Carrier WeatherMaker 50TC 17-30 Series Installation and user guide

Manufacturer reserves the right to discontinue, or change at any time, specifications or designs without notice and without incurring obligations.
Catalog No. 04-53500227-01 Printed in U.S.A. Form 50TC-17-30-02SM Pg 1 1-21 Replaces: 50TC-17-30-01SM
Service and Maintenance Instructions
CONTENTS
SAFETY CONSIDERATIONS . . . . . . . . . . . . . . . . . . . 2
UNIT ARRANGEMENT AND ACCESS . . . . . . . . . . . . 2
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Routine Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . 3
Seasonal Maintenance . . . . . . . . . . . . . . . . . . . . . . . . 3
SUPPLY FAN (BLOWER) SECTION . . . . . . . . . . . . . . 4
Supply Fan Assembly . . . . . . . . . . . . . . . . . . . . . . . . . 4
STAGED AIR VOLUME (SAV) CONTROL: 2-SPEED
FAN WITH VARIABLE FREQUENCY
DRIVE (VFD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Staged Air Volume (SAV) Indoor Fan Speed
System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Identifying Factory Option . . . . . . . . . . . . . . . . . . . . . 6
Unit Installation with SAV Option . . . . . . . . . . . . . . . 6
ADDITIONAL VFD INSTALLATION AND
TROUBLESHOOTING . . . . . . . . . . . . . . . . . . . . . . . 6
MOTOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Replacing the Motor . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Changing Fan Wheel Speed by Changing
Pulleys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
CONDENSER COIL SERVICE . . . . . . . . . . . . . . . . . . . 8
Round Tube Plate Fin (RTPF) Condenser Coil . . . . . 8
Recommended Condenser Coil Maintenance and
Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
EVAPORATOR COILS . . . . . . . . . . . . . . . . . . . . . . . . . 9
Coil Maintenance and Cleaning Recommendation . 9
Refrigerant System Pressure Access Ports . . . . . . 10
HUMIDI-MIZER®ADAPTIVE DEHUMIDIFICATION
SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Humidi-MiZer System Components . . . . . . . . . . . . 11
Operating Sequences . . . . . . . . . . . . . . . . . . . . . . . . 11
Humidi-MiZer Modes . . . . . . . . . . . . . . . . . . . . . . . . . 12
THERMOSTATIC EXPANSION VALVE (TXV) . . . . . 16
TXV Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Refrigerant System Pressure Access Ports . . . . . . 17
PURON (R-410A) REFRIGERANT . . . . . . . . . . . . . . 18
Refrigerant Charge . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Using the Cooling Charging Charts . . . . . . . . . . . . 18
COOLING CHARGING CHARTS . . . . . . . . . . . . . . . . 19
COMPRESSORS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Lubrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Replacing the Compressor . . . . . . . . . . . . . . . . . . . 23
Compressor Rotation . . . . . . . . . . . . . . . . . . . . . . . . 23
Filter Drier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Adjusting the Condenser-Fan . . . . . . . . . . . . . . . . . 23
TROUBLESHOOTING THE COOLING SYSTEM . . . 24
CONVENIENCE OUTLETS . . . . . . . . . . . . . . . . . . . . 25
Non-Powered Type . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Unit-Powered Type . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Wet in Use Convenience Outlet Cover . . . . . . . . . . .25
GFCI Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . .25
Fuse On Powered Type . . . . . . . . . . . . . . . . . . . . . . .26
Using Unit-Mounted Convenience Outlets . . . . . . .26
Installing a Weatherproof Cover . . . . . . . . . . . . . . . .26
SMOKE DETECTORS . . . . . . . . . . . . . . . . . . . . . . . . .26
System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26
Controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27
Smoke Detector Locations . . . . . . . . . . . . . . . . . . . .27
FIOP Smoke Detector Wiring and Response . . . . .28
Sensor and Controller Tests . . . . . . . . . . . . . . . . . . . 29
Detector Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . .30
INDICATORS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31
Normal State . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31
Alarm State . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31
Resetting Alarm and Trouble Condition Trips . . . .32
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32
PROTECTIVE DEVICES . . . . . . . . . . . . . . . . . . . . . . .32
Compressor Protection . . . . . . . . . . . . . . . . . . . . . . .32
SUPPLY (INDOOR) FAN MOTOR PROTECTION . . .32
Control Circuit, 24v . . . . . . . . . . . . . . . . . . . . . . . . . .33
PremierLink™ Control . . . . . . . . . . . . . . . . . . . . . . . .33
RTU Open Control System . . . . . . . . . . . . . . . . . . . .33
ECONOMI$ER SYSTEMS . . . . . . . . . . . . . . . . . . . . . .33
EconoMi$er IV Standard Sensors . . . . . . . . . . . . . .37
EconoMi$er® X (Factory Option) . . . . . . . . . . . . . . .42
PRE-START-UP/START-UP . . . . . . . . . . . . . . . . . . . .56
START-UP, GENERAL . . . . . . . . . . . . . . . . . . . . . . . .56
Unit Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . .56
Additional Installation/Inspection . . . . . . . . . . . . . .56
Return-Air Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . .56
Outdoor-Air Inlet Screens . . . . . . . . . . . . . . . . . . . . .56
Compressor Mounting . . . . . . . . . . . . . . . . . . . . . . . .57
Internal Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57
Refrigerant Service Ports . . . . . . . . . . . . . . . . . . . . .57
Compressor Rotation . . . . . . . . . . . . . . . . . . . . . . . .57
Cooling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57
Ventilation (Continuous Fan) . . . . . . . . . . . . . . . . . .57
START-UP, PREMIERLINK CONTROLS . . . . . . . . . .57
START-UP, RTU-OPEN CONTROLS . . . . . . . . . . . . .57
FASTENER TORQUE VALUES . . . . . . . . . . . . . . . . .57
APPENDIX A —MODEL NUMBER
NOMENCLATURE . . . . . . . . . . . . . . . . . . . . . . . . . .58
APPENDIX B —PHYSICAL DATA . . . . . . . . . . . . . . .60
APPENDIX C —FAN PERFORMANCE . . . . . . . . . . .69
APPENDIX D —WIRING DIAGRAMS . . . . . . . . . . . .79
APPENDIX E —MOTORMASTER SENSOR
LOCATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .92
START-UP CHECKLIST . . . . . . . . . . . . . . . . . . . . .CL-1
WeatherMaker®50TC**17-30
Single Package Rooftop Unit
with Electric Cooling and Optional Electric Heat
with Puron® (R-410A) Refrigerant

2
SAFETY CONSIDERATIONS
Installation and servicing of air-conditioning equipment can be
hazardous due to system pressure and electrical components. Only
trained and qualified service personnel should install, repair, or
service air-conditioning equipment.
Untrained personnel can perform basic maintenance functions of
cleaning coils and filters and replacing filters. All other operations
should be performed by trained service personnel. When working
on air-conditioning equipment, observe precautions in the
literature, tags and labels attached to the unit, and other safety
precautions that may apply.
Follow all safety codes, including ANSI (American National
Standards Institute) Z223.1. Wear safety glasses and work gloves.
Use quenching cloth for unbrazing operations. Have fire
extinguisher available for all brazing operations.
It is important to recognize safety information. This is the safety-
alert symbol . When you see this symbol on the unit and in
instructions or manuals, be alert to the potential for personal
injury.
Understand the signal words DANGER, WARNING, CAUTION,
and NOTE. These words are used with the safety-alert symbol.
DANGER identifies the most serious hazards which will result in
severe personal injury or death. WARNING signifies hazards
which could result in personal injury or death. CAUTION is used
to identify unsafe practices, which may result in minor personal
injury or product and property damage. NOTE is used to highlight
suggestions which will result in enhanced installation, reliability,
or operation.
UNIT ARRANGEMENT AND ACCESS
General
Figures 1 and 2 show general unit arrangement and access
locations.
CAUTION
PERSONAL INJURY HAZARD
Failure to follow this caution may result in personal injury.
Sheet metal parts may have sharp edges or burrs. Use care and
wear appropriate protective clothing, safety glasses and gloves
when handling parts and servicing air conditioning equipment.
WARNING
FIRE, EXPLOSION HAZARD
Failure to follow this warning could result in death, serious
personal injury and/or property damage.
Never use air or gases containing oxygen for leak testing or for
operating refrigerant compressors. Pressurized mixtures of air
or gases containing oxygen can lead to an explosion.
WARNING
FIRE, EXPLOSION HAZARD
Failure to follow this warning could result in death, serious
personal injury and/or property damage.
Never use non-certified refrigerants in this product. Non-
certified refrigerants could contain contaminates that could
lead to unsafe operating conditions. Use ONLY refrigerants
that conform to AHRI Standard 700.
WARNING
UNIT OPERATION AND SAFETY HAZARD
Failure to follow this warning could cause personal injury,
death and/or equipment damage.
This system uses R-410A refrigerant, which has higher
pressures than R-22 and other refrigerants. No other
refrigerant may be used in this system. Gage set, hoses, and
recovery system must be designed to handle R-410A
refrigerant. If unsure about equipment, consult the equipment
manufacturer.
CAUTION
UNIT DAMAGE HAZARD
Failure to follow this caution may result in reduced unit
performance or unit shutdown.
High velocity water from a pressure washer, garden hose, or
compressed air should never be used to clean a coil. The force
of the water or air jet will bend the fin edges and increase
airside pressure drop.
IMPORTANT: Failure to follow this ALERT could result in
an unnecessary evacuation of the facility.
Pressing the controller’s test/reset switch for longer than seven
seconds will put the duct detector into the alarm state and acti-
vate all automatic alarm responses.
CAUTION
ELECTRICAL SHOCK HAZARD
Failure to follow this warning could cause personal injury or
death.
Before performing service or maintenance operations on the
fan system, shut off all unit power and lockout/tag-out the unit
disconnect switch. DO NOT reach into the fan section with
power still applied to unit.
WARNING
ELECTRICAL OPERATION HAZARD
Failure to follow this warning could result in personal injury or
death.
Units with convenience outlet circuits may use multiple
disconnects. Check convenience outlet for power status before
opening unit for service. Locate its disconnect switch, if
appropriate, and open it. Lock-out and tag-out this switch, if
necessary.
IMPORTANT: Lockout/tag-out is a term used when electri-
cal power switches are physically locked, preventing power
to the unit. A placard is placed on the power switch, alert-
ing personnel that the power is disconnected.

3
Fig. 1 — Access Panels and Components, Front
Fig. 2 — Typical Access Panel Locations, Rear
Routine Maintenance
These items should be part of a routine maintenance program, to
be checked every month or two, until a specific schedule for each
can be identified for this installation:
QUARTERLY INSPECTION (AND 30 DAYS AFTER INI-
TIAL START)
The 50TC units should be inspected and serviced every three
months.
• Return air filter replacement
• Outdoor hood inlet filters cleaned
• Belt tension checked
• Belt condition checked
• Pulley alignment checked
• Fan shaft bearing locking collar tightness checked
• Condenser coil cleanliness checked
• Condensate drain checked
Seasonal Maintenance
These items should be checked at the beginning of each season (or
more often if local conditions and usage patterns dictate).
AIR CONDITIONING
• Condenser fan motor mounting bolts tightness
• Compressor mounting bolts
• Condenser fan blade positioning
• Control box cleanliness and wiring condition
• Wire terminal tightness
• Refrigerant charge level
• Evaporator coil cleaning
• Evaporator blower motor amperage
HEATING
• Heat exchanger flue passageways cleanliness
• Gas burner condition
• Gas manifold pressure
• Heating temperature rise
ECONOMIZER OR OUTSIDE AIR DAMPER
• Inlet filters condition
• Check damper travel (economizer)
• Check gear and dampers for debris and dirt
AIR FILTERS AND SCREENS
Each unit is equipped with return air filters. If the unit has an econ-
omizer, it will also have an outside air screen. If a manual outside
air damper is added, an inlet air screen will also be present.
Each of these filters and screens will need to be periodically re-
placed or cleaned.
RETURN AIR FILTERS
Return air filters are disposable fiberglass media type. Access to
the filters is through the small lift-out panel located on the rear
side of the unit, above the evaporator/return air access panel. (See
Fig. 1.)
Removing the Return Air Filters
1. Remove the return air filter and indoor coil access panel. See
Fig. 1.
2. Reach inside and remove filters from the filter rack.
3. Replace these filters as required with similar replacement fil-
ters of same size.
4. Re-install the return air filter and indoor coil access panel.
OUTDOOR AIR HOOD
Outside air hood inlet screens are permanent aluminum-mesh type
filters. See Fig. 2. Inspect these screens for cleanliness. Remove
the screens when cleaning is required. Clean by washing with hot
low-pressure water and soft detergent and replace all screens be-
fore restarting the unit. Observe the flow direction arrows on the
side of each filter frame.
ECONOMIZER AND MANUAL OUTSIDE AIR SCREENS
This air screen is retained by spring clips under the top edge of the
hood. (See Fig. 3.)
To remove the filter, remove screws in horizontal filter retainers
on leading edge of hood. Slide filters out. To re-install filters, slide
clean or new filters into hood side retainers. Once positioned, re-
install horizontal filter retainer.
OUTDOOR AIR
HOOD
CONTROL BOX
ACCESS PANEL RETURN AIR
FILTER AND
INDOOR COIL
ACCESS PANEL
SUPPLY FAN
HEATING SECTION
GAS SECTION
ACCESS PANEL
OUTDOOR
FANS/MOTORS
DISCONNECT
CONVENIENCE
OUTLET
COMPRESSOR
(CIRCUIT A)
CONDENSER
COIL
(CIRCUIT A)
CONDENSER COIL
CIRCUIT A
CONDENSER COIL
CIRCUIT B
COMPRESSOR
CIRCUIT B
CAUTION
EQUIPMENT DAMAGE HAZARD
Failure to follow this CAUTION can result in premature wear
and damage to equipment.
DO NOT OPERATE THE UNIT WITHOUT THE RETURN
AIR FILTERS IN PLACE.
Dirt and debris can collect on heat exchangers and coils
possibly resulting in a small fire. Dirt buildup on components
can cause excessive current used resulting in motor failure.

4
Fig. 3 — Filter Installation
Economizer Inlet Air Screen
This air screen is retained by spring clips under the top edge of the
hood. (See Fig. 4.)
Remove screens be removing the screws in the horizontal clips on
the leading edge of the hood. Slide the filters out. See Fig. 4.
Install the filters by sliding clean or new filters into the hood side
retainers. Once positioned, re-install the horizontal clips.
Fig. 4 — Inlet Air Screen Installation
SUPPLY FAN (BLOWER) SECTION
Supply Fan Assembly
The supply fan system consists of two forward-curved centrifugal
blower wheels mounted on a solid blower shaft that is supported
by two greasable pillow block concentric bearings. A fixed-pitch
driven fan pulley is attached to the fan shaft and an adjustable-
pitch driver pulley is mounted on the motor. The pulleys are con-
nected using a V-belt. (See Fig. 5.)
VERTICAL SUPPLY MODELS
The two fan wheels used on the vertical supply models are the
same: 15-in. diameter x 15-in. width. This arrangement provides
uniform airflow distribution across the width of the evaporator
coil, electric heater, and into the supply duct.
HORIZONTAL SUPPLY MODELS
The horizontal supply models have two different fan wheel sizes
on a single shaft. The front side wheel is 18-in. diameter x 15-in.
wide, while the rear side fan is 15-in. diameter x 11-in. wide. This
arrangement promotes uniform airflow across the width of the
evaporator coil and heater assembly while using a supply outlet on
the rear side of the unit.
NOTE: This major difference in the fan system design makes it
impossible to field-convert the 50TC unit’s supply fan outlet
configuration.
Fig. 5 — Supply Fan Arrangements
BELT
Check the belt condition and tension quarterly. Inspect the belt for
signs of cracking, fraying or glazing along the inside surfaces.
Check belt tension by using a spring-force tool, such as Brown-
ing’s “Belt Tension Checker” (P/N 1302546 or equivalent tool);
tension should be 6 lb at a 5/8-in. (1.6 cm) deflection when mea-
sured at the center line of the belt span. This point is at the center
of the belt when measuring the distance between the motor shaft
and the blower shaft.
NOTE: Without the spring-tension tool, place a straight edge
across the belt surface at the pulleys, then push down on the belt at
mid-span using one finger until a 1/2-in. (1.3 cm) deflection is
reached.
CAUTION
ELECTRICAL SHOCK HAZARD
Failure to follow this warning could cause personal injury or
death.
Before performing service or maintenance operations on the
fan system, shut off all unit power and lockout/tag-out the unit
disconnect switch. DO NOT reach into the fan section with
power still applied to unit.
17 1/4”
DIVIDER
BAROMETRIC
RELIEF
CLEANABLE
ALUMINUM
FILTER FILTER
HOOD
FILTER
CLIP
OUTSIDE
AIR
VERTICAL SUPPLY FANS
HORIZONTAL SUPPLY FANS
15” X 15” SUPPLY FANS
15” X 11” SUPPLY FAN
18” X 15” SUPPLY FAN

5
Adjusting the Belt Tension
Use the following steps to adjust the V-belt tension. See Fig. 6.
1. Loosen the four motor mounting nuts that attach the motor to
the blower rail.
2. Loosen the two jack bolt locking nuts beneath the motor
mounting plate. Turn the jack bolt locking nut counterclock-
wise to loosen.
3. Turn the jack bolts counterclockwise to loosen and clockwise
to tighten.
4. Adjust the V-belt for proper tension.
5. Make sure the fan shaft and motor shaft are parallel before
tightening the motor mount nuts. See Fig. 6.
6. Make adjustments as necessary.
7. Tighten the four motor mounting nuts.
8. Check the V-belt tension. Make adjustments as necessary.
9. Re-tighten the four motor mounting nuts.
10. Tighten both jack bolt locking nuts securely.
Replacing the V-belt
1. Use a belt with same section type or similar size. Do not sub-
stitute a “FHP” or notched type V-belt.
2. Loosen (turn counterclockwise) the motor mounting plate
front bolts and rear bolts. See Fig. 7.
3. Loosen (turn counterclockwise) the jack bolt lock nuts.
Loosen (turn counterclockwise) the jack bolts, relieving the
belt tension and allowing easy removal of the belt by hand.
4. Remove the belt by gently lifting the old belt over one of the
pulleys.
5. Install the new belt by gently sliding the belt over both pul-
leys, then tighten (turn clockwise) the jack bolts, sliding the
motor plate away from the fan housing until proper belt ten-
sion is achieved.
6. Check the alignment of the pulleys, adjust if necessary. See
Fig. 6.
7. Tighten all bolts attaching the motor to the motor plate.
8. Tighten all jack bolt jam nuts by turning clockwise.
9. Check the tension after a few hours of runtime and re-adjust
as required. See Fig. 7.
Fig. 6 — Checking Blower Motor Belt Tension
Fig. 7 — Belt Drive Motor Mounting
ADJUSTABLE-PITCH PULLEY ON MOTOR
The motor pulley is an adjustable-pitch type that allows a servicer
to implement changes in the fan wheel speed to match as-installed
ductwork systems. The pulley consists of a fixed flange side that
faces the motor (secured to the motor shaft) and a movable flange
side that can be rotated around the fixed flange side that increases
or reduces the pitch diameter of this driver pulley. (See Fig. 7.)
As the pitch diameter is changed by adjusting the position of the
movable flange, the centerline on this pulley shifts laterally, along
the motor shaft. This creates a requirement for a realignment of
the pulleys after any adjustment of the movable flange. Also reset
the belt tension after each realignment. The factory settings of the
adjustable pulley is five turns open from full closed.
Check the condition of the motor pulley for signs of wear. Glazing
of the belt contact surfaces and erosion on these surfaces are signs
of improper belt tension and/or belt slippage. Pulley replacement
may be necessary.
Changing Fan Speed
1. Shut off the main unit power supply, and use the approved
lockout/tag-out procedures.
2. Loosen the belt by loosening the motor adjustment bolts as
described in the Belt Adjustment section.
3. Loosen the movable pulley flange setscrew. (See Fig. 7.)
4. Screw the movable flange toward fixed flange to increase
speed and away from fixed flange to decrease speed.
CAUTION
EQUIPMENT DAMAGE HAZARD
Failure to follow this CAUTION can result in premature wear
and damage to equipment.
Do not use a screwdriver or a pry bar to place the new V-belt in
the pulley groove. This can cause stress on the V-belt and the
pulley resulting in premature wear on the V-belt and damage
to the pulley.
BROWNING BELT
TENSION CHECKER
STRAIGHTEDGE
1/2”
(1.3 cm)
BELT
DEFLECTION
MOTOR
V-BELT
MOTOR ADJUSTMENT
BOLTS (4)
JACKBOLT LOCKING NUT (2)
MOTOR MOUNTING PLATE
JACKBOLT (2)

6
Increasing fan speed increases load on the motor. Do not
exceed maximum speed specified in the Product Data or
motor amperage listed on the unit rating plate.
5. Set the movable flange at the nearest keyway or flat of the
pulley hub and tighten the setscrew to torque of 72 ± 5 in.-lb
(8.14 ± 0.56 Nm).
Aligning the Fan and Motor Pulleys
1. Loosen the fan pulley setscrews.
2. Slide the fan pulley along the fan shaft. Make angular align-
ment by loosening the motor from its mounting. See Fig. 8.
3. Tighten the fan pulley setscrews and motor mounting bolts to
torque specifications.
4. Recheck the belt tension. See Fig. 6.
Fig. 8 — Supply-Fan Pulley Adjustment
BEARINGS
This fan system uses bearings featuring concentric split locking
collars. The collars are tightened through a cap screw bridging the
split portion of the collar. The cap screw has a Torx T25 socket
head. To tighten the locking collar: Hold the locking collar tightly
against the inner race of the bearing and torque the cap screw to
65 to 70 in-lb. (7.4 to 7.9 Nm). See Fig. 9.
Fig. 9 — Tightening Locking Collar
STAGED AIR VOLUME (SAV) CONTROL: 2-
SPEED FAN WITH VARIABLE FREQUENCY
DRIVE (VFD)
Staged Air Volume (SAV) Indoor Fan Speed
System
NOTE: The SAV option is not available on units with Humidi-
MiZer adaptive humidification system.
The SAV system utilizes a fan speed control board and Variable
Frequency Drive (VFD) to automatically adjust the indoor fan
motor speed in sequence with the unit’s ventilation, cooling and
heating operation. Conforming to ASHRAE 90.1 2010 Standard
Section 6.4.3.10.b, during the first stage of cooling operation the
SAV system will adjust the fan motor to provide 66% of the de-
sign airflow rate for the unit. When the call for the second stage of
cooling is required, the SAV system will allow the design airflow
rate for the unit established (100%). During the heating mode, the
SAV system will allow total design airflow rate (100%) operation.
During ventilation mode, the SAV system will operate the fan mo-
tor at 66% speed.
Identifying Factory Option
This section only applies to units that meet the criteria detailed in
Table 1. See Appendix A for the model number nomenclature
breakdown.
Unit Installation with SAV Option
50TC ROOFTOP
Refer to the base unit installation instructions for standard required
operating and service clearances.
NOTE: The Remote VFD Keypad is a field-installed option. It is
not included as part of the factory-installed VFD option. See
“Variable Frequency Drive (VFD) Installation, Setup and Trouble-
shooting Supplement” for wiring schematics and performance
charts and configuration. See Fig. 10 for location of the VFD as
mounted on the various 50TC models.
Fig. 10 — VFD Location for 50TC 15-27.5 Units
ADDITIONAL VFD INSTALLATION AND
TROUBLESHOOTING
Additional installation, wiring and troubleshooting information
for the VFD can be found in the following manuals: “Variable Fre-
quency Drive (VFD) Installation, Setup and Troubleshooting Sup-
plement.”
MOTOR
When replacing the motor, use the following steps. See Fig. 11.
STRAIGHT EDGE
MUST BE PARALLEL
WITH BELT
SETSCREWS
MOTOR AND
FANSHAFTS
MUST BE
PARALLEL
FIXED FLANGE
MOVABLE
FLANGE
SINGLE - GROOVE
FAN PULLEY
MOTOR PULLEY
T --- 2 5 T O R X S O C K E T
HEAD CAP SCREW
LOCKING COLLAR
Table 1 — Model-Size / VFD Option Indicator
UNIT POSITION
IN MODEL NUMBER
VDP FIOP
INDICATOR
50TC 17-30 17 G, J
VARIABLE
FREQUENCY
DRIVE (VFD)

7
Fig. 11 — Replacing Belt Driven Motor
Replacing the Motor
1. Turn off all electrical power to the unit. Use approved lock-
out/tag-out procedures on all electrical power sources.
2. Remove the cover on the motor connection box.
3. Disconnect all electrical leads to the motor.
4. Loosen the two jack bolt jamnuts on the motor mounting
bracket.
5. Turn the two jack bolts counterclockwise until the motor
assembly moves closer to the blower pulley.
6. Remove the V-belt from the blower pulley and motor pulley.
7. Loosen the four mounting bracket bolts and lock washers.
8. Remove four bolts, four flat washers, four lock washers and
four nuts attaching the motor mounting plate to the unit. Dis-
card all lock washers.
9. Remove the motor and motor mounting bracket from the unit.
10. Remove four bolts, flat washers, lock washers and single
external-tooth lock washer attaching the motor to the motor
mounting plate. Discard all lock washers and external-tooth
lock washer.
11. Lift the motor from the motor mounting plate and set aside.
12. Slide the motor mounting band from the old motor.
13. Slide the motor mounting band onto the new motor and set
the motor onto the motor mounting plate.
14. Remove the variable pitch pulley from the old motor and
attach it to the new motor.
15. Inspect the variable pitch pulley for cracks and wear. Replace
the pulley if necessary.
16. Secure the pulley to the motor by tightening the pulley set-
screw to the motor shaft.
17. Insert four bolts and flat washers through the mounting holes
on the motor and into holes on the motor mounting plate.
18. On one bolt, place a new external-tooth lock washer between
the motor and motor mounting band.
19. Make sure the teeth of the external-tooth lock washer make
contact with the painted base of the motor. This washer is
essential for properly grounding the motor.
20. Install four new lock washers and four nuts on the bolts on the
bottom of the motor mounting plate, but do not tighten the
mounting bolts at this time.
21. Set the new motor and motor mounting bracket back onto the
unit. See Fig. 11.
22. Install four bolts, four flat washers, four new lock washers
and four nuts attaching the motor assembly to the unit, but do
not tighten the mounting bolts at this time.
23. Install the motor drive V-belt to the motor pulley and blower
wheel pulley. See CAUTION.
24. Align the motor pulley and blower wheel pulley using a
straight edge. See Fig. 8.
25. Adjust the V-belt tension using the adjustment tool.
26. Turn the two jack bolts clockwise, moving the motor
assembly away from the blower pulley, increasing the V-
belt tension.
27. Tighten the four bolts securing the motor mounting brackets
to the unit. Torque bolts to 120 ± 12 in.-lb (14 ± 1.4 Nm).
28. Remove the cover on the motor connection box.
29. Re-connect all electrical leads to the motor and replace the
connection box cover.
30. Re-connect all electrical power to the unit. Remove lockout
tags on all electrical power sources.
31. Start the unit and allow to run for a designated period.
32. Shut off the unit and make any necessary adjustments to
the V-belt tension or the motor and blower wheel pulley
alignment.
Changing Fan Wheel Speed by Changing
Pulleys
The horsepower rating of the belt is primarily dictated by the pitch
diameter of the smaller pulley in the drive system (typically the
motor pulley in these units). Do not install a replacement motor
pulley with a smaller pitch diameter than provided on the original
factory pulley. Change fan wheel speed by changing the fixed fan
pulley (larger pitch diameter to reduce wheel speed, smaller pitch
diameter to increase wheel speed) or select a new system with
both pulleys and matching belt(s).
Before changing pulleys to increase fan wheel speed, check the
fan performance at the target speed and airflow rate to determine
new motor loading (bhp). Use the fan performance tables or use
the Packaged Rooftop Builder software program. Confirm that the
motor in this unit is capable of operating at the new operating con-
dition. Fan shaft loading increases dramatically as wheel speed is
increased.
CAUTION
EQUIPMENT DAMAGE HAZARD
Failure to follow this CAUTION can result in premature wear
and damage to equipment.
Do not use a screwdriver or a pry bar to place the new V-belt in
the pulley groove. This can cause stress on the V-belt and the
pulley resulting in premature wear on the V-belt and damage
to the pulley.
BLOWER PULLEY
V-BELT
MOTOR PULLEY
MOTOR
MOTOR MOUNTING
BRACKET BOLTS (4)
MOTOR MOUNTING
BRACKET (2)
JACK BOLT JAM NUT (2)
JACK BOLT (2)
CAUTION
EQUIPMENT DAMAGE HAZARD
Failure to follow this caution can result in equipment damage.
Drive packages cannot be changed in the field. For example: a
standard drive cannot be changed to a high static drive. This
type of change will alter the unit’s certification and could re-
quire heavier wiring to support the higher amperage draw of
the drive package.

8
To reduce vibration, replace the motor’s adjustable pitch pulley
with a fixed pitch pulley (after the final airflow balance adjust-
ment). This will reduce the amount of vibration generated by the
motor/belt-drive system.
To determine variable pitch pulley diameter, perform the follow-
ing calculation:
1. Determine full open and full closed pulley diameter.
2. Subtract the full open diameter from the full closed diameter.
3. Divide that number by the number of pulley turns open from
full closed.
This number is the change in pitch datum per turn open.
EXAMPLE:
• Pulley dimensions 2.9 to 3.9 (full close to full open)
• 3.9 - 2.9 = 1-in.
• 1 divided by 5 (turns from full close to full open)
• 0.2 change in pulley diameter per turn open
• 2.9 + 0.2 = 3.1 pulley diameter when pulley closed one
turn from full open.
CONDENSER COIL SERVICE
Round Tube Plate Fin (RTPF) Condenser Coil
The condenser coil is fabricated with round tube copper hairpins
and plate fins of various materials and/or coatings (see the model
number nomenclature in Appendix A to identify the materials pro-
vided in this unit). The coil may be one-row or composite-type
two-row. Composite two-row coils are two single-row coils fabri-
cated with a single return bend end tubesheet.
Recommended Condenser Coil Maintenance
and Cleaning
Routine cleaning of coil surfaces is essential to maintain proper
operation of the unit. Elimination of contamination and removal of
harmful residues will greatly increase the life of the coil and ex-
tend the life of the unit. The following maintenance and cleaning
procedures are recommended as part of the routine maintenance
activities to extend the life of the coil.
REMOVE SURFACE LOADED FIBERS
Surface loaded fibers or dirt should be removed with a vacuum
cleaner. If a vacuum cleaner is not available, a soft non-metallic
bristle brush may be used. In either case, the tool should be ap-
plied in the direction of the fins. Coil surfaces can be easily dam-
aged (fin edges can be easily bent over and damage to the coating
of a protected coil) if the tool is applied across the fins.
NOTE: Use of a water stream, such as a garden hose, against a
surface loaded coil will drive the fibers and dirt into the coil. This
will make cleaning efforts more difficult. Surface loaded fibers
must be completely removed prior to using low-velocity clean wa-
ter rinse.
PERIODIC CLEAN WATER RINSE
A periodic clean water rinse is very beneficial for coils that are ap-
plied in coastal or industrial environments. However, it is very im-
portant that the water rinse is made with a very low-velocity water
stream to avoid damaging the fin edges. Monthly cleaning as de-
scribed is recommended.
ROUTINE CLEANING OF COIL SURFACES
Periodic cleaning with Totaline® environmentally sound coil
cleaner is essential to extend the life of coils. This cleaner is avail-
able from Carrier Replacement Components Division as P/N:
P902-0301 for a one-gallon (3.8L) container, and P902-0305 for a
5-gallon (18.9L) container. It is recommended that all coils, in-
cluding standard aluminum, pre-coated, copper/copper or E-coat-
ed coils be cleaned with the Totaline environmentally sound coil
cleaner as described below.
Coil cleaning should be part of the unit’s regularly scheduled
maintenance procedures to ensure long life of the coil. Failure to
clean the coils may result in reduced durability in the environment.
Avoid use of:
• coil brighteners
• acid cleaning prior to painting
• high pressure washers
• poor quality water for cleaning
Totaline environmentally sound coil cleaner is a nonflammable,
hypoallergenic, non bacterial, USDA accepted biodegradable
agent that will not harm the coil or surrounding components such
as electrical wiring, painted metal surfaces, or insulation. Use of
non-recommended coil cleaners is strongly discouraged since coil
and unit durability could be affected.
Two-Row Coils
Clean coil as follows:
1. Turn off unit power and tag the disconnect.
2. Remove the top panel screws on the condenser end of the
unit.
3. Remove the condenser coil corner post. See Fig. 12.
4. Lift and hold the top cover open.
5. Hold the top pan open by placing the coil corner post between
the top panel and center post. See Fig. 13.
6. Remove the screws securing the coil to the compressor plate
and compressor access panel.
7. Remove the fasteners holding the coil sections together at the
return end of the condenser coil. Carefully separate the outer
coil section 3 to 4 in. from the inner coil section. See Fig. 14.
8. Clean the outer surfaces with a stiff brush in the normal man-
ner. Use a water hose or other suitable equipment to flush
down between the 2 coil sections to remove dirt and debris.
9. Secure the inner and outer coil rows together with a field-sup-
plied fastener.
10. Reposition the outer coil section and remove the coil corner
post from between the top panel and center post. Reinstall the
coil corner post and access panel.
11. Replace all screws.
CAUTION
UNIT DAMAGE HAZARD
Failure to follow this caution can result in reduced unit perfor-
mance or unit shutdown.
Use only the recommended approved cleaning procedures for
proper system performance.

9
Fig. 12 — Cleaning Condenser Coil
Fig. 13 — Propping Up Top Panel
Fig. 14 — Separating Coil Sections
EVAPORATOR COILS
The evaporator coil uses the traditional round-tube, plate-fin
(RTPF) technology. Tube and fin construction consists of vari-
ous optional materials and coatings (see Appendix A). Coils are
multiple-row. On two-compressor units, the evaporator coil is a
face split design, meaning the two refrigerant circuits are inde-
pendent in the coil. The bottom portion of the coil will always be
circuit A, with the top of the coil being circuit B.
Coil Maintenance and Cleaning Recommendation
Routine cleaning of coil surfaces is essential to maintain proper
operation of the unit. Elimination of contamination and removal of
harmful residues will greatly increase the life of the coil and ex-
tend the life of the unit. The following maintenance and cleaning
procedures are recommended as part of the routine maintenance
activities to extend the life of the coil.
REMOVING SURFACE LOADED FIBERS
Surface loaded fibers or dirt should be removed with a vacuum
cleaner. If a vacuum cleaner is not available, a soft non-metallic
bristle brush can be used. In either case, the tool should be applied
in the direction of the fins. Coil surfaces can be easily damaged.
Applying the tool across the fin edges can cause the edges to be
easily bent over, damaging the coating of a protected coil.
NOTE: Use of a water stream, such as a garden hose, against a
surface-loaded coil will drive the fibers and dirt into the coil. This
will make cleaning efforts more difficult. Surface-loaded fibers
must be completely removed prior to using a low-velocity clean
water rinse. A vacuum cleaner or a soft-bristled brush should be
used to remove surface-loaded fibers and dirt.
PERIODIC CLEAN WATER RINSE
A periodic clean-water rinse is very beneficial for coils that are
used in coastal or industrial environments. However, it is very im-
portant that the water rinse is made with a very low-velocity water
stream to avoid damage to the fin edges. Monthly cleaning, as de-
scribed below, is recommended.
ROUTINE CLEANING OF EVAPORATOR COIL SURFACES
Monthly cleaning with Totaline environmentally sound coil clean-
er is essential to extend the life of the coils. This cleaner is avail-
able from Carrier Replacement Parts Division (P/N: P902-0301
for a one-gallon (3.8L) container, and P/N: P902-0305 for a 5-gal-
lon (18.9L) container). It is recommended that all round tube coils
be cleaned as described below. Coil cleaning should be part of the
unit’s regularly scheduled maintenance procedures to ensure a
long life for the coil. Failure to clean the coils can result in reduced
durability in the environment. When cleaning the coils, avoid use
of the following:
• coil brighteners
• acid cleaning prior to painting
• high pressure washers
• poor quality water for cleaning
Totaline environmentally sound coil cleaner is a nonflammable,
hypoallergenic, non bacterial, USDA accepted biodegradable
agent that will not harm the coil or surrounding components such
as electrical wiring, painted metal surfaces, or insulation. Use of
non-recommended coil cleaners is strongly discouraged since coil
and unit durability could be affected.
Totaline Environmentally Sound Coil Cleaner Application
Equipment
• 21/2 gallon garden sprayer
• Water rinse with low velocity spray nozzle

10
Totaline Environmentally Sound Coil Cleaner Application
Instructions
1. Proper protection such as safety glasses, gloves and pro-
tective clothing are recommended during mixing and
application.
2. Remove all surface loaded fibers and dirt with a vacuum
cleaner as described above.
3. Thoroughly wet finned surfaces with clean water and a low
velocity garden hose, being careful not to bend fins.
4. Mix Totaline environmentally sound coil cleaner in a 21/2 gal-
lon (9.6 L) garden sprayer according to the instructions
included with the cleaner. The optimum solution temperature
is 100°F (38°C).
NOTE: Do NOT USE water in excess of 130°F (54°C), as the en-
zymatic activity will be destroyed.
5. Thoroughly apply Totaline environmentally sound coil
cleaner solution to all coil surfaces, including finned area,
tube sheets and coil headers.
6. Hold the garden sprayer nozzle close to finned areas and
apply cleaner with a vertical, up-and-down motion.
7. Avoid spraying in a horizontal pattern to minimize potential
for fin damage.
8. Make sure the cleaner thoroughly penetrates deep into the
finned areas.
9. Interior and exterior finned areas must be thoroughly cleaned.
10. Finned surfaces should remain wet with cleaning solution for
10 minutes.
11. Make sure surfaces are not allowed to dry before rinsing.
Reapply cleaner as needed to ensure 10 minute saturation is
achieved.
12. Thoroughly rinse all surfaces with low-velocity clean water
using a downward rinsing motion of the spray nozzle. Protect
fins from damage from the spray nozzle.
EVAPORATOR COIL METERING DEVICES
The metering devices are multiple fixed-bore devices (Acutrol)
swedged into the horizontal outlet tubes from the liquid header, lo-
cated at the entrance to each evaporator coil circuit path. These are
non-adjustable. Service requires replacing the entire liquid header
assembly.
To check for possible blockage of one or more of these metering
devices, disconnect the supply fan contactor (IFC) coil, then start
the compressor and observe the frosting pattern on the face of the
evaporator coil. A frost pattern should develop uniformly across
the face of the coil starting at each horizontal header tube. Failure
to develop frost at an outlet tube can indicate a plugged or a miss-
ing orifice.
Refrigerant System Pressure Access Ports
There are two access ports in the system - on the suction tube near
the compressor and on the discharge tube near the compressor.
These are brass fittings with black plastic caps. The hose connec-
tion fittings are standard 1/4-in. SAE male flare couplings.
The brass fittings are two-piece High Flow valves, with a re-
ceptacle base brazed to the tubing and an integral spring-closed
check valve core screwed into the base (see Fig. 15). This
schrader valve is permanently assembled into this core body
and cannot be serviced separately; replace the entire core body
if necessary. Service tools are available from RCD (P/N P920-
0010) that allow the replacement of the schrader valve core
without having to recover the entire system refrigerant charge.
Apply compressor refrigerant oil to the schrader valve core’s
bottom o-ring. Install the fitting body with 96 ± 10 in.-lb
(10.85 ± 1.13 Nm) of torque; do not overtighten.
NOTE: The High-Flow valve has a black plastic cap with a rubber
o-ring located inside the cap. This rubber o-ring must be in place
in the cap to prevent refrigerant leaks.
EXAMPLE:
Model 50TC*D28
Circuit A (from Fig. 15)
Outdoor Temperature. . . . . . . . . . . . . . . . . . . . . . . . . . 85°F (29°C)
Suction Pressure. . . . . . . . . . . . . . . . . . . . . . . . . 125 psig (860 kPa)
Suction Temperature should be . . . . . . . . . . . . . . . . . . 63°F (17°C)
Circuit B (from Fig. 15)
Outdoor Temperature. . . . . . . . . . . . . . . . . . . . . . . . . . 85°F (29°C)
Suction Pressure. . . . . . . . . . . . . . . . . . . . . . . . . 120 psig (830 kPa)
Suction Temperature should be . . . . . . . . . . . . . . . . . . 58°F (14°C)
CAUTION
PERSONAL INJURY HAZARD
Failure to follow this caution can result in severe personal inju-
ry and reduced unit performance.
High velocity water from a pressure washer, garden hose, or
compressed air should never be used to clean a coil. The force
of the water or air jet will bend the fin edges and increase air-
side pressure drop.
High velocity water from a pressure washer can cause severe
injury upon contact with exposed bodily tissue. Always direct
the water stream away from the body.
CAUTION
UNIT DAMAGE HAZARD
Failure to follow this caution may result in accelerated
corrosion of unit parts.
Harsh chemicals, household bleach or acid or basic cleaners
should not be used to clean outdoor or indoor coils of any kind.
These cleaners can be very difficult to rinse out of the coil and
can accelerate corrosion at the fin/tube interface where
dissimilar materials are in contact. If there is dirt below the
surface of the coil, use the environmentally balanced coil
cleaner.

11
Fig. 15 — CoreMax1Access Port Assembly
HUMIDI-MIZER®ADAPTIVE DEHUMIDIFICA-
TION SYSTEM
Units with the factory-equipped Humidi-MiZer option are capable
of providing multiple modes of improved dehumidification as a
variation of the normal cooling cycle. See Fig 18. The design of
the Humidi-MiZer system allows for two humidity control modes
of operation of the rooftop unit, utilizing a common subcooling/re-
heat dehumidification coil located downstream of the standard
evaporator coil. This allows the rooftop unit to operate in both a
dehumidification (Subcooling) mode and a hot gas (Reheat) mode
for maximum system flexibility. The Humidi-MiZer package is
factory-installed and will operate whenever there is a dehumidifi-
cation requirement present.
The Humidi-MiZer system is initiated based on an input from a
discrete input from a mechanical space or return air humidistat.
Humidi-MiZer System Components
The Humidi-MiZer System uses the standard unit compressor(s),
evaporator coil and Round Tube-Plate Fin (RTPF) condenser coil.
Additional refrigeration system hardware includes a subcooler/re-
heat coil and control solenoid valves. On some models, the evapo-
rator coil includes a TXV as a standard feature. Units with Humi-
di-MiZer FIOP also include a factory-installed head pressure con-
trol system (Motormaster I) to provide proper liquid pressure
during reheat modes. Unique system controls include a reheat re-
lay mode, and evaporator coil freezestat, and secondary low pres-
sure switch. See Fig. 16. See Fig. 17 and Table 2 (on page 14) for
Reheat Control input/output (I/O) connections.
SUBCOOLER/REHEAT COIL
The Subcooler/Reheat Coil is mounted across the leaving face of
the unit’s evaporator coil. The coil is a one-row design with two
separate circuits.
• 3-Way Solenoid Valve
• Hot Gas Bypass Solenoid Valve
• Relay Reheat Board (RHB)
• Evaporator Freeze Protection Thermostat
• Low Outdoor Temperature Lockout Switch
• Secondary Low Pressure Switch
• Head Pressure Control
Operating Sequences
The Humidi-MiZer system provides three sub-modes of opera-
tion: Normal Cooling (see Fig. 18), Subcooling Reheat1 (see
Fig. 19) and Hot Gas Reheat2 (see Fig. 20).
The Reheat1 and Reheat2 modes are available when the unit is not
in a heating mode and when the Low Ambient Lockout Switch is
closed.
Fig. 16 — Humidi-MiZer Valve Locations
Fig. 17 — Reheat Control Board (RCB)
1. CoreMax is a registered trademark of Fastest, Inc.
5/8” HEX 0.47
30°
0.596
1/2-20 UNF RH
1/2” HEX
45°
WASHER
O-RING
7/16-20 UNF RH
DEPRESSOR PER AHRI 720
+.01/-.035
FROM FACE OF BODY
This surface provides a metal to metal seal when
torqued into the seat. Appropriate handling is
required to not scratch or dent the surface.
SEAT CORE
(Part No. EC39EZ067)
RH1.A
RH2.A
RH1.B
RH2.B

12
When there is only a single cooling demand (thermostat Y1 alone
or with thermostat Y2), one or both circuits will operate in Re-
heat2 mode. Both solenoids are energized in both circuits. See
Fig. 20, Hot Gas Reheat Schematic for system refrigerant flow.
When there is both cooling demand (thermostat Y1 demand) and
dehumidification demand, circuit 1 will operate in Reheat1 mode
(Subcooling, Fig. 19) and circuit will operated in Reheat2 mode
(Reheat, Fig. 20). In Reheat1 mode, the 3-way solenoid valve is
energized, opening the reheat coil to the refrigeration flow path
providing sub-cooling to the liquid before it enters the TXV. See
Table 3 for further details on Humid-MiZer system operating
modes. See Table 4 for details on troubleshooting the Humidi-
MiZer system.
Humidi-MiZer Modes
NORMAL COOLING
During the Normal Cooling mode, the liquid refrigerant flows
from the outdoor condenser through the normally open (NO)
Cooling System Valve (CSV) to the expansion device. Both the
Reheat1 (RH1.x) and Reheat2 (RH2) valves are closed during the
normal cooling mode.
During the Normal Cooling mode, the refrigerant flows from the
outdoor compressor through the condenser coil. The Reheat2
(RH2.x) is closed, preventing the refrigerant from bypassing the
condenser coil. The refrigerant then flows through the open Re-
heat2 (RH1.x) 3-way valve to the TXV Metering Device, bypass-
ing the Humidi-MiZer coil, and finally passing through the evapo-
rator coil before returning to the outdoor compressor. See Fig 18.
REHEAT1 (SUBCOOLING MODE)
The Reheat1 or Subcooling mode will be engaged to satisfy part-
load-type conditions when there is a space call for cooling and de-
humidification. Although the temperature could have dropped and
decreased the sensible load in the space, the outdoor and/or space
humidity levels could have risen. A typical scenario could be
when the outside air is 85°F (29°C) with 70% to 80% relative hu-
midity (RH). Desired Sensible Heat Ratio (SHR) for equipment in
this scenario is typically from 0.4 to 0.7. The Humidi-MiZer unit
will initiate the Dehumidification mode when both the space
temperature and humidity are above the temperature and humidity
setpoints while attempting to meet both setpoint requirements.
Once the humidity requirement is met, the unit can continue to op-
erate in normal cooling mode to meet any remaining sensible ca-
pacity load. Alternatively, if the sensible load is met and humidity
levels remain high, the unit can switch to Hot Gas Reheat mode or
Reheat2 mode to provide neutral, dehumidified air.
During the Reheat1 or Subcooling mode, the liquid refrigerant
flows from the outdoor compressor through the condenser coil to
the Reheat1 (RH1.x) 3-way valve and on to the Humid-Mizer coil.
The Reheat2 (RH2.x) valve is closed. The liquid refrigerant then
passes through the Humid-Mizer coil and then a metering device
or Thermostatic Expansion Valve (TXV). From the TXV, the liq-
uid refrigerant passes through the evaporator coil and back to the
outdoor comprssor. See Fig 19.
REHEAT2 (HOT GAS REHEAT MODE)
This Reheat2 or Hot Gas Reheat mode is used when dehumidifi-
cation is required without a need for cooling, such as when the
outside air is at a neutral temperature, but high humidity exists.
This situation requires the equipment to operate at a low SHR of
0.0 to 0.2. With no cooling requirement calling for dehumidifica-
tion, the Humidi-MiZer adaptive dehumidification system will en-
ergize both compressors, opening the two hot gas bypass valves,
allowing refrigerant flow to the Humidi-MiZer coil to reheat the
unit’s supply air to a neutral temperature.
The hot bypassed refrigerant liquid (gas or two-phase mixture) ex-
its the outdoor compressor and passes through the open Reheat1
(RH1.x) at the same time it passes through the condenser coil to
the open Reheat2 (Rh2.x) to the Humidi-MiZer coil. After the re-
frigerant passes through the Humidi-MiZer coil, it enters a TXV
metering device, decreasing the air pressure, and on to the evapo-
rator coil. The refrigerant is subcooled in this coil to a temperature
approaching the evaporator leaving air temperature. The liquid re-
frigerant then returns to the outdoor compressor. See Fig. 20.
The refrigerant enters the TXV and evaporator coil at a tempera-
ture lower than the temperature in the standard cooling operation.
This lower temperature increases the latent capacity of the evapo-
rator. The refrigerant passes through the evaporator turning it into
a superheated vapor. The air passing over the evaporator coil be-
comes colder than it would during normal operation. As this same
air passes over the Humidi-MiZer Reheat Coil, it will be warmed
to the neutral supply air temperature.
Fig. 18 — Normal Cooling Mode – Humidi-MiZer System
CONDENSER COIL HUMIDI-MIZER COIL
EVAPORATOR COIL
COMPRESSOR
OUTDOOR AIR
INDOOR AIR
RH2.x
VALVE
RH1.x
VALVE
TXV
VALVE
= CLOSED VALVE
= OPEN VALVE
= 3-WAY VALVE

13
Fig. 19 — Subcooling Mode (Reheat 1) – Humidi-MiZer System
Fig. 20 — Hot Gas Reheat Mode (Reheat 2) – Humidi-MiZer System
CONDENSER COIL HUMIDI-MIZER COIL
EVAPORATOR COIL
COMPRESSOR
OUTDOOR AIR
INDOOR AIR
RH2.x
VALVE
RH1.x
VALVE
TXV
VALVE
= CLOSED VALVE
= OPEN VALVE
= 3-WAY VALVE
CONDENSER COIL HUMIDI-MIZER COIL
EVAPORATOR COIL
COMPRESSOR
OUTDOOR AIR
INDOOR AIR
RH2.x
VALVE
RH1.x
VALVE
TXV
VALVE
= CLOSED VALVE
= OPEN VALVE
= 3-WAY VALVE

14
LEGEND
Table 2 — Humidi-MiZer Reheat Control Board I/O
POINT NAME TYPE CONNECTION PIN
NUMBER UNIT CONNECTION NOTE
Humidistat/LTLO DI, 24VAC J1A - 1 (1) LTLO
Thermostat W1 DI, 24VAC J1A - 2 (2) CTB - REHEAT - 4
Econ Y1 DI, 24VAC J1A - 6 (6) CTB - REHEAT - 5
Thermostat G DI, 24VAC J1B - 1 (7) CTB - REHEAT - 1
24V Power (J1) 24VAC J1B - 3 (9) CTB - R
24V Power (J2) 24 VAC J2 - 1 CTB - R
Econ Y2 DI, 24VAC J1B - 5 (11) CTB - REHEAT - 7 2 - circ only
COMP1 DO, 24VAC J1A - 5 (5) CTB - HEAT - 6
IFM DO, 24VAC J1B - 4 (8) CTB - REHEAT - 2
COMP2 DO, 24VAC J1B - 4 (10) CTB - REHEAT - 8
LSV DO, 24VAC J2 - 2 FTP (BLK)
DSV1 DO, 24VAC J2 - 3 DSV
NOT LSV DO, 24VAC J2 - 4 2 - circ only
DSV2 DO, 24VAC J2 - 5 2 - circ only
COMP — Compressor
CTB — Control Terminal Board
DI — Discrete Input (switch)
DO — Discrete Output (switch)
DSV — Discharge (gas) Solenoid Valve
ECON — Economizer
FPT — Freeze Protection Thermostat
IFM — Indoor (supply) Fan Motor
LSV — Liquid Solenoid Valve
LTLO — Low Temperature Lockout
REHEAT — Connection Strip REHEAT (on CTB)
Table 3 — Inputs/Modes/Outputs Summary
INPUT
MODE
OUTPUT
Y1 Y2 W1 G HUM/
LTLO
COMP
1
COMP
2IFM LSV1 LSV2 LSV NOT DSV1 DSV2
OFF OFF OFF ON OFF Normal Fan OFF OFF ON=G OFF OFF ON=R OFF OFF
ON OFF OFF On OFF Normal Cool1 ON=Y1 OFF ON=G OFF OFF ON=R OFF OFF
ON ON OFF ON OFF Normal Cool2 ON=Y2 ON ON=G OFF OFF ON=R OFF OFF
OFF OFF ON X OFF Normal Heat 1 OFF OFF ON=G OFF OFF ON=R OFF OFF
OFF OFF OFF ON ON Reheat Dehumidify ON ON ON=G ON ON OFF ON=R ON=R
ON OFF OFF ON ON Subcool Cir1/
Reheat Cir2
Cool1 and Cool2 /
Subcool-Dehumidify ON ON ON=G ON ON OFF OFF ON=R
ON ON OFF ON ON Subcool Cir1
and Cir2
Cool1 and Cool2 /
Subcool-Dehumidify ON ON ON=G ON ON OFF OFF OFF
OFF OFF ON X ON Heat Override Heat 1 OFF OFF ON=G OFF OFF ON=R OFF OFF
OFF OFF ON+
W2 X ON Heat Override Heat 1 and 2 OFF OFF ON=G OFF OFF ON=R OFF OFF

15
LEGEND
Table 4 — Humidi-MiZer Troubleshooting
PROBLEM CAUSE REMEDY
Subcooling Reheat Mode Will
Not Activate
General cooling mode problem See Cooling Service Troubleshooting (Table 5).
No dehumidification demand See No Dehumidification Demand, below.
CRC relay operation See CRC Relay Operation, below.
Circuit RLV, CLV or LDV valve problem See CLV, RLV or LDV Valve Operation, below.
Hot Gas Reheat Mode Will Not
Activate
General cooling mode problem See Cooling Service Troubleshooting (Table 5).
No dehumidification demand See No Dehumidification Demand, below.
CRC relay operation See CRC Relay Operation, below.
Circuit RLV, CLV or LDV valve problem See CLV, RLV or LDV Valve Operation, below.
Circuit RDV valve is not open See RDV Valve Operation, below.
Outdoor temperature too low Check the LTLO is functioning properly.
No Dehumidification Demand
Relative humidity setpoint too low — Humidistat Check/reduce setting on accessory humidistat.
Relative humidity setpoint too low — RH sensor On units with DDC, verify the RH sensor is reading properly and
that the setpoint is set properly.
No humidity signal Check wiring. Check humidistat or humidity sensor.
CRC Relay Operation
No 24V signal to input terminals
Check the dedicated Humidi-MiZer transformer for voltage or
tripped circuit breaker.
Check wiring.
Check transformer and circuit breaker.
No power to output terminals Check wiring.
Relay outputs do not change state Replace faulty relay.
RLV, CLV or LDV Valve
Operation
No 24V signal to input terminals
Check CRC Relay Operation.
Check Wiring.
Check transformer and circuit beaker or fuses.
Solenoid coil burnout
Check continuous over-voltage is less than 10%.
Check under-voltage is less than 15%.
Check for missing coil assembly parts.
Check for damaged valve enclosing tube.
Stuck valve Replace valve. Replace filter drier.
RDV Valve Operation
(NOTE: Normally Closed
When De-energized)
No 24V signal to input terminals
Check RDV relay operation.
Check wiring.
Check transformer and circuit breaker or fuses.
Solenoid coil burnout
Check continuous over-voltage is less than 10%.
Check under-voltage is less than 15%.
Check for missing coil assembly parts.
Check for damaged valve enclosing tube.
Stuck valve Replace valve. Replace filter drier.
Low Latent Capacity in
Subcooling or Hot Gas
Reheat Modes
CLV valve open or leaking See CLV Valve Operation, above.
Low Sensible Capacity in
Normal Cool or Subcooling
Reheat Modes
RDV valve open or leaking See RDV Valve Operation, above.
Low Suction Pressure and
High Superheat During
Normal Cool Mode
General cooling mode problem See Cooling Service Troubleshooting (Table 5).
RDV valve open or leaking See RDV Valve Operation, above.
Low Suction Pressure and
High Discharge Pressure
General cooling mode problem See Cooling Service Troubleshooting (Table 5).
Both RLV and CLV valves closed See RLV and CLV Valve Operation, above.
RDV Valve Cycling On/Off Hot Gas Reheat mode low suction pressure
limit
Normal Operation During Mixed Circuit Subcooling and Hot Gas
Reheat Modes at Lower Outdoor Temperatures.
Circuit B Will Not Operate
With Circuit A Off
Normal operation. Motormaster outdoor fan
control requires operation of circuit A. None
CRC — Cooling/Reheat Control
CLV — Cooling Liquid Valve
RLV — Reheat Liquid Valve
RH — Relative Humidity
RDV — Reheat Discharge Valve

16
THERMOSTATIC EXPANSION VALVE (TXV)
All two-stage 50TC units with Humidi-Mizer have a factory-
installed nonadjustable thermostatic expansion valve (TXV).
The TXV will be a bi-flow, bleed port expansion valve with an
external equalizer. TXVs are specifically designed to operate
with Puron or R-22 refrigerant, use only factory authorized
TXVs. See Fig. 21.
Fig. 21 — Thermostatic Expansion Valve (TXV)
Operation
TXV Operation
The TXV is a metering device that is used in air conditioning and
heat pump systems to adjust to changing load conditions by main-
taining a preset superheat temperature at the outlet of the evapora-
tor coil.
The volume of refrigerant metered through the valve seat is de-
pendent upon the following:
1. Superheat temperature is sensed by the cap tube sensing bulb
on suction the tube at the outlet of evaporator coil. This tem-
perature is converted into pressure by refrigerant in the bulb
pushing downward on the diaphragm which opens the valve
using the push rods.
2. The suction pressure at the outlet of the evaporator coil is
transferred through the external equalizer tube to the under-
side of the diaphragm.
3. The needle valve on the pin carrier is spring loaded, exert-
ing pressure on the underside of the diaphragm. Therefore,
the bulb pressure equals the evaporator pressure (at the out-
let of the coil) plus the spring pressure. If the evaporator
load increases, the temperature increases at the bulb, which
increases the pressure on the topside of the diaphragm,
pushing the carrier away from the seat, opening the valve
and increasing the flow of refrigerant. The increased refrig-
erant flow causes increased leaving evaporator pressure
which is transferred through the equalizer tube to the under-
side of the diaphragm. This causes the pin carrier spring
pressure to close the TXV valve. The refrigerant flow is
effectively stabilized to the load demand with a negligible
change in superheat.
REPLACING TXV
1. Disconnect all AC power to the unit. Use approved lockout/
tag-out procedures.
2. Using the gage set approved for use with Puron (R-410A)
refrigerant, recover all refrigerant from the system.
3. Remove the TXV support clamp.
4. Disconnect the liquid line at the TXV inlet.
5. Remove the liquid line connection at the TXV inlet.
6. Remove the equalizer tube from the suction line of the coil.
Use a tubing cutter to cut the brazed equalizer line approxi-
mately 2-in. (50 mm) above the suction tube.
7. Remove the bulb from the vapor tube above the evaporator
coil header outlet.
8. Install the new TXV; avoid damage to the tubing or the valve
when attaching the TXV to the distributor. Protect the TXV
against over-temperature conditions by using wet rags and
directing the torch flame tip away from the TXV body. Con-
nect the liquid line to the TXV inlet by repeating the above
process.
9. Attach the equalizer tube to the suction line. If the replace-
ment TXV has a flare nut on its equalizer line, use a tubing
cutter to remove the mechanical flare nut from the equalizer.
Then use a coupling to braze the equalizer line to the stub
(previous equalizer line) in the suction line.
10. Attach the TXV bulb in the same location as the original (in
the sensing bulb indent), wrap the bulb in protective insula-
tion and secure using the supplied bulb clamp. See Fig. 22
and 23.
11. Route the equalizer tube through the suction connection
opening (large hole) in the fitting panel and install the fitting
panel in place.
12. Sweat the inlet of the TXV marked “IN” to the liquid line.
Avoid excessive heat which could damage the valve.
13. Check for leaks.
14. Evacuate the system completely and then recharge.
15. Remove the lockout/tag-out on the main power switch and
restore power to the unit.
16. Complete the charging procedure.
OUTLET
INLET
PUSHRODS
DIAPHRAGM
NEEDLE
VALVE
SPRING
DISTRIBUTOR
FEEDER TUBES
CAPILLARY TUBE
COIL
BULB
EXTERNAL EQUALIZER TUBE
CAUTION
PERSONAL INJURY HAZARD
Failure to follow this caution can result in injury to personnel
and damage to components.
Always wear approved safety glasses, work gloves and other
recommended Personal Protective Equipment (PPE) when
working with refrigerants.

17
Fig. 22 — TXV Sensor Bulb Locations
Fig. 23 — TXV Sensor Valve Insulation
Refrigerant System Pressure Access Ports
There are two access ports in the system: on the suction tube near
the compressor, and on the discharge tube near the compressor.
These are brass fittings with black plastic caps. The hose connec-
tion fittings are standard 1/4-in. SAE male flare couplings. See
Fig. 15.
The brass fittings are two-piece High Flow valves, with a recepta-
cle base brazed to the tubing and an integral spring-closed check
valve core screwed into the base. This check valve is permanently
assembled into this core body and cannot be serviced separately;
replace the entire core body if necessary. Service tools are avail-
able from RCD that allow the replacement of the check valve core
without having to recover the entire system refrigerant charge.
Apply compressor refrigerant oil to the check valve core’s bottom
o-ring. Install the fitting body with 96 ±10 in.-lb of torque; do not
over-tighten.
TXV SENSOR
BULB
CLAMP
CIRCUIT 1
CIRCUIT 2
TXV
(CIRCUIT 2)
TXV
(CIRCUIT 1)
TXV SENSOR
BULBS
TXV
SENSOR
BULBS
DIRECTION OF
REFRIGERANT FLOW
EQUALIZER TUBE
FROM TXV VALVE
CAPILLARY TUBE
TO TXV
15.9 mm
(REF)
TXV SENSOR BULB
SENSOR BULB
INDENT
SENSOR BULB
INSULATION

18
PURON (R-410A) REFRIGERANT
This unit is designed for use with Puron (R-410A) refrigerant. Do
not use any other refrigerant in this system.
Puron (R-410A) refrigerant is provided in pink (rose) colored cyl-
inders. These cylinders are available with and without dip tubes;
cylinders with dip tubes will have a label indicating this feature.
For a cylinder with a dip tube, place the cylinder in the upright po-
sition (access valve at the top) when removing liquid refrigerant
for charging. For a cylinder without a dip tube, invert the cylinder,
with the access valve located on the bottom, when adding liquid
refrigerant.
Because Puron (R-410A) refrigerant is a blend, it is strongly rec-
ommended that refrigerant always be removed from the cylinder
as a liquid. Admit liquid refrigerant into the system in the dis-
charge line when breaking the refrigerant system vacuum while
the compressor is OFF. Only add refrigerant (liquid) into the suc-
tion line while the compressor is operating. If adding refrigerant
into the suction line, use a commercial metering/expansion device
at the gage manifold; remove liquid from the cylinder, pass it
through the metering device at the gage set, and then pass it into
the suction line as a vapor. Do not remove Puron (R-410A) refrig-
erant from the cylinder as a vapor.
Refrigerant Charge
Unit panels must be in place when the unit is operating during the
charging procedure. To prepare the unit for charge adjustment, use
the following instructions.
NO CHARGE
Use standard evacuating techniques. Evacuate the system down to
500 microns and let set for 10 minutes to determine if the system
has a refrigerant leak. If the evacuation level raises to
1100 microns and stabilizes, then the system has moisture in it and
should be dehydrated as GTAC2-5 recommends.
If the system continues to rise above 1100 microns, then the sys-
tem has a leak and should be pressurized and leak tested using ap-
propriate techniques as explained in GTAC2-5. After evacuating
the system, weigh in the specified amount of refrigerant as listed
on the unit's rating plate.
LOW-CHARGE COOLING
Using the Cooling Charging Charts (Fig. 19-22), vary the refriger-
ant until the conditions of the appropriate chart are met. Note the
charging charts are different from the type normally used. These
charts are based on charging the units to the correct superheat for
the various operating conditions. Accurate pressure gage and tem-
perature sensing devices are required. Connect the pressure gage
to the service port on the suction line. Mount the temperature sens-
ing device on the suction line and insulate it so the outdoor ambi-
ent temperature does not affect the reading. Indoor-air cfm must
be within the normal operating range of the unit.
EXAMPLE:
Model 50TC*D28
Circuit A
Outdoor Temperature. . . . . . . . . . . . . . . . . . . . . . . . . . 85°F (29°C)
Suction Pressure. . . . . . . . . . . . . . . . . . . . . . . . . 125 psig (860 kPa)
Suction Temperature should be . . . . . . . . . . . . . . . . . . 63°F (17°C)
Circuit B
Outdoor Temperature. . . . . . . . . . . . . . . . . . . . . . . . . . 85°F (29°C)
Suction Pressure. . . . . . . . . . . . . . . . . . . . . . . . . 120 psig (830 kPa)
Suction Temperature should be . . . . . . . . . . . . . . . . . . 58°F (14°C)
Using the Cooling Charging Charts
Take the outdoor ambient temperature and read the suction
pressure gage. Refer to the chart to determine what the suction
temperature should be. If the suction temperature is high, add
refrigerant.
If the suction temperature is low, carefully recover some of the
charge. Recheck the suction pressure as the charge is adjusted.
Select the appropriate unit charging chart from Fig. 19-22.
Note the outdoor ambient temperature and read the suction pres-
sure gage. Refer to the chart to determine what the suction tem-
perature should be. If the suction temperature is high, add refriger-
ant. If the suction temperature is low, carefully recover some of the
charge. Recheck the suction pressure as the charge is adjusted.
For 17-28 sizes, perform this procedure once for Circuit A (using
the Circuit A chart) and once for Circuit B (using the Circuit B
chart).
CAUTION
UNIT DAMAGE HAZARD
Failure to follow this caution may result in damage to
components.
The compressor is in a R-410A refrigerant system and uses a
polyolester (POE) oil. This oil is extremely hygroscopic,
meaning it absorbs water readily. POE oils can absorb
15 times as much water as other oils designed for HCFC and
CFC refrigerants. Avoid exposure of the oil to the atmosphere.

19
COOLING CHARGING CHARTS
Fig. 24 — Cooling Charging Chart - 15, 17.5 Ton (Circuit A)
Fig. 25 — Cooling Charging Chart - 15, 17.5 Ton (Circuit B)
°
°F 35 40 45 50 55 60 65 70 75 80 85 90 95 100
C 1.7 4.4 7.2 10.0 12.8 15.6 18.3 21.1 23.9 26.7 29.4 32.2 35.0 37.8
185.0
175.0
165.0
155.0
145.0
135.0
125.0
115.0
105.0
95.0
85.0
75.0
Suction Pressure (psig)
Suction Temperature
50HE501045-C
115F / 46.1C
105F / 40.6C
95F / 35.0C
85F / 29.4C
75F / 23.9C
65F / 18.3C
55F / 12.8C
45F / 7.2C
COOLING CHARGING CHART
15 and 17.5 Ton - Circuit A
°
°F 35 40 45 50 55 60 65 70 75 80 85 90 95 100
C 1.7 4.4 7.2 10.0 12.8 15.6 18.3 21.1 23.9 26.7 29.4 32.2 35.0 37.8
185.0
175.0
165.0
155.0
145.0
135.0
125.0
115.0
105.0
95.0
85.0
75.0
Suction Pressure (psig)
Suction Temperature 50HE501046-C
115F / 46.1C
105F / 40.6C
95F / 35.0C
85F / 29.4C
75F / 23.9C
65F / 18.3C
55F / 12.8C
45F / 7.2C
COOLING CHARGING CHART
15 and 17.5 Ton - Circuit B

20
Fig. 26 — Cooling Charging Chart - 20 Ton (Circuit A)
Fig. 27 — Cooling Charging Chart - 20 Ton (Circuit B)
°
°F 35 40 45 50 55 60 65 70 75 80 85 90 95 100
C 1.7 4.4 7.2 10.0 12.8 15.6 18.3 21.1 23.9 26.7 29.4 32.2 35.0 37.8
185.0
175.0
165.0
155.0
145.0
135.0
125.0
115.0
105.0
95.0
85.0
75.0
Suction Pressure (psig)
Suction Temperature
50HE501089-C
115F / 46.1C
105F / 40.6C
95F / 35.0C
85F / 29.4C
75F / 23.9C
65F / 18.3C
55F / 12.8C
45F / 7.2C
COOLING CHARGING CHART
20 Ton - Circuit A
°
°F 35 40 45 50 55 60 65 70 75 80 85 90 95 100
C 1.7 4.4 7.2 10.0 12.8 15.6 18.3 21.1 23.9 26.7 29.4 32.2 35.0 37.8
185.0
175.0
165.0
155.0
145.0
135.0
125.0
115.0
105.0
95.0
85.0
75.0
Suction Pressure (psig)
Suction Temperature
50HE501090-C
115F / 46.1C
105F / 40.6C
95F / 35.0C
85F / 29.4C
75F / 23.9C
65F / 18.3C
55F / 12.8C
45F / 7.2C
COOLING CHARGING CHART
20 Ton - Circuit B