Lennox SL18XP1, XC17 Installation Instruction

INSTALLATION

2018 Lennox Industries Inc.

Dallas, Texas, USA

THIS MANUAL MUST BE LEFT WITH THE

HOMEOWNER FOR FUTURE REFERENCE

General

This SL18XP1 outdoor heat pump with all-aluminum coil
is designed for use with HFC-410A refrigerant only. This
unit must be installed with an approved indoor air handler
or coil. See the Lennox SL18XP1 Product Specifications
bulletin (EHB) for matching indoor components.

These instructions are intended as a general guide and do
not supersede local codes in any way. Consult authorities
having jurisdiction before installation.

NOTICE !

For more in-depth information, consult the Installa
tion and Service Procedures manual, available as
Corp.1406-L10 on LennoxPROS.com or through the
Technical Support department at 800-453-6669.

INSTRUCTIONS

Dave Lennox Signature
Collection SL18XP1 System

HEAT PUMPS
507468-01
7/2018

WARNING

Improper installation, adjustment, alteration, service or
maintenance can cause property damage, personal inju
ry or loss of life.

Installation and service must be performed by a licensed
professional installer (or equivalent) or service agency.

CAUTION

Before attempting to perform any service or mainte
nance, turn the electrical power to unit OFF at discon
nect switch.

®

STEP 1 -- SETTING THE UNIT -- Clearances

NOTES:

See NOTES

See

NOTES

See NOTES

NOTICE: Specific applications may require adjustment of the listed installation clearances to provide protection for

the unit from physical damage or to avoid conditions which limit operating efficiency. (Example: Clearances may
have to be increased to prevent snow or ice from falling on the top of the unit. Additional clearances may also be
required to prevent air recirculation when the unit is installed under a deck or in another tight space.)

See

NOTES

Control

Box

Service clearance of 30 in. must be maintained on one of the sides
adjacent to the control box.

Clearance to one of the other three sides must be 36 in.

Clearance to one of the remaining two sides may be 12 in. and the
final side may be 6 in.

A clearance of 24 in. must be maintained between two units.

48 in. clearance required on top of unit.

FIGURE 1

Page 1

STEP 1 -- SETTING THE UNIT (Continued) -- Unit Dimensions/Placement

UNIT DIMENSIONS - INCHES (MM)

39-1/2
(1003)

DISCHARGE AIR

ELECTRICAL INLETS

37 (940) [-024 AND -030]
41 (1041) [-036 AND -042]
47 (1194) [-048 AND -060]

VAPOR LINE
INLET

LIQUID LINE
INLET

4-7/16

18-1/2

(470)

(113)

8 (203)

1 (25)

SIDE VIEW ACCESS VIEW

UNIT SUPPORT
FEET

35-1/2

(902)

16-7/8

(429)

8-3/4
(222)

3-1/8

(79)

30-3/4

(781)

BASE WITH ELONGATED LEGS

26-7/8

(683)

3-3/4 (95)

4-5/8
(117)

Page 2

STEP 1 -- SETTING THE UNIT (Continued)

-- Unit Placement

CAUTION

As with any mechanical equipment, contact with sharp
sheet metal edges can result in personal injury. Take
care while handling this equipment and wear gloves and
protective clothing.

WARNING

To prevent personal injury, as well as damage to panels,
unit or structure, observe the following:

While installing or servicing this unit, carefully stow all
removed panels so that the panels will not cause injury
to personnel, objects or nearby structures. Also, take
care to store panels where they will not be subject to
damage (e.g., being bent or scratched).

While handling or stowing the panels, consider any
weather conditions (especially wind) that may cause
panels to be blown around and damaged.

NOTICE !

Roof Damage!
This system contains both refrigerant and oil. Some

rubber roofing material may absorb oil, causing the
rubber to degrade. Failure to follow this notice
could result in damage to roof surface.

IMPORTANT !

Exhaust vents from dryers, water heaters and
furnaces should be directed away from the outdoor
unit. Prolonged exposure to exhaust gases and the
chemicals contained within them may cause
condensation to form on the steel cabinet and other
metal components of the outdoor unit. This will
diminish unit performance and longevity.

SLAB MOUNTING

Install unit level or, if on a slope, maintain slope tolerance of 2
degrees (or 2 inches per 5 feet [50 mm per 1.5 m]) away from
building structure.

BUILDING

STRUCTURE

DISCHARGE AIR

MOUNTING
SLAB

GROUND LEVEL

FIGURE 3

ELEVATED SLAB MOUNTING USING FEET

EXTENDERS

Use additional 2” SCH 40 male threaded adapters which can be
threaded into the female threaded adapters to make additional
adjustments to the level of the unit.

2” (50.8MM) SCH 40
FEMALE THREADED
ADAPTER

2” (50.8MM) SCH 40
MALE THREADED
ADAPTER

PLACEMENT

INSTALL UNIT AWAY

FROM WINDOWS

TWO 90 ELBOWS INSTALLED IN LINE SET

WILL REDUCE LINE SET VIBRATION

FIGURE 2

BASE

LEG DETAIL

FIGURE 4

IMPORTANT !

This model is designed for use in check / expansion
valve systems only. An indoor expansion valve ap
proved for use with HFC-410A refrigerant must be
ordered separately and installed prior to operating
the system.

Page 3

SL18XP1 SERIES

STEP 1 -- SETTING THE UNIT (Continued) -- Unit Placement

STABILIZING UNIT ON UNEVEN SURFACES

SLAB MOUNTING

#10 X 1/2” LONG SELF-DRILLING

SHEET METAL SCREWS

STABILIZING BRACKET

(18 GAUGE METAL — 2” WIDTH;

HEIGHT AS REQUIRED)

COIL

BASE PAN

Always use stabilizers when unit is
raised above the factory height.
(Elevated units could become unsta

#10 X 1-1/4” LONG HEX HD SCREW

Concrete slab — use two plastic anchors
(hole drill 1/4”)

AND FLAT WASHER

CORNER POST

ble in gusty wind conditions.)
Stabilizers may be used on any unit

installed on unstable and uneven
surfaces.

DECK TOP MOUNTING

Stabilizing bracket (18 gauge metal — 2” [50.8mm] width; height as required); bend to form
right angle as shown below.

MINIMUM ONE

PER SIDE

!

IMPORTANT !

Unit Stabilizer Bracket

(field-provided):

SAME FASTENERS AS
SLAB SIDE MOUNTING.

Install one bracket per side (minimum). For extra stability, install
two brackets per side, two inches (51mm) from each corner.

WIND BARRIER

Install the unit a minimum of six inches (152 mm)
above the roof surface to avoid ice build-up around
the unit. Locate the unit above a load-bearing wall
or area of the roof that can adequately support the
unit. Consult local codes for rooftop applications.

If coil must be installed facing prevailing winter
winds, a wind barrier should be constructed. Size
barrier at least the same height and width as out
door unit. Install barrier 24 inches (610 mm) from
the sides of the unit in the direction of prevailing
winds.

FOR EXTRA

STABILITY

INLET AIR

PREVAILING WINTER

WINDS

WIND BARRIER

INLET AIR

24”

(610)

INLET AIR

FIGURE 5

Page 4

STEP 2 -- ELECTRICAL -- Circuit Sizing
and Wire Routing

In the U.S.A., wiring must conform with current local codes
and the current National Electric Code (NEC). In Canada,
wiring must conform with current local codes and the current
Canadian Electrical Code (CEC).

Refer to the furnace or air handler installation instructions
for additional wiring application diagrams and refer to unit
nameplate for minimum circuit ampacity and maximum
overcurrent protection size.

24VAC TRANSFORMER

Use the transformer provided with the furnace or air han
dler for low‐voltage control power (24VAC - 40 VA mini
mum).

ELECTROSTATIC

DISCHARGE

(ESD)

Precautions and

Procedures

CAUTION

Electrostatic discharge can affect
electronic components. Take care
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. Touch hand and all tools on an
unpainted unit surface before
performing any service procedure to
neutralize electrostatic charge.

WARNING

Electric Shock Hazard. Can cause injury
or death. Unit must be grounded in
accordance with national and local
codes.

Line voltage is present at all components
when unit is not in operation on units with
single‐pole contactors. Disconnect all
remote electric power supplies before
opening access panel. Unit may have
multiple power supplies.

IMPORTANT !

If unit is equipped with a crankcase heater, it should
be energized 24 hours before unit start-up to pre
vent compressor damage as a result of slugging.

1. Size Circuit and Install Disconnect: Refer to the unit

nameplate for minimum circuit ampacity, and maxi
mum fuse or circuit breaker size (HACR per NEC).
Install power wiring and properly sized disconnect
switch.

NOTE — Units are approved for use only with copper
conductors. Ground unit at disconnect switch or connect
to an earth ground.

2. Install Thermostat: Install room thermostat (ordered

separately) on an inside wall in the center of the condi
tioned area and 5 feet (1.5m) from the floor. The ther
mostat should not be installed on an outside wall or
where it can be affected by sunlight or drafts.

NOTE — 24VAC, Class II circuit connections are made in
the control box.

Page 5

SL18XP1 SERIES

A. ROUTE CONTROL WIRES — NON-COMMUNICATING

Install low voltage control wiring from outdoor to indoor unit and from
thermostat to indoor unit. All low voltage wiring must enter unit through
provided field-installed busing installed in electrical inlet.

Run 24VAC control wires through hole with grommet.
Make 24VAC control wire connections to heat pump control (A175).

NOTE — Do not bundle any excess 24VAC control wires inside control box.

NOTE — Wire tie provides low voltage wire strain relief and maintains

B

separation of field-installed low and high voltage circuits.

NOTE — For proper voltages, select control wires gauge per table below.

WIRE RUN LENGTH AWG# INSULATION TYPE

LESS THAN 100' (30 METERS) 18 TEMPERATURE RATING

MORE THAN 100' (30 METERS) 16 35ºC MINIMUM.

B. ROUTE CONTROL WIRES — COMMUNICATING

A

Maximum length of wiring (18 gauge) for all connections on the RSBus is 1500 feet (457 meters). Wires should be color-coded, with a temperature
rating of 95ºF (35ºC) minimum, and solid-core (Class II Rated Wiring). All low voltage wiring must enter unit through provided field-installed bushing
installed in electrical inlet.

Communicating systems using the iComfort®-enabled thermostat require four thermostat wires between the thermostat and the furnace/air han
dler control and four wires between the outdoor unit and the furnace/air handler control. When a thermostat cable with more than four wires is used,
the extra wires must be properly connected to avoid electrical noise (see illustration below).

Use a wire nut to bundle the four unused wires at each end of the cable. Each bundle should also include an additional wire that should be connected
on each end to the C terminal as shown in the figure below.

iComfort®-enabled

iComfort®-enabled

Indoor Unit

Outdoor Unit

HOLE

CONTROL
(A175)

Single Wire To C

iComfort®-enabled

Terminal

Single Wire To C
Terminal

Unused Wires

Unused Wires

ROUTE HIGH VOLTAGE AND GROUND WIRES

Any excess high voltage field wiring should be trimmed and secured away from any low voltage field wiring. To facilitate a conduit, a
cutout is located in the bottom of the control box. Connect conduit to the control box using a proper conduit fitting.

WATERTIGHT

CONDUIT FITTING

WATERTIGHT

FLEXIBLE CONDUIT

TO SERVICE

DISCONNECT BOX

GROUND LUG*

CONTACTOR

ELECTRICAL INLET (CONTROL WIRING —
LOW VOLTAGE). USE BUSHING
PROVIDED IN BAG ASSEMBLY HERE.

CONTROL BOX

ELECTRICAL

INLET (HIGH

VOLTAGE)

WIRING ENTRY

POINTS

* Attach field-provided
green ground wire to
provided ground lug.

NOTE - Grounding wire
must be a single, contin
uous wire run from unit
ground lug to earth
ground. DO NOT splice

wire.

ACCESS VIEW

thermostat

FIGURE 6

Page 6

STEP 2 -- ELECTRICAL (Continued) -- Outdoor Control (A175) Jumpers and Terminals

J4 - COMPRESSOR

SHIFT DELAY

30

SECOND DELAY

(DEFAULT)

0

SECOND DELAY

30

J2 - SECOND-STAGE

LOCK-IN

TEMPERATURE

(TWO-STAGE HEAT PUMP ONLY)

55

DEGREE
TARGET

50
DEGREE
TARGET

45
DEGREE
TARGET

40

DEGREE

TARGET (DEFAULT)

55

50

45

55

50

45

55

50

45

55

50

45

40

7-SEGMENT DISPLAY

PUSH BUTTON

J3 - DEFROST AUTO

(HEAT PUMP ONLY)

JUMPER ON PINS 1 AND 2

DEFROST AUTO ENABLED

DEFROST AUTO DISABLED (DEFAULT)

JUMPER ON PINS 2 AND 3

ON

OFF

J1 - DEFROST TERMINATION

0

SECOND-STAGE LOCK-IN

40

40

TEMPERATURE

TEMPERATURE

MAX

TARGET

90

MAX

90
DEGREE
TARGET

90

70
DEGREE
TARGET

MAX

MAX

(HEAT PUMP ONLY)

70

50

(DEFAULT WHEN JUMPER IS

REMOVED OR MISSING)

70

50

DEGREE
TARGET

(DEFAULT)

90

70

50

90

90

70

50

MAX

50

MAX

90

70

50

DS TO R LINK - EDA
APPLICATION

(TWO-STAGE UNIT ONLY)

40

NOTE - LINK NOT APPLICABLE TO SINGLE-STAGE
UNIT. CUTTING LINK WILL HAVE NO AFFECT ON
OPERATION OF SINGLE-STAGE UNITS.

CUT FOR HUMIDITROL® - ENHANCED
DEHUMIFICATION ACCESSORY (EDA)
APPLICATIONS.

J1 - DEFROST TERMINATION TEMPERATURE

1. The J1 jumper is factory set to 50°F (10°C). This jumper can also be set to 70°F, 90°F, 100°For MAX
(21°C, 32°C, 38°C and MAX). If a jumper is not present on J1, the default termination temperature is MAX.

NOTE  Colder climates could require a higher defrost termination temperature setting to maintain a clear coil.

2. If the J1 jumper is set to MAX, defrost will run maximum defrost sequence.

J3 - DEFROST AUTO

1. Defrost Auto can be set to either ON or OFF. Factory default setting is OFF. Note: If the jumper is miss

ing the default is OFF.

2. Defrost Auto is set to OFF - Defrost will run and terminate based on J1 setting.

3. Defrost Auto is set to ON - Defrost termination setting may differ from the actual J1 jumper setting. The

actual defrost termination will be determined based on the following rules:

A.. The first defrost after the unit is powered up, or the first defrost after cooling call will terminate based

on the J1 setting.

B.. The control accumulates heating runtime between defrost cycles:

 Heating time between defrost is less than 50 minutes - The defrost termination temperature

will be increased for the next defrost cycle based on current termination setting. If current ter
mination setting is <70°F then the next defrost termination will be 90°F. If J1 is set at >70°F or
MAX the next defrost termination will be MAX.

 Heating time between defrosts is longer than 1 hour for 2 consecutive heating cycles

- The defrost termination will be decreased for the next defrost cycle. If the termination is set
at 50°F, 70°F, or 90°F, then defrost termination will follow the J1 jumper setting. If the J1 is set
to MAX, then the next defrost termination will be 90°F.

C.. If J1 is set to MAX, the system will always run at MAX when accumulated compressor OFF time

is longer than 30 minutes and ambient temperature is less than 35°F.

D.. When the ambient sensor temperature is higher than 40°F, and J1 is set to MAX, defrost termina

tion will be 90°F. If J1 is to 50°F, 70°F, 90°F or 100°F , defrost termination will follow the J1 setting.

FIGURE 7

Page 7

SL18XP1 SERIES

STEP 2 -- ELECTRICAL (Continued) -- Field Control Wiring

The following two illustrations provide examples of control wiring connections when using a non-communicating thermostat.
For examples of control wiring in complete- or partial-communicating systems, see the iComfort®-enabled thermostat
Quick Start Guide which is provided with the thermostat.

Single−Stage

Heat Pump Control

2

W

L

Y2

Y1

O

DS

C

i−

i+

R

Air Hander Control

DS

O

5

6

L

H

DH

R

C

Y1

Y2

G

W3

3

W2

W1

ComfortSense[ 7000 Thermostats

Catalog # Y0349 or Y2081

R

On−board link

G

W2

W1

O

L

H

D

B

Y2
Y1

Low voltage thermostat
wiring

Flat metal jumper

1

C

4

T
T

1. Thermostat T terminals are used for outdoor sensor input. Sensor provides input for thermostat's outdoor

temperature display (optional).

2. R to L connection is required for this model only when used with the ComfortSense

®

7000 thermostat - (catalog

number Y0349). Resistor Kit (catalog number 47W97) is required and must be ordered separately.

3. Air handler control ships from factory with metal jumpers installed across W1, W2 and W3. For single-stage electric

heat, do not remove factory-installed metal jumper.

4. Air handler control ships from factory with metal jumpers installed across W1, W2 and W3. For two-stage electric
heat, remove factory-installed metal jumper between W1 and W2. Then, connect thermostat wire between the air
handler control's W2 and the thermostat's W2 terminal.

5. Cut on-board link (clippable wire) from R-O HEAT PUMP for heat pump applications.

6. Cut on-board link (clippable wire) DS-R for Humiditrol

®

or Harmony III applications. This will slow the indoor blower

motor to the lowest speed setting. See air handler installation instruction or product specification bulletin for lowest
fan speed information.

FIGURE 8

Page 8

Single−Stage

Heat Pump Control

W

L

Y2

Y1

O

DS

Furnace Control

DS

O

4

L

H

DH

R

ComfortSense[ 7000 Thermostats

Catalog # Y0349 or Y2081

R

3

G

W2

W1

O

L

H

On−board link

Low voltage thermostat
wiring

2

C

i−

C

Y1

Y2

G

i+

R

W2

Y2
Y1

C

D

B

1

T

W1

T

1. Thermostat T terminals are used for outdoor sensor input. Sensor provides input for thermostat's outdoor tempera

ture display (optional).

2. R to L connection is required for this model only when used with the ComfortSense

®

7000 thermostat - (catalog

number Y0349). Resistor Kit (catalog number 47W97) is required and must be ordered separately.

3. Cut on-board link W951 (clippable wire) from R-O HEAT PUMP for heat pump applications.

4. Cut on−board link (clippable wire) DS−R for Humiditrol

®

or Harmony III applications. This will slow the indoor

blower motor to the lowest speed setting. See furnace installation instruction or product specification bulletin for
lowest fan speed information.

NOTE - To use furnace to temper air during defrost, wire optional temper kit (67M41) between the W terminal of the heat
pump control (A175) and the W1 terminal on the furnace control. The temper kit cycles the furnace on and off during the
defrost cycle. It also protects the heat pump compressor from high pressures during defrost.

FIGURE 9

Page 9

SL18XP1 SERIES

STEP 3 -- REFRIGERANT PIPING —
Flushing Existing Line Set & Indoor Coil

Flush the existing line set per the following instruc

tions. For more information, refer to the Installation
and Service Procedures manual available on
LennoxPROS.com. CAUTION - DO NOT attempt to
flush and re-use existing line sets or indoor coil
when the system contains contaminants (i.e., com
pressor burn out).

NOTE - When installing refrigerant lines longer than 50
feet, refer to the Refrigerant Piping Design and Fabrication
Guidelines manual available on LennoxPROS.com (Corp.
9351-L9), or contact the Technical Support Department
Product Application group for assistance.

NOTE - For new or replacement line set installation refer to
Service and Application Note - Corp 9112-L4 (C-91-4).

TABLE 1

REFRIGERANT LINE SET — INCHES (MM)

Model

-024 and

-030

-036, -042
and -048

Liquid

Line

3/8” (10) 3/4” (19)

3/8” (10) 7/8” (22)

Vapor

Line

L15 line set sizes are depen

dent on matching system com

ponents. See SL18XP1 Engi

neering Handbook to determine

correct line set sizes.

L15

Line Sets

Feet (Meters)

WARNING

When using a high pressure gas such as
nitrogen to pressurize a refrigeration 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

Refrigerant can be harmful if it is inhaled. Refrigerant
must be used and recovered responsibly.

Failure to follow this warning may result in personal injury
or death.

WARNING

Fire, Explosion and Personal Safety Haz
ard. Failure to follow this warning could re
sult 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 fire
and/or an explosion, that could result in
property damage, personal injury or death.

-060 3/8” (10)

NOTE — Some applications may require a field-provided 7/8” to
1-1/8” adapter.

1-1/8”

(29)

Field-Fabricated

IMPORTANT !

If this unit is being matched with an approved line
set or indoor unit coil that was previously charged
with mineral oil, or if it is being matched with a coil
which was manufactured before January of 1999,
the coil and line set must be flushed prior to installa
tion. Take care to empty all existing traps. Polyol es
ter (POE) oils are used in Lennox units charged with
HFC-410A refrigerant. Residual mineral oil can act
as an insulator, preventing proper heat transfer. It
can also clog the expansion device and reduce sys
tem performance and capacity.

Failure to properly flush the system per this instruc
tion and the detailed Installation and Service Proce
dures manual will void the warranty.

WARNING

Polyol ester (POE) oils used with HFC-410A
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 !

Some scroll compressors have an internal vacuum
protection devices that will unload scrolls when
suction pressure goes below 20 psig. A hissing
sound will be heard when the compressor is run
ning unloaded. The protection device will reset
when pressure in system rises above 40 psig. This
is normal operation. DO NOT replace compressor.

Page 10

STEP 4 -- REFRIGERANT PIPING -- Removing Existing Indoor Metering Device

TYPICAL EXISTING FIXED ORIFICE

1A

DISTRIBUTOR

ASSEMBLY

1. On fully cased coils, remove the coil access and plumbing panels.

2. Remove any shipping clamps from the liquid line and distributor as
sembly.

3. Using two wrenches, disconnect liquid line from liquid line orifice hous
ing. Take care not to twist or damage distributor tubes during this pro
cess.

4. Remove and discard fixed orifice, valve stem assembly (if present)
and Teflon® washer as illustrated above.

5. Use a field-provided fitting to temporarily reconnect the liquid line to the
indoor unit's liquid line orifice housing.

(UNCASED COIL SHOWN)

DISTRIBUTOR TUBES

LIQUID LINE ORIFICE HOUSING

TEFLON® RING

FIXED ORIFICE

REMOVE AND DISCARD

WHITE TEFLON

(IF PRESENT)

®

SEAL

LIQUID LINE ASSEMBLY

(INCLUDES STRAINER)

REMOVAL PROCEDURE

OR

BRASS NUT

1B

TWO-PIECE PATCH PLATE

(UNCASED COIL ONLY)

CONNECT GAUGES AND EQUIPMENT FOR
FLUSHING PROCEDURE

2

CYLINDER CONTAINING
CLEAN HCFC-22* TO BE
USED FOR FLUSHING
(Positioned to deliver liquid

A

refrigerant)

1

VAPOR LINE

SERVICE VALVE

EXISTING

INDOOR

UNIT

LIQUID LINE SERVICE

VALV E

RECOVERY

CYLINDER

VAPOR

LIQUID

OUTDOOR

B

NEW

UNIT

OPENED

C

D

RECOVERY MACHINE

A. HCFC-22 cylinder with clean refrigerant* (positioned to deliver liquid

refrigerant) to the vapor service valve.

B. HCFC-22 gauge set (low side) to the liquid line valve.
C. HCFC-22 gauge set center port to inlet on the recovery machine with an

empty recovery tank connected to the gauge set.

D. Connect recovery tank to recovery machine per machine instructions.

GAUGE

MANIFOLD

LOW HIGH

CLOSED

TANK
RETURN

INLET

DISCHARGE

TYPICAL EXISTING EXPANSION VALVE REMOVAL
PROCEDURE (UNCASED COIL SHOWN)

ORIFICE

HOUSING

EQUALIZER
LINE

STUB END

TEFLON
RING

VAPOR

CHECK

EXPANSION

VALV E

®

LIQUID LINE

ASSEMBLY WITH

BRASS NUT

LINE

TEFLON

RING

SENSING

LIQUID LINE

DISTRIBUTOR

TUBES

DISTRIBUTOR

ASSEMBLY

MALE EQUALIZER

LINE FITTING

SENSING BULB

1. On fully cased coils, remove the coil access and plumbing panels.

2. Remove any shipping clamps from the liquid line and distributor
assembly.

3. Disconnect the equalizer line from the expansion valve equalizer
line fitting on the vapor line.

4. Remove the vapor line sensing bulb.

5. Disconnect the liquid line from the expansion valve at the liquid line
assembly.

6. Disconnect the expansion valve from the liquid line orifice housing.
Take care not to twist or damage distributor tubes during this
process.

7. Remove and discard expansion valve and the two Teflon® rings.

8. Use a field-provided fitting to temporarily reconnect the liquid line to
the indoor unit's liquid line orifice housing.

FLUSHING LINE SET

The line set and indoor unit coil must be flushed with at least the same

3

amount of clean refrigerant* that previously charged the system.
Check the charge in the flushing cylinder before proceeding.

1. Set the recovery machine for liquid recovery and start the recovery

machine. Open the gauge set valves to allow the recovery
machine to pull a vacuum on the existing system line set and indoor
unit coil.

2. Position the cylinder of clean HCFC-22* for delivery of liquid

refrigerant and open its valve to allow liquid refrigerant to flow into
the system through the vapor line valve. Allow the refrigerant to
pass from the cylinder and through the line set and the indoor unit
coil before it enters the recovery machine.

3. After all of the liquid refrigerant has been recovered, switch the

recovery machine to vapor recovery so that all of the HCFC-22
vapor is recovered. Allow the recovery machine to pull the system
down to 0.

4. Close the valve on the inverted HCFC-22 cylinder and the gauge

set valves. Pump the remaining refrigerant out of the recovery
machine and turn the machine off.

®

LINE

LIQUID

LINE

*IMPORTANT - Clean refrigerant is any refrigerant in a system that has not had compressor burn out. If the system
has experienced burn out, it is recommended that the existing line set and indoor coil be replaced.

FIGURE 10

Page 11

SL18XP1 SERIES

STEP 5 -- REFRIGERANT PIPING -- Brazing Procedures

PIPING PANEL REMOVAL / PREPARING LINE SET

Remove piping panel to access service valves. Cut

1

ends of the refrigerant lines square (free from nicks or
dents) and debur the ends. The pipe must remain
round. Do not crimp end of the line.

CUT AND DEBUR

LINE SET SIZE MATCHES

SERVICE VALVE CONNECTION

SERVICE VALVE

COPPER TUBE

REDUCER

CONNECTION

STUB

REFRIGERANT LINE

LINE SET SIZE IS SMALLER

THAN CONNECTION

CAP AND CORE REMOVAL

Remove service cap and core from both the vapor

2

and liquid line service ports.

SERVICE PORT CAP

SERVICE PORT
CORE

LIQUID LINE SERVICE VALVE

SERVICE PORT
CORE

SERVICE
PORT CAP

VAPOR LINE

DO NOT CRIMP SERVICE VALVE

CONNECTOR WHEN PIPE IS

SMALLER THAN CONNECTION

SERVICE VALVE

ATTACH THE MANIFOLD GAUGE SET FOR BRAZING
LIQUID AND VAPOR LINE SERVICE VALVES

3

A Connect gauge set low pressure side to liquid line service valve (service port).
B Connect gauge set center port to bottle of nitrogen with regulator.
C With valve core removed from the vapor line service port, nitrogen flow will have an exit point.

HIGHLOW

ATTACH

GAUGES

VAPOR LINE SERVICE PORT MUST BE OPEN

AND SERVICE PORT CORE REMOVED TO AL

LOW EXIT POINT FOR NITROGEN FLOW

VAPOR LINE

INDOOR

UNIT

LIQUID LINE

C

LIQUID LINE SERVICE

VAPOR LINE

SERVICE

VALV E

VALV E

A

B

OUTDOOR

UNIT

NITROGEN

FIGURE 11

Page 12

CAUTION

Brazing alloys and flux contain materials which are
hazardous to your health.

Avoid breathing vapors or fumes from brazing
operations. Perform operations only in well-ventilated
areas.

Wear gloves and protective goggles or face shield to
protect against burns.
Wash hands with soap and water after handling brazing
alloys and flux.

WRAP SERVICE VALVES

To help protect service valve seals during brazing, wrap water-saturated cloths around service valve bodies and copper tube stubs. Use

4

additional water-saturated cloths under the valve body to protect the base paint.

FLOW NITROGEN

Flow regulated nitrogen (at 1 to 2 psig) through the refrigeration

5

gauge set into the valve stem port connection on the liquid service
valve and out of the vapor valve stem port. See steps 3A, 3B and 3C
on previous page and below for manifold gauge setup.

BRAZE LINE SET

Cloths must remain water-saturated throughout the brazing and

6

cool-down process.

A. Braze liquid line to liquid line service valve.

B. Braze vapor line to vapor service valve.

FIRE, PERSONAL INJURY, OR PROPERTY DAMAGE

may result if you do not wrap a water-saturated cloth around
both liquid and vapor line service valve bodies and copper
tube stub while brazing the line set! The braze, when
complete, must be quenched with water to absorb any
residual heat.

Do not open service valves until refrigerant lines and
indoor coil have been leak-tested and evacuated. Refer
to Installation and Service Procedures manual found on
DAVENET.

WARNING

Danger of fire. Bleeding the refrigerant
charge from only the high side may result
in pressurization of the low side shell and
suction tubing. Application of a brazing
torch to a pressurized system may result
in ignition of the refrigerant and oil
mixture. Check the high and low
pressures before applying heat.

WARNING

VAPOR LINE

WATER-SATURATED CLOTHS

IMPORTANT !

Allow braze joint to cool. Apply additional
water-saturated cloths to help cool brazed
joints. Do not remove water-saturated cloths
until piping has cooled. Temperatures above
250ºF will damage valve seals.

LIQUID LINE

6B

6A

WHEN BRAZING LINE SET TO

SERVICE VALVES, POINT FLAME

AWAY FROM SERVICE VALVE.

VAPOR LINE SERVICE PORT
MUST BE OPEN AND SERVICE
PORT CORE REMOVED TO AL

LOW EXIT POINT FOR NITRO

GEN FLOW

PREPARATION FOR NEXT STEP

After all connections have been brazed, disconnect manifold gauge set from service ports. Apply additional water-saturated cloths to both

7

services valves to cool piping. Once piping is cool, remove all water-saturated cloths.

WATER SATURATED

FIGURE 12

Page 13

CLOTHS

SL18XP1 SERIES

STEP 6 -- INSTALLING INDOOR EXPANSION VALVE

THIS OUTDOOR UNIT IS DESIGNED FOR USE IN SYSTEMS THAT USE A CHECK EXPANSION VALVE METERING DEVICE. SEE THE LENNOX SL18XP1
PRODUCT SPECIFICATION BULLETIN (EHB) FOR APPROVED EXPANSION VALVE KITS AND APPLICATION INFORMATION.

THE EXPANSION VALVE UNIT CAN BE INSTALLED INTERNAL OR
EXTERNAL TO THE INDOOR COIL. IN APPLICATIONS WHERE AN

TWO PIECE

PATCH PLATE

(UNCASED

COIL ONLY)

DISTRIBUTOR

TUBES

DISTRIBUTOR

ASSEMBLY

MALE EQUALIZER LINE

FITTING (SEE

EQUALIZER LINE
INSTALLATION FOR
FURTHER DETAILS)

SENSING BULB INSULATION IS REQUIRED
IF MOUNTED EXTERNAL TO THE COIL
CASING. SEE SENSING BULB
INSTALLATION FOR BULB POSITIONING.

(Uncased Coil Shown)

LIQUID LINE

ORIFICE

HOUSING

STUB

END

TEFLON
RING

EQUALIZER
LINE

EXPANSION

VALV E

®

LIQUID LINE

ASSEMBLY WITH

BRASS NUT

VAPOR

LINE

UNCASED COIL IS BEING INSTALLED IN A FIELD-PROVIDED
PLENUM, INSTALL THE CHECK EXPANSION VALVE IN A MANNER
WHICH PROVIDES ACCESS FOR FIELD SERVICING OF THE
EXPANSION VALVE. REFER TO BELOW ILLUSTRATION FOR
REFERENCE DURING INSTALLATION OF EXPANSION VALVE
UNIT.

®

TEFLON

RING

A. REMOVE THE FIELD-PROVIDED FITTING THAT TEMPORARILY RECON

NECTED THE LIQUID LINE TO THE INDOOR UNIT'S DISTRIBUTOR ASSEM

SENSING

LINE

LIQUID LINE

BLY.

B. INSTALL ONE OF THE PROVIDED TEFLON

STUBBED END OF THE EXPANSION VALVE AND LIGHTLY LUBRICATE THE
CONNECTOR THREADS AND EXPOSE SURFACE OF THE TEFLON
WITH REFRIGERANT OIL.

C. ATTACH THE STUBBED END OF THE EXPANSION VALVE TO THE LIQUID

LINE ORIFICE HOUSING. FINGER TIGHTEN AND USE AN APPROPRIATE
LY SIZED WRENCH TO TURN AN ADDITIONAL 1/2 TURN CLOCKWISE AS
ILLUSTRATED IN THE FIGURE ABOVE, OR 20 FT-LB.

D. PLACE THE REMAINING TEFLON

OF THE EXPANSION VALVE. LIGHTLY LUBRICATE CONNECTOR
THREADS AND EXPOSE SURFACE OF THE TEFLON
ERANT OIL.

E. ATTACH THE LIQUID LINE ASSEMBLY TO THE EXPANSION VALVE. FIN

GER TIGHTEN AND USE AN APPROPRIATELY SIZED WRENCH TO TURN
AN ADDITIONAL 1/2 TURN CLOCKWISE AS ILLUSTRATED IN THE FIGURE
ABOVE OR 20 FT-LB.

9 O'CLOCK TO

3 O'CLOCK

BULB

12

®

BULB

9

WASHER AROUND THE OTHER END

12

11

10

8

7

®

RINGS AROUND THE

ON LINES SMALLER THAN
7/8”, MOUNT SENSING
BULB BETWEEN THE 9 AND
3 O'CLOCK POSITIONS.

1

2

4

5

6

®

RING WITH REFRIG

3

1/2 TURN

®

RING

SENSING BULB INSTALLATION

A. ATTACH THE VAPOR LINE SENSING BULB IN THE PROPER

ORIENTATION AS ILLUSTRATED TO THE RIGHT USING THE
CLAMP AND SCREWS PROVIDED.

NOTE - CONFIRM PROPER THERMAL CONTACT BETWEEN
VAPOR LINE AND CHECK EXPANSION BULB BEFORE INSU
LATING THE SENSING BULB ONCE INSTALLED.

B. CONNECT THE EQUALIZER LINE

FROM THE EXPANSION VALVE TO
THE EQUALIZER VAPOR PORT ON
THE VAPOR LINE. FINGER
TIGHTEN THE FLARE NUT PLUS
1/8 TURN (7 FT-LBS) AS ILLUS
TRATED BELOW.

10

9

11

12

8

7

6

EQUALIZER LINE INSTALLATION

REMOVE AND DISCARD EITHER THE FLARE SEAL CAP OR FLARE
NUT WITH COPPER FLARE SEAL BONNET FROM THE EQUALIZER
LINE PORT ON THE VAPOR LINE AS ILLUSTRATED IN THE FIGURE
TO THE RIGHT.

1/8 TURN

1

2

3

4

5

VAPOR LINE

FLARE SEAL CAP

FIGURE 13

BULB

ON 7/8” AND LARGER LINES,
MOUNT SENSING BULB AT
EITHER THE 4 OR 8 O'CLOCK
POSITION. NEVER MOUNT

12

BULB

OR

THE SENSING BULB ON
BOTTOM OF LINE.

NOTE - NEVER MOUNT

THE SENSING BULB ON

BOTTOM OF LINE.

FLARE NUT

COPPER FLARE
SEAL BONNET

MALE BRASS EQUALIZER
LINE FITTING

VAPOR LINE

Page 14

STEP 7 -- LEAK TEST

HIGHLOW

MANIFOLD GAUGE SET

OUTDOOR UNIT

B

TO VAPOR

SERVICE VALVE

NOTE - Position
canister to deliver
liquid refrigerant.

NITROGEN

CONNECT GAUGE SET

A Connect the high pressure hose of an HFC-410A manifold gauge set to the vapor valve service port.

1

2

NOTE — Normally, the high pressure 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.

B With both manifold valves closed, connect the cylinder of HFC-410A refrigerant to the center port of

the manifold gauge set.

NOTE — Later in the procedure, the HFC-410A container will be replaced by the nitrogen container.

TEST FOR LEAKS

After the line set has been connected to the indoor and outdoor units, check the line set connections
and indoor unit for leaks. Use the following procedure to test for leaks:

A With both manifold valves closed, connect the cylinder of HFC-410A refrigerant to the center port of

the manifold gauge set. Open the valve on the HFC-410A cylinder (vapor only).

B Open the high pressure side of the manifold to allow HFC-410A into the line set and indoor unit.

Weigh in a trace amount of HFC-410A. [A trace amount is a maximum of two ounces (57 g) refriger
ant or three pounds (31 kPa) pressure.] Close the valve on the HFC-410A cylinder and the valve on
the high pressure side of the manifold gauge set. Disconnect the HFC-410A cylinder.

C Connect a cylinder of nitrogen with a pressure regulating valve to the center port of the manifold

gauge set.

D Adjust nitrogen pressure to 150 psig (1034 kPa). Open the valve on the high side of the manifold gauge

set in order to pressurize the line set and the indoor unit.

E After a few minutes, open one of the service valve ports and verify that the refrigerant added to the

system earlier is measurable with a leak detector.

F After leak testing, disconnect gauges from service ports.

HFC-410A

A

FIGURE 14

Page 15

SL18XP1 SERIES

STEP 8 -- EVACUATION

Evacuating the system of non-condensables is critical for proper operation of the unit. Non-condensables are defined as any
gas that will not condense under temperatures and pressures present during operation of an air conditioning system. Non­condensables and water suction combine with refrigerant to produce substances that corrode copper piping and com
pressor parts.

WARNING

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

MANIFOLD

LOW

GAUGE SET

HIGH

LINE SET AND INDOOR COIL

CONNECT GAUGE SET

NOTE — Remove cores from service valves (if not al
ready done).

A Connect low side of manifold gauge set

with 1/4 SAE in-line tee to vapor line
service valve

B Connect high side of manifold gauge

set to liquid line service valve

C Connect micron gauge available

connector on the 1/4 SAE in-line tee.

D Connect the vacuum pump (with

vacuum gauge) to the center port of the
manifold gauge set. The center port line
will be used later for both the HFC-410A
and nitrogen containers.

NITROGEN

OUTDOOR

UNIT

A

A34000 1/4 SAE TEE WITH
SWIVEL COUPLER

500

C

MICRON

GAUGE

TO VAPOR

SERVICE VALVE

HFC-410A

(INVERTED)

VACUUM PUMP

B

FIGURE 15

EVACUATE LINE SET AND INDOOR COIL

The unit is shipped with a factory refrigerant charge. The
liquid and vapor line valves were closed after final testing
at the factory. Do not operate these valves until the line set
and indoor coil have been evacuated and leak checked, or
the charge is lost.

NOTE - Do not use any portion of the factory charge for
purging or leak testing. The factory charge is for filling the
system only after a complete evacuation and leak check
has been performed.

Line set and indoor coil should be evacuated using the rec
ommended deep vacuum method of 500 microns. If deep
vacuum equipment is not available, the alternate triple
evacuation method may be used by following the specified
procedure.

TO LIQUID LINE
SERVICE VALVE

D

RECOMMEND

MINIMUM 3/8” HOSE

If vacuum must be interrupted during the evacuation pro
cedure, always break vacuum with dry nitrogen.

Deep Vacuum Method

The deep vacuum method requires a vacuum pump cap
able of pulling a vacuum to 500 microns and a vacuum
gauge capable of accurately measuring this vacuum level.
The deep vacuum method is the most positive way of as
suring a system is free of air and water.

Watch the vacuum gauge as the system is pulling down.
The response of the gauge is an indicator of the condition
of the system (refer to figure 15).

With no leaks in the system, allow the vacuum pump to run
for 30 minutes minimum at the deep vacuum level.

Page 16

Deep Vacuum Gauge Response and

System Conditions

FIGURE 16

Triple Evacuation Method

The triple evacuation method should only be used when
system does not contain any water in liquid form and vacu
um pump is only capable of pulling down to 28 inches of
mercury (711mm Hg). Refer to figure 17 and proceed as
follows:

Triple Evacuation Sequence

EVACUATE

BREAK VACUUM WITH DRY NITROGEN

WAIT

EVACUATE

4. Close nitrogen valve and allow system to stand for one
hour. During this time, dry nitrogen will diffuse
throughout the system, absorbing moisture.

5. Repeat this procedure as indicated in figure 17.

6. After the final evacuate sequence, confirm there are
no leaks in the system. If a leak is found, repeat the en
tire process after repair is made.

7. 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.

8. Disconnect the manifold hose from the vacuum pump
and connect it to an inverted cylinder of HFC*410A
positioned to deliver liquid refrigerant. Open the mani
fold gauge valve 1 to 2 psig in order to release the va
cuum in the line set and indoor unit.

9. Perform the following:

 Close manifold gauge valves.

 Shut off HFC*410A cylinder.

 Slowly open the service valves.

 Refer to the charging sticker on the unit to com

plete the outdoor unit installation.

Charging

The SL18XP1 unit is factory-charged with enough
HFC-410A refrigerant to accommodate a 15-foot length of
refrigerant piping. Charge should be checked and adjusted
using the tables provided on the charging procedure stick
er on the unit access panel. Detailed information is given in
the SL18XP1 Installation and Service Procedures manual,
which is available on DaveNet.

Heat Pump Control -- Defrost Operation

BREAK VACUUM WITH DRY NITROGEN

WAIT

EVACUATE

CHECK FOR TIGHT, DRY SYSTEM (IF IT HOLDS DEEP VACUUM)

CHARGE SYSTEM

FIGURE 17

1. Pull system down to 28 inches of mercury (711mm Hg)
and allow pump to continue operating for an additional
15 minutes.

2. Close manifold valves or valve at vacuum pump and
shut off vacuum pump.

3. Connect a nitrogen cylinder and regulator to system
and fill with nitrogen until system pressure is 2 psig.

A full description of the heat pump control can be found in
the detailed installation and service procedure manual
available on DaveNet. The defrost termination pins (E47)
must be set on the heat pump control prior to starting the
system to ensure proper defrost operation.

The heat pump control (A175) measures differential tem
peratures to detect when the system is performing poorly
because of frost build-up on the outdoor coil. The heat
pump control self-calibrates when the defrost system
starts and after each system defrost cycle. The heat pump
control monitors ambient temperature, outdoor coil tem
perature, and total run-time to determine when a defrost
cycle is required. The coil temperature sensor is designed
with a spring clip to allow mounting to the outside coil tub
ing. The location of the coil sensor is important for proper
defrost operation.

NOTE - The heat pump control 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 heat pump control initiates de
frost cycles.

Page 17

SL18XP1 SERIES

Homeowner Information

CAUTION

Before attempting to perform any service or mainte
nance, turn the electrical power to unit OFF at discon
nect switch.

In order to ensure peak performance, your system must be
properly maintained. Clogged filters and blocked airflow
prevent your unit from operating at its most efficient level.
The system should be inspected and serviced before each
cooling and heating season by a licensed professional
HVAC service technician (or equivalent).

Heat Pump Operation

Your new Lennox heat pump has several characteristics
that you should be aware of:

 Heat pumps satisfy heating demand by delivering large

amounts of warm air into the living space. This is quite
different from gas‐ or oil‐fired furnaces or an electric fur
nace which deliver lower volumes of considerably hotter
air to heat the space.

 Do not be alarmed if you notice frost on the outdoor coil

in the winter months. Frost develops on the outdoor coil
during the heating cycle when temperatures are below
45°F (7°C). An electronic control activates a defrost
cycle lasting 5 to 15 minutes at preset intervals to clear
the outdoor coil of the frost.

 During the defrost cycle, you may notice steam rising

from the outdoor unit. This is a normal occurrence. The
thermostat may engage auxiliary heat during the defrost
cycle to satisfy a heating demand; however, the unit will
return to normal operation at the conclusion of the de
frost cycle.

Homeowner Maintenance

The following maintenance may be performed by the
homeowner.

 Contact a licensed professional HVAC technician to

schedule inspection and maintenance appointments for
your equipment before each heating and cooling sea
son.

 Check the indoor unit filter each month and replace the

filter, if necessary.
Have your Lennox dealer show you where your indoor
unit filter is located. It will be either at the indoor unit (in
stalled internal or external to the cabinet) or behind a re
turn air grille in the wall or ceiling. Check the filter monthly
and clean or replace it as needed.
Disposable filters should be replaced with a filter of the
same type and size.

 Check the indoor unit drain line for obstructions monthly.

The indoor coil is equipped with a drain pan to collect
condensate formed as your system removes humidity
from the inside air. Have your dealer show you the loca
tion of the drain line and how to check for obstructions.
(This would also apply to an auxiliary drain, if installed.)

 Check the area around the outdoor unit monthly and re

move any obstructions that may restrict airflow to the

outdoor unit. This would include grass clippings, leaves,
or papers that may have settled around the unit.

 Trim shrubbery away from the unit and periodically

check for debris which collects around the unit.

 During the winter months, keep the snow level below the

louvered panels.

NOTE - The filter and all access panels must be in place
any time the unit is in operation. If you are unsure about the
filter required for your system, call your Lennox dealer for
assistance.

IMPORTANT !

Sprinklers and soaker hoses should not be installed
where they could cause prolonged exposure to the
outdoor unit by treated water. Prolonged exposure
of the unit to treated water (i.e., sprinkler systems,
soakers, waste water, etc.) will corrode the surface
of steel and aluminum parts, diminish performance
and affect longevity of the unit.

Thermostat Operation

See the thermostat homeowner manual for instructions on
how to operate your thermostat.

Pre-Service Check

If your system fails to operate, check the following before
calling for service:

 Verify room thermostat settings are correct.
 Verify that all electrical disconnect switches are ON.
 Check for any blown fuses or tripped circuit breakers.
 Verify unit access panels are in place.
 Verify air filter is clean.
 If service is needed, locate and write down the unit model

number and have it handy before calling.

Extended Power Outage

The heat pump is equipped with a compressor crankcase
heater which protects the compressor during cold weather
operation.

If power to your unit has been interrupted for several hours
or more, set the room thermostat selector to the EMER
GENCY HEAT setting to obtain temporary heat without the
risk of serious damage to the heat pump.

In EMERGENCY HEAT mode, all heating demand is satis
fied by auxiliary heat; heat pump operation is locked out.
After a six‐hour compressor crankcase warm‐up period,
the thermostat can be switched to the HEAT setting and
normal heat pump operation may resume.

Professional Maintenance

Your heating and air conditioning system should be inspec
ted and maintained twice each year (before the start of the
cooling and heating seasons) by a licensed professional
HVAC technician. You can expect the technician to check
the following items. These checks may only be conduc

ted by a licensed professional HVAC technician.
Outdoor Unit

1. Inspect component wiring for loose, worn or damaged
connections. Also check for any rubbing or pinching of
wires. Confirm proper voltage plus amperage of out
door unit.

Page 18

2. Check the cleanliness of outdoor fan and blade condi
tion (cracks) and clean or replace them, if necessary.

3. Inspect base pan drains for debris and clean as neces
sary.

4. Inspect the condition of refrigerant piping and confirm
that pipes are not rubbing copper-to-copper. Also,
check the condition of the insulation on the refrigerant
lines. Repair, correct, or replace as necessary.

5. Test capacitor. Replace as necessary.

6. Inspect contactor contacts for pitting or burn marks.
Replace as necessary.

7. Check outdoor fan motor for worn bearings/bushings.
Replace as necessary.

2. Inspect and clean or replace air filters in indoor unit.

3. Check the cleanliness of indoor blower and clean
blower, if necessary.

4. Inspect the indoor coil drain pans and condensate
drains for rust, debris, obstructions, leaks or cracks.
Pour water in pans to confirm proper drainage from the
pan through to the outlet of the pipe. Clean or replace
as necessary.

5. Inspect and clean indoor coil, if necessary.

6. Inspect the condition of the refrigerant lines and con
firm that pipes are not rubbing copper-to-copper. Also,
ensure that refrigerant pipes are not being affected by
indoor air contamination. Check condition of insulation
on the refrigerant lines. Repair, correct, or replace as
necessary.

8. Inspect and clean outdoor coils, if necessary and note

any damage to coils or signs of leakage.

NOTICE !

Failure to follow instructions will cause damage to
the unit.
This unit is equipped with an aluminum coil. Alu
minum coils may be damaged by exposure to solu
tions with a pH below 5 or above 9. The aluminum
coil should be cleaned using potable water at a
moderate pressure (less than 50psi). If the coil can
not be cleaned using water alone, Lennox recom
mends use of a coil cleaner with a pH in the range of
5 to 9. The coil must be rinsed thoroughly after
cleaning.
In coastal areas, the coil should be cleaned with
potable water several times per year to avoid corro
sive buildup (salt).

Indoor Unit (Air Handler or Furnace)

1. Inspect component wiring for loose, worn or damaged
connections. Confirm proper voltage plus amperage
of indoor unit.

7. Inspect the duct system for leaks or other problems.
Repair or replace as necessary.

8. Check for bearing/bushing wear on indoor blower mo
tor. Replace as necessary.

9. If your heat pump is matched with a gas- or oil-fired fur
nace for auxiliary heating, indoor unit service will also
include inspection and cleaning of the burners, and a
full inspection of the gas valve, heat exchanger and
flue (exhaust) system.

General System Test with System Operating

1. Your technician should perform a general system test.
He will turn on the air conditioner to check operating
functions such as the startup and shutoff operation.
He will also check for unusual noises or odors, and
measure indoor/outdoor temperatures and system
pressures as needed. He will check the refrigerant
charge per the charging sticker information on the out
door unit.

2. Verify that system total static pressure and airflow set
tings are within specific operating parameters.

3. Verify correct temperature drop across indoor coil.

Page 19

SL18XP1 SERIES

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 properly to correctly perform
compressor 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).

SL18XP1 Start-Up and Performance Checklist

Customer Address

Indoor Unit Model Serial

Outdoor Unit Model Serial

Solar Module Mfg and Model Serial

Notes:

START-UP CHECKS

Refrigerant Type:

Rated Load Amps Actual Amps Rated Volts Actual Volts

Condenser Fan Full Load Amps Actual Amps:

COOLING MODE

Vapor Pressure: Liquid Pressure:

Supply Air Temperature: Ambient Temperature: Return Air Temperature:

HEATING MODE

Vapor Pressure: Liquid Pressure:

Supply Air Temperature: Ambient Temperature: Return Air Temperature:

System Refrigerant Charge (Refer to manufacturer's information on unit or installation instructions for required
subcooling and approach temperatures.)

Subcooling:

Saturated Condensing Temperature (A)

minus Liquid Line Temperature (B)

Approach:

Liquid Line Temperature (A)

minus Outdoor Air Temperature (B)

Indoor Coil Temp. Drop (18 to 22°F)

Return Air Temperature (A)

minus Supply Air Temperature (B)

A — B = SUBCOOLING

A — B = APPROACH

A — B = COIL TEMP DROP

Page 20