United CoolAir VariCool VAV User manual

VariCool® VAV
Installation, Operation and Maintenance Manual
Effective August 2018
Water-Cooled and Chilled Water,
Variable Air Volume

Installation, Operation and Maintenance Manual
VariCool®VAV
3
Subject to change without notice. 10.20-IM (0818)
Contents
Contents � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 3
Wiring Diagram � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 4
Important Notice� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 5
Use of Symbols� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 5
General Information � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 6
EQUIPMENT INSPECTION. . . . . . . . . . . . . . . . . . . . . . 6
HANDLING. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
LOCATION AND CLEARANCES . . . . . . . . . . . . . . . . . . 6
UNIT DIMENSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
UNIT WEIGHT � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 9
UNIT INSTALLATION � � � � � � � � � � � � � � � � � � � � � � � � � � � 10
Vibration Absorbers . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Refrigerant Connections . . . . . . . . . . . . . . . . . . . . . . . 10
Duct Connections. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Water Piping / Water Flow . . . . . . . . . . . . . . . . . . . . . . 12
Water Connections. . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Recommended Field Installed Externally� � � � � � � � � � � 12
Condensate Drain Connection . . . . . . . . . . . . . . . . . . . 12
ELECTRICAL CONNECTIONS . . . . . . . . . . . . . . . . . . 13
SINGLE POINT DISCONNECT (OPTION) . . . . . . . . . 13
SERVICE DISCONNECT. . . . . . . . . . . . . . . . . . . . . . . 13
Supply Air Temperature Sensor . . . . . . . . . . . . . . . . . . 14
Return Air Temperature Sensor (Option) . . . . . . . . . . . 14
Duct Mount Installation. . . . . . . . . . . . . . . . . . . . . . . . . 14
Wall Mount Installation . . . . . . . . . . . . . . . . . . . . . . . . . 14
Return Air Sensor Wiring . . . . . . . . . . . . . . . . . . . . . . . 15
Return Air RH Sensor (Option). . . . . . . . . . . . . . . . . . . 15
Outdoor Air Sensor (Option). . . . . . . . . . . . . . . . . . . . . 15
Duct Mount Installation. . . . . . . . . . . . . . . . . . . . . . . . . 15
Outdoor Air Sensor Wiring . . . . . . . . . . . . . . . . . . . . . . 15
Return Air RH Sensor (Option). . . . . . . . . . . . . . . . . . . 15
High Static Pressure Switch. . . . . . . . . . . . . . . . . . . . . 15
Remote Alarm Output (Option). . . . . . . . . . . . . . . . . . . 16
Remote Water Pump (Option) . . . . . . . . . . . . . . . . . . . 16
O/A Damper Control (Option). . . . . . . . . . . . . . . . . . . . 16
Smoke Detector/Fire Stat (Option). . . . . . . . . . . . . . . . 16
Remote On/Off Control (Option) . . . . . . . . . . . . . . . . . 16
SEQUENCE OF OPERATION . . . . . . . . . . . . . . . . . . . 16
MARVEL PLUS CONTROLLER. . . . . . . . . . . . . . . . . . 16
Maintenance Procedures� � � � � � � � � � � � � � � � � � � � � � � � 17
Filters� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 17
Cleaning The Water-Cooled Condenser� � � � � � � � � � � � 17
Blowers � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 17
Blower Motors� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 17
Blower Speed Adjustment � � � � � � � � � � � � � � � � � � � � � � � 18
Blower Bearing Lubrication� � � � � � � � � � � � � � � � � � � � � � 18
Belts� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 18
Refrigerant Systems� � � � � � � � � � � � � � � � � � � � � � � � � � � � 19
Evaporator And Air-Cooled Condenser Coils � � � � � � � 19
Finned Coil Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Water Side Economizer Coil . . . . . . . . . . . . . . . . . . . . 20
Water Valves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Hard Start Kit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Checking Hot Gas Bypass Valve . . . . . . . . . . . . . . . . . 20
Adjustment Of Hot Gas Bypass Valve . . . . . . . . . . . . . 20
Sequence Of Operation Cooling - - Air-Cooled . . . . . . 21
Cooling - - Water-Cooled . . . . . . . . . . . . . . . . . . . . . . . 21
Cooling - - Chilled Water . . . . . . . . . . . . . . . . . . . . . . . 21
Heating (Other Than Heat Pump) . . . . . . . . . . . . . . . . 21
Heating (Heat Pump, Water Source) . . . . . . . . . . . . . . 21
Troubleshooting � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 22
Limited Warranty � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 26
Limited Warranty for Hermetic Compressors � � � � � � � 27
Limited Warranty Condensing Section � � � � � � � � � � � � 28
Limited Warranty for Hermetic Compressors � � � � � � � 29
Air-Cooled Unit � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 30
Start-Up Procedures (R-410a Systems). . . . . . . . . . 30–31
Air-Cooled Unit � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 32
Water-Cooled Unit � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 34
Start-Up Procedures (R-410a Systems). . . . . . . . . . 34–35
Water-Cooled Unit � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 36
VARICOOL - Model Number Designation � � � � � � � � � � � 38

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Wiring Diagram
United CoolAir provides a wiring schematic for each unit produced. To retrieve the diagram for your unit please visit
www�unitedcoolair�com, on your computer or mobile device, scroll to the footer section or Home/industry-resources,
enter your serial number in the Serial Search eld and press return to retrieve your product-wiring diagram.
Your serial number is a combination of the year, month and sequential order of build date.
This action will return the Model number, Job Number and the wiring diagram for viewing as well as downloading.
NOTE: Only units shipped since November 2016 are available on the site, for older units please contact the factory directly
at 717-843-4311.

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The electrical hazard icon indicates the presence of an electrical hazard which
could result in electrical shock or death.
The warning icon indicates a potentially hazardous situation which could result
in death or serious bodily injury if not avoided.
The caution icon indicates a potentially hazardous situation which may result in
minor or moderate injury if not avoided.
The information icon indicates a situation that may result in equipment or
property damage. The information provided alerts the reader to relevant facts
and/or conditions.
ELECTRICAL
HAZARD
WARNING
CAUTION
INFORMATION
Important Notice
This publication includes warnings, cautions and information icons that point out safety related issues or conditions as well
as other pertinent information relative to a safe installation, service or maintenance situation. The following icons should be
interpreted as follows:
This manual is the property of the owner�
Please be sure to leave it with the owner when you leave the job�
Use of Symbols
NOTE: If the unit design was ordered specic to the
application or installation, please refer to the Addendum
at the end of this product literature� The unit may have
features or options specic to this job or application so
please refer to the addendum for details� The addendum
will also list the specic United CoolAir Job Number
or eld reference Job Name. Examples of unit design
specic to unit ordered will include product dimensions,
special control sequences and remote condenser /
condensing sections�

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General Information
VariCool units are cooling and optional heating systems
designed to effectively and efciently maintain tenant
occupied spaces within oor by oor building structures.
Each VariCool unit delivers continuous air ow at varied
air volumes and constant temperature to maintain tenant
occupied space settings through eld supplied VAV terminal
outlet boxes. Each unit is designed for optimal energy
efciency, reliability, IAQ, and lowered sound levels. Each
occupant then controls their specic zone by adjusting
temperature setting allowing the VAV terminal outlet box to
open to provide conditioned air. As the VAV box opens, the
VariCool automatically adjusts to maintain the systems static
pressure set point.
Multiple VariCool Systems may be networked together for
unit lead lag, back up/assist, and system rotation. Options
are available for linking each system through a facilities
Building Management System (BMS).
Each unit is shipped in two/three pieces (depends on model
size) for ease on movement to the location of installation.
EQUIPMENT INSPECTION
Upon receiving the unit, carefully inspect all sections for visible
or concealed interior/exterior damage. If damage occurred
during transit, contact the freight carrier immediately and le
a damage claim report. Inspect the unit data plate to verify
that the model unit that was ordered is the correct unit being
received. All accessory components for the application that
must be eld installed are shipped loose in one or several
boxes in the compressor section.
HANDLING
Use extreme caution so that damage does not occur when
moving each section to the location of installation. The unit
may be moved to the location of installation by crane, fork lift,
hand truck, or roller bars. Units are provided with lifting rings
for rigging and movement by crane. Spreader bars must be
used to protect section cabinet structure during movement.
Protection must be used so that damage to the cabinet
does not occur when using cables or slings. Be certain each
section is well supported when moving. When using dollies,
fork lifts, hand trucks, or roller bars, make sure the sections
base rails are well supported and the weight of the sections
are distributed evenly so that dropping or damage does not
occur during movement.
LOCATION AND CLEARANCES
The unit should be installed in an equipment room located
away from occupied tenant spaces. Careful consideration
should be taken during system layout and installation to allow
for minimum required service clearances for the VariCool
unit. Minimum clearances provided are worst case scenario.
If the clearances were less around the cooling coil section
and a cooling coil had to be replaced, it would be difcult to
maneuver the coil around the unit unless a service access
door(s) to the mechanical room were located next to the
VariCool’s cooling coil end. Figure 1 – Service Clearances
and Table 1 show minimum clearance requirements for each
model unit. If the unit has an optional water side economizer
coil, the distance for service clearance must be maintained
from the edge of the lter rack which will mount onto the
economizer section on larger units but DX cooling coil
on smaller units as the economizer coil will be mounted
internally on smaller systems.

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TABLE 1- SERVICE CLEARANCES
Unit Model (A) Dim (B) Dim
AV*8 – AV*16 30” 30”
AV*20-AV*30 42” 36”
AV*32-AV*60 50” 36”
UNIT DIMENSIONS
Figure 2 – Unit Dimensions and Table 2 show the dimensions
of each unit section. Note: If the System has the Water Side
Economizer Coil option, the unit will have a fourth section
that will be attached onto the Cooling Coil/Return Air Inlet
end of the unit. This has been labeled with the dimension
Tx on the diagram and it will vary depending on the lter
options desired.
FIGURE 1 – Service Clearances

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FIGURE 2 – Unit Dimensions
TABLE 2 – Unit Dimensions
MODEL A B C D E F G H I J K L M N P R S
AV*08
68 68 32 32 38 30
16 26 8 21
TBD TBD 21.5
20
TBD 5 50
AV*10
40AV*12 18 32 7 18
AV*16
AV*20
80 80
35
35 48 32 20
36
7.5
22
TBD TBD 21
40
TBD 5 66
AV*24
60AV*26 44 18
AV*30
AV*32
98 100 52 62 36 30
42
11
29
1.5 97 4 80 10.5 4.5 86
AV*36
AV*40
AV*44
52 24
AV*48
AV*52
AV*56
AV*60
Tx – Filter Rack dimensions are as follows:
T1 – 7” width when a standard 2” Filter is ordered
T2 – 9.5” width with extra ltration option includes a 2” plus 4” lter back to back

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UNIT WEIGHT
Table 3 – Unit Weight shows the weights of each model. The
weight of each unit is listed as a standard VariCool without
options. Table 4 – Optional Component Weight references
the weights of each optional component or upgrade package.
When calculating the weight for each unit, the weight of each
optional component must be added to the standard VariCool
unit weight shown in Table 3.
MODEL BLOWER (lbs) EVAPORATOR (lbs) CONDENSER (lbs) TOTAL (lbs)
AVW08 588 521 592 1701
AVW10 617 550 642 1809
AVW12 699 562 732 1993
AVW16 757 619 796 2172
AVW20 1134 856 910 2900
AVW24 1270 954 1046 3270
AVW26 1305 954 1196 3455
AVW30 1305 989 1216 3510
AVW32 1735 1256 1697 4688
AVW36 1787 1325 1673 4785
AVW40 1805 1387 1847 5039
AVW44 1953 1422 1899 5274
AVW48 1953 1479 1942 5374
AVW52 2087 1489 2227 5803
AVW56 2155 1535 2247 5937
AVW60 2155 1593 2287 6035
Table 3 – Unit Weight

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UNIT INSTALLATION
Install the unit using the following procedures. Consideration
must be taken for proper condensate drain installation. Slight
elevation of the VariCool unit may be required for installation
of the condensate drain. Methods for elevating the VariCool
units are support rails, concrete pad(s), or spring isolators.
1� Once the unit’s sections have been moved to the
location of installation, locate the factory provided
mounting hardware, which has been pre-installed in the
holes where the sections will be connected together.
2� Using the appropriate size wrenches, remove the
mounting hardware and set in a safe location for
connecting the sections together during installation.
Vibration Absorbers
When installing the VariCool on a concrete pad, support
rails, or other methods other then spring isolation, use of
vibration absorbers is recommended to prevent transmission
of possible vibration.
3� Figure 3 – Vibration Pads shows the recommended
points for vibration absorbent pads (eld provided). We
recommend the use of a minimum 1” thick Neoprene
vibration absorbent pad under each point shown in
Figure 3. Models AV*09 through AV*16 only require the
pads under the corners only.
FIGURE 3 – Vibration Pads
4� Place each vibration isolator into positions shown in
Figure 3, and then move the compressor and cooling
coil section into the location of installation being careful
not to damage the quick connect refrigerant piping.
5� Fasten the cooling coil section bottom half to the
compressor section using the mounting hardware
removed in Step 2.
6� Allow the hardware to remain only hand tight until the
Blower Section is installed.
INFORMATION
IMPORTANT: Before proceeding with
the installation of the Supply Air Blower
Section, we recommend connecting the
refrigerant quick connect connections
otherwise it may be difcult to make the
connections.
Refrigerant Connections
The DX Cooling Coil section refrigerant circuit is connected
to the compressor/condenser section using quick-connect
refrigerant connections. If the VariCool unit is a split system
with a Remote Air Cooled Condenser, refer to the section on
Split Systems. If the VariCool was ordered as a packaged
system, connecting refrigerant tubing will be fairly simple.
The quick connect ttings are self-sealing so they do not
permit refrigerant ow until they are completely tight. Follow
these steps for a packaged system:
7� Remove the caps on the quick connect refrigerant
lines.
8� Using a small amount of National 150 or 3G brand
refrigerant oil, lightly lubricate the threads of the
quick connect ttings. (5 to 6 droplets of oil are
recommended)
9� Align each quick connect tting and hand thread the
Female Quick Connect ttings onto the Male Quick
Connect ttings as shown in Figure 4 – Quick Connect.

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FIGURE 4 – Quick Connect
INFORMATION
NOTE: Be certain to count the number
of complete thread rotations. Observe
the number of turns reference Table 6 to
determine how tight to make the quick
connect couplings
10� Continue to hand thread until slight resistance is
observed.
11� Once slight resistance is evident, continue to tighten
the ttings using appropriate size wrenches listed in
Table 5.
TABLE 5
QC-Size Wrench # Full Turns
3/8” 1-3/16” 6
1/2” 1-3/16” 6
5/8” 1-5/8” 7-3/4
3/4” 1-5/8” 7-3/4
7/8” 1-5/8” 8
1-1/8” 2” 8
12� If the quick connect still feels loose, tighten just a bit
more until complete resistance is evident.
INFORMATION
NOTE: Once tight, refrigerant should be
able to pass through the quick connect
couplings. If problems with low refrigerant
pressure appear during system startup,
double check the tightness of these quick
connect couplings as loose ttings will
restrain full refrigerant ow.
13� Move the Blower Section into position of installation
making sure the side that the blower can be seen will
mate up with the large opening in the Cooling Coil
Section.
14� Lift the blower section up onto the Compressor Section.
15� Use the remaining mounting hardware to connect the
Blower Section to the Cooling Coil Section.
16� Using the appropriate size wrenches, hand-tighten all
mounting hardware.
INFORMATION
Note: seismic isolators are shipped
completely locked into position. Once
the blower section is installed the spring
isolators adjusted to loosen the blower on
isolators. The blower should be allowed to
oat on the isolators approximately ½" to
1" side to side and back and fourth.
17� Once the supply air blower is installed, the spring
isolators under the supply air blower must be
loosened. It is the responsibility of the installing
contractor to loosen the spring isolators. These
isolators are tightened for shipping purposes only.
They must be loosened for proper operation.
Apply oil to male threads
Female Fitting
Male Fitting
Clockwise Rotation

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Duct Connections
A supply air plenum must be eld fabricated and attached
to the supply air outlet with a exible duct collar. Follow
appropriate guidelines for typical ducting installation.
Provide a duct length that is 3 to 4 times the diameter of
the plug fan wheel before making the rst transition. Provide
turning vanes when required. Attach the supply air plenum
Water Piping / Water Flow
As a standard, units shall have a shell and tube water cooled
condenser. The end plates of the shell and tube condenser
are fully removable for brush cleaning when soft deposits or
scale have formed internal to the condenser coil. Table 6 lists
the water ow and water pressure drops for each model unit.
Tube and tube water cooled condensers may be substituted.
Water Connections
Do not reduce water inlet and outlet connections as this will
restrain water ow and increase water pressure. The inlet
water line should have a strainer accessible for periodic
cleaning. Both the inlet and outlet water lines should have
eld installed water shut-off valves (Gate or Ball type valves).
The shutoff valves are required for maintenance, system
repairs, or long periods of system shut down.
TABLE 6 – Flow Rates/PSI Drop
Model GPM PSI
AVW8 24 4
AVW10 30 6
AVW12 36 7
AVW16 48 8
AVW20 60 6
AVW24 72 8
AVW26 78 10
AVW30 90 14
AVW32 96 8
AVW36 108 10
AVW40 120 6
AVW44 132 7
AVW48 144 8
AVW52 162 10
AVW56 168 12
AVW60 180 14
Recommended Field Installed
Externally
Condensate Drain Connection
Each VariCool unit has a condensate drain connection on
the Cooling Coil section. For systems with the Water Side
Economizer coil option, condensate drain connections are
provided
A condensate drain trap must be eld fabricated and
installed onto the 1" IPS drain connection. Each trap must
then be piped to a common waste drain. Refer to Figure
5 – Condensate Trap for reference dimensions. Units are
equipped with a 1" male IPS connection.
For systems with the Water Side Economizer coil option,
each individual section (Cooling Coil and Water Side
Economizer sections) must be piped individually with a
separate drain trap. Once each section has a drain trap, they
may be connected together by a tee and piped to a common
waste drain.
The depth of the condensate trap will vary due to the model of
the unit ordered and eld requirements. The purpose of the
trap is to neutralize the negative pressure created within the
blower cabinet. Refer to the order specications for external
static pressure (ESP) to calculate the depth required for the
“A” Dimension shown in Figure 5. The A Dimension must
equal or exceed the negative pressure developed by the
supply air blower. If it does not, the condensate will not drain
properly and may allow the drain pan to overow. The lower
leg of the trap must maintain a minimum depth of 3-1/2” to
maintain a water seal on during all operating conditions.
Plug each section’s (Cooling Coil and optional Water Side
Econo Coil) opposite side drain connection as shown.

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FIGURE 5 – CONDENSATE TRAP
ELECTRICAL CONNECTIONS
All electrical wiring must be in accordance with NEC (National
Electrical Code) and state and local building codes. Refer to
the specications section or the unit’s data tag for the unit’s
power requirements. The main power entrance for each
VariCool unit is located directly above the electrical box.
SINGLE POINT DISCONNECT (OPTION)
If the VariCool unit has through the door single point power
disconnect option, turn the disconnect switch to the ON
position.
SERVICE DISCONNECT
A eld installed fused single point power service disconnect
is required. Install the service disconnect in accordance
with NEC, State, and Local building codes. NEC guidelines
require the unit’s disconnect be installed within sight of the
unit.
A factory provided power block is installed internal to the
VariCool’s electrical control panel. Route the main power
wires in accordance with electrical codes to the eld provided
unit disconnect and terminate them on the line side of the
disconnect. Route the power wires from the Load side of
the eld provided service disconnect to the unit power block
inside the electrical panel.
A ground termination point is located within the VariCool’s
electrical control panel.
INFORMATION
NOTE: Conduit is not an acceptable
ground source. A separate ground conduct
must be connected from Earth Ground to
the factory supplied ground lug internal to
the unit.
SENSOR FIELD MOUNTING & WIRING
All sensors and optional components that must be eld
installed and wired to the electrical control panel must be
wired as shown on the electrical diagram provided with the
unit and the instructions listed below.
Static Pressure Transducer
The static pressure transducer is factory installed internal to
the main electrical panel and wired back to the main control
board. Pneumatic tubing (eld supplied) must be connected
from the “HIGH” connection to a point approximately 2/3rds
the distance down the straightest length of supply air ducting.
NOTE: Make certain there are no kinks in the pneumatic
tubing.
1� Drill a hole into the ducting at a right angle. Place
approximately 1/8” of the high pressure tube into the
duct at a right angle. The end of the pneumatic tubing
must be cut at and make a right angle for the tube to
pick up the correct air pressure reading.
2� Use a clamp to secure the tube to the ducting.
3� Make certain the end of the tube is cut ush at a 90
degree right angle. This tube must be located in
ambient air.
The static pressure transducer is preset to read from 0”
to 2.5” W.C. The VariCool’s controller will read the preset
conguration. If a lower pressure conguration is desired,
use the manufacturer’s provided literature to re-congure for
the sensor to read the desired lower pressure setting.
INFORMATION
NOTE: The VariCool’s controller for sensor
calibration must also be readjusted. This
is explained under sensor calibration in
the Marvel Plus controller section.

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Supply Air Temperature Sensor
The supply air temperature sensor is typically factory
installed. If the sensor is factory installed, it will be connected
to terminal strip TB2 terminals 3 and 4. It will have a
label around the sensor wire stating “SUPPLY SENSOR
FACTORY INSTALLED”.
In some cases, the sensor must be eld installed in the
straightest length of supply air duct for uniform air ow. The
location of the sensor must be relatively close to the duct
pressure transducer but must not impede the airow to the
inlet of the transducer. A few feet from the transducer is
recommended.
1� Cut out the mounting template provided with the
sensor.
2� Select the location to mount the sensor and drill a hole
through the supply air duct at least ¾” in diameter.
3� Using a 7/64” drill bit; drill the three fastening screw
holes located on the template for the fastening ring.
4� Remove the duct sensor’s mounting ring from the duct
probe and position it over the holes previously drilled in
the duct.
5� Use three #6 x ¾” Pan Head sheet metal screws and
fasten bracket to the duct.
6� Place the probe into the supply air duct.
7� Use the screw provided to tighten the clamping ring.
Using a minimum 18-20 AWG 300 volt rated two conductor
shielded cable with drain wire make the following electrical
connections.
8� The supply air temperature sensor is non-polarity
observant. Connect from one NTC terminal inside the
supply air temperature sensor to TB2-3.
9� Connect the other NTC terminal inside the temperature
sensor to TB2-4.
10� Connect the drain wire to ground at the VariCool’s
electrical control panel end only.
Return Air Temperature Sensor (Option)
The Return Air Temperature Sensor is provided for units
with the Morning Warmup option. If the unit has the
Airside Economizer option or optional Humidication/
Dehumidication, a Humidity Sensor will also be provided.
The unit Return Air Sensor must be eld installed in the return
air ducting, Return Air Plenum, Open Return Air Plenum as
close to the VariCool unit’s Filter Rack as possible. Since
United CoolAir may not know the application, please specify
the type of sensor (wall or duct mount) required for eld
installation. Typically if the return air is Open Plenum, a wall
mount sensor is recommended. If the return air is ducted
into the unit, a duct mount sensor is recommended.
BE AWARE: If the unit has optional humidity control,
polarity must be observed when making
electrical connections�
1� Cut out the mounting template provided with the
sensor.
Duct Mount Installation
2� Select the location to mount the sensor and drill a hole
through the supply air duct at least ¾” in diameter.
3� Using a 7/64” drill bit; drill the three fastening screw
holes located on the template for the fastening ring.
4� Remove the duct sensor’s mounting ring from the duct
probe and position it over the holes previously drilled in
the duct.
5� Use three #6 x ¾” Pan Head sheet metal screws and
fasten bracket to the duct.
6� Place the probe into the supply air duct.
7� Use the screw provided to tighten the clamping ring.
Wall Mount Installation
If mounting directly to drywall, use the enclosed template
and the screws and wall anchors enclosed with the sensor.
A switch box may also be used. A three position switch box
is recommended but a single position switch box rotated
90 degrees and mounted to a rigid surface will also sufce.

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Subject to change without notice. 10.20-IM (0818)
Return Air Sensor Wiring
Using a minimum 18-20 AWG 300 volt rated two conductor
shielded cable with drain wire make the following electrical
connections.
Note: Use a minimum two conductor cable for temperature
only. Use a minimum ve conductor for the temperature and
humidity sensor.
8� The supply air temperature sensor is non-polarity
observant. Connect from one NTC terminal inside the
supply air temperature sensor to TB3-NTC.
9� Connect the other NTC terminal inside the temperature
sensor to TB3-NTC.
10� Connect the drain wire to ground at the VariCool’s
electrical control panel end only.
Return Air RH Sensor (Option)
If the Return Air Sensor has the Humidity Sensor for optional
humidity control or Airside Economizer, continue with steps
11, 12, and 13.
11� Connect the terminal marked G+ to terminal TB3-G+.
12� Connect the terminal marked TB3- M to M.
13� Connect terminal Hout to terminal TB3-Hout.
Outdoor Air Sensor (Option)
The outdoor air temperature and humidity sensor is required
for Airside Economizer function. An outdoor air temperature
sensor is required for the Heat Pump option. The unit
Outdoor Air Sensor must be eld installed in the outdoor air
ducting.
BE AWARE: If the unit has optional humidity sensor
because of the Airside Economizer control,
polarity must be observed when making
electrical connections�
14� Cut out the mounting template provided with the
sensor.
Duct Mount Installation
15� Select the location to mount the sensor and drill a hole
through the supply air duct at least ¾” in diameter.
16� Using a 7/64” drill bit; drill the three fastening screw
holes located on the template for the fastening ring.
17� Remove the duct sensor’s mounting ring from the duct
probe and position it over the holes previously drilled in
the duct.
18� Use three #6 x ¾” Pan Head sheet metal screws and
fasten bracket to the duct.
19� Place the probe into the supply air duct.
20� Use the screw provided to tighten the clamping ring.
Outdoor Air Sensor Wiring
Using a minimum 18-20 AWG 300 volt rated two conductor
shielded cable with drain wire make the following electrical
connections.
Note: Use a minimum two conductor cable for temperature
only. Use a minimum ve conductor for the temperature and
humidity sensor.
21� The supply air temperature sensor is non-polarity
observant. Connect from one NTC terminal inside the
supply air temperature sensor to TB4-NTC.
22� Connect the other NTC terminal inside the temperature
sensor to TB4-NTC.
23� Connect the drain wire to ground at the VariCool’s
electrical control panel end only.
Return Air RH Sensor (Option)
If the Return Air Sensor has the Humidity Sensor for optional
humidity control or Airside Economizer, continue with steps
24, 25, and 26.
24� Connect the terminal marked G+ to terminal TB4-G+.
25� Connect the terminal marked TB4- M to M.
26� Connect terminal Hout to terminal TB4-Hout.
High Static Pressure Switch
The high static pressure switch is factory installed in the
electrical control box. This switch is factory wired into the
electrical controls for alarm if a high duct pressure condition
occurs. Pneumatic tubing must be eld installed from this
switch to a location ½ to 2/3rds the distance down the
straightest length of the supply air duct.
INFORMATION
Make certain there are no kinks in the
pneumatic tubing.

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1� Drill a hole large enough to insert the pneumatic tubing
into the ducting at a 90 degree right angle.
2� Place approximately 1/8” of the high pressure tube into
the duct at the 90 degree right angle. The end of the
pneumatic tubing must be cut at and make a right
angle for the tube to pick up the correct air pressure
reading.
3� Use a clamp to secure the tube to the ducting and
route it back to the high static pressure switch.
4� Place the other end of this tubing onto the high
pressure end of the switch.
5� Install a second tube onto the low pressure side of the
pressure switch and route it to a room neutral pressure
location.
6� Again, make certain the end of the tube is cut ush at
a 90 degree right angle. This tube must be located in
ambient air.
Remote Alarm Output (Option)
A dry contact closure on alarm option may be provided
upon request. During an alarm condition, the Remote Alarm
output can be used to energize a eld provided and installed
alarm indicator light or buzzer.
If the system has this option, wire the electrical hot or
common side of the device being energized into terminals
TB2- 9 and TB2-10. The control circuit voltage must be 24
VAC and less than 1 amp inductive.
Remote Water Pump (Option)
If the system has the Remote Water Pump ON/OFF control
option, the hot or common side of the water pump’s starter
must be wired to terminals TB2-7 and TB2-8. The control
circuit voltage must be less than 250 VAC and not exceed
10 amps inductive loading.
O/A Damper Control (Option)
If the system has the Optional Outdoor Air Damper control,
the control signal to drive the eld provided damper actuator
must be wired through the factory provided terminals TB2-11
and TB2-12. The control circuit voltage must be 24 VAC and
not exceed1 amp inductive loading.
Smoke Detector/Fire Stat (Option)
If Smoke Detector or Fire Stat shutdown option is required,
a voltage free dry normally closed contact opens on alarm
must be eld provided from the device and wired back to the
VariCool’s Control Panel. Terminate from the device contact
termination points to the factory provided terminals TB2-18
and TB2-19.
Remote On/Off Control (Option)
With the Remote On/Off Control option, the unit will start
when a voltage free dry contact closure is provided to
Terminals TB2-20 and TB2-21. This closure may be provided
by a eld provided building management system or switch.
SEQUENCE OF OPERATION
DANGER: Be aware that fast moving fan drives and high
horsepower blowers/motors can cause injuries. Before
applying power to the VariCool unit, make sure all service
access doors are closed and latched to prevent injuries from
doors from blowing open or fast moving drives. Connect
power to the unit at the main power supply. Next, apply
power at the eld installed service disconnect switch and/
or optional factory supplied single point power disconnect.
MARVEL PLUS CONTROLLER
The VariCool system is designed to operate using a double
microprocessor design control system called a Marvel Plus.
The Marvel Plus control system incorporates a Marvel Plus
Main Board Control and a Marvel Plus Wall Mount Control
and display.
The Marvel Plus Main Board microprocessor is a 16 bit
microprocessor programmable controller with onboard
ash memory (6 Megabytes) to ensure better performance.
An onboard real time clock card allows for setting up of
occupancy schedules and recording of alarm occurrence for
storing of alarm history. Each Marvel Plus has the ability to
record up to 36 alarms/faults under an alarm history page to
allow technicians to view alarm history and temperatures
when the alarm occurred. Marvel Plus Main Boards allow
for connection some of the more widely used Building
Management Systems without requiring a Gateway to
interface.
The Marvel Plus Wall Controller is a terminal unit used to
interface with the Marvel Plus Main Board Controller through
the onboard display and keypad. The software stored in the
ash memory of the Marvel Plus Main Board was designed
with menu driven pages allowing customers to easily
navigate through the menus and submenus for setup of their
systems.
Note: See Our Marvel manual for operating instructions�
http://www.unitedcoolair.com/user-les/le/controls/
Marjiom.pdf

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VariCool®VAV
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Subject to change without notice. 10.20-IM (0818)
ELECTRICAL HAZARD
Turn OFF power and lockout service
before conducting any maintenance. Keep
hands, clothing and tools clear of electrical
terminals.
WARNING
Make sure to keep hands and clothing
clear of any moving belts, blowers and
motors while performing any maintenance.
Failure to do so could result in death or
serious bodily injury.
CAUTION
Any maintenance should be conducted
by qualied HVAC service personnel only.
Potentially hazardous situations which
may result in personal injury, equipment or
property damage.
Filters
Do NOT run unit without lters.
Throwaway lters are supplied which are pleated extended
surface type. Filters should be checked monthly for dirt
accumulation and changed when necessary. Replacement
lters must be the same type as originally supplied.
INFORMATION
Unit must be shut off at the disconnect
switch before the lters are serviced. Be
sure to check that the air ow direction
arrows on the lters point in the correct
direction of air ow.
Cleaning The Water-Cooled
Condenser
Any uid that is used to carry the heat away through the
condenser contains, minerals, dust from a cooling tower or
other foreign materials. Over time these contaminants will
build up on the walls of the heat exchanger.
This scale or fouling will result in a reduction in water ow,
less water temperature difference between inlet and outlet,
high condensing temperature and higher uid pressure drop.
All of these affect the operating performance and efciency
of the system and need to be addressed.
Cleaning a water-cooled condenser helps to improve the
heat transfer rate, reduce operational cost, restore efciency,
prolong heat exchanger life and reduce pressure drop
pumping costs. Deposits from water or water treatments,
such as scale, lime, rust or mud are removed.
Each installation is unique. Therefore, the uid quality and
operating conditions will dictate when the heat exchanger
needs to be cleaned.
During the start-up process record the water pressure drop
across the heat exchanger. Also record the inlet and outlet
water temperatures. After a period of time these values can
be checked to see how much loss of operating performance
has occurred. If a 10% or greater change has occurred, it
would be benecial to clean the heat exchanger.
There are a number of commercially available products for
cleaning a heat exchanger. Follow all industry practices to
safely and effectively clean the heat exchanger.
Blowers
Disconnect power and lockout the service before doing any
service or maintenance.
Air-cooled units are provided with adjustable belt drive
blower packages for both the evaporator and condensing
sections. Check that the blower wheel is tight on the shaft
and does not contact the housing. Bearings are permanently
sealed, but should be checked periodically for signs of wear.
Check for restrictions or foreign material in the air circuit.
The drive may be adjusted for different static pressures. If
such an adjustment is made, check that the motor current
draw does not exceed the motor nameplate current by more
than 10%.
Blower Motors
All blower motors are equipped with thermal overload
protectors.
WARNING
Open disconnects to unit before doing
any service or maintenance. A motor that
is off on thermal overload can start any
time when the automatic thermal overload
resets.
Maintenance Procedures

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VariCool®VAV
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Subject to change without notice. 10.20-IM (0818)
Blower Speed Adjustment
Blower speed may be changed by adjusting the variable
diameter sheave provided on the blower drive motor.
Sheave may be adjusted by removing the belt and loosening
the setscrew located in the hub of the outer ange. With the
setscrew loosened, the ange may be turned clockwise
to increase blower speed or counter-clockwise to reduce
blower speed.
Typically the motor and drive packages have been sized and
designed for the specic CFM and external static pressure
(ESP) of the application. Before making any changes conrm
what the performance was designed for and what the actual
performance is.
INFORMATION
Setscrew must be positioned directly
above the at section of the threaded
sheave shaft before tightening to hold
adjustment.
INFORMATION
Reduction of airow through excessive
external air friction losses, lowered blower
speed operation with dirty lters, or
obstructed air ow may result in excessive
condensation at air outlets, short cycling,
or total unit shut- down due to evaporator
coil icing.
INFORMATION
Verify that the motor current draw does
not exceed the motor nameplate current
by more than 10%.
Blower Bearing Lubrication
INFORMATION
Unit must be shut off at the disconnect
switch before the blowers are serviced.
Bearings on the smaller units are permanently sealed, but
should be checked periodically for signs of wear.
Larger units have pillow block bearings. Bearings will need
to be lubricated based on the use of the equipment.
Duty Grease Interval
Low Usage 12 Months
Periodic 6 Months
Continuous 1 – 2 Months
Use a high quality lithium grease for blower pillow block
bearings. Wipe off the “Zerk” tting with a rag before adding
grease so as not to introduce dirt into the bearing.
Slowly rotate the shaft while pumping it in. Pump the grease
in slowly so as not to blow out the bearing seal. When the
grease starts to “seep” out of the bearing you have put in
enough new lubricant.
Over lubricating can cause a bearing to fail from overheating
or it can blow out the seal.
Both excessive or inadequate grease may cause premature
failure. Provided there is some grease in the bearings for
lubrication, under lubrication is better than over lubrication
as grease can easily be added but not removed. Always
allow a slight bead around the circumference of the seals to
protect the bearing from foreign matter and helps ush out
the bearing as well.
Wipe off the “Zerk” tting with a rag after adding grease
Belts
Excessive belt tension is the number one cause for blower
bearing failure. Proper belt tension and pulley alignment are
essential for trouble free operation.
Deection is the amount the belt gives when force is applied,
usually by nger, to the belt at the approximate center point
to the belt span.
Insufcient deection indicates that the belt tension is
entirely too tight, and if not loosened somewhat, noise due
to excessive vibration, premature bearing failure, shortened
belt life, and a reduction in supply air blower performance
may result. Tight belts may also overload the motor and
cause the efciency to drop considerably or even premature
motor failure as well.
Excessive deection is an indication that the belt is not tight
enough. If not corrected, slippage may occur causing loss of
blower speed and belt failure. The belts will glaze then crack
or even break due to increased temperatures caused by
slippage. Belts may slip during start-up, but slipping should
stop as soon as the fan reaches full speed.
If the midpoint (midway between the blower and motor shaft)
of the belt is pressed inward, there should be about 1/2” to a
1” of deection when the belt is properly tensioned.

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Subject to change without notice. 10.20-IM (0818)
Refer to Figure 10 – Belt Tensioning below.
Figure 10 – Belt Tensioning
For proper tensioning, an excellent method to use is listed in
the following equation.
Deection = Belt Span
64
Belt span is in inches from center pulley to center pulley (see
Figure 10).
Belt tension is adjusted by using the adjusting bolt on the
end of the motor mounting frame.
Check the alignment of the sheaves to make sure that the
sheave faces are in the same plane. Check this by placing
a straight edge across the face of the sheaves. Any gap
between the edge and sheave faces indicates misalignment
Note: This alignment method is only valid when the width of
the surfaces between the belt edges is the same for
both sheaves� When they are not equal or when using
adjustable pitch pulleys, adjust so that the belts have
approximately equal tension� Both shafts should be
at right angles to the belt� Check the setscrew and/or
bushing bolt tightness�
Belts tend to stretch somewhat after installation. Recheck
belt tension after several hours of operation.
Refrigerant Systems
All refrigerant circuits contain a liquid line sight glass. If
bubbles appear in the sight glass, the system is either
undercharged with refrigerant or there may be a restriction in
the liquid line upstream of the sight glass. However, bubbles
will appear every now and then in units with the hot gas
bypass option. Bubbles will also appear upon compressor
start up, but normally clear to pure liquid after a few minutes
of operation.
The sight glass contains a moisture indicator which changes
color when moisture is present in the refrigerant circuit. This
indicator is the circular dot in the center of the sight glass.
If the color of this indicator is blue, the refrigerant is okay.
When the indicator is pink or purple, an abnormal condition
exists, servicing is required.
INFORMATION
After installation and during equipment
start-up, the sight glass may appear pink
or purple. This occurs during prolonged
periods of non-operation and should turn
blue after several hours (up to 12) of
operation.
Evaporator And Air-Cooled
Condenser Coils
The nned coils in a unit should be checked at least every
six (6) months or more frequently based on experience of
the specic application.
Evaporator nned coils can become “fouled” due to a build
up of contaminants in the air path that are not caught or
captured in the air lters. Over time this build up on the n
surface can reduce heat transfer and increased resistance
to air ow. The end result might be higher operating costs or
occupant discomfort
A dirty condenser coil will cause high condensing pressures,
resulting in higher power consumption and possibly system
shut-down by high pressure safety control. A dirty evaporator
coil will reduce unit capacity and eventually will cause system
shut-down by the low pressure safety control.
Finned Coil Cleaning
Before cleaning any nned coils, remove the lters. Remove
any large debris or visible dirt accumulation.
WARNING
Make sure to follow all safety precautions
when cleaning any coil with a commercially
available coil cleaner. Follow all
recommendations for safety clothing and
gear. Failure to follow all safety instructions
could result in death or serious injury.
CAUTION
Clean coils only with cold water and a
suitable detergent or a commercially
available coil cleaner. DO NOT use hot
water or steam to clean a coil containing
refrigerant as this may cause a high
pressure situation that could damage
the coil and associated safety devices or
refrigerant components.
Deection Point
Belt Span