INSTALLATION AND MAINTENANCE
INSTRUCTIONS
SCU Series
Split System Air Conditioner
WARNING
The equipment covered in this manual is to be installed by trained and experienced
service and installation technicians. Improper installation, modification, service or use
can cause electrical shock, fire, explosion or other conditions which may cause per-
sonal injury, death or property damage. Use appropriate safety gear including safety
glasses and gloves when installing this equipment.
WARNING
Risk of electrical shock. Disconnect all remote
power supplies before installing or servicing
any portion of the system. Failure to discon-
nect power supplies can result in property
damage, personal injury or death.
TABLE OF CONTENTS
INSTALLATION....................................... 2
START-UP .............................................. 5
MAINTENANCE ..................................... 5
WIRING DIAGRAMS .............................. 6
WARRANTY ........................................... 8
WARNING
Installation and servicing of air conditioning
equipment can be hazardous due to internal
refrigerant pressure and live electrical compo-
nents. Only trained and qualified service
personnel should install or service this equip-
ment. Installation and service performed by
unqualified persons can result in property
damage, personal injury or death.
Manufactured By
A.A.C.
A Lennox International Company
421 Monroe Street
Bellevue, OH 44811
WARNING
Before performing maintenance operations on
system, turn off all main power switches to
indoor and outdoor units. Turn off accessory
heater power switch if applicable. Electrical
shock could cause personal injury or death.
Save these instructions for future reference
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# 41718L098
Page 1
Minimum Clearances
TO
POWER
SUPPLY
THERMOSTAT
WEATHERPROOF
DISCONNECT
SWITCH
TO
INDOOR
UNIT
48" OVERHEAD
CLEARANCE
NEC CLASS 1
WIRING
12" CLEARANCE
TO
EVAPORATOR
COIL
NEC CLASS 2
WIRING
NAMEPLATE
LOCATION
24" SERVICE
ACCESS CLEARANCE
SEAL OPENING(S)
WITH PERMAGUM
OR EQUIVALENT
12" CLEARANCE
BOTH SIDES
NOTE: ALL OUTDOOR WIRING
MUST BE WEATHERPROOF
Figure 1
Refrigerant Piping Connections
3. Route tubing to fittings on the outdoor unit vapor and
liquid service valves using properly sized refrigerant
grade tubing. Run the refrigerant tubing in as direct a
path as possible avoiding unnecessary turns and
bends.
Check the indoor piston orifice to see if it matches the
required piston for the indoor and outdoor combina-
tion being installed. Refer to the refrigerant charge
label located on the inside of the outdoor unit access
panel for the correct piston orifice size requirements.
Replace the piston orifice with the correct size if this
size is not already installed in the indoor coil.
4. Ensure that the vapor line is insulated properly and
that both vapor and liquid lines are not in direct
contact with floors, walls, ductwork, floor joists or
other piping.
For optimum system performance, indoor coils
should be washed with a suitable detergent to remove
any residue from the coil manufacturing processes.
5. After wrapping the service valves with a wet rag,
braze the tubing to the valve connections.
Refer to the following instructions when making the
refrigerant piping connections:
6. After brazing the tubing connections at the indoor coil,
leak test the refrigerant tubing and indoor coil.
1. The unit has been factory charged with refrigerant
(R22) suitable for a matched indoor coil and 20 feet of
properly sized refrigerant tubing. Refer to the unit
rating plate for the exact amount of this factory charge.
7. Following the leak test, evacuate the indoor coil and
line set to a minimum of 500 microns to remove
contamination and moisture.
8. After evacuation, open both the vapor and liquid
service valves fully.
2. Refer to the refrigerant charge label located on the
inside surface of the outdoor unit access panel.
Locate the outdoor and indoor models being installed
and note any refrigerant adjustments that must be
made to the system. Adjustments to the system
charge must also be made if an interconnecting line
set other than 20 feet is installed.
# 41718L098
Page 3
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Factory charge contains refrigerant for condenser, evapo-
rator and 20 feet of 3/8” line set. For line set other than 20
feet, adjust charge at 0.60 oz. per foot of 3/8” o.d. liquid
line and 1.2 oz. per foot of 1/2”. To obtain optimum
performance, system charge should be weighed in
accordance to amount specified on unit rating plate and
any adjustments for additional line length over 20 feet, as
stated above.
toward the compressor. For long vertical risers, additional
traps are recommended for each additional 20 feet of pipe
to insure proper oil movement.
A crankcase heater is recommended for applications
where additional field added charge results in a system
with a reciprocating compressor requiring more than 6 lbs.
of refrigerant or a scroll compressor requiring more than
10 lbs. of refrigerant.
System performance may be verified by using the
refrigerant charging labels provided with each unit.
In air conditioning systems, horizontal suction lines should
be slightly sloped toward the condensing unit. Piping must
avoid dips or low spots can collect oil. To aid in the return
of oil, a trap should be installed at the bottom of any
suction riser. The top end of the riser must be pitched
Suction Line Sizes
Liquid Line Sizes
LINE SET LENGTH AND SIZE
LINE SET LENGTH AND SIZE
BTU/HR 12 FT. 25 FT.
50 FT. 75 FT. 100 FT.
BTU/HR 12 FT. 25 FT.
50 FT.
3/8
75 FT. 100 FT.
12,000
18,000
24,000
30,000
36,000
42,000
48,000
60,000
3/4
3/4
3/4
3/4
7/8
7/8
7/8
7/8
3/4
3/4
3/4
3/4
7/8
7/8
7/8
7/8
3/4
3/4
3/4
3/4
7/8
7/8
7/8
7/8
3/4
3/4
3/4
3/4
12,000
18,000
24,000
30,000
36,000
42,000
48,000
60,000
3/8
3/8
3/8
3/8
3/8
3/8
3/8
3/8
3/8
3/8
3/8
3/8
3/8
3/8
3/8
3/8
3/8
3/8
3/8
3/8
3/8
1/2
1/2
1/2
3/8
3/8
3/8
1/2
1/2
1/2
1/2
1/2
3/8
3/8
3/8
3/8
3/8
3/8
3/8
3/4
7/8
7/8
7/8
7/8
1 1/8
1 1/8
1 1/8
1 1/8
1 1/8
1 1/8
1 1/8
Table 2
Table 3
For installations exceeding 100 feet, contact the Armstrong Air Conditioning Inc.
Technical Services Department at (419) 483-4840.
Page 4
# 41718L098
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START-UP
MAINTENANCE
WARNING
The procedure for start-up of the unit is as follows:
1. Operate the unit for a period of at least 15 minutes to
allow for pressures and temperatures to stabilize.
Unless matched with an indoor section using an
expansion valve, the superheat method can be used
to check the system refrigerant charge. It should be
noted that this method is not accurate at low load
conditions or at outdoor ambients above 106° F.
Before performing maintenance operations on
system, turn off all main power switches to
indoor and outdoor units. Turn off accessory
heater power switch if applicable. Electrical
shock could cause personal injury or death.
Homeowner Maintenance
2. Using accurate gauges and temperature measuring
devices, determine the suction line pressure and
temperature as well as the outdoor ambient tempera-
ture.
Leaves and other large obstructions should be carefully
removed from the outdoor coil surfaces without damaging
the fin surface of the coil.
3. Refer to the refrigerant charging instruction label
located on the inside of the outdoor unit access panel.
Locate the intersection of the measured outdoor
temperature and suction line pressure on the chart.
Routinely clean or change the indoor air filter. Should the
coil become dirty, thus restricting airflow, call a qualified
service person to carefully clean the coil surface.
Dealer Maintenance
4. If the suction line temperature is higher than the
intersection temperature, the system is undercharged.
If the actual suction line temperature is lower than the
chart temperature, the system is overcharged.
An annual inspection by a qualified service person should
be performed to ensure continued quality performance.
Outdoor coil surfaces should be cleaned, taking care not
to damage the fin surface of the coil.
DischargeThermostat (if used)
Some models come equipped with a discharge thermostat
(loss of charge control) to guard against the compressor
overheating from loss of charge. The temperature cut out
for this control is set at 250°F, as determined by compres-
sor manufacturer’s recommendation. Discharge tem-
peratures exceeding 250°F will cause compressor oil
breakdown that will lead to premature compressor
failure. If the control trips during unit operation, a problem
exists within the system. Check for the following as
possible causes:
Several weep holes located in the unit base should be
inspected and cleaned, if necessary, to ensure that proper
drainage can occur.
All electrical wiring and connections should be inspected;
as should all physical connections of individual compo-
nents within the units.
•
•
Low system charge
High discharge pressures
A thorough inspection of the system should be made to
determine the cause. The discharge gas temperature may
be verified by attaching an electronic type thermometer or
thermocouple to the discharge line near the control.
The control resets automatically. If the unit does not have
a discharge thermostat, an add-on kit is available.
# 41718L098
Page 5
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CONNECTION
DIAGRAM
EQUIPMENT GROUND
FAN
CAPACITOR
LINE VOLTAGE - FACTORY
LINE VOLTAGE - FACTORY (IF USED)
LINE VOLTAGE - FIELD
LOW VOLTAGE - FACTORY
LOW VOLTAGE - FACTORY (IF USED)
LOW VOLTAGE - FIELD
FAN
MOTOR
BROWN
VIOLET
RED
COMP
T2
T1
T3
CONTACTOR
NOTE:
T1
L1
L2
L3
BLACK
REPLACEMENT WIRE MUST
BE THE SAME GAGE AND
INSULATION THICKNESS,
105° APPLIANCE WIRING
MATERIAL.
T2
T3
YEL
YEL
DISCHARGE
THERMOSTAT
(IF USED)
HIGH PRESS
SWITCH
(IF USED)
REFER TO RATING
CONNECT TO “C” AND
“Y” TERMINALS OF
INDOOR CONTROL
CIRCUIT HAVING MIN.
40 VA, 24 VOLT N.E.C.
CRANK CASE
HEATER
(IF USED)
PLATE FOR LINE
VOLTAGE 3 PHASE
POWER SUPPLY. USE
MINIMUM 75°C
COPPER WIRE ONLY.
CLASS II TRANSFORMER.
SCHEMATIC
OF POWER
CIRCUIT
OUTDOOR POWER SUPPLY
L3
T3
L2
L1
T1
CRANKCASE HEATER
COMPRESSOR
CONTACTOR
(IF USED)
T2
COMPRESSOR
MOTOR
T2
T3
T1
FAN
MOTOR
TYPICAL
SCHEMATIC
OF CONTROL
CIRCUIT
R
COMPRESSOR
CONTACTOR COIL
HIGH PRESSURE
SWITCH (IF USED)
DISCHARGE THERMOSTAT
(IF USED)
C
Y
THERMOSTAT TERMINALS
PART NO. 38942D005
Figure 3
Page 6
# 41718L098
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START
YEL
ASSIST
CONNECTION
DIAGRAM
START CAP.
DEVICE
(IF USED)
(IF USED)
START RELAY
(IF USED)
COM
FAN HERM
2
1
5
LINE VOLTAGE - FACTORY
LINE VOLTAGE - FACTORY (IF USED)
LINE VOLTAGE - FIELD
LOW VOLTAGE - FACTORY
LOW VOLTAGE - FACTORY (IF USED)
LOW VOLTAGE - FIELD
FAN
COMP
RUN
CAP
RED
RED
BROWN
BLK
VIOLET
NOTE:
BLK
IF ANY OF THE ORIGINAL
WIRE IS REPLACED, THE
SAME SIZE AND TYPE WIRE
MUST BE USED.
RED
CONTACTOR
COMP
C
T1
T2
L1
L2
RR
S
L1
L2
T1
T2
YEL
BLK
RED
GROUND
SCREW
YEL
ALT.
CONTACTOR
HIGH PRESSURE
SWITCH
DISCHARGE
THERMOSTAT
(IF USED)
(IF USED)
CRANK CASE
HEATER
BLUE
TO SINGLE PHASE
(IF USED)
POWER SUPPLY PER
RATING PLATE WITH
MINIMUM 75°C COPPER
WIRE ONLY. CIRCUIT
PROTECTION PER
RATING PLATE.
CONNECT TO “C” AND
“Y” TERMINALS OF
LOW PRESSURE
SWITCH
INDOOR CONTROL
(IF USED)
C C
CIRCUIT HAVING MIN.
40 VA, 24 VOLT N.E.C.
CLASS II TRANSFORMER.
LOAD
TIME DELAY RELAY
T'STAT
(IF USED)
SCHEMATIC OF POWER CIRCUIT
GROUND
SCREW
OUTDOOR POWER SUPPLY
L1
L2
T2
CRANKCASE HEATER
COMPRESSOR
CONTACTOR
(IF USED)
T1
R
COMPRESSOR
C
MOTOR
S
5
2
R
COMPRESSOR
RUN
CAPACITOR
START
START RELAY
(IF USED)
ASSIST
DEVICE
(IF USED)
1
START CAPACITOR
(IF USED)
FAN
MOTOR
TYPICAL
SCHEMATIC
OF CONTROL
CIRCUIT
TDC
R
COMPRESSOR
CONTACTOR COIL
HIGH PRESSURE
TIME DELAY
LOW PRESSURE
DISCHARGE THERMOSTAT
SWITCH
RELAY
SWITCH
(IF USED)
(IF USED)
(IF USED)
(IF USED)
C
Y
THERMOSTAT TERMINALS
PART NO. 38602D008
Figure 4
# 41718L098
Page 7
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Limited Warranty
August 1, 1997
This warranty gives you specific legal rights and you may have other rights
which vary from state/province to state/province.
Warrantor: Armstrong Air Conditioning Inc., 421 Monroe St., Bellevue, OH 44811
Armstrong Air Conditioning Inc. products are available under the following names: Air Ease, Armstrong Air, American Aire, Concord
Subject to the limitations stated in this warranty, we warrant to the first buyer for use the residential heating, cooling or heat pump unit,
when installed, operated and maintained as required by this warranty, to be free of defects in workmanship or material for a period of five
years (two years for commercial equipment) from the time of installation. We will replace any defective component without cost or
expense to you except for the costs of delivery and labor for removal and replacement of the defective component.
The SCU 12, 13 and E Series carry a 10 year compressor warranty. All other SCU Series air conditioners carry a 5 year compres-
sor warranty.
Warranty Begins
The warranty period begins when the installation is complete and the product is ready to operate. You must be able to verify this date
whenever a warranty claim is made. Original bill of sale, installer’s invoice or other similar document will suffice. If the beginning date
cannot be verified, we will consider warranty coverage to begin six months after the date the product was shipped from our factory.
Limitations on Implied Warranties
Implied warranties of merchantability or, to the extent applicable, fitness for a particular purpose are limited to five years, the same
duration as the basic limited written warranty provided herein. Some states/provinces do not allow limitations on how long an implied
warranty of merchantability or fitness lasts, so the above limitations or exclusions may not apply to you.
Only Warranty
This written Limited Warranty is the only warranty made by the warrantor; this warranty is in lieu of and excludes all other warranties,
express or implied. The warrantor does not authorize any person to provide any other warranty or to assume for it any further obligation
in connection with the warranted product.
What is NOT Covered
1. Cabinets or cabinet pieces.
2. Normal maintenance items such as filters, fan belts, fuses or other consumable items.
3. Damage caused by misuse, failure to maintain properly, accidents or acts of God.
4. External wiring, piping, venting or attachment of accessory products not integral to our product, including without limitation,
humidifier, air cleaner, vent damper, thermostat or other mechanical devices not manufactured by the warrantor.
5. Products that have been operated in a corrosive atmosphere where a concentration of acids, halogenated hydrocarbons or
other corrosive elements causes deterioration to metal surfaces or integral components. NOTE: Operation in a corrosive
atmosphere is considered abuse and voids this warranty.
6. Products that have NOT been installed in accordance with our published installation instructions, applicable local, state/
provincial or national codes, ACCA published standards.
7. Products that have NOT been installed by competent, qualified installers.
8. Products that have been moved from their original place of installation.
Warranty on Replacement Components
Any replacement component furnished by us will assume the remaining (unused) portion of the Limited Warranty.
Consequential Damages
The warrantor shall not be responsible for any consequential damages caused by any defect in the product. Some state/provinces do not
allow the exclusion or limitations of incidental or consequential damages, so the above limitation or exclusion may not apply to you.
NOTE: After the first year, in the event that a gas or oil heat exchanger is no longer being manufactured by the warrantor, the warrantor
will allow a credit equal to the then current wholesale price of an equivalent heat exchanger towards the purchase of a new Armstrong gas
or oil furnace.
This product must be installed, used and cared for in accordance with the instruction manual. You are responsible for required periodic
maintenance or service, such as changing or cleaning of air filters and lubrication or cleaning of components. Failure to properly install,
operate or maintain your unit voids this warranty.
Owner Record
Model # ________________________ Serial # _________________ Installation Date __________________
INSTALLED BY:
Dealer _____________________________________________________________________________________
Address ____________________________________________________________________________________
Telephone # ____________________________
License # _______________________________
Page 8
# 41718L098
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