56A87

Mounting Box − US 31461

Canada 33A09 33A09 33A09 33A09 33A09

Refrigerant
Line Set

15 ft. (4.6 m) length L15−65−15 L15−65−15 L15−65−15 L15−65−15 Field Fabricate

30 ft. (9 m) length L15−65−30

40 ft. (12 m) length L15−65−40 L15−65−40 L15−65−40 L15−65−40 Field Fabricate

50 ft. (15 m) length L15−65−50 L15−65−50 L15−65−50 L15−65−50 Field Fabricate

SignatureStatt Programmable Thermostat 51M28 51M28 51M28 51M28 51M28

Time Delay Relay Kit 58M81 58M81 58M81 58M81 58M81

NOTE  Extremes of operating range are plus 10% and minus 5% of line voltage.

1

Refrigerant charge sufficient for 15 ft. (4.6 m) length of refrigerant lines.

2

Refer to National or Canadian Electrical Code manual to determine wire, fuse and disconnect size requirements.

3

HACR type breaker or fuse.

10J42 10J42 81J69 81J69

15 lbs. (7 kg) 15 lbs. (7 kg) 15 lbs. (7 kg) 15 lbs. (7 kg)

31461 31461 31461 31461

L15−65−30 L15−65−30 L15−65−30 Field Fabricate

Page 2

I−APPLICATION

All major components (indoor blower and coil) must be
matched according to Lennox recommendations for the
compressor to be covered under warranty. Refer to the En­gineering Handbook for approved system matchups. A
misapplied system will cause erratic operation and can re­sult in early compressor failure.

II−Unit Components

ELECTROSTATIC DISCHARGE (ESD)

Precautions and Procedures

CAUTION

Electrostatic discharge can affect electronic
components. Take precautions during unit instal­lation and service to protect the unit’s electronic
controls. Precautions will help to avoid control
exposure to electrostatic discharge by putting
the unit, the control and the technician at the
same electrostatic potential. Neutralize electro­static charge by touching hand and all tools on an
unpainted unit surface before performing any
service procedure.

A−Two−Stage Scroll Compressor (B1)

TWO−STAGE MODULATED SCROLL

slider ring

solenoid actuator coil

FIGURE 1

The scroll compressor design is simple, efficient and re­quires few moving parts. A cutaway diagram of the scroll
compressor is shown in figure 1.The scrolls are located in
the top of the compressor can and the motor is located just
below. The oil level is immediately below the motor.

The scroll is a simple compression concept centered
around the unique spiral shape of the scroll and its inherent
properties. Figure 2 shows the basic scroll form. Two iden­tical scrolls are mated together forming concentric spiral
shapes (figure 3). One scroll remains stationary, while the
other is allowed to orbit" (figure 4). Note that the orbiting
scroll does not rotate or turn but merely orbits" the station­ary scroll.

SCROLL FORM

FIGURE 2

CROSS−SECTION OF SCROLLS

DISCHARGE
PRESSURE

TIPS SEALED BY

DISCHARGE PRESSURE

DISCHARGE

STATIONARY

SCROLL

SUCTION

ORBITING SCROLL

FIGURE 3

The counterclockwise orbiting scroll draws gas into the out­er crescent shaped gas pocket created by the two scrolls
(figure 4 − 1). The centrifugal action of the orbiting scroll
seals off the flanks of the scrolls (figure 4 − 2). As the orbiting
motion continues, the gas is forced toward the center of the
scroll and the gas pocket becomes compressed (figure 4

−3). When the compressed gas reaches the center, it is dis­charged vertically into a chamber and discharge port in the
top of the compressor (figure1). The discharge pressure
forcing down on the top scroll helps seal off the upper and
lower edges (tips) of the scrolls (figure 3). During a single or­bit, several pockets of gas are compressed simultaneously
providing smooth continuous compression.

The scroll compressor is tolerant to the effects of liquid re­turn. If liquid enters the scrolls, the orbiting scroll is allowed
to separate from the stationary scroll. The liquid is worked
toward the center of the scroll and is discharged.
Due to its efficiency, the scroll compressor is capable of
drawing a much deeper vacuum than reciprocating com­pressors. Deep vacuum operation can cause internal fusite
arcing resulting in damaged internal parts and will result in
compressor failure. This type of damage can be detected
and will result in denial of warranty claims. The scroll com­pressor can be used to pump down refrigerant as long as
the pressure is not reduced below 7 psig.

NOTE − During operation, the head of a scroll compressor
may be hot since it is in constant contact with discharge
gas.

The scroll compressors in all HPXA19 model units are de­signed for use with R410A refrigerant and operation at high
pressures. Compressors are shipped from the factory with
3MA (32MMMA) P.O.E. oil. See electrical section in this
manual for compressor specifications.

Page 3

TWO−STAGE OPERATION

The two−stage scroll compressor operates like any stan-

dard scroll compressor with the exception the two−stage

compressor modulates between first stage (low capacity

approximately 67%) and second stage (high capacity).

Modulation occurs when gas is bypassed through bypass

ports (figure 5 bypass ports open) in the first suction pock-

et. This bypassing of gas allows the compressor to operate

on first stage (low capacity) if thermostat demand allows.

Indoor thermostat setting will determine first or second

HOW A SCROLL WORKS

MOVEMENT OF ORBIT

SUCTION

ORBITING

SUCTION

POCKET

SCROLL

stage operation. The compressor will operate on first−stage
until demand is satisfied or the indoor temperature reaches
the thermostat set point calling for second−stage.

Second−stage (high capacity) is achieved by blocking the
bypass ports (figure 5 bypass ports closed) with a slider
ring. The slider ring begins in the open position and is con­trolled by a 24VDC internal solenoid. On a Y2 call the inter-
nal solenoid closes the slider ring, blocking the bypass
ports and bringing the compressor to high capacity. Two−
stage modulation can occur during a single thermostat de­mand as the motor runs continuously while the compressor
modulates from first−stage to second− stage.

SUCTION

INTERMEDIATE

PRESSURE

GAS

CRESCENT

SHAPED GAS

POCKET

3

12

FLANKS

SUCTION

STATIONARY SCROLL

SEALED BY

CENTRIFUGAL

FORCE

SUCTION

4

HIGH

PRESSURE

GAS

FIGURE 4

TWO−STAGE MODULATION

Bypass Ports

Closed

High Capacity

DISCHARGE

POCKET

Bypass Ports

Open

Low Capacity

FIGURE 5

Page 4

INTERNAL SOLENOID (L34)

Procedure

The internal unloader solenoid controls the two−stage op­eration of the compressor by shifting a slide ring mecha­nism to open two by−pass ports in the first compression
pocket of the scrolls in the compressor. The internal sole­noid is activated by a 24 volt direct current solenoid coil.
The coil power requires 20VAC. The internal wires from the
solenoid in the compressor are routed to a 2 pin fusite con­nection on the side of the compressor shell. The external
electrical connection is made to the compressor with a
molded plug assembly. This plug contains a full wave recti­fier that converts 24 volt AC into 24 volt DC power to power
the unloader solenoid. Refer to unit diagram for internal cir­cuitry view of plug.

If it is suspect the unloader is not operating properly, check
the following

IMPORTANT

This performance check is ONLY valid on systems
that have clean indoor and outdoor coils, proper air­flow over coils, and correct system refrigerant
charge. All components in the system must be func­tioning proper to correctly perform compressor
modulation operational check. (Accurate measure­ments are critical to this test as indoor system load­ing and outdoor ambient can affect variations be­tween low and high capacity readings).

STEP 1 Confirm low to high capacity compressor
operation

Tools required

Refrigeration gauge set

Digital volt/amp meter

Electronic temperature thermometer

On-off toggle switch

1. Turn main power "OFF" to outdoor unit.

2. Adjust room thermostat set point above (heating op­eration on heat pump) or below (cooling operation) the
room temperature 5ºF.

3. Remove control access panel. Install refrigeration
gauges on unit. Attach the amp meter to the common
(black wire) wire of the compressor harness. Attach
thermometer to discharge line as close as possible to
the compressor.

4. Turn toggle switch "OFF" and install switch in series
with Y2 wire from room thermostat.

5. Cycle main power "ON."

6. Allow pressures and temperatures to stabilize be­fore taking any measured reading (may take up to 10
minutes).

NOTE − Block outdoor coil to maintain a minimum of 375
psig during testing).

7. Record all of the readings for the Y1 demand on
table 1.

8. Close switch to energize Y2 demand.

9. Allow pressures and temperatures to stabilize be­fore taking any measured reading (this may take up to
10 minutes).

10. Record all of the readings of Y2 demand on table

1.

NOTE − On new installations or installations that have
shut down for an extended period of time, if the com­pressor does not cycle from low stage to high stage on
the first attempt, it may be necessary to recycle the com­pressor back down to low stage and back up to high
stage a few times in order to get the bypass seals to
properly seat

Compare Y1 readings with Y2 readings in table 1. Some
readings should be higher, lower or the same. If the
readings follow what table 1 specifies, the compressor is
operating and shifting to high capacity as designed. If the
readings do not follow what table 1 specifies, continue to
step 2 to determine if problem is with external solenoid
plug power.

Page 5

TABLE 1

Compressor Operation

Unit Readings

Y1 −

1st-Stage

Expected Results

Compressor

Voltage Same
Amperage Higher

Condenser Fan motor

Amperage Same or Higher

Temperature

Ambient Same
Outdoor Coil Discharge Air Higher in Cooling

Lower in Heating

Compressor Discharge Line Higher
Indoor Return Air Same
Indoor Coil Discharge Air Lower in Cooling

Higher in Heating

Pressures

Suction (Vapor) Lower
Liquid Higher

Y2 −

2nd-Stage

STEP 2 Confirm DC voltage output on compressor
solenoid plug

A − Compressor solenoid plug WITH built in full wave−

rectifier (LSOM I) that converts 24 volt AC into 24 volt
DC power. See Table 1 for units equipped with the
LSOM I.

1. Shut power off to outdoor unit.

2. Supply 24 volts AC control voltage to the wire ends
of the full wave rectifier plug. Listen for a click" as the
solenoid is energized. See figure 6.

apply 24vac

meter

compressor

fusite

terminals

rectifier plug leads

solenoid fusite

terminals

compressor

FIGURE 6

3. Unplug the full wave rectifier plug from the fusite
connection on the compressor.

4. Turn the low voltage power back onto the unit. Sup­ply 24VAC to the wires of the full wave rectifier plug. Set
volt meter to DC volts and measure the DC voltage at
the female connector end of the full wave rectifier plug.
The DC voltage reading should be 1.5 to 3 volts lower
than the input voltage to the plug wire leads. (EX: Input
voltage is 24VAC output voltage is 22VDC).
See figure 7.

rectifier plug leads

apply 24vac

compressor

fusite

terminals

compressor

solenoid

fusite

terminals

meter

FIGURE 7

If the above checks verify that the solenoid plug is pro­viding power to cycle into high capacity operation, con­tinue to step 3 to determine if problem is with solenoid
coil in compressor

Page 6

STEP 3 Confirm internal unloader solenoid has prop­er resistance

1. Shut all power off to unit (main and low voltage)

2. Unplug the molded plug from the compressor sole­noid 2−pin fusite.

3. Using a volt meter set on the 200 ohm scale

Replace the Compressor under these conditions:

Bad Solenoid

a. Measure the resistance at the 2−pin fusite. The resist­ance should be 32 to 60 ohms depending on compressor
temperature. If no resist ancereplace compressor.

b. Measure the resistance from each fusite pin to
ground. There should not be continuity to ground. If so­lenoid coil is grounded, replace compressor.

Good Solenoid

a. Seals not shifting, replace compressor
b. Slider ring not shifting, replace compressor.

B−Contactor (K1)

The compressor is energized by a contactor located in the
control box. All XP19 units are single phase and use single−
pole contactors.

C−Low Pressure Switch (S87)

The XP19 is equipped with an auto−reset low pressure
switch which is located on the suction line. The switch shuts
off the compressor when the suction pressure falls below
the factory setting. This switch is ignored during the first 90
seconds of compressor start up, during defrost operation,
90 seconds after defrost operation, during test mode and
when the outdoor temperature drops below 15°F.

The switch closes when it is exposed to 55 psig and opens
at 25 psig. It is not adjustable.

D−High Pressure Switch (S4)

E−Capacitor (C12)

The compressor in XP19−024, −036, −048 and −060 units

use a permanent split capacitor (see unit wiring diagram).

The capacitor is located inside the unit control box. Ratings

are on capacitor side.

F−Condenser Fan with
Variable Speed Motor(B4)

The variable speed condenser fan motor (figure 14) used in all

units is a three-phase, electronically controlled d.c. brushless

motor (controller converts single phase a.c. to three phase

d.c.), with a permanent-magnet-type rotor, manufactured by

GE. Because this motor has a permanent magnet rotor it does

not need brushes like conventional D.C. motors. The motors

consist of a control module and motor . Internal components

are shown in figure 15. The stator windings are split into three

poles which are electrically connected to the controller. This ar-

rangement allows motor windings to be turned on and off in

sequence by the controller.

The controller is primarily an a.c. to d.c. converter. Con-

verted d.c. power is used to drive the motor. The control-

ler contains a microprocessor which monitors varying

conditions inside the motor (such as motor workload).

G−Contactor (K1)

The compressor is energized by a contactor located in the
control box. All HPXA19 units are single phase and use single−
pole contactors.

H−Low Pressure Switch (S87)

IMPORTANT

Pressure switch settings for R410A refrigerant will
be significantly higher than units with R22.

An auto-reset, single-pole/single-throw high pressure switch
is located in the liquid line. This switch shuts off the compres­sor when liquid line pressure rises above the factory setting.
The switch is normally closed and is permanently adjusted to
trip (open) at 640 +
ure 13 for switch location.

10 psi and close at 448 + 10 psi. See fig-

Page 7

The HPXA19 is equipped with an auto−reset low pressure
switch which is located on the suction line. The switch shuts
off the compressor when the suction pressure falls below
the factory setting. This switch is ignored during the first 90
seconds of compressor start up, during defrost operation,
90 seconds after defrost operation, during test mode and
when the outdoor temperature drops below 15°F.

The switch closes when it is exposed to 55 psig and opens
at 25 psig. It is not adjustable.

I−High Pressure Switch (S4)

IMPORTANT

Pressure switch settings for R410A refrigerant will
be significantly higher than units with R22.

An auto-reset, single-pole/single-throw high pressure switch
is located in the liquid line. This switch shuts off the compres­sor when liquid line pressure rises above the factory setting.
The switch is normally closed and is permanently adjusted to
trip (open) at 640 +
ure 13 for switch location.

J−Low Ambient Thermostat (S23)

Second−stage low ambient thermostat S23 (figure 8) is a
SPST thermostat located in the compressor compartment.
The control uses a cap-tube sensor to monitor the tempera­ture inside the compressor compartment. The cap-tube
sensor is coiled adjacent to the control.

Temperature Sensor

(Cap-Tube)

10 psi and close at 448 + 10 psi. See fig-

(Second−Stage)

Low Ambient Thermostat S23

Regional climatic conditions may require the control to be ad­justed to a different setting. The adjustment screw is located
on the control. A hole cut into the bottom shelf of the control
box provides access to the control from the compressor
compartment. See figure 9.

Adjusting Low Ambient Thermostat

Adjustment screw can be
reached by inserting a screw­driver through the slot in control
box.

Turn screw clockwise to increase

switchover temperature.

FIGURE 9

Figure 10 shows the adjustment range of the control. Turn
adjustment screw clockwise to raise the switchover tem­perature and counterclockwise to lower the switchover
temperature.

Low Ambient Thermostat

49

adjustment

screw

FIGURE 8

S23 continually monitors the temperature inside the com­pressor compartment. When compressor compartment
temperature drops below the control setpoint, the control
closes. When the control closes, the contacts shunt across
Y1 and Y2 inside the unit. When Y1 heating demand is
present and S23 is closed, the compressor will run in high
capacity. The compressor will operate in high capacity
mode anytime there is a Y1 heating call from indoor ther­mostat, until the units control box warms and S23 opens.

S23 has field adjustable setpoints. Temperature differential
(difference between cut-in and cut-out) is fixed and cannot
be adjusted. Table 2 shows S23 control setpoints. The con­trol is factory set to close at 40+
and reset at 50+

2°F on a temperature rise.

2°F on a temperature drop

TABLE 2

Control Setpoints

Low Ambient Thermostat

Adjustable Range

Cut-In

(Close on Temperature Drop)

Cut-Out

(Open on Temperature Rise)

Factory

Setting

40+2°F 37+2°F 55+2°F

50+2°F 47+2°F 65+2°F

Min. Max.

43

*40

37

55

FIGURE 10

K−Reversing Valve (L1)

A refrigerant reversing valve with an electromechanical so­lenoid is used to reverse refrigerant flow during unit opera­tion. The reversing valve is energized during cooling de­mand and during defrost.

L−Transformer (T46)

Transformer T46 is located in the control box and is ener­gized any time the compressor is operating.

M−Solenoid Relay (K195)

Relay K195 is N.O. SPDT relay located in the control box.
On a Y2 call K195−1 closes allowing AC voltage from
(T46) to the two pin full wave rectifier plug (D4).

N−Rectifier Plug (D4)

D4 is a molded assembly that plugs into the compressor.
On a Y2 call D4 converts 24 volts AC to 24 volts DC. The
DC voltage energizes solenoid L34, allowing the com­pressor to operate at full capacity.

Page 8

O−Discharge Line Thermostat (S5)

S5 is an automatic reset SPST N.C. switch which opens on
temperature rise. S5 is located on the discharge line and
wired in series with S4 high pressure switch on the defrost
control board. When discharge line temperature rises to

8°F the switch opens and shuts down the compres-

275° +
sor. The switch resets when discharge line temperature
drops to 225° +

11°F.

P−Dual Capacitor (C12)

The compressor and fan in HPXA19−024, −036, −048 and

−060 units use permanent split capacitor motors. A single
dual" capacitor is used for both the fan motor and the com­pressor (see unit wiring diagram). The two sides (fan and
compressor) of the capacitor have different mfd ratings and
may change with each compressor. The capacitor is located
inside the unit control box.

Q−Condenser Fan Motor (B4)

HPXA19−024, −036, −048 and −060 units use single−phase
PSC fan motors which require a run capacitor. The FAN"
side of the dual capacitor is used for this purpose. In all
units, the outdoor fan is controlled by the compressor con­tactor. See ELECTRICAL DATA and SPECIFICATIONS
section for more information. See figure 11 if condenser fan
motor replacement is necessary. Rain shield location is
critical on the condenser fan assembly. Two shields are
used in unison to prevent moisture from entering the motor
bearings. Installing the shields to close to the bearing hub
will create noise and may affect operation. Installing too far
away will allow moisture to enter the bearing, resulting in
motor failure. See figure 12.

"A" SEE TABLE 3

Condenser fan
and motor

FIGURE

11

TABLE 3

HPXA19 UNIT "A" DIM. + 1/8"

−024, −036 1 1/16"

−038

−048

−060

RAIN SHIELD LOCATION

(See figure 14 for HPXA19−038)

Critical Dimension

plastic

shield

fiber
shield

FIGURE 12

FAN
GUARD

Wiring

Drip loop

1 3/16"

1/4" (.250)

run capacitor

start capacitor

(−024 unit only)

system

operation monitor

defrost control

charge compensator
(−038 and −048 units)

TXV/check valve

discharge line

compressor terminal plug

vapor line

low pressure switch

discharge temperature

thermostat

HPXA19 PARTS ARRANGEMENT

outdoor fan

(variable speed

on 038 units)

contactor

vapor valve

and

gauge port

two−stage compressor

filter drier

high pressure switch

FIGURE 13

Page 9

R−Condenser Fan with
Variable Speed Motor(B4)
(−038 only)

The variable speed condenser fan motor (figure 14) used in all
HPXA19−038 units is a three-phase, electronically controlled
d.c. brushless motor (controller converts single phase a.c. to
three phase d.c.), with a permanent-magnet-type rotor,
manufactured by GE. Because this motor has a permanent
magnet rotor it does not need brushes like conventional D.C.
motors. The motors consist of a control module and motor .
Internal components are shown in figure 15. The stator wind­ings are split into three poles which are electrically connected
to the controller. This arrangement allows motor windings to be
turned on and off in sequence by the controller.

The controller is primarily an a.c. to d.c. converter. Con­verted d.c. power is used to drive the motor. The control­ler contains a microprocessor which monitors varying
conditions inside the motor (such as motor workload).

The controller uses sensing devices to know what position
the rotor is in at any given time. By sensing the position of
the rotor and then switching the motor windings on and off
in sequence, the rotor shaft turns the blower.

motor speed and allows the motor to compensate for varying
load conditions as sensed by the controller. In this case, the
controller monitors the static workload on the motor and var­ies motor rpm in order to maintain constant airflow (cfm).

Motor rpm is continually adjusted internally to maintain
constant static pressure against the fan blade. The control­ler monitors the static work load on the motor and motor
amp-draw to determine the amount of rpm adjustment.
Blower rpm is adjusted internally to maintain a constant
cfm. The amount of adjustment is determined by the incre­mental taps which are used and the amount of motor load­ing sensed internally. The motor constantly adjusts rpm to
maintain a specified cfm.

Initial Power Up

When line voltage is applied to the motor, there will be a
large inrush of power lasting less than 1/4 second. This in­rush charges a bank of DC filter capacitors inside the con­troller. If the disconnect switch is bounced when the discon­nect is closed, the disconnect contacts may become
welded. Try not to bounce the disconnect switch when ap­plying power to the unit.

VARIABLE SPEED CONDENSER FAN MOTOR

RED

YELLOW

BLACK

RED

BLUE

motor

control module

FIGURE 14

BLOWER MOTOR COMPONENTS

STATOR

(WINDINGS)

BEARING

OUTPUT

SHAFT

ROTOR

FIGURE 15

Internal Operation

The condenser fan motor is a variable speed motor with RPM
settings at 700 (Y1) and 820 (Y2). The variation in speed is
accomplished each time the controller switches a stator wind­ing (figure14) on and off, it is called a pulse." The length of
time each pulse stays on is called the pulse width." By vary­ing the pulse width the controller varies motor speed (called
pulse-width modulation"). This allows for precise control of

The DC filter capacitors inside the controller are connected
electrically to the speed tap wires. The capacitors take
approximately 5 minutes to discharge when the disconnect
is opened. For this reason it is necessary to wait at least 5
minutes after turning off power to the unit before attempting
to service motor.

DANGER

Disconnect power from unit and wait at
least five minutes to allow capacitors
to discharge before attempting to ser­vice motor. Failure to wait may cause
personal injury or death.

Motor Start-Up

At start-up, the motor may gently rock back and forth for a
moment. This is normal. During this time the electronic
controller is determining the exact position of the rotor.
Once the motor begins turning, the controller slowly
eases the motor up to speed (this is called soft-start").
The motor may take as long as 10-15 seconds to reach
full speed. If the motor does not reach 200rpm within 13
seconds, the motor shuts down. Then the motor will im­mediately attempt a restart. The shutdown feature pro­vides protection in case of a frozen bearing or blocked
fan blade. The motor may attempt to start eight times. If
the motor does not start after the eighth try, the controller
locks out. Reset controller by momentarily turning off
power to unit.

Page 10

Rain shield location is critical on the condenser fan assem­bly. Installing the shields to close to the bearing hub will
create noise and may affect operation. Installing too far
away will allow moisture to enter the bearing resulting in
motor failure. See figure 16 .

S−Filter Drier

A filter drier designed for all HPXA19 model units is factory

installed in the liquid line. The filter drier is designed to re-

move moisture and foreign matter, which can lead to com-

pressor failure.

RAIN SHIELD LOCATION

(−038 only)

3"

Critical

Dimension

plastic

shield

fiber
shield

FIGURE 16

Troubleshooting

If first or second stage thermostat call for cool is present
and the variable speed condenser fan motor does not ener­gize, check voltage at the breaker box. If voltage is present
do the following and reference figure 17.

1− Check for 240 volts between the compressor RED wi-

res.

2− Initiate a first stage call for cool. Check for 24 volts be-

tween the fan motor YELLOW wire and fan motor
BLACK wire.

3− Initiate a second stage call for cool. Check for 24 volts

between the fan motor YELLOW wire and fan motor
BLACK wire, then check for 24 volts between the fan
motor BLUE wire and fan motor BLACK.

4− Repeat steps 1 through 3 with a HEAT call.

Moisture and / or Acid Check

Because POE oils absorb moisture, the dryness of the

system must be verified any time the refrigerant sys-

tem is exposed to open air. A compressor oil sample

must be taken to determine if excessive moisture has been

introduced to the oil. Table 4 lists kits available from Lennox

to check POE oils.

If oil sample taken from a system that has been exposed to

open air does not test in the dry color range, the filter drier

MUST be replaced.

IMPORTANT

Replacement filter drier MUST be approved for
R410A refrigerant and POE application.

Foreign Matter Check

It is recommended that a liquid line filter drier be replaced

when the pressure drop across the filter drier is greater

than 4 psig.

T−Accumulator (HPXA19−060 only)

ALL 5 ton HPXA19 units are equipped with an accumulator.

The purpose of the accumulator is to trap and evaporate all

liquid refrigerant returning to the compressor.

1st Stage (low capacity − 700 rpm)

RED

B4

RED

YELLOW

BLUE

BLACK

common

Y1

Y2

240V

240V

24V

0V

24V

2nd Stage (High capacity − 820 rpm)

RED

B4

RED

YELLOW

BLUE

BLACK

common

Y1

Y2

240V

240V

24V

24V

24V

FIGURE 17

U−Charge Compensator

HPXA19−038 and −048 series units are equipped with a

charge compensator located in the vapor line between the

reversing valve and outdoor coil manifold. The compensa-

tor is used to collect and store excess refrigerant in the

heating mode. Figure 18 shows operation of the charge

compensator.

In heating mode, the vapor line passing through the charge

compensator tank is cooler than the liquid line. Excess re-

frigerant (condensed liquid) from the indoor coil is trapped

by the compensator. The vapor line is cooler than the liquid

line so liquid migrates from the liquid line to the compensa-

tor tank where it is stored. In cooling mode, the vapor line

passing through the charge compensator tank is hotter

than the liquid line. Stored liquid is boiled and forced back

into the liquid line for circulation.

Page 11

TABLE 4

KIT CONTENTS TUBE SHELF LIFE

10N46 − Refrigerant Analysis Checkmate−RT700

10N45 − Acid Test Tubes Checkmate−RT750A (three pack)

10N44 − Moisture Test Tubes

74N40 − Easy Oil Test Tubes

74N39 − Acid Test Kit Sporlan One Shot − TA−1

Checkmate − RT751 Tubes (three
pack)

Checkmate − RT752C Tubes (three
pack)

2 − 3 years @ room temperature. 3+
years refrigerated

6 − 12 months @ room temperature. 2
years refrigerated

2 − 3 years @ room temperature. 3+
years refrigerated

CHARGE COMPENSATOR OPERATION

COOLING MODE

Vapor Line

(To Outdoor Coil)

Compensator Tank

During cooling mode, the va­por line is hotter than the liq­uid line. Stored liquid is
heated (boiled) and forced
back into circulation.

Stored Liquid

To Liquid Line

To be Circulated

Through Indoor Coil

Vapor Line

(From Compressor Discharge Port)

HEATING MODE

Vapor Line

(From Outdoor Coil)

Compensator Tank

During heating mode, the va­por line is cooler than the liq­uid line. Excess refrigerant is
forced into the charge com­pensator where it condenses
and collects.

Excess Refrigerant

To be Condensed and Stored

as Liquid

Vapor Line

(To Compressor Suction Port)

FIGURE 18

V−Lennox System Operation Monitor (A132)

The Lennox system operation monitor (LSOM) is a 24 volt
powered module wired directly to the indoor unit . See diag­nostic module A132 on wiring diagram and figure 19. The
LSOM is located in the control box and is used to trouble
shoot problems in the system. The module has three LED’s
for troubleshooting: GREEN indicates power status, YEL­LOW indicates an abnormal condition and RED indicates
thermostat demand, but compressor not operating. See
table 5 for troubleshooting codes.

IMPORTANT

The LSOM is not a safety component and cannot
shut down or control the HPXA19. The LSOM is a
monitoring device only.

W−Crankcase Heater (HR1)

Compressors in all units are equipped with a 70 watt belly­band type crankcase heater. HR1 prevents liquid from ac­cumulating in the compressor. HR1 is controlled by the
crankcaseheater thermostat.

X− Crankcase heater Thermostat (S40)

Thermostat S40 controls the crankcase heater in all units.
S40 is located on the liquid line. When liquid line tempera­ture drops below 50° F the thermostat S40 closes energizing
HR1. The thermostat will open, de−energizing HR1 once liq­uid line temperature reaches 70° F .

System Operation Monitor

LE
D

Y

C

R

LED’s

FIGURE 19

Y−Defrost System

The demand defrost controller uses basic differential tem­perature means to detect when the system performs poor­ly because of ice build−up on the outdoor coil. The control­ler also uses self−calibrating" principles to calibrate itself
when the system starts and after every time the system
defrosts. The control board has the following compo­nents: defrost relays, anti−short cycle timed−off control,
pressure switch/safety control, 5−trip lockout circuit, test
mode pins, ambient and coil temperature sensors, field
selectable termination temperature pins, and a field low
voltage connection terminal strip. See figure 20.

The control monitors ambient temperature, outdoor coil
temperature and total run time to determine when a de­frost cycle is required. Two temperature probes are per­manently attached to the control. The coil temperature
probe is designed with a spring clip to allow mounting to
the outside coil tubing. The location of the coil sensor is
important for proper defrost operation. See figure 21 for
coil sensor location. The ambient temperature sensor is
located in the PVC tube next to the filter drier.

NOTE − The logic of the demand defrost board accurately
measures the performance of the system as frost accumu­lates on the outdoor coil. This typically will translate into
longer running time between defrost cycles as more frost
accumulates on the outdoor coil before the board initiates
defrost cycles.

Page 12

TABLE 5

System Operation Monitor LED Troubleshooting Codes

Status LED

Green Power" Module has power. 24VAC control power is present at the module terminal.

Red Trip"

Yellow Alert"

Flash Code 1
(Does not apply to heat
pump or to two−stage
split systems)

Yellow Alert"

Flash Code 2

Yellow Alert"

Flash Code 3

Yellow Alert"

Flash Code 4

Yellow Alert"

Flash Code 5

Status LED Description

Thermostat demand signal
Y1 is present, but the com­pressor is not running.
Heat pump only−Trip light will
be on during defrost board 5
minute delay with Y thermo­stat call.

Long Run Time

Compressor is running ex­tremely long run cycles

System Pressure Trip

Discharge or suction pres­sure out of limits or compres­sor overloaded

Short Cycling

Compressor is
running
only briefly

Locked Rotor

Open Circuit

Status LED Troubleshooting Information

1

Compressor protector is open.

2

Outdoor unit power disconnect is open.

3

Compressor circuit breaker or fuse(s) is open.

4

Broken wire or connector is not making contact.

5

Low pressure switch open if present in the system.

6

Compressor contactor has failed to close.

1

Low refrigerant charge.

2

Evaporator blower is not running.

3

Evaporator coil is frozen.

4

Faulty metering device.

5

Condenser coil is dirty

6

Liquid line restriction (filter drier blocked if present)

7

Thermostat is malfunctioning.

1

High head pressure.

2

Condenser coil poor air circulation (dirty, blocked, damaged).

3

Condenser fan is not running.

4

Return air duct has substantial leakage.

5

If low pressure switch is present, check Flash Code 1 information.

1

Thermostat demand signal is intermittent.

2

Time delay relay or control board is defective.

3

If high pressure switch is present, check Flash Code 2 information.

4

If low pressure switch is present, check Flash Code 1 information.

1

Run capacitor has failed.

2

Low line voltage (contact utility if voltage at disconnect is low).

3

Excessive liquid refrigerant in the compressor.

4

Compressor bearings are seized.

1

Outdoor unit power disconnect is open.

2

Unit circuit breaker or fuse(s) is open.

3

Unit contactor has failed to close.

4

High pressure switch is open and requires manual reset.

5

Open circuit in compressor supply wiring or connections.

6

Unusually long compressor protector reset time due to extreme ambient temperature.

7

Compressor windings are damaged.

1

Yellow Alert"

Flash Code 6

Yellow Alert"

Flash Code 7

Yellow Alert"

Flash Code 8

Yellow Alert"

Flash Code 9

Open Start Circuit

Current only in run circuit

Open Run Circuit

Current only in start circuit

Welded Contactor

Compressor always runs

Low Voltage

Control circuit < 17VAC

Run capacitor has failed.

2

Open circuit in compressor start wiring or connections.

3

Compressor start winding is damaged.

1

Open circ uit in compress or start wiring or connections.

2

Compressor start winding is damaged.

1

Compressor contactor failed to open.

2

Thermostat demand signal not connected to module.

1

Control circuit transformer is overloaded

2

Low line voltage (contact utility if voltage at disconnect is low.)

Flash code number corresponds to a number of LED flashes, followed by a pause, and then repeated.

TRIP and ALERT LEDs flashing at the same time indicates that the control circuit voltage is too low for operation.

Reset ALERT flash code by removing 24VAC power from monitor. Last ALERT flash code will display for 1 minute after monitor is powered on.

Page 13

Component Locations Will

Vary With Board Manufacture

pressure

switch
circuit

connections

reversing valve

connections

coil

sensor

COIL SENSOR LOCATION

HPXA19−036/−048/−060

Coil sensor should be on

the 5th hairpin from the

bottom on the outside loop.

HPXA19−024

Coil sensor should be on the

6th hairpin from the top on

the outside loop.

DELAY

Y2

FIGURE 20

HPXA19−038

Coil sensor should be on

the 8th hairpin down from

the top on the outside loop.

FIGURE 21

r

defrost board

test pins

diagnostic LEDs

24V terminal

strip connections

Y2

field select

temperature pins

ambient

sensor

The temperature probes cannot be removed from the con­trol. The control and the attached probes MUST be re­placed as a unit. Do not attempt to cut or splice probe wires.

Diagnostic LEDs

The defrost board uses two LEDs for diagnostics. The
LEDs flash a specific sequence according to the diagnos­tic condition. See table 6.

HI−PS/LO−PS Terminals

High pressure switch (S4) is factory wired into the defrost
board HI−PS terminals. When (S4) trips, the defrost board
will cycle off the compressor and the strike counter in the
board will count one strike.
Low pressure switch (S87) is factory wired into the defrost
board LO−PS terminals. When (S87) trips, the defrost
board will cycle off the compressor and the strike counter
in the board will count one strike.
(S87) is ignored during certain conditions:

 During the defrost cycle and 90 seconds after the

termination of defrost

 When the average ambient sensor temperature is

below 15 F (−9)

 For 90 seconds following the start up of the

compressor

 During "Test" mode

5−Strike Lockout Feature

 The internal control logic of the board counts the pres-

sure switch trips only while the Y1 (Input) line is active. If
a pressure switch opens and closes four times during a
Y1 (Input), the control logic will reset the pressure switch
trip counter to zero at the end of the Y1 (Input). If the
pressure switch opens for a fifth time during the current
Y1 (Input), the control will enter a lockout condition.

 The 5−strike pressure switch lockout condition can be

reset by cycling OFF the 24−volt power to the control
board or by shorting the TEST pins. All timer functions
(run times) will also be reset.

 If a pressure switch or discharge line thermostat switch

opens while the Y1 Out line is engaged, a 5−minute short
cycle will occur after the switch closes.

DELAY" Option

The defrost board has a field selectable function to reduce
occasional noise that may occur while the unit is cycling in
and out of defrost mode. When a jumper is installed on the
DELAY" pins, the compressor will cycle off for 30 seconds
going in and out of defrost mode.

NOTE − 30 second off cycle is not functional when
jumpering TEST" pins.

Page 14

LED 1 LED 2 Condition Possible Cause(s) Solution

prope

2

Improper refrigerant charge

pp , p

pp g p

leaks. Replace metering device

OFF OFF Power problem

ON ON Coil sensor problem

OFF ON Ambient sensor problem

FLASH FLASH Normal operation

ON OFF

ON FLASH

FLASH ON

ALTERNATING

FLASH

The demand defrost control board initiates a defrost cycle based on either frost detection or time.
Frost Detection − If the compressor runs longer than 34 minutes and the actual difference between the clear coil and frosted coil temperatures exceeds

the maximum difference allowed by the control, a defrost cycle will be initiated.

IMPORTANT − The demand defrost control board will allow a greater accumulation of frost and will initiate fewer defrost cycles than a time/temperature
defrost system.

Time − If 6 hours of heating mode compressor run time has elapsed since the last defrost cycle while the coil temperature remains below 35°F (2°C),
the demand defrost control will initiate a defrost cycle.

Actuation − 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. If the board is not calibrated, a defrost cycle will be initiated after 34 minutes of heating mode compressor run time. The control
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 period. If the board fails to calibrate, another defrost cycle will be initiated after 90 minutes of heating mode compressor run time. Once the
defrost board is calibrated, it will use demand defrost logic to initiate a defrost cycle. A demand defrost system initiates defrost when the difference be­tween the clear coil and frosted coil temperatures exceeds the maximum difference allowed by the control OR after 6 hours of heating mode compressor
run time has been logged since the last defrost cycle.

Termination − The defrost cycle ends when the coil temperature exceeds the termination temperature or after 14 minutes of defrost operation. If the
defrost is terminated by the 14−minute timer, another defrost cycle will be initiated after 34 minutes of run time.

Test Mode − When Y1 is energized and 24V power is being applied to the board, a test cycle can be initiated by placing the termination temperature
jumper across the Test" pins for 2 to 5 seconds. If the jumper remains across the Test" pins longer than 5 seconds, the control will ignore the test pins
and revert to normal operation. The jumper will initiate one cycle per test.

Operational Description

The defrost control board has three basic operational
modes: normal, defrost, and calibration.

The demand defrost board monitors the O line, to deter­mine the system operating mode (heat/cool), outdoor am­bient temperature, coil temperature (outdoor coil) and
compressor run time to determine when a defrost cycle is
required.

When a defrost cycle is initiated, the control energizes the
reversing valve solenoid and turns off the condenser fan.
The control will also put 24VAC on the W1 (auxiliary heat)
line. The unit will stay in this mode until either the coil sen­sor temperature is above the selected termination temper­ature, the defrost time of 14 minutes has been completed,
or the room thermostat demand cycle has been satisfied.
(If the temperature select shunt is not installed, the default
termination temperature will be 100°F.) If the room

ALTERNATING

FLASH

Normal Mode

Defrost Mode

TABLE 6

Defrost Control Board Diagnostic (5 strike)

1

No power (24V) to board terminals

R & C.

2

Board failure.

1

Coil temperature outside of sensor

range.

2

Faulty sensor wiring connections at

board or poor sensor contact on coil.

3

Sensor failure.

1

Ambient temperature outside of

sensor range.

2

Faulty sensor wiring connections at

board or sensor.

3

Sensor failure.

Unit operating normally or in standby
mode.

5−Strike pressure lockout
(Short test pins or reset
24V power to board to
override lockout)

Low pressure switch circuit
open during Y1 demand

High pressure switch or
discharge thermostat
switch circuit open during
Y1 demand

5−minute delay
(Jumper test pins to over­ride delay)

Demand Defrost Operation

1

Restricted air flow over indoor or

outdoor coil.

2

Im

3

tion.

4

Poor contact between coil sensor

and coil.

Thermostat demand for cooling or
heat pump operation. Unit operating
in 5−minute anti−short−cycle mode.

r refrigerant charge.

Improper metering device opera-

thermostat demand cycle terminates the cycle, the defrost
cycle will be held until the next room thermostat demand
cycle. If the coil sensor temperature is still below the se­lected termination temperature, the control will continue
the defrost cycle until the cycle is terminated in one of the
methods mentioned above. If a defrost is terminated by
time and the coil temperature did not remain above 35°F
(2°C) for 4 minutes, the control will go into the 34−minute
Time/Temperature mode.

The board is considered uncalibrated when power is ap­plied to the board, after cool mode operation, or if the coil
temperature exceeds the termination temperature when it
is in heat mode.

Calibration of the board occurs after a defrost cycle to en­sure that there is no ice on the coil. During calibration, the
temperature of both the coil and the ambient sensor are
measured to establish the temperature differential which is
required to allow a defrost cycle.

Page 15

1

Check control transformer power

(24V).

2

If power is available and LED(s) are

unlit, replace board and all sensors.

1

Sensor function will resume when
coil temperature is between −20°F
and 110°F.

2

Check sensor wiring connections at

board and sensor contact on coil.

3

Replace board and all sensors.

1

Sensor function will resume when
coil temperature is between −20°F
and 110°F.

2

Check sensor wiring connections at

board and sensor.

3

Replace board and all sensors.

None required.

1

Remove any blockages or restric-

tions. Check outdoor fan motor for
proper operation.

2

.

Check approach, superheat & sub-

cooling temperatures.

3

Check system pressures. Repair

4

Make sure that sensor is properly

positioned on coil and that firm con­tact is established. Refer to service
manual for proper placement.

None required.

Calibration Mode

.

Z−Start Capacitor (C7) −024 model only

All 2 ton HPXA19 units are equipped with a start capacitor
(C7). The capacitor is located in the control box and wired
in parallel with the compressor side of the dual capacitor.
C7 is de−energized by potential relay K31 when the com­pressor nears full speed.

AA−Potential Relay (K31) −024 model only

III−REFRIGERANT SYSTEM

Field refrigerant piping consists of liquid and vapor lines
from the outdoor unit (sweat connections). Use Lennox
L15 series line sets as shown in table 7.
Separate liquid and suction service ports are provided at
the service valves for connection of gauge manifold during
charging procedure. Figure 22 shows HPXA19 refrigerant
flow and gauge manifold connections.

All 2 ton HPXA19 units are equipped with potential relay
K31, which controls the operation of the starting circuit. The
relay is located inside the control box and is normally
closed when contactor K1 is de−energized. When K1 is en­ergized the compressor begins start up. K31 remains
closed closed during start up and capacitor C7 remains in
the circuit. When the compressor reaches 75% of its
speed, K31 is energized, de−energizing capacitor C7.

HPXA19 COOLING CYCLE

(Showing Gauge Manifold Connections)

OUTDOOR UNIT

DISTRIBUTOR

EXPANSION/

CHECK VALVE

LOW

PRESSURE

HIGH

PRESSURE

BIFLOW

FILTER / DRIER

MUFFLER

OUTDOOR

COIL

Model

−024,−
036

−038

−048

−060

Valve Field Size

Connections

Liquid

Line

3/8 in.

10 mm

3/8 in.

10 mm

3/8 in.

10 mm

3/8 in.

10 mm

REVERSING VALVE

Vapor

Line

7/8 in.

22 mm

7/8 in.

22 mm

1−1/8 in.

29 mm

1−1/8 in.

29 mm

TABLE 7

Recommended Line Set

Liquid

Line

3/8 in.

10 mm

3/8 in.

10 mm

3/8 in.

10 mm

3/8 in.

10 mm

DIRECTION OF REFRIGERANT FLOW.

REFRIGERANT WILL FLOW IN OPPOSITE

DIRECTION IN HEATING CYCLE.

Vapor

Line

7/8 in.

19 mm

15 ft. − 50 ft.

4.6 m − 15 m

7/8 in.

22 mm

7/8 in.

22 mm

15 ft. − 50 ft.

4.6 m − 15 m

15 ft. − 50 ft.

4.6 m − 15 m

1−1/8 in.

29 mm

NOTE − ARROWS INDICATE

INDOOR UNIT

Fabricated

L15

Line Sets

L15−65

L15−65

L15−65

Field

GAUGE MANIFOLD

TO

R410A

DRUM

LIQUID

LINE

SERVICE

PORT

COMPRESSOR

SUCTION
SERVICE

PORT

NOTE−Use gauge ports on vapor line valve and liquid valve for evacuating refrigerant lines
and indoor coil. Use suction gauge port to measure suction pressure during charging.

FIGURE 22

Page 16

VAPOR

LINE

VALV E

EXPANSION/CHECK

VALV E

INDOOR

COIL

A−Service Valves

IMPORTANT

Only use Allen wrenches of sufficient hardness
(50Rc − Rockwell Harness Scale min). Fully in­sert the wrench into the valve stem recess.
Service valve stems are factory torqued (from 9
ft lbs for small valves, to 25 ft lbs for large
valves) to prevent refrigerant loss during ship­ping and handling. Using an Allen wrench rated
at less than 50Rc risks rounding or breaking off
the wrench, or stripping the valve stem recess.

Access the liquid line and vapor line service valves (figures
23 and 24) and gauge ports are used for leak testing, eva­cuating, charging and checking charge. See table 8 for
torque requirements.

Each valve is equipped with a service port which has a fac­tory−installed Schrader valve. A service port cap protects
the Schrader valve from contamination and serves as the
primary leak seal.

TABLE 8

Part Recommended Torque

To Close Service Valve:

1 − Remove stem cap with an adjustable wrench.

2 − Using service wrench and hex head extension, turn

stem clockwise to seat valve. Tighten it firmly.

NOTE − Use a 3/16" hex head extension for liquid line
size.

3 − Replace stem cap. Tighten finger tight, then tighten an

additional 1/6 turn.

Vapor Line (Ball Type) Valve

Vapor line service valves function the same way as the oth­er valves, the difference is in the construction. These
valves are not rebuildable. If a valve has failed, you must
replace it. A ball valve valve is illustrated in figure 24.

The ball valve is equipped with a service port with a factory−
installed Schrader valve. A service port cap protects the
Schrader valve from contamination and assures a leak−
free seal.

Liquid Line Service Valve

(Valve Closed)

service

port cap

service port

Service valve cap 8 ft.− lb. 11 NM

Sheet metal screws 16 in.− lb. 2 NM

Machine screws #10 28 in.− lb. 3 NM

Compressor bolts 90 in.− lb. 10 NM

Gauge port seal cap 8 ft.− lb. 11 NM

IMPORTANT

Service valves are closed to the outdoor unit and
open to line set connections. Do not open the valves
until refrigerant lines have been leak tested and
evacuated. All precautions should be exercised to
keep the system free from dirt, moisture and air.

To Access Schrader Port:

1 − Remove service port cap with an adjustable wrench.
2 − Connect gauge to the service port.
3 − When testing is complete, replace service port cap.

Tighten finger tight, then an additional 1/6 turn.

To Open Service Valve:

1 − Remove stem cap with an adjustable wrench.
2 − Using service wrench and hex head extension, back

the stem out counterclockwise as far as it will go.

NOTE − Use a 3/16" hex head extension for liquid line
size.

3 − Replace stem cap and tighten it firmly. Tighten finger

tight, then tighten an additional 1/6 turn.

insert hex

wrench here

stem cap

Liquid Line Service Valve

(Valve Open)

service

port cap

schrader

valve

stem

cap

Service Port Is Open

To Line Set When Valve Is

Closed (Front Seated)

insert hex

wrench here

FIGURE 23

to

indoor coil

to outdoor coil

service port

to

indoor coil

to outdoor coil

(valve front seated)

Page 17

Vapor Line (Ball Type) Service Valve

(Valve Open)

To open: rotate stem counter-clockwise 90°.

Schrader

valve

service

port

field side

Use Adjustable Wrench

To close: rotate stem clockwise 90°.

service port

ball

(shown open)

cap

unit side

stem cap

stem

FIGURE 24

IV−CHARGING

Units are factory charged with the amount of R410A refrig­erant indicated on the unit rating plate. This charge is
based on a matching indoor coil and outdoor coil with 15 ft.
(4.6m) line set. For varying lengths of line set, refer to table
9 for refrigerant charge adjustment.

TABLE 9

Liquid Line Set

Diameter

3/8 in.

(10mm)

Ozs. per 5 ft. (grams per 1.5m) adjust

from 15 ft. (4.6m) line set*

3 ounces per 5 feet

(85g per 1.5m)

*If line length is greater than 15 ft. (4.6m), add this amount.
If line length is less than 15 ft. (4.6), subtract this amount.

A−Leak Testing

After the line set has been connected to the indoor and out­door units, the line set connections and indoor unit must be
checked for leaks.

WARNING

Refrigerant can be harmful if inhaled. Refrigerant
must be used and recovered responsibly. Failure
to follow this warning can lead to injury or death.

WARNING

Danger of explosion!
When using a high pressure gas such

as dry nitrogen to pressurize a refrig­erant or air conditioning system, use
a regulator that can control the pres­sure down to 1 or 2 psig (6.9 to 13.8
kPa).

WARNING

Fire, Explosion and Personal Safety
Hazard.
Failure to follow this warning could
result in damage, personal injury or
death.
Never use oxygen to pressurize or
purge refrigeration lines. Oxygen,
when exposed to a spark or open
flame, can cause damage by fire
and / or an explosion, that can re­sult in personal injury or death.

Using an Electronic Leak Detector

1 − Connect a cylinder of R410A to the center port of the

manifold gauge set.

2 − With both manifold valves closed, open the valve on

the R410A cylinder (vapor only).

3 − Open the high pressure side of the manifold to allow

the R410A into the line set and indoor unit. Weigh in a
trace amount of R410A . [A trace amount is a maximum
of 2 ounces (57 g) or 3 pounds (31 kPa) pressure.]
Close the valve on the R410A cylinder and the valve
on the high pressure side of the manifold gauge set.
Disconnect the R410A cylinder.

4 − Connect a cylinder of nitrogen with a pressure regulat-

ing valve to the center port of the manifold gauge set.

5 − Connect the manifold gauge set high pressure hose to

the vapor valve service port. (Normally, the high pres-

sure hose is connected to the liquid line port; however,
connecting it to the vapor port better protects the man­ifold gauge set from high pressure damage.)

6 − Adjust the nitrogen pressure to 150 psig (1034 kPa).

Open the valve on the high side of the manifold gauge
set which will pressurize line set and indoor unit.

7 − After a few minutes, open a refrigerant port to ensure

the refrigerant you added is adequate to be detected.
(Amounts of refrigerant will vary with line lengths.)
Check all joints for leaks. Purge nitrogen and R410A
mixture. Correct any leaks and recheck.

IMPORTANT

Leak detector must be capable of sensing HFC re­frigerant.

B−Evacuating

Evacuating the system of noncondensables is critical for
proper operation of the unit. Noncondensables are defined
as any gas that will not condense under temperatures and
pressures present during operation of an air conditioning
system. Noncondensables and water vapor combine with
refrigerant to produce substances that corrode copper pip­ing and compressor parts.

Page 18

IMPORTANT

Use a thermocouple or thermistor electronic vacuum
gauge that is calibrated in microns. Use an instrument
that reads from 50 microns to at least 23,000 microns.

1 − Connect the manifold gauge set to the service valve

ports as follows:

 low pressure gauge to vapor line service valve
 high pressure gauge to liquid line service valve

2 − Connect micron gauge.

3 − Connect the vacuum pump (with vacuum gauge) to the

center port of the manifold gauge set.

4 − Open both manifold valves and start vacuum pump.

5 − Evacuate the line set and indoor unit to an absolute

pressure of 23,000 microns (29.01 inches of mercu­ry). During the early stages of evacuation, it is desir­able to close the manifold gauge valve at least once to
determine if there is a rapid rise in absolute pressure.
A rapid rise in pressure indicates a relatively large leak.
If this occurs, repeat the leak testing procedure.

NOTE − The term absolute pressure means the total
actual pressure within a given volume or system,
above the absolute zero of pressure. Absolute pres­sure in a vacuum is equal to atmospheric pressure mi­nus vacuum pressure.

6 − When the absolute pressure reaches 23,000 microns

(29.01 inches of mercury), close the manifold gauge
valves, turn off the vacuum pump and disconnect the
manifold gauge center port hose from vacuum pump.
Attach the manifold center port hose to a nitrogen cylin­der with pressure regulator set to 150 psig (1034 kPa)
and purge the hose. Open the manifold gauge valves
to break the vacuum in the line set and indoor unit.
Close the manifold gauge valves.

WARNING

Danger of Equipment Damage.
Avoid deep vacuum operation. Do not use com­pressors to evacuate a system.
Extremely low vacuums can cause internal arcing
and compressor failure.
Damage caused by deep vacuum operation will
void warranty.

7 − Shut off the nitrogen cylinder and remove the manifold

gauge hose from the cylinder. Open the manifold
gauge valves to release the nitrogen from the line set
and indoor unit.

8 − Reconnect the manifold gauge to the vacuum pump,

turn the pump on, and continue to evacuate the line set
and indoor unit until the absolute pressure does not
rise above 500 microns (29.9 inches of mercury) within
a 20−minute period after shutting off the vacuum pump
and closing the manifold gauge valves.

9 − When the absolute pressure requirement above has

been met, disconnect the manifold hose from the vacu­um pump and connect it to an upright cylinder of R410A
refrigerant. Open the manifold gauge valves to break
the vacuum from 1 to 2 psig positive pressure in the line
set and indoor unit. Close manifold gauge valves and
shut off the R410A cylinder and remove the manifold
gauge set.

C−Charging

This system is charged with R410A refrigerant which oper­ates at much higher pressures than R22. The check/ex­pansion valve provided with the unit is approved for use
with R410A. Do not replace it with a valve designed for use
with R22. This unit is NOT approved for use with coils which
include metering orifices or capillary tubes.

Processing Procedure

The unit is factory−charged with the amount of R410A re­frigerant indicated on the unit rating plate. This charge is
based on a matching indoor coil and outdoor coil with a 15
foot (4.6m) line set. For varying lengths of line set, refer to
table 9 for refrigerant charge adjustment. .

IMPORTANT

Mineral oils are not compatible with R410A. If oil
must be added, it must be a polyol ester oil.

It is desirable to charge the system in the cooling cycle if
weather conditions permit. However, if the unit must be
charged in the heating season, one of the following proce­dures must be followed to ensure proper system charge.

Weighing in the Charge TXV Systems –

Outdoor Temp. < 65F (18C)

If the system is void of refrigerant, or if the outdoor ambient
temperature is cool, the refrigerant charge should be
weighed into the unit. Do this after any leaks have been re­paired.

1 − Recover the refrigerant from the unit.
2 − Conduct a leak check, then evacuate as previously

outlined.
3 − Weigh in the unit nameplate charge.
If weighing facilities are not available or if you are charging

the unit during warm weather, follow one of the other proce­dures outlined below.

Subcooling Method

Outdoor Temp. < 65°F (18°C)

When the outdoor ambient temperature is below 65°F
(18°C), use the subcooling method to charge the unit. It
may be necessary to restrict the air flow through the out­door coil to achieve pressures in the 325−375 psig
(2240−2585 kPa) range. These higher pressures are nec­essary for checking the charge. Block equal sections of air
intake panels and move obstructions sideways until the liq­uid pressure is in the 325−375 psig (2240−2585 kPa) range.
Figure 25 shows a four sided unit for example..

Page 19

Blocking Outdoor Coil

Outdoor coil should be

blocked one side

at a time with cardboard

or plastic sheet until proper

testing pressures

are reached.

cardboard or
plastic sheet

FIGURE 25

1 − With the manifold gauge hose still on the liquid service

port and the unit operating stably, use a digital ther-

mometer to record the liquid line temperature.

2 − At the same time, record the liquid line pressure reading.

3 − Use a temperature/pressure chart for R410A to deter-

mine the saturation temperature for the liquid line pres-

sure reading. See table 14.

4 − Subtract the liquid line temperature from the saturation

temperature (according to the chart) to determine sub-

cooling. (Saturation temperature − Liquid line tem-

perature = Subcooling)

5 − Compare the subcooling value with those in table 10. If

subcooling is greater than shown, recover some refrig-

erant. If subcooling is less than shown, add some re-

frigerant. Be aware of the R410A refrigerant cylinder. It

will be light maroon−colored. Refrigerant should be

added through the vapor line valve in the liquid state.

Some R410A cylinders are equipped with a dip

tube that allows you to draw liquid refrigerant from

the bottom of the cylinder without turning the cyl-

inder upside−down. The cylinder will be marked if it

is equipped with a dip tube.

TABLE 10

2nd stage High Capacity

Model Number

HPXA19−024 11.0 + 1 (6 + .5)

HPXA19−036 8.5 + 1 (4.7 + .5)

HPXA19−038 10.5 + 1 (5.8 + .5)

HPXA19−048 7.5 + 1 (4.1 + .5)

HPXA19−060 7.0 + 1 (3.9 + .5)

Conversion Temp. − Liquid Line Temp. °F (°C)

Subcooling Values

Charging Using Normal Operating Pressures

and the Approach Method

Outdoor Temp. >

The following procedure is intended as a general guide and
is for use on expansion valve systems only. For best results,
indoor temperature should be 70°F (21°C) to 80°F (26°C).
Monitor system pressures while charging.

1 − Record outdoor ambient temperature using a digital

thermometer.

2 − Attach high pressure gauge set and operate unit for

several minutes to allow system pressures to stabilize.

3 − Compare stabilized pressures with those provided in

tables 12 and 13, Normal Operating Pressures." Mi­nor variations in these pressures may be expected due
to differences in installations. Significant differences
could mean that the system is not properly charged or
that a problem exists with some component in the sys­tem. Pressures higher than those listed indicate that
the system is overcharged. Pressures lower than
those listed indicate that the system is undercharged.
Verify adjusted charge using the approach method.

Approach Method

4 − Use the same digital thermometer used to check out-

door ambient temperature to check liquid line tempera­ture. Verify the unit charge using the approach method.

5 − The difference between the ambient and liquid temper-

atures should match values given in table 11. If the val­ues don’t agree with the those in table 11, add refriger­ant to lower the approach temperature or recover re­frigerant from the system to increase the approach
temperature.

TABLE 11

2nd Stage High Capacity

Model Number

HPXA19−024 4.0 + 1 (2.2 + .5)

HPXA19−036 7.0 + 1 (3.9 + .5)

HPXA19−038 4.0 + 1 (2.2 + .5)

HPXA19−048 8.0 + 1 (4.4 + .5)

HPXA19−060 10.0 + 1 (5.6 + .5)

Liquid Line Temp. − Outdoor Ambient °F (°C)

65F (18C)

Approach Temperature

IMPORTANT

Use table 12 and table 13 as a general guide when
performing maintenance checks. This is not a proce­dure for charging the unit (Refer to Charging/Check­ing Charge section). Minor variations in these pres­sures may be expected due to differences in installa­tions. Significant differences could mean that the
system is not properly charged or that a problem ex­ists with some component in the system.

Page 20

NORMAL OPERATING PRESSURES

Outdoor Coil

)

Outdoor Coil

p

)

Coil

Coil

(Liquid ±10 and Vapor ±5 psig)

Outdoor Coil

Entering Air

Temp. °F (°C

65 (18.3) 217 143 227

75 (23.9) 250 145 262

85 (29.4) 291 147 305

95 (35.0) 336 149 352

105 (40.6) 386 151 403

115 (49.0) 440 153 458

HPXA19−024 HPXA19−036 HPXA19−038 HPXA19−048 HPXA19−060

Liquid Vapor Liquid

Second Stage (High Capacity)

Outdoor Coil

Entering Air
Tem

65 (18.3) 222 143 244

75 (23.9) 256 145 282

85 (29.4) 302 145 325

95 (35.0) 349 147 377

105 (40.6) 403 149 428

115 (49.0) 464 152 488

. °F (°C

HPXA19−024 HPXA19−036 HPXA19−038 HPXA19−048 HPXA19−060

Liquid Vapor Liquid

TABLE 12

COOLING OPERATION

First Stage (Low Capacity)

Vapor

142

145

146

148

152

155

Vapor

136

139

142

144

146

148

Liquid Vapor Liquid Vapor Liquid Vapor

222 142 222 140 225 140

255 145 258 143 259 142

295 146 298 145 293 146

343 148 343 147 356 147

390 153 402 147 408 147

446 156 452 152 455 151

Liquid Vapor Liquid Vapor Liquid Vapor

231 133 232 134 249 126

263 139 266 136 289 134

305 142 309 139 330 140

354 145 359 142 378 143

403 147 410 144 433 146

461 149 468 147 492 149

Outdoor

Coil

Entering

Air

40 (4.4) 321 99 296

50 (10) 340 120 310

Outdoor

Entering

Air Temp.

20 (−7.0) 273 68 277

30 (−1.0) 296 80 296

40 (4.4) 321 95 321

50 (10) 341 11 5 341

HPXA19−024 HPXA19−036 HPXA19−038 HPXA19−048 HPXA19−060

Liquid Vapor Liquid

HPXA19−024 HPXA19−036 HPXA19−038 HPXA19−048 HPXA19−060

Liquid Vapor Liquid

TABLE 13

NORMAL OPERATING PRESSURES

HEATING OPERATION

(Liquid ±10 and Vapor ±5 psig)

First Stage (Low Capacity)

Vapor

95

112

Liquid Vapor Liquid Vapor Liquid Vapor

308 97 315 97 319 93

323 116 330 114 335 111

Second Stage (High Capacity)

Vapor

60

74

88

104

Liquid Vapor Liquid Vapor Liquid Vapor

288 59 294 60 300 57

308 74 303 75 312 70

316 90 314 90 323 83

330 108 325 106 339 97

Page 21

Table 14

R410A Temperature/Pressure Chart

Temperature°FPressure

Psig

32 100.8 63 178.5 94 290.8 125 445.9
33 102.9 64 181.6 95 295.1 126 451.8

34 105.0 65 184.3 96 299.4 127 457.6

35 107.1 66 187.7 97 303.8 128 463.5

36 109.2 67 190.9 98 308.2 129 469.5

37 111.4 68 194.1 99 312.7 130 475.6

38 113.6 69 197.3 100 317.2 131 481.6

39 115.8 70 200.6 101 321.8 132 487.8

40 118.0 71 203.9 102 326.4 133 494.0

41 120.3 72 207.2 103 331.0 134 500.2

42 122.6 73 210.6 104 335.7 135 506.5

43 125.0 74 214.0 105 340.5 136 512.9

44 127.3 75 217.4 106 345.3 137 519.3

45 129.7 76 220.9 107 350.1 138 525.8

46 132.2 77 224.4 108 355.0 139 532.4

47 134.6 78 228.0 109 360.0 140 539.0

48 137.1 79 231.6 110 365.0 141 545.6

49 139.6 80 235.3 111 370.0 142 552.3

50 142.2 81 239.0 112 375.1 143 559.1

51 144.8 82 242.7 113 380.2 144 565.9

52 147.4 83 246.5 114 385.4 145 572.8

53 150.1 84 250.3 115 390.7 146 579.8

54 152.8 85 254.1 116 396.0 147 586.8

55 155.5 86 258.0 117 401.3 148 593.8

56 158.2 87 262.0 118 406.7 149 601.0

57 161.0 88 266.0 119 412.2 150 608.1

58 163.9 89 270.0 120 417.7 151 615.4

59 166.7 90 274.1 121 423.2 152 622.7

60 169.6 91 278.2 122 428.8 153 630.1

61 172.6 92 282.3 123 434.5 154 637.5

62 195.5 93 286.5 124 440.2 155 645.0

Temperature°FPressure

Psig

Temperature°FPressure

Psig

Temperature°FPressure

Psig

Page 22

V−SERVICE AND RECOVERY

VI−MAINTENANCE

WARNING

WARNING

Polyol ester (POE) oils used with R410A refrigerant
absorb moisture very quickly. It is very important
that the refrigerant system be kept closed as much
as possible. DO NOT remove line set caps or ser­vice valve stub caps until you are ready to make
connections.

IMPORTANT

Use recovery machine rated for R410 refrigerant.

If the HPXA19 system must be opened for any kind of ser­vice, such as compressor or filter drier replacement, you
must take extra precautions to prevent moisture from en­tering the system. The following steps will help to minimize
the amount of moisture that enters the system during re­covery of R410A.

1 − Use a regulator−equipped nitrogen cylinder to break

the system vacuum. Do not exceed 5 psi. The dry ni­trogen will fill the system, and will help purge any mois­ture.

2 − Remove the faulty component and quickly seal the

system (using tape or some other means) to prevent
additional moisture from entering the system.

3 − Do not remove the tape until you are ready to install

new component. Quickly install the replacement com­ponent.

4 − Evacuate the system to remove any moisture and oth-

er non−condensables.

The HPXA19 system MUST be checked for moisture
any time the sealed system is opened.

Any moisture not absorbed by the polyol ester oil can be re­moved by triple evacuation. Moisture that has been ab­sorbed by the compressor oil can be removed by replacing
the filter drier.

IMPORTANT

Evacuation of system only will not remove mois­ture from oil. Filter drier must be replaced to elimi­nate moisture from POE oil.

Electric shock hazard. Can cause inju­ry or death. Before attempting to per­form any service or maintenance, turn
the electrical power to unit OFF at dis­connect switch(es). Unit may have
multiple power supplies.

Maintenance and service must be performed by a quali­fied installer or service agency. At the beginning of each
cooling or heating season, the system should be checked
as follows:

Outdoor Unit

1 − Clean and inspect outdoor coil (may be flushed with a

water hose). Ensure power is off before cleaning.

2 − Outdoor unit fan motor is prelubricated and sealed. No

further lubrication is needed.

3 − Visually inspect all connecting lines, joints and coils for

evidence of oil leaks.
4 − Check all wiring for loose connections.
5 − Check for correct voltage at unit (unit operating).
6 − Check amp−draw on outdoor fan motor and compres-

sor (high and low capacity).
7 − Inspect drain holes in coil compartment base and

clean if necessary.

NOTE − If owner complains of insufficient cooling, the unit
should be gauged and refrigerant charge checked. Refer to
section on refrigerant charging in this instruction.

Indoor Coil

1 − Clean coil if necessary.

2 − Check connecting lines, joints and coil for evidence of

oil leaks.

3 − Check condensate line and clean if necessary.

Indoor Unit

1 − Clean or change filters.
2 - Lennox blower motors are prelubricated and permanent-

ly sealed. No more lubrication is needed.

3 − Adjust blower speed for cooling. Measure the pressure

drop over the coil to determine the correct blower CFM.

Refer to the unit information service manual for pressure

drop tables and procedure.
4 − Belt Drive Blowers − Check belt for wear and proper

tension.

5 − Check all wiring for loose connections.

6 − Check for correct voltage at unit.

7 − Check amp−draw on blower motor.

Page 23

VII−DIAGRAM / OPERATING SEQUENCE

HPXA19−024, 036, −048 & −060

Page 24

Sequence of Operation HPXA19−024/060

First Stage Cool (low capacity)

Transformer from indoor unit supplies 24VAC power to
the thermostat and outdoor unit controls.

1− Internal wiring energizes terminal O by cooling mode

selection, energizing the reversing valve. Cooling de­mand initiates at Y1 in the thermostat.

2− 24VAC passes through high pressure switch S4 and

discharge thermostat switch S5 energizing compres­sor contactor K1.
HPXA19−024 − Compressor begins start up. Relay
K31 remains closed during start up and capacitor
C7 remains in the circuit. As compressor speeds up
K31 is energized, de−energizing capacitor C7.

3− K1−1 N.O. closes energizing compressor B1 and out-

door fan motor B4. Transformer T46 is also energized.

4− Solenoid L34 is NOT energized. The slider ring re-

mains open limiting compressor to low capacity.

Second Stage Cool (high capacity)

5− Second stage thermostat demand energizes solenoid

relay K195. K195−1 closes sending voltage to rectifier
plug D4. D4 converts the AC voltage to DC voltage and
energizes L34 unloader solenoid. L34 then closes the
slider ring, allowing the compressor to operate at high
capacity.

Heating

A− Ambient temperature ABOVE S23 low ambient
thermostat setting. S23 remains open.

1− Internal wiring de−energizes terminal O by heating

mode selection, de−energizing the reversing valve.
Heating demand initiates at Y1.

2− 24VAC passes through high pressure switch S4 and

discharge thermostat switch S5 energizing compres­sor contactor K1.

3− K1−1 N.O. closes, energizing compressor, outdoor fan

motor and transformer T46.

4− Solenoid L34 is NOT energized. The slider ring re-

mains open limiting compressor to low capacity.

B− Ambient temperature BELOW S23 low ambient
thermostat setting. S23 closes shunting Y1 and Y2.

1− Internal wiring de−energizes terminal O by heating

mode selection, de−energizing the reversing valve.
Thermostat calls for heating demand.

2− 24VAC passes through high pressure switch S4 and

discharge thermostat switch S5 energizing compres­sor contactor K1.

3− K1−1 N.O. closes, energizing compressor, outdoor fan

motor and transformer T46.

4− Heat demand energizes solenoid relay K195. K195−1

closes sending voltage to rectifier plug D4. D4 con­verts the AC voltage to DC voltage and energizes L34
unloader solenoid. L34 then closes the slider ring, al­lowing the compressor to operate at full capacity.

Defrost Mode

When a defrost cycle is initiated, the control ener­gizes the reversing valve solenoid and turns off the
condenser fan. The control will also put 24VAC on
the W1" (auxiliary heat) line. The unit will stay in this
mode until either the coil sensor temperature is
above the selected termination temperature, the de­frost time of 14 minutes has been completed, or the
room thermostat demand cycle has been satisfied.
(If the temperature select shunt is not installed, the
default termination temperature will be 100°F.) If the
room thermostat demand cycle terminates the
cycle, the defrost cycle will be held until the next
room thermostat demand cycle. If the coil sensor
temperature is still below the selected termination
temperature, the control will continue the defrost
cycle until the cycle is terminated in one of the meth­ods mentioned above. If a defrost is terminated by
time and the coil temperature did not remain above
35°F (2°C) for 4 minutes the control will go to the
34−minute Time/Temperature mode.

Page 25

HPXA19−038 with Variable Speed Motor

3

4

2

1

Page 26

Sequence of Operation HPXA19−038

First Stage Cool (low capacity)

Transformer from indoor unit supplies 24VAC power to
the thermostat and outdoor unit controls.

1− Internal wiring energizes terminal O by cooling mode

selection, energizing the reversing valve. Cooling de­mand initiates at Y1in the thermostat.

2− 24VAC passes through high pressure switch S4 and

discharge thermostat switch S5 energizing compres­sor contactor K1.

3− K1−1 N.O. closes energizing compressor B1,trans-

former T46 and outdoor fan motor B4. Variable speed
condenser fan motor operates on low speed (yellow
tap).

4− Solenoid L34 is NOT energized. The slider ring re-

mains open limiting compressor to low capacity.

Second Stage Cool (high Capacity)

5− Second stage thermostat demand energizes solenoid

relay K195. K195−1 closes sending voltage to rectifier
plug D4. D4 converts the AC voltage to DC voltage and
energizes L34 unloader solenoid. L34 then closes the
slider ring, allowing the compressor to operate at full
capacity. Variable speed condenser fan motor oper­ates on high speed (blue tap).

Heating

A− Ambient temperature ABOVE S23 low ambient
thermostat setting. S23 remains open.

1− Internal wiring de−energizes terminal O by heating

mode selection, de−energizing the reversing valve.
Heating demand initiates at Y1.

2− 24VAC passes through high pressure switch S4 and

discharge thermostat switch S5 energizing compres­sor contactor K1.

3− K1−1 N.O. closes, energizing compressor B1, trans-

former T46 and outdoor fan motor B4. Variable speed
condenser fan motor operates on low speed (yellow
tap).

4− Solenoid L34 is NOT energized. The slider ring re-

mains open limiting compressor to low capacity.

B− Ambient temperature BELOW S23 low ambient
setting. S23 closes shunting Y1 and Y2.

1− Internal wiring de−energizes terminal O by heating

mode selection, de−energizing the reversing valve. In­door thermostat calls for heating demand.

2− 24VAC passes through high pressure switch S4 and

discharge thermostat switch S5 energizing compres­sor contactor K1.

3− K1−1 N.O. closes, energizing compressor B1, trans-

former T46 and outdoor fan motor B4. Variable speed
condenser fan motor operates on high speed (blue
tap).

4− Heat demand energizes solenoid relay K195. K195−1

closes sending voltage to rectifier plug D4. D4 con­verts the AC voltage to DC voltage and energizes L34
unloader solenoid. L34 then closes the slider ring, al­lowing the compressor to operate at full capacity.

Defrost Mode

When a defrost cycle is initiated, the control ener­gizes the reversing valve solenoid and turns off the
condenser fan. The control will also put 24VAC on
the W1" (auxiliary heat) line. The unit will stay in this
mode until either the coil sensor temperature is
above the selected termination temperature, the de­frost time of 14 minutes has been completed, or the
room thermostat demand cycle has been satisfied.
(If the temperature select shunt is not installed, the
default termination temperature will be 100°F.) If the
room thermostat demand cycle terminates the
cycle, the defrost cycle will be held until the next
room thermostat demand cycle. If the coil sensor
temperature is still below the selected termination
temperature, the control will continue the defrost
cycle until the cycle is terminated in one of the meth­ods mentioned above. If a defrost is terminated by
time and the coil temperature did not remain above
35°F (2°C) for 4 minutes, the control will go to the
34−minute Time/Temperature mode.

Page 27