Lennox International Inc Air Conditioner Dave Lennox Signature Collection XC21 System User Manual
INSTALLATION  
INSTRUCTIONS  
E2012 Lennox Industries Inc.  
Dallas, Texas, USA  
Dave Lennox Signature®  
Collection XC21 System  
AIR CONDITIONERS  
506923−01  
7/2012  
Litho U.S.A.  
Supersedes 4/2012  
THIS MANUAL MUST BE LEFT WITH THE  
HOMEOWNER FOR FUTURE REFERENCE  
WARNING  
Improper installation, adjustment, alteration, service or  
maintenance can cause property damage, personal inju-  
ry or loss of life.  
WARNING  
The State of California has determined that this product  
may contain or produce a chemical or chemicals, in very  
low doses, which may cause serious illness or death. It  
may also cause cancer, birth defects, or reproductive  
harm.  
Installation and service must be performed by a licensed  
professional installer (or equivalent) or service agency.  
CAUTION  
General  
Before attempting to perform any service or mainte-  
nance, turn the electrical power to unit OFF at discon-  
nect switch.  
This XC21 outdoor unit is designed for use with HFC−410A  
refrigerant only. This unit must be installed with an ap-  
proved indoor unit. See the Lennox XC21 Product Specifi-  
cations bulletin (EHB) for approved indoor component  
match ups.  
NOTICE !  
For more in−depth information, consult the Installa-  
tion and Service Procedures manual, available as  
Corp.1007−L2 on DaveNet or through the Technical  
Support department at 800−453−6669.  
These instructions are intended as a general guide and do  
not supersede local codes in any way. Consult authorities  
having jurisdiction before installation.  
STEP 1 −− SETTING THE UNIT −− Clearances  
MINIMUM CLEARANCE  
ABOVE UNIT  
CLEARANCE ON ALL SIDES ꢀ INCHES (MILLIMETERS)  
6 (152)  
NOTES:  
S Clearance to access panel must be 30  
30 (762)  
inches (762mm).  
48 (1219)  
S Clearance to one of the other three  
sides must be 36 inches (914mm).  
12 (305)  
S Clearance to one of the remaining two  
sides may be 12 inches (305mm) and  
the final side may be  
(152mm).  
6
inches  
36 (914)  
MINIMUM CLEARANCE BETWEEN TWO UNITS  
ACCESS PANEL  
24  
(610)  
LINE SET  
CONNECTIONS  
REAR VIEW OF UNIT  
FIGURE 1  
Page 1  
7/2012  
506923−01  
*2P72012*  
*P506923-01*  
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STABILIZING UNIT ON UNEVEN SURFACES  
PLACEMENT  
#10 X 1/2" LONG  
SELF−DRILLING  
SHEET METAL  
INSTALL UNIT AWAY  
FROM WINDOWS  
COIL  
SCREWS  
STABILIZING BRACKET  
(18 GAUGE METAL ꢀ 2"  
WIDTH; HEIGHT AS  
REQUIRED)  
BASE PAN  
#10 X 1−1/4" LONG  
HEX HD SCREW AND  
FLAT WASHER  
CORNER POST  
Concrete slab ꢀ use two  
plastic anchors (hole drill 1/4")  
TWO 90_ ELBOWS INSTALLED IN LINE SET  
WILL REDUCE LINE SET VIBRATION  
!
IMPORTANT !  
FIGURE 2  
Unit Stabilizer Bracket Use  
(field−provided):  
Always use stabilizers when unit is raised  
above the factory height.  
(Elevated units could become unstable in  
gusty wind conditions.)  
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  
Stabilizers may be used on any unit installed  
on unstable and uneven surfaces.  
FIGURE 5  
STEP 2 −− REFRIGERANT PIPING −− Flush-  
ing Existing Line Set & Indoor Coil  
MOUNTING  
SLAB  
Flush the existing line set per the following instruc-  
tions. For more information, refer to the Installation  
and Service Procedures manual available on Dave-  
Net. CAUTION −DO NOT attempt to flush and re−use ex-  
isting line sets or indoor coil when the system con-  
tains contaminants (i.e., compressor burn out).  
GROUND LEVEL  
FIGURE 3  
ELEVATED SLAB MOUNTING USING FEET  
EXTENDERS  
NOTE − When installing refrigerant lines longer than 50  
feet, refer to the Refrigerant Piping Design and Fabrication  
Guidelines manual available on DaveNet (Corp. 9351−L9),  
or contact the Technical Support Department Product Ap-  
plication group for assistance.  
Use additional 2" SCH 40 male  
threaded adapters which can  
be threaded into the female  
ADAPTER  
2" (50.8MM) SCH 40  
FEMALE THREADED  
threaded adapters to make  
additional adjustments to the  
level of the unit.  
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)  
2" (50.8MM)  
SCH 40 MALE  
THREADED  
ADAPTER  
Models  
Liquid  
Line  
Vapor/  
Suction  
Line  
L15 Line Set  
−024, −036  
and−048  
3/8 (10)  
7/8 (22)  
L15 line set sizes are  
dependent on unit match up.  
See XP21 Engineering  
Handbook to determine  
correct line set sizes.  
BASE  
LEG DETAIL  
−060  
3/8 (10)  
1−1/8ꢁ (29) Field Fabricated  
NOTE ꢀ Some applications may required a field−provided 7/8" to  
1−1/8" adapter.  
FIGURE 4  
Page 3  
XC21 SERIES  
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IMPORTANT !  
WARNING  
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.  
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.  
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.  
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).  
IMPORTANT !  
Some scroll compressors have an internal vacuum  
protector that will unload scrolls when suction pres-  
sure goes below 20 psig. A hissing sound will be  
heard when the compressor is running unloaded.  
Protector will reset when low pressure in system is  
raised above 40 psig. DO NOT REPLACE COM-  
PRESSOR.  
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.  
CAUTION  
As with any mechanical equipment, contact with sharp  
sheet metal edges can result in personal injury. Take  
care while handling this equipment.  
Page 4  
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STEP 2 −− REFRIGERANT PIPING −− Removing Existing Indoor Metering Device  
TYPICAL EXISTING FIXED ORIFICE  
REMOVAL PROCEDURE  
(UNCASED COIL SHOWN)  
TYPICAL EXISTING EXPANSION VALVE REMOVAL  
PROCEDURE (UNCASED COIL SHOWN)  
OR  
1B  
1A  
STUB END  
TWO−PIECE PATCH PLATE  
(UNCASED COIL ONLY)  
LIQUID LINE  
ORIFICE  
HOUSING  
DISTRIBUTOR TUBES  
EXPANSION  
VALVE  
LIQUID LINE ORIFICE HOUSING  
DISTRIBUTOR  
TUBES  
®
TEFLON  
RING  
®
TEFLON RING  
FIXED ORIFICE  
BRASS NUT  
®
TEFLON  
RING  
SENSING  
LINE  
DISTRIBUTOR  
ASSEMBLY  
DISTRIBUTOR  
ASSEMBLY  
EQUALIZER  
LINE  
REMOVE AND DISCARD  
®
WHITE TEFLON SEAL  
(IF PRESENT)  
LIQUID LINE ASSEMBLY  
(INCLUDES STRAINER)  
LIQUID LINE  
ASSEMBLY WITH  
BRASS NUT  
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.  
MALE EQUALIZER  
LINE FITTING  
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.  
VAPOR  
LINE  
LIQUID  
LINE  
SENSING BULB  
1. On fully cased coils, remove the coil access and plumbing panels.  
4. Remove and discard fixed orifice, valve stem assembly (if present)  
®
and Teflon washer as illustrated above.  
2. Remove any shipping clamps from the liquid line and distributor  
assembly.  
5. Use a field−provided fitting to temporarily reconnect the liquid line to the  
indoor unit’s liquid line orifice housing.  
3. Disconnect the equalizer line from the check expansion valve  
equalizer line fitting on the vapor line.  
4. Remove the vapor line sensing bulb.  
CONNECT GAUGES AND EQUIPMENT FOR  
FLUSHING PROCEDURE  
5. Disconnect the liquid line from the check expansion valve at the liquid  
line assembly.  
2
6. Disconnect the check expansion valve from the liquid line orifice  
housing.Take care not to twist or damage distributor tubes during this  
process.  
CYLINDER CONTAINING  
CLEAN HCFC−22 TO BE  
USED FOR FLUSHING  
(Positioned to deliver liquid  
refrigerant)  
GAUGE  
MANIFOLD  
®
A
7. Remove and discard check expansion valve and the two Teflon rings.  
LOW  
HIGH  
8. Use a field−provided fitting to temporarily reconnect the liquid line to the  
indoor unit’s liquid line orifice housing.  
1
NEW  
OUTDOOR  
UNIT  
VAPOR LINE  
SERVICE VALVE  
FLUSHING LINE SET  
OPENED  
CLOSED  
The line set and indoor unit coil must be flushed with at least the same  
3
EXISTING  
INDOOR  
UNIT  
amountof clean refrigerant that previously charged the system. Check  
the charge in the flushing cylinder before proceeding.  
B
LIQUID LINE SERVICE  
VALVE  
1. Set the recovery machine for liquid recovery and start the recovery  
machine. Open the gauge set valves to allow the recovery machine to  
RECOVERY  
CYLINDER  
TANK  
RETURN  
pull a Bvacuum on the existing system line set and indoor unit coil.  
2. Position the cylinder of clean HCFC−22 for delivery of liquid refrigerant  
C
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.  
INLET  
D
DISCHARGE  
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.  
1. HCFC−22 cylinder with clean refrigerant (positioned to deliver liquid  
refrigerant)to the vapor service valve.  
2. HCFC−22 gauge set (low side) to the liquid line valve.  
4. Close the valve on the inverted HCFC−22 drum and the gauge set  
valves. Pump the remaining refrigerant out of the recovery machine  
and turn the machine off.  
3. HCFC−22 gauge set center port to inlet on the recovery machine with an  
empty recovery tank connected to the gauge set.  
4. Connect recovery tank to recovery machine per machine instructions.  
FIGURE 6  
Page 5  
XC21 SERIES  
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STEP 2 −− REFRIGERANT PIPING −− Brazing Procedures  
CAP AND CORE REMOVAL  
PIPING PANEL REMOVAL / PREPARING LINE SET  
Remove service cap and core from both the suction /  
vapor and liquid line service ports.  
SERVICE PORT CAP  
Remove piping panel to access service valves. Cut  
2
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.  
SERVICE PORT  
CORE  
CUT AND DEBUR  
LINE SET SIZE MATCHES  
SERVICE VALVE CONNECTION  
SERVICE VALVE  
CONNECTION  
COPPER TUBE  
STUB  
REDUCER  
LIQUID LINE SERVICE VALVE  
LINE SET SIZE IS SMALLER  
THAN CONNECTION  
REFRIGERANT LINE  
SERVICE PORT  
CORE  
SERVICE  
PORT CAP  
SUCTION / VAPOR LINE  
SERVICE VALVE  
DO NOT CRIMP SERVICE VALVE  
CONNECTOR WHEN PIPE IS  
SMALLER THAN CONNECTION  
ATTACH THE MANIFOLD GAUGE SET FOR BRAZING  
LIQUID AND SUCTION / 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 suction / vapor line service port, nitrogen flow will have an exit point.  
LOW  
HIGH  
ATTACH  
GAUGES  
SUCTION / VAPOR SERVICE PORT MUST BE  
OPEN AND SERVICE PORT CORE REMOVED  
TO ALLOW EXIT POINT FOR NITROGEN FLOW  
B
SUCTION /  
VAPOR LINE  
SERVICE  
VALVE  
C
SUCTION / VAPOR  
LINE  
OUTDOOR  
UNIT  
INDOOR  
UNIT  
NITROGEN  
LIQUID LINE SERVICE  
VALVE  
LIQUID LINE  
A
FIGURE 7  
Page 6  
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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.  
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.  
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  
4additionalwater−saturated cloths under the valve body to protect the base paint.  
5
FLOW NITROGEN  
WARNING  
Flow regulated nitrogen (at 1 to 2 psig) through the refrigeration  
gauge set into the valve stem port connection on the liquid service  
valve and out of the suction / vapor valve stem port. See steps 3A, 3B  
and 3C on previous page and below for manifold gauge setup.  
FIRE, PERSONAL INJURY, OR PROPERTY DAMAGE  
may result if you do not wrap a water−saturated cloth around  
both liquid and suction 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.  
BRAZE LINE SET  
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.  
Cloths must remain water−saturated throughout the brazing and  
cool−down process.  
6
1. Braze liquid line to liquid line service valve.  
2. Braze suction / vapor line to suction / vapor service  
valve.  
WHEN BRAZING LINE SET TO  
SERVICE VALVES, POINT FLAME  
AWAY FROM SERVICE VALVE.  
6B  
SUCTION / VAPOR SERVICE  
PORT MUST BE OPEN AND  
SERVICE PORT CORE RE-  
MOVED TO ALLOW EXIT POINT  
FOR NITROGEN FLOW  
SUCTION / 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.  
6A  
LIQUID LINE  
WATER−SATURATED  
CLOTHS  
PREPARATION FOR NEXT STEP  
After all connections have been brazed, disconnect manifold gauge set from service ports. Apply additional water−saturated cloths to both  
services valves to cool piping. Once piping is cool, remove all water−saturated cloths.  
7
FIGURE 8  
Page 7  
XC21 SERIES  
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STEP 3 −− INSTALLING INDOOR EXPANSION VALVE  
This outdoor unit is designed for use in systems that include an expansion valve metering device. See the XC21 Product  
Specifications bulletin (EHB) for approved expansion valve kit match−ups and application information. The expansion valve  
can be installed internal or external to the indoor coil. In applications where an uncased coil is being installed in a field−pro-  
vided plenum, install the expansion valve in a manner that will provide access for future field service of the expansion valve.  
Refer to below illustration for reference during installation of expansion valve.  
®
3. Install one of the provided Teflon rings around the  
stubbed end of the expansion valve and use refrigerant  
oil to lightly lubricate the connector threads and ex-  
INDOOR EXPANSION VALVE INSTALLATION  
®
posed surface of the Teflon ring.  
TWO−PIECE  
PATCH PLATE  
4. Attach the stubbed end of the expansion valve to the  
liquid line orifice housing. Finger tighten, then use an  
appropriately sized wrench to turn an additional 1/2  
turn clockwise as illustrated in the figure to the right, or  
tighten to 20 ft−lb.  
(Uncased Coil Shown)  
1/2 Turn  
(UNCASED  
STUB  
END  
LIQUID LINE  
ORIFICE  
COIL ONLY)  
12  
1
11  
10  
EXPANSION  
VALVE  
HOUSING  
2
DISTRIBUTOR  
TUBES  
9
8
3
®
®
5. Place the remaining Teflon washer around the other  
end of the expansion valve. Lightly lubricate connector  
TEFLON  
RING  
4
5
7
6
®
threads and expose surface of the Teflon ring with  
refrigerantoil.  
6. Attach the liquid line assembly to the expansion valve.  
Finger tighten, then use an appropriately sized wrench  
to turn an additional 1/2 turn clockwise as illustrated in  
the figure above or tighten to 20 ft−lb.  
®
TEFLON  
RING  
SENSING  
LINE  
DISTRIBUTOR  
ASSEMBLY  
EQUALIZER  
LINE  
LIQUID LINE  
ASSEMBLY WITH  
BRASS NUT  
SENSING BULB INSTALLATION  
1. Attach the vapor line sensing bulb in the proper orienta-  
tion as illustrated below using the clamp and screws  
provided.  
MALE EQUALIZER LINE  
FITTING (SEE  
EQUALIZER LINE  
INSTALLATION FOR  
DETAILS)  
VAPOR  
LINE  
2. NOTE − Though it is preferred to have the sensing bulb  
installedon a horizontal run of the vapor line, installation  
on a vertical run of piping is acceptable if necessary.  
NOTE ꢀ Confirm proper thermal contact between vapor line  
and expansion bulb before insulating the sensing bulb.  
1/8 Turn  
Sensing bulb insulation is required if  
expansion valve is installed external to the  
coil casing. See sensing bulb installation for  
bulb positioning.  
12  
LIQUID LINE  
3. Connect the equalizer line from the expansion valve to  
the equalizer vapor port on the vapor line. Finger tighten  
the flare nut, then tighten an additional 1/8 turn (7 ft−lbs)  
as illustrated to the right.  
1
5
11  
10  
2
9
8
3
4
7
6
EQUALIZER LINE INSTALLATION  
ON LINES SMALLER THAN  
7/8", MOUNT SENSING  
BULB AT EITHER THE 3 OR  
9 O’CLOCK POSITION.  
1. 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 below.  
VAPOR LINE  
2. Remove the field−provided fitting that temporarily reconnected  
the liquid line to the indoor unit’s distributor assembly.  
12  
BULB  
BULB  
FLARE SEAL CAP  
FLARE NUT  
VAPOR LINE  
ON 7/8" AND LARGER LINES,  
MOUNT SENSING BULB AT  
EITHER THE 4 OR 8 O’CLOCK  
POSITION. NEVER MOUNT  
THE SENSING BULB ON  
BOTTOM OF LINE.  
COPPER FLARE  
SEAL BONNET  
OR  
12  
MALE BRASS EQUALIZER  
LINE FITTING  
BULB  
BULB  
VAPOR LINE  
NOTE ꢀ NEVER MOUNT THE SENSING  
BULB ON BOTTOM OF LINE.  
FIGURE 9  
Page 8  
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STEP 4 −− LEAK TEST AND EVACUATION  
LOW  
HIGH  
MANIFOLD GAUGE SET  
OUTDOOR UNIT  
A
B
TO VAPOR  
SERVICE VALVE  
NOTE − Position  
canister to deliver  
liquid refrigerant.  
NITROGEN  
HFC−410A  
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.  
FIGURE 10  
Page 9  
XC21 SERIES  
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STEP 4 −− LEAK TEST AND EVACUATION (Continued)  
EVACUATION  
CONNECT GAUGE SET  
HIGH  
LOW  
NOTE ꢀ Remove cores from service valves (if not already done).  
3
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 available micron gauge connector  
on the 1/4 SAE in−line tee.  
OUTDOOR  
UNIT  
MANIFOLD  
GAUGE SET  
1/4 SAE TEE WITH SWIVEL  
COUPLER  
A
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.  
500  
MICRON  
GAUGE  
C
TO VAPOR  
SERVICE VALVE  
NITROGEN  
NOTE − Position  
canister to deliver  
liquid refrigerant.  
HFC−410A  
B
VACUUM PUMP  
TO LIQUID LINE  
SERVICE VALVE  
D
EVACUATE THE SYSTEM  
RECOMMEND  
MINIMUM 3/8" HOSE  
4
A. Open both manifold valves and start the vacuum pump.  
B. Evacuate the line set and indoor unit to an absolute pressure of 23,000 microns (29.01 inches of mercury).  
NOTEꢀ During the early stages of evacuation, it is desirable to close the manifold gauge valve at least once. 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 above zero within a given volume or system. Absolute pressure in a  
vacuum is equal to atmospheric pressure minus vacuum pressure.  
C. When the absolute pressure reaches 23,000 microns (29.01 inches of mercury),  
perform the following:  
WARNING !  
Possible equipment damage.  
S
S
S
S
S
Close manifold gauge valves.  
Close valve on vacuum pump.  
Turn off vacuum pump.  
Avoid deep vacuum operation. Do not use  
system.  
Disconnect manifold gauge center port hose from vacuum pump.  
compressors to evacuate  
a
Attach manifold center port hose to a nitrogen cylinder with pressure  
regulatorset to 150 psig (1034 kPa) and purge the hose.  
Extremely low vacuum can cause internal  
arcing and compressor failure. Damage  
caused by deep vacuum operation will  
void warranty.  
S
S
Open manifold gauge valves to break the vacuum in the line set and indoor  
unit.  
Close manifold gauge valves.  
D. 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.  
E. 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.  
F. When the absolute pressure requirement above has been met, disconnect the manifold hose from the vacuum pump and connect it to a  
cylinder of HFC−410A positioned to deliver liquid refrigerant. Open the manifold gauge valve 1 to 2 psig in order to release the vacuum in the line  
set and indoor unit.  
G. Perform the following:  
S
S
S
Close manifold gauge valves.  
Shut off HFC−410A cylinder.  
1/6 TURN  
Reinstall service valve cores by removing manifold hose from service valve. Quickly install cores with core  
tool while maintaining a positive system pressure.  
12  
1
11  
7
2
S
Replace stem caps and finger tighten them, then tighten an additional one−sixth (1/6) of a turn as illustrated.  
10  
9
3
4
8
5
6
FIGURE 11  
Page 10  
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STEP 5 −− 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,  
IMPORTANT !  
wiring must conform with current local codes and the current  
Canadian Electrical Code (CEC).  
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.  
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.  
CAUTION  
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 can affect  
electronic components. Take care  
during unit installation and service to  
protect the unit’s electronic controls.  
ELECTROSTATIC  
DISCHARGE  
(ESD)  
Precautions and  
Procedures  
Precautions will help to avoid control  
exposure to electrostatic discharge by  
putting the unit, the control and the  
technician at the same electrostatic  
WARNING  
Electric Shock Hazard. Can cause injury  
or death. Unit must be grounded in  
accordance with national and local  
codes.  
potential. Touch hand and all tools on an  
before  
unpainted  
unit  
surface  
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.  
performing any service procedure to  
neutralize electrostatic charge.  
INSTALL THERMOSTAT  
SIZE CIRCUIT AND INSTALL DISCONNECT  
SWITCH  
Install room thermostat (ordered separately) on an  
inside wall in the center of the conditioned area and  
5 feet (1.5m) from the floor. The thermostat should  
not be installed on an outside wall or where it can be  
affected by sunlight or drafts.  
2
1
Refer to the unit nameplate for minimum circuit  
ampacity, and maximum fuse or circuit breaker size  
(HACR per NEC). Install power wiring and properly  
sized disconnect switch.  
SERVICE  
DISCONNECT  
SWITCH  
THERMOSTAT  
5 FEET  
(1.5M)  
NOTE ꢀ 24VAC, Class II circuit connections are made  
in the control box.  
NOTE ꢀ Units are approved for use only with copper  
conductors. Ground unit at disconnect switch or  
connect to an earth ground.  
FIGURE 12  
Page 11  
XC21 SERIES  
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A. ROUTE CONTROL WIRES ꢀ NON−COMMUNICATING  
3
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 outdoor control (A175).  
CONTROL  
(A175)  
NOTE ꢀ Do not bundle any excess 24VAC control wires inside control box.  
B
NOTE ꢀ Wire tie provides low voltage wire strain relief and maintains  
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  
MORE THAN 100’ (30 METERS) 16  
TEMPERATURE RATING  
35ºC MINIMUM.  
HOLE  
A
B. ROUTE CONTROL WIRES ꢀ COMMUNICATING  
Maximumlength of wiring (18 gauge) for all connections on the RSBus is 1500 feet (457 meters). Wires should be color−coded, with a temperature rating  
º
º
of 95 F (35 C) minimum, and solid−core (Class II Rated Wiring). All low voltage wiring must enter unit through provided field−installed busing installed in  
electrical inlet.  
Communicatingsystems using the icomfortt−enabled thermostat require four thermostat wires between the thermostat and the furnace/air handler con-  
trol 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.  
icomfortt−enabled  
icomfortt−enabled  
Indoor Unit  
Outdoor Unit  
icomfortt−enabled  
thermostat  
Single Wire To C  
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.  
GROUND LUG*  
4
WATERTIGHT  
CONTROL BOX  
CONDUIT FITTING  
* Attach field−provided  
green ground wire to  
provided ground lug.  
ELECTRICAL  
INLET (HIGH  
VOLTAGE)  
CONTACTOR  
WATERTIGHT FLEX-  
IBLE CONDUIT  
NOTE − Grounding wire  
must be a single, contin-  
uous wire run from unit  
ground lug to earth  
ground. DO NOT splice  
wire.  
WIRING ENTRY  
POINTS  
TO SERVICE  
DISCONNECT BOX  
ELECTRICAL INLET (CONTROL WIRING ꢀ  
LOW VOLTAGE). USE BUSHING  
PROVIDED IN BAG ASSEMBLY HERE.  
ACCESS VIEW  
FIGURE 13  
Page 12  
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STEP 5 −− ELECTRICAL (Continued) −− Outdoor Control (A175) Jumpers and Terminals  
Communication System  
The Lennox icomfortt−enabled thermostat must be  
used in communicating applications.  
The jumper settings and link are default settings and ONLY control  
system operation if configuration settings in the icomfortt−enabled  
thermostatare not available.  
NOTE ꢀ Fan cycling routine when activated will cycle the  
fan ON for five minutes if the outdoor ambient air  
temperature is between 15ºF and 35ºF and the  
compressor has been OFF for 25 to 30 minutes. This  
option is to help reduce the potential for ice build up on the  
orifice ring during system OFF cycles that are greater  
than 25 to 30 minutes.  
Non−Communicating System  
The unit will operate based on jumper settings and R−TO− DS link on  
the MAIN CONTROL. All unit setting changes must be done at the  
MAIN CONTROL. The Lennox ComfortSense7000 thermostat  
may be used, as well as other non−communicating electronic−only  
thermostats.  
J3 ALL UNITS)  
FAN CYCLING  
7−SEGMENT  
DISPLAY  
JUMPER ON  
FAN ON FOR 5 MINUTES  
ON  
Set up of jumpers on  
replacement outdoor  
control.  
PUSH  
BUTTON  
JUMPER OFF  
DISABLE (DEFAULT)  
OFF  
SEE NOTE ABOVE FOR FURTHER DETAILS.  
J1 (HP ONLY)  
DEFROST TERMINATION TEMPERATURE  
(HP ONLY) J4  
COMPRESSOR SHIFT DELAY  
100  
DEGREE  
TARGET  
30  
SECOND DELAY  
(DEFAULT)  
30  
90  
90  
DEGREE  
TARGET  
0
SECOND DELAY  
0
(DEFAULT WHEN JUMPER IS  
REMOVED OR MISSING)  
70  
DEGREE  
TARGET  
(TWO−STAGE HEAT  
PUMP ONLY) J2  
SECOND−STAGE LOCK−IN  
TEMPERATURE  
50  
DEGREE  
TARGET  
55  
(DEFAULT)  
DEGREE  
TARGET  
DS TO R TWO−STAGE UNIT  
ONLY)  
50  
DEGREE  
TARGET  
®
Cut for Humiditrol − Enhanced  
Dehumification Accessory (EDA)  
applications.  
45  
DEGREE  
NOTE − LINK NOT APPLICABLE TO  
ONE−STAGE UNITS. CUTTING LINK WILL  
HAVE NO AFFECT ON OPERATION OF  
ONE−STAGE UNITS.  
TARGET  
40  
DEGREE  
TARGET (DEFAULT)  
FIGURE 14  
Page 13  
XC21 SERIES  
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STEP 5 −− 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 icomfortt−enabled thermostat Quick  
Start Guide which is provided with the thermostat.  
Air Handler  
ComfortSense[ 7000 Thermostats  
Catalog # Y0349 or Y2081  
7
DS  
XC21 Two−Stage  
Air Conditioner Control  
R
G
O
W
L
On−board link  
W2  
Low voltage thermostat  
wiring  
L
H
Flat metal jumper  
Y2  
Y1  
W1  
O
DH  
O
L
R
DS  
C
H
C
2
D
B
Y1  
5
Y2  
Y2  
Y1  
6
1
G
W3  
R
C
3
W2  
W1  
T
T
4
1. Thermostat T terminals are used for outdoor sensor input. Use for thermostat’s outdoor temperature display (optional).  
®
2. R to L connection is required for this model when using the ComfortSense 7000 − catalog number Y0349 only. Resistor Kit (catalog number 47W97)  
required and ordered separately.  
3. Air handler control ships from factory with metal jumpers installed across W1, W2 and W3. For one−stage electric heat, do not remove factory  
installed metal jumpers.  
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 to 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 Y1−Y2 2 STAGE COMPR for two−stage compressor and two−speed fan operation.  
®
6. Cut loop jumper (clippable wire) DS to R on two−stage units for Humiditrol applications. This will slow the outdoor unit’s fan speed to a specific  
RPM. A wire must be installed between the DS terminals on the air handler and outdoor unit controls.  
®
7. Cut on−board link (clippable wire) DS−R for Humiditrol or Harmony IIIt applications. This will slow the indoor blower motor to the lowest speed  
setting. See air handler installation instruction or engineering handbook for lowest fan speed information.  
FIGURE 15  
Page 14  
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Furnace  
ComfortSense[ 7000 Thermostats  
5
Catalog # Y0349 or Y2081  
XC21 Two−Stage Air  
Conditioner Control  
DS  
O
R
G
W
L
On−board link  
W2  
Low voltage thermostat  
wiring  
L
H
Y2  
Y1  
W1  
O
DH  
O
L
R
DS  
C
H
C
2
D
B
Y1  
3
Y2  
G
Y2  
Y1  
4
1
R
C
W2  
W1  
T
T
1. Thermostat T terminals are used for outdoor sensor input. Use for thermostat’s outdoor temperature display (optional).  
®
2. R to L connection is required for this model when using the ComfortSense 7000 − catalog number Y0349 only. Resistor Kit (catalog number  
47W97) required and ordered separately.  
3. Cut on−board link W915 (clippable wire) for two−stage operation.  
®
4. Cut loop jumper (clippable wire) DS to R on two−stage units for Humiditrol applications. This will slow the outdoor unit’s fan speed to a specific  
RPM. A wire must be installed between the DS terminals on the furnace and outdoor unit controls.  
®
5. Cut on−board link (clippable wire) DS−R for Humiditrol or Harmony IIIt applications. This will slow the indoor blower motor to the lowest speed  
setting. See furnace installation instruction or engineering handbook for lowest fan speed information.  
FIGURE 16  
Page 15  
XC21 SERIES  
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2. Adjust room thermostat set point 5ºF above (heating  
operation) or 5ºF below (cooling operation) the room  
temperature.  
Charging  
The XC21 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 sticker on the  
unit access panel. Detailed information is given in the  
XC21 Installation and Service Procedures manual, which  
is available on DaveNet.  
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. Install switch in series with Y2  
wire from room thermostat. (See note ** in the Field  
Operational Checklist on page 17).  
Start−Up Checklists  
TWO−STAGE COMPRESSOR PERFORMANCE  
Use this procedure to verify part- and full-load capacity op-  
eration of the two-stage compressor.  
5. Cycle main power ON.  
6. Allow pressures and temperatures to stabilize before  
taking any reading (may take up to 10 minutes).  
IMPORTANT !  
7. Record all of the readings for the Y1 demand.  
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).  
8. Close switch to energize Y2 demand. Verify power is  
going to compressor solenoid (see note ** in the Field  
Operational Checklist on page 17).  
9. Allow pressures and temperatures to stabilize before  
taking any reading (may take up to 10 minutes).  
10. Record all of the readings with the Y1 and Y2 demand.  
TOOLS REQUIRED  
11. If temperatures and pressures change in the direction  
noted in chart, the compressor is properly modulating  
from low to high capacity. (If no amperage, pressures  
or temperature readings change when this test is per-  
formed, the compressor is not switching between low  
and high capacity and replacement is necessary.)  
S Refrigeration gauge set  
S Digital volt/amp meter  
S Electronic temperature thermometer  
S On-off toggle switch  
PROCEDURE  
1. Turn main power OFF to outdoor unit.  
12. After testing is complete, return unit to original set up.  
Page 16  
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XC21 Field Operational Checklist  
Cooling***  
Heating***  
Unit Readings  
Y1  
First  
Stage  
Expected results  
during Y2 demand  
(toggle switch ON)  
Y2  
Second  
Stage  
Expected results  
during Y2 demand  
(toggle switch ON)  
Y1  
First Stage  
Y2 Second  
Stage  
Compressor  
Voltage  
Same  
Same  
Amperage  
Higher  
Higher  
Condenser Fan motor  
Amperage  
Same or Higher  
Same or Higher  
Temperature  
Ambient  
Same  
Higher  
Higher  
Same  
Lower  
Same  
Lower  
Higher  
Same  
Higher  
Outdoor Coil Discharge Air  
Compressor Discharge Line  
Indoor Return Air  
Indoor Coil Discharge Air  
Pressures  
Suction (Vapor)  
Liquid  
Lower  
Higher  
Down  
Higher  
Note − Unit may have a low ambient control or control that locks in second−stage operation below its set point. It may be necessary to remove a wire  
from the control when performing this check.  
**  
On the XC21 units, the System Operation Monitor controls the second−stage solenoid coil in compressor.  
Cooling Mode Operation − Block outdoor coil to maintain a minimum of 375 psig during testing.  
***  
Page 17  
XC21 SERIES  
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XC21 Start−Up and Performance Checklist  
Customer  
Address  
Serial  
Indoor Unit Model  
Outdoor Unit Model  
Solar Module Mfg and Model  
Notes:  
Serial  
Serial  
START−UP CHECKS  
Refrigerant Type:  
Rated Load Amps  
Actual Amps  
Rated Volts  
Actual Volts  
Condenser Fan Full Load Amps  
COOLING MODE  
Actual Amps:  
Vapor Pressure:  
Liquid Pressure:  
Supply Air Temperature:  
HEATING MODE  
Ambient Temperature:  
Return Air Temperature:  
Return Air Temperature:  
Vapor Pressure:  
Liquid Pressure:  
Supply Air Temperature:  
Ambient Temperature:  
System Refrigerant Charge (Refer to manufacturer’s information on unit or installation instructions for required  
subcooling and approach temperatures.)  
Subcooling:  
A
A
A
ꢀ
ꢀ
ꢀ
B
B
B
=
=
SUBCOOLING  
APPROACH  
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)  
= COIL TEMP DROP  
Return Air Temperature (A)  
minus Supply Air Temperature (B)  
Page 18  
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Routine Maintenance  
Homeowner Information  
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.  
CAUTION  
Before attempting to perform any service or mainte-  
nance, turn the electrical power to unit OFF at discon-  
nect switch.  
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.  
Cleaning of the outdoor unit’s coil should be performed by  
a licensed professional service technician (or equivalent).  
Contact your dealer and set up a schedule (preferably  
twice a year, but at least once a year) to inspect and ser-  
vice your outdoor unit. The following maintenance may be  
performed by the homeowner.  
1. Ask your Lennox dealer to show you where your indoor  
unit’s filter is located. It will be either at the indoor unit  
(installed internal or external to the cabinet) or behind  
a return air grille in the wall or ceiling. Check the filter  
monthly and clean or replace it as needed.  
2. Disposable filters should be replaced with a filter of the  
same type and size.  
IMPORTANT !  
3. The indoor evaporator 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 location of the drain line and how to check for  
obstructions. (This would also apply to an auxiliary  
drain, if installed.)  
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 ComfortSense 7000 or icomfortt−enabled ther-  
Outdoor Coil  
The outdoor unit must be properly maintained to ensure its  
proper operation.  
mostat homeowner manual for instructions on how to oper-  
ate your thermostat.  
Preservice Check  
S Please contact your dealer to schedule proper inspec-  
If your system fails to operate, check the following before  
calling for service:  
tion and maintenance for your equipment.  
S Make sure no obstructions restrict airflow to the outdoor  
S
S
S
S
S
S
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.  
unit.  
S Grass clippings, leaves, or shrubs crowding the unit can  
cause the unit to work harder and use more energy.  
S Keep shrubbery trimmed away from the unit and periodi-  
Verify air filter is clean.  
cally check for debris which collects around the unit.  
S Keep snow level below the louvered panels to ensure  
If service is needed, locate and write down the unit  
model number and have it handy before calling.  
proper performance.  
Page 19  
XC21 SERIES  
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