Dometic SMX II Operating and installation instructions

DX Modulating A/C System  INSTALLATION • OPERATION
Revised: 08-29-06
L-0952  English
Part Number: LP-28
For DX Modulating SMX II Control Systems using
SMXII and SMXir displays

3English
L-0952
Table of Contents
Modulating A/C Systems • Introduction
Drawings and Diagrams ................................................................... 4
Air Conditioner Basics ...................................................................... 4
The Effect of Seawater Temperature ................................................ 4
The Modulating System .................................................................... 4
How it Works in General ................................................................... 4
How it Works in Detail ...................................................................... 5
Subsystems ..................................................................................... 6
Condensate Drain ............................................................................ 6
Modulating A/C System • Installation
Installation Procedures ..................................................................... 7
Electrical System ............................................................................. 7
Voltage and Frequency ..................................................................... 7
Installing The Condensing Unit
Selecting the Site ............................................................................. 7
Site Location Checklist ..................................................................... 7
Mounting the Condensing Unit ......................................................... 7
Installing the Seawater Cooling System
Importance of a Self-Draining System .............................................. 8
Through-Hull Inlet Fitting .................................................................. 8
Seacock ........................................................................................... 8
Strainer ............................................................................................. 8
Seawater Pump ................................................................................ 8
Manifolds .......................................................................................... 8
Overboard Discharge ....................................................................... 9
Seawater Piping ............................................................................... 9
Bonding ............................................................................................ 9
Installing The Cooling/Heating Unit
Selecting the Site ............................................................................. 9
Site Location Checklist ..................................................................... 9
Mounting the Cooling/Heating Unit ................................................. 10
Installing the Refrigerant Tubing ...................................................... 10
Installing The Air Distribution System
Return Air Grill ............................................................................... 10
Ducts .............................................................................................. 10
Ducting Guidelines ......................................................................... 10
Discharge Air Grill .......................................................................... 11
Installing the Cooling Unit Control
SMX II Control System ................................................................... 11
Installing the Power/Logic Box ........................................................ 11
Installing the SMXir Keypad/Display ............................................... 11
SMX Interconnect Cable ................................................................ 11
Installing the Temperature Sensor .................................................. 12
Installing the Pump Relay
Location .......................................................................................... 12
Operation ....................................................................................... 12
Voltage and Triggers ....................................................................... 12
Electrical Connections
General Electrical Notes ................................................................ 12
Three Phase Power ........................................................................ 13
Final Inspection
Inspecting the Seawater Cooling System ....................................... 13
Inspecting the Condensing Unit ...................................................... 13
Inspecting the Cooling/Heating Unit ............................................... 13
Inspecting the Refrigerant Connections .......................................... 14
Inspecting the Air Distribution System ............................................ 14
Inspecting the Control and Electrical Wiring ................................... 14
Charging the System with Refrigerant
Initial Charging, New System ......................................................... 14
Adjusting the Charge ...................................................................... 15
Removing Refrigerant from the System .......................................... 16
Initial Start Up ................................................................................. 16
Modulating A/C Systems • Operation
Operating Instructions - SMX II Control Systems
The SMX Keypad/Display ............................................................... 17
The SMXir Remote Control ............................................................ 18
Basic Operation
Power On ....................................................................................... 19
System Off ..................................................................................... 19
Selecting Setpoint .......................................................................... 19
Displaying Temperature .................................................................. 19
Cool Mode ...................................................................................... 19
Heat Mode ...................................................................................... 19
Automatic Changeover ................................................................... 19
Manual Fan Speed Control ............................................................. 19
Automatic Fan Speed Control ......................................................... 19
Adjusting Brightness ...................................................................... 19
Using The Humidity Control Routine ............................................... 19
Custom Programming Record ........................................................ 20
Programming the SMX II System
Programming Summary Table ........................................................ 21
Factory Memory Reset ................................................................... 21
Auxiliary (Electric) Heat .................................................................. 21
Fahrenheit/Celsius Display ............................................................. 21
Setpoint Differential ........................................................................ 21
Fan Response Differential .............................................................. 21
Continuous Or Intermittent Fan ...................................................... 22
Low Fan Speed Adjustment ............................................................ 22
High Fan Speed Adjustment ........................................................... 22
Temperature Calibration ................................................................. 22
Humidity Control Program
Programming The Time Period ....................................................... 23
Programming The Dehumidification Time ....................................... 23
Recommended Humidity Control Settings ...................................... 23
Fault Shutdowns and Error Messages
Software Error ................................................................................ 23
DeterminingYour Software Version Number ................................... 24
Compressor Time Delay 24
Owner Maintenance
Condensate Drains ......................................................................... 24
Air Filters ........................................................................................ 24
Seawater Connections ................................................................... 24
Seawater Pump .............................................................................. 24
Seawater Strainer ........................................................................... 24
Refrigerant Gas .............................................................................. 24
Winterizing the System .................................................................. 24
Trouble Shooting 24
Limited Warranty Periods 26
Owner’s Limited Warranty 27
Description of Figures 29
Cruisair Worldwide Service Dealer Locator 41

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L-0952 Introduction
Modulating A/C Systems • Introduction
Warning
This manual contains essential information concerning
the safe and proper installation and operation of
your Cruisair air conditioning system. If there are
any statements or procedures in this manual that you
do not understand, contact the Dometic Applications
Department for assistance. Phone [phone]
(8am - 5pm US Eastern Time), Fax [phone], or
email [e-mail], attention applications
department.
Notice
US federal law prohibits the intentional release of
refrigerant gases into the environment, including the
R-22 refrigerant used in most Cruisair air conditioning
systems. Special care must be taken when installing,
charging, and servicing Cruisair equipment to prevent
any loss of refrigerant. Only EPA certified technicians
with the proper equipment should perform service on
the refrigerant circuit of the system.
Drawings and Diagrams
The figures that are referenced throughout this manual can
be found immediately after the warranty section of the
manual. In addition, some Cruisair equipment will be shipped
with specific installation sheets or wiring diagrams that may
supercede the information located in this manual.
Air Conditioner Basics
The basic principle of an air conditioner is the movement of
heat. In a direct expansion (DX) water-cooled air conditioner,
heat is transferred from the cabin air to the refrigerant in the
cooling unit. The refrigerant is routed back to the condensing
unit where the heat is transferred to the seawater.
The heat exchange process relies on the movement of both
cabin air and seawater to work effectively. If airflow or
seawater flow is compromised, the efficiency of the system
will drop, and the unit could shut down on one of its safety
protection devices, or eventually become damaged.
Part of the cooling process, in addition to lowering the air
temperature, is the removal of moisture from the air. This
lowers the humidity, which makes the area feel more
comfortable, and helps keep the boat dry, reducing mold
growth and other moisture related problems.
The Effect of Seawater Temperature
The efficiency of the system is dependent on both the
seawater and cabin temperatures. The air conditioner works
best when the seawater temperature is below 90°F (32°C).
The unit will operate at higher water temperatures, but at
reduced capacity. As the water temperature rises, so does
the refrigerant pressure. A high-pressure safety switch will
shut the unit down if the water temperature gets too hot, or if
there is a loss of cooling water flow.
Warning
Do not operate your A/C unit in water that is colder than
38°F (3.3°C). Doing so could lead to water freezing in
the condenser coil, which can cause damage to the unit.
The Modulating System
Unlike a standard DX remote condensing unit system, the
Cruisair modulating system allows independent thermostatic
control of up to five cooling units, all run by one compressor.
The FM type modulating condensing unit is cooling only. If
heat is desired, the cooling units should be ordered with the
optional electric heating element. One advantage to this is
that an individual unit can be in heating mode even when the
rest of the system is cooling.
How it Works in General
The Modulating System air conditioner consists of a special
condensing unit and multiple evaporators (cooling/heating
units), connected by copper refrigerant lines. The cooling/
heating unit, located in the cabin or area to be cooled,
consists of a blower, an evaporator coil and an optional
electric heater. Each area has an SMX microprocessor
control which allows independent control over that zone.
The condensing unit, located in the engine room or machin-
ery space, consists of a compressor, seawater condenser,
compressor relay, and other electrical and refrigeration
components.
Refrigerant lines connect the condensing unit to each
cooling unit, and a pair of signal wires run from each cooling
unit to the compressor relay on the condensing unit to signal
the compressor to run.
The cooling/heating unit blower draws warm humid cabin air
across the fins on the evaporator where the heat from the air
is transferred to the refrigerant in the evaporator coil. As this
happens, moisture in the air is captured on the evaporator
coil in the form of condensation and drips into the base pan.
As the refrigerant absorbs the heat from the cabin air, it
evaporates from a liquid into a gas. The compressor then
compresses the hot gas and pumps it through the outer tube

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L-0952 Introduction
in the condenser coil. The seawater pump circulates rela-
tively cool seawater through the inner tube in the condenser
coil. The heat from the refrigerant is exchanged to the
seawater and discharged overboard. This cools the refriger-
ant and condenses it into a liquid. The liquid refrigerant is
then passed through the evaporator coil and the cycle
repeats. Removing heat and moisture from the cabin air
lowers its temperature and humidity levels. In the electric
heat mode, a solenoid valve on the cooling/heating unit
closes and stops the flow of refrigerant through that one unit
while the blower remains on. The electric heater energizes,
warming the cabin air as it is drawn over the heating ele-
ments. The conditioned air is blown through the ducting and
out the supply air grill(s).
The Modulating system can operate up to five independently
controlled cooling/heating units at one time. Unlike the typical
“split” system, the Modulating system adjusts to the number
of cooling/heating units that are on line and operational. The
control and setpoint of any zone can be set to the desired
temperature, heating or cooling, and the Modulating system
will condition that zone accordingly. Note that the cooling
units must have the optional electric heaters to heat the
cabin.
The cabin controls are independent of each other and relay
a signal to the condensing unit, turning it on in the cooling
mode. If the cabin control is set for heating, a solenoid valve
stops the flow of refrigerant through the cooling/heating unit’s
evaporator coil and energizes the electric heater. The
Modulating system is designed to provide the most flexibility
in independent zone control of any split refrigerant-based
system by providing heating or cooling at the same time, but
in different cabins.
How it Works in Detail
The Condensing Unit
The modulating condensing unit consists of the compressor,
the receiver, the heat exchanger or condenser coil, a hot gas
by-pass valve and a “de-superheat” valve, the associated
electrical components, and the system service valves. These
parts work together to compress the expanded refrigerant,
flowing back from the cooling unit to the compressor, into a
high-pressure state. The compressed refrigerant then
passes through the heat exchanger (condenser coil) where it
gives up the heat that was absorbed in the cooling (evapora-
tor) coil. It is then condensed to a liquid state as it flows to
the liquid receiver. The process is repeated as the refrigerant
flows back to the cooling unit. The bypass valve senses the
increased pressure when a cooling unit is removed from the
system, such as when an area is thermostatically satisfied,
and allows the refrigerant to flow back to the suction side of
the compressor.
When cooling is called for by the thermostat control of one of
the cooling/heating units, a signal is sent to the
compressor
relay
. This signal relays power to the compressor allowing it
to operate. As the system comes on, low-pressure refrigerant
gas flows back from the cooling/heating units to the
accumu-
lator.
The accumulator is a storage place for the refrigerant
and ensures that only gas, and not liquid, refrigerant makes
it back into the compressor. The
compressor then com-
presses the refrigerant into a high-pressure gas and dis-
charges it into the
condenser coil. The high-pressure hot
refrigerant gas is cooled and condenses into a high-pressure
liquid as it passes through the outer tube of the condenser
coil. The heat from the refrigerant gas is exchanged to the
seawater, which flows through the inner tube of the con-
denser coil, and is pumped overboard. The refrigerant then
flows into the
receiver that stores the liquid refrigerant on its
way back to the cooling/heating units.
If all cooling/heating units (up to five) are on and running
then the system operates just like standard remote DX
equipment. However, as cooling/heating units cycle off and
the suction pressure coming back from those units starts to
get lower, the Modulating System starts to compensate for
the changes in refrigerant pressure and temperature
extremes. The two unique components on the condensing
unit that serve to balance the system are the
Hot Gas
Bypass Valve
and the “De-Superheat” TX Valve .
The Hot Gas Bypass Valve is positioned between the suction
line leading into the accumulator and the discharge line
coming out of the compressor. If the
suction pressure gets to
low
(<55psi) then the Hot Gas Bypass Valve opens and
helps to raise the suction side pressure.
The TX Valve is positioned between the receiver and the
accumulator and senses the temperature of the suction line
leading into the compressor. If the
suction temperature gets
too high
then the TX Valve opens and flashes cool refrigerant
from the receiver to the accumulator, lowering the tempera-
ture of the gas going into the compressor. If the suction side
pressure drops below 35psi then the low-pressure switch will
open. The condensing unit is also equipped with a high-
pressure switch that opens when the discharge pressure
rises above 425psi. (See Figure 12)
The Refrigerant Lines and Manifolds
The refrigerant lines are made of copper tube that is sized
for the BTU load of the system. The suction lines are always
larger than the discharge lines. The suction lines must be
insulated. They supply both liquid and gas refrigerant to and
from the evaporators and the condensing unit. Typically, the
condensing unit lines are larger and will connect to a
refrigerant manifold. At the manifold, the lines will reduce in
size to supply the independent evaporators. (See Figure 11.)

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L-0952 Introduction
The Cooling/Heating Units
The cooling/heating units are independently controlled and
are located in the cabin areas. They consist of a blower, air
heat exchanger, electric heat element, solenoid valve and
control. In the cooling mode, the control sends a signal to the
condensing unit to operate. The solenoid valve opens
allowing the refrigerant to pass through the air exchanger.
The fan’s control and setpoint operation are typical to any
thermostatically controlled system. Once the setpoint is
reached, the unit slows, and then closes the solenoid valve
automatically. As the temperature rises, the unit will turn on
again and continue this cycle maintaining the desired room
temperature.
If heat is needed, the solenoid valve closes, stopping the
flow of refrigerant through the evaporator coil. The electric
heat elements are energized and the fan turns on. Once the
setpoint is reached, the unit slows, and then turns off
automatically. This cycle will continue also, maintaining the
desired room temperature.
The SMX Control
The SMX control is a microprocessor cabin control that
works in conjunction with the condensing unit’s compressor
relay. Once the control is set for either cooling or heating
mode and the setpoint is selected, the SMX will automati-
cally maintain the desired room temperature. It will cycle the
blower on and off, conditioning the cabin air. It will also send
a signal to the condensing unit energizing the compressor in
the cooling mode. In the heating mode, the signal is relayed
from the compressor to the electric heating elements in the
air handler, heating the air in the cabin.
The Compressor Relay
The compressor relay is located on the condensing unit and
is the hub for the evaporators. It has a series of relays (called
“triggers”), one for each evaporator in the system. As the
evaporators call for cooling, a signal is sent to the relay box.
This signal energizes a trigger, which in turn relays current to
the compressor. Any number of triggers can be energized at
the same time commanding the compressor to run. The
triggers are independent components and can be added or
replaced as needed. This control box is in addition to the
standard start components required for the compressor.
Subsystems
Subsystems are purchased separately because of the many
variations and options available. These include the seawater,
air distribution, and control subsystems.
Seawater System
The seawater system consists of an inlet through-hull fitting,
water shut-off valve, strainer, pump, and overboard dis-
charge fitting, all connected by hose or piping. If a single
seawater pump serves multiple condensing units, then a
pump relay and water manifold are required.
Air Distribution System
Cabin air is drawn into the cooling unit through a return air
grill. It is then cooled (or warmed if the electric heat option is
installed) and blown back into the cabin through a ducting
system. The air should be discharged high in the cabin and
away from the return air grill to ensure good circulation. An
air filter is located on the cooling unit or on the return air grill
and must be cleaned regularly.
System Controls
The SMX II microprocessor circuit board, controlled by the
SMXir keypad/display, provides a comfortable environment
and ensures overall system protection. With over 22 pro-
grammable functions, the SMX can be customized to suit
any environmental application. The SMX monitors incoming
line voltage and extremes in refrigerant pressure, and will
shut the system down to prevent damage if necessary.
Condensate Drain
When the air conditioner is running in the cooling mode,
moisture is removed from the air by the evaporator coil. This
condensation is then caught in a drain pan and must be
drained off to a sump or overboard. In humid climates the
system can produce a large amount of condensate water
that could cause significant damage to your boat if the drain
system doesn’t work properly.

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L-0952 Installation
Installation Procedures
This section covers the installation procedures for the
Cruisair Modulation System, including electrical connections
and SMXir control installation. Please read and understand
this manual before attempting to install any equipment.
Electrical System
Cruisair air conditioning systems are available for use with
common power supplies throughout the world. In the United
States and most of North and South America, the systems
are 115V or 230V, 60Hz, single phase AC (alternating
current). In Europe and most of Asia, power systems are
typically 230V 50Hz single phase.
The compressors used in Cruisair Modulating condensing
units are only available in 230V single phase, 230V 3-phase,
or 380/460V 3-phase. On 380/460V 3-phase units there is a
separate lower voltage circuit for the controls, either 115V or
230V. On some power systems this can be supplied by using
one input line and the neutral. If not, a separate control
power feed or a transformer will be required.
Running and starting loads of an air conditioning system are
often the largest electrical loads on a boat. It is important that
the power supply system is large enough to handle these
loads. Contact an electrician if you are not sure about the
proper wiring procedures. Always follow local and ABYC
codes for proper wiring guidelines.
Voltage and Frequency
The voltage rating of a unit is a nominal rating. The available
power supply voltage may be higher or lower by as much as
10% and the system will still operate properly. For example,
at 60 Hz, voltages my range from 110VAC to 120VAC, or
208VAC to 240VAC, or 440VAC to 480VAC. In a 50Hz
environment, common voltages range from 220V to 240V, or
380V to 415V.
When choosing a system, the voltage and frequency must
be known. While standard 60Hz equipment can often be run
at 50Hz, it will experience a 17% drop in performance.
However, 50Hz equipment can not be run at 60Hz because
the 50Hz motor will run too fast and become damaged.
Seawater pumps will lose even more performance at 50Hz
due to the nature of centrifugal pumps.
Dedicated 50Hz units will give full performance at 50Hz, and
should be used when the system is going to be run exclu-
sively at 50Hz. If a boat is traveling in 50Hz and 60Hz
environments, then 60Hz equipment should be installed, with
special attention to sizing (especially the pumps) so that the
system performs to expectations. When running 60Hz
Modulating A/C System • Installation
equipment at 50Hz, the voltage should be reduced by 17%
to prevent overheating a motor.
Installing The Condensing Unit
Ignition Protection Warning
Most Cruisair remote condensing units meet federal
requirements for ignition protection. However, there are
some condensing units, such as those with 3-phase
compressors, which are not ignition protected. Do not
install non-ignition protected units in spaces containing
gasoline engines, tanks, LPG/CPG cylinders, regulators,
valves or fuel line fittings. Failure to comply may result in
injury or death.
Selecting the Site
Cruisair condensing units are designed to be installed in any
convenient location. The unit is normally placed in the engine
room or other machinery space, but it can be located in the
living areas. The condensing unit will produce condensation
so a drain line from the drip pan is needed in these installa-
tions. The space around the unit can be insulated to reduce
noise if desired. The unit is internally cooled and does not
require ventilation. The location selected should provide for
access to refrigerant, seawater, and electrical connections
and be accessible for service. It should be installed on a flat,
horizontal surface away from direct spray from engine air
intakes or water wash-down.
Site Location Checklist
• Adequate space for access to refrigerant, seawater and
electrical connections.
• Accessible for service and maintenance.
• Flat, horizontal surface.
• Away from direct spray from engine air intakes or water
wash-down.
Mounting the Condensing Unit
Orient the condensing unit (Figure 1) so the refrigerant,
electrical connections and service ports are accessible. Use
the supplied “L” brackets to bolt the unit down. Fasten the
mounting base pan securely in such a way that the unit can
be removed for future service if need be.
Do not remove any covers, caps or fittings that may expose
any wiring or refrigerant. Only remove these items when you
are ready to complete the installation. Removal of any covers
may result in damage to the electrical components. Removal
of the caps or fittings may result in refrigerant loss.

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L-0952 Installation
Installing the Seawater Cooling System
The seawater system consists of a scoop-type thru-hull
fitting, water shut-off valve or seacock, strainer, seawater
pump, water hose and overboard discharge fitting. If more
than one condensing unit is using a single seawater pump, a
water manifold and pump relay are also needed.
Importance of a Self-Draining System
Along with restricted ducting, a poorly plumbed seawater
system is one of the most common installation problems on
marine air conditioners. When water flow is lost, not only will
the air conditioning units no longer cool or heat, the units
and pump could be damaged from running dry.
When using a centrifugal seawater pump, it is imperative that
the seawater piping be routed continually uphill from the
through-hull inlet, valve, and strainer to the pump and then
up to the condenser, then smoothly up or down to the
overboard discharge, without any dips or loops, and with
only one high point in the system (usually the condenser coil
or the overboard discharge). This is said to be self-draining
because all water would drain out of the piping if the boat
were lifted out of the water.
Whenever air gets into the system, which can happen in
heavy seas or during a sharp turn, it can become trapped in
the pump. Because a centrifugal pump cannot pump air,
water flow through the system is lost.
A self-draining seawater system will allow air in the piping to
rise naturally through the pump and then be expelled
overboard. It will also make winterizing the system much
easier. Figure 6 shows a properly plumbed system and some
common plumbing mistakes.
Through-Hull Inlet Fitting
A separate thru-hull fitting and seacock should be used for
each seawater pump. Do not attempt to draw seawater from
the engine or generator thru-hull fitting. A scoop-type thru-
hull is preferred for all installations. It should be installed
facing forward and located as far below the water line and as
close to the keel as possible, where it will always be under-
water. Beware of the change of location of the thru hull fitting
relative to the waterline, given the motion of the boat. The
ideal location is ahead of the stuffing boxes and aft of the
forward engine bulkhead.
To install the through-hull fitting, drill a properly sized hole for
the fitting. Place a bead of marine, underwater sealant
around the fitting and secure it through the hull. Tighten the
nut onto the fitting.
Seacock
A bronze, full flow seacock (ball valve type) should be
installed directly onto the through-hull fitting. Use Teflon tape
or other sealant on the threads. The seacock must be
accessible and easy to close in case of emergency, or to
clean the strainer.
Strainer
A seawater strainer must be installed between the seacock
and the pump, and should be situated to provide easy
access for cleaning. The strainer must be located vertically
above the seacock and below the pump. Make sure the
water flow through the strainer is in the correct direction.
Some strainers have an arrow that shows correct flow
direction.
Mount the strainer to a bulkhead so it is properly supported
before connecting hoses. Use Teflon tape or other sealant on
pipe threads.
Seawater Pump
Centrifugal pumps are not self-priming, and must be
mounted so that they are below the heeled waterline in any
given operating condition. The pump should be located so
that it is accessible for future service.
Mount the pump so the outlet is above the pump and
directed upward so air can escape thus preventing an air
lock in the pump head. The head on some pumps can be
rotated to allow mounting on a vertical bulkhead. (See
Figure 4.)
Self-priming pumps are available if the pump cannot be
mounted below the waterline.
Required seawater flow rate is 4 gpm per ton
(12,000 Btu/hr) of condensing unit capacity.
Manifolds
If one seawater pump is serving multiple condensing units,
then a seawater manifold will be needed to supply water to
each unit. This can be as simple as a TEE for two units, or a
custom made manifold for three or more units. It is very
important to consider manifold orientation so that all con-
densing units get the proper flow of water.
See Figure 5 for manifold information. A manifold can also be
used on the outlets of the condensing units when using a
single overboard discharge.

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L-0952 Installation
Overboard Discharge
The overboard fitting should be located 1 to 2 inches (25-50
mm) above the vessel’s water line. This is to facilitate visual
confirmation of water flow, but close enough to the water to
minimize splashing noise. If the overboard discharge fitting
must be installed below the heeled water line, then a
seacock must be installed per ABYC standards.
Seawater Piping
• Use only reinforced marine grade hose or other suitable
piping (PVC, CPVC, cupronickel, or stainless steel).
• Double clamp all hose connections, reversing clamps.
• Use only plastic, bronze, or stainless steel fittings (do not
use brass).
• Avoid loops or dips in the hose runs.
• Make sure enough hose is used to allow future removal of
components.
• Use the correct size hose, fittings, and components.
See the table below for proper sizing. Note that the pump
inlet piping (including through-hull and strainer) may need
to be larger than the outlet pipe size. Do not use pump
connections to determine hose size.
• Use larger hose when the run is longer than 16 feet (5m).
• Required seawater flow rate is 4 gpm per ton (12,000 Btu/
hr) of condensing unit capacity.
Bonding
All metallic parts in contact with seawater must be connected
to the vessel’s bonding system. This includes the through-
hulls, strainer, bronze pumps, manifolds, and the condensing
unit(s).
Installing The Cooling/Heating Unit
Safety Warning
A Cruisair cooling/heating unit should never be placed
such that it can circulate carbon monoxide, fuel vapors
or other noxious fumes into the boat’s living spaces.
Failure to follow this precaution could result in serious
injury or death.
Ignition Protection Warning
Cooling/heating units do not meet federal requirements
for ignition protection. Do not install in spaces containing
gasoline engines, tanks, LPG/CPG cylinders, regulators,
valves or fuel line fittings. Failure to comply may result in
injury or death.
Safety Warning
Do not terminate air handler condensate drain lines
within 3 feet (1m) of any outlet of engine exhaust
systems, nor in a compartment housing an engine or
generator, nor in a bilge, unless the drain is properly
connected to a sealed condensate or shower sump
pump. Exhaust and/or bilge fumes can travel up a drain
line and mix with the return air blowing into living areas.
Selecting the Site
Typically the unit is located in the cabin under a bunk or in a
locker. The discharge air must be ducted from the cooling
unit to a grill as high as possible (minimum three feet [1m]
above the floor) and away from the return air grill for good air
circulation.
It is not necessary that the coil be placed directly behind the
return air grill, but an unobstructed path must be provided for
the air to get to the coil. A 2" (50mm) space in front of the coil
must be maintained if it is not directly behind the return air
grill.
Site Location Checklist
• Unit is not located in an engine room or near an internal
combustion engine.
• There is no obstruction of airflow from return air grill to
coil.
• Accessible for service and maintenance, including the
return air filter.
• Adequate space for condensate drain connections.
• Flat, horizontal and sturdy mounting location.
• Condensate drain can be run continuously downhill from
unit to overboard fitting or sump.
• Space is sealed from the bilge, engine room, exhaust
fumes or outside air.
• Maximum copper tubing run between condensing unit and
cooling unit is 50 ft. (15m)
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10 English
L-0952 Installation
Mounting the Cooling/Heating Unit
Mount the cooling/heating unit (Figure 2) so the condensate
drip pan is beneath the unit. Use the integral mounting
brackets to secure the unit in place. Make sure the unit has
access for service. The blower, solenoid valve, and the
heater elements should be accessible. The electrical junction
box should be mounted in a location with easy access.
Route the condensate drain hose steadily downhill so that
the condensate flows freely to an overboard fitting or sump.
Do not permit condensation to puddle in the bilge. Cruisair
cooling/heating units have two condensate drains on
opposite corners. It is recommended to use both drains for
best results. If only one condensate drain is used then plug
the other fitting. Use Teflon tape on the hose barbs for a
watertight seal. The two drains may be teed together,
providing there is a minimum drop of 2" (50mm) from the
drain pan to the tee fitting. After the condensate drain
installation is complete, test the installation by pouring a
quart of water into the pan and checking for good flow.
Installing the Refrigerant Tubing
Caution
Be careful when bending the extension tubes on the
evaporators. Do not allow the tubing to kink and do not
twist or bend the tubing at the connection point close to
the coil or the joints may crack. If bending by hand make
large radius bends. Use a tube bender if a tight bend is
required.
Use refrigerant-grade soft copper tubing to connect the
cooling units to the condensing unit. See Figure 11 for
correct tubing sizes. Distribution manifolds or TEE connec-
tions may be used to split the refrigerant lines from the
condensing unit to the cooling units.
Only use refrigerant-grade seamless soft copper tubing.
Never use any type of plastic or rubber hose.
The tubes can run uphill, downhill, or sloping as required,
and can have as many bends as necessary. Avoid shard
bends that could result in kinks in the tubing.
The refrigerant distribution manifolds or TEE connections
should be located to provide (as close as possible) equal
length tubing runs between the manifold and each of the
cooling units. All flare connections should be made in an
accessible location for future service.
The suction line must be insulated with closed-cell foam
insulation. Do not insulate the suction and discharge lines
together. When sliding the insulation over the tubes, cover
the open ends to prevent debris and moisture from contami-
nating the refrigerant circuit. After checking for leaks, insulate
the flare joints at the condensing unit, distributors, and
cooling units. Secure the tubing every 3 feet (1m) as neces-
sary for support.
The copper tubing is connected to the condensing unit,
distribution manifolds, and cooling units with flare joints. To
prevent refrigerant leaks, flares must be formed correctly
with the proper flaring tool. Only 45-degree single flares
should be used. Flares should be made following the
instructions of the particular flaring tool. Make sure to slide
the flare nut onto the tube before flaring. A drop of oil on the
tube can help the process. The surface of the flare must be
smooth and free of defects to ensure that the joint won’t leak.
The flare should be large enough in diameter to fill the nut
completely.
Use only forged, long-stem flare nuts, such as supplied with
Cruisair equipment. Flare nuts should be tightened until the
nut ceases to offer resistance to tightening. This is the point
where the flared portion of the copper tubing is beginning to
flow under the force of the nut being tightened.
Installing The Air Distribution System
Refer to Figure 3 for a typical installation and to Figure 7 for
proper grill and duct sizes.
Return Air Grill
The return air grill should be located so there is unobstructed
airflow to the unit’s evaporator coil. Ducting between the
return air grill and the cooling unit is not normally necessary
and should be avoided. The grill may be located on a side
opposite the evaporator coil so long as airflow to the coil is
unobstructed. Cross sectional area of the airflow path must
not be less than that of the evaporator coil face.
An air filter must be used to prevent the evaporator coil from
collecting dirt and lint. The filter can be located on the
evaporator coil or at the return air grill. Cooling units are
supplied with an air filter, but if that filter is not easily acces-
sible for periodic cleaning, then use a filter on the return air
grill.
Ducts
Insulated flexible ducting or built-in ducting must be used to
route air from the blower to the discharge grill.
Ducting Guidelines
Secure duct to blower or transition box (plenum) with screws
and duct tape. When using insulated flexible ducting, make
sure inner duct is secured and sealed to the adapter before
pulling insulation over connection.
Plenums, or transition boxes are used with flexible ducting to
split and route the discharge air as needed. Figure 8 shows
several plenum configurations.

11 English
L-0952 Installation
• Ducting must be properly sized for the airflow. If the duct
run is longer than 10 feet (3m), use the next larger duct
size.
• Use of insulated duct is recommended, and is mandatory
when used in high heat areas or where condensation
might occur.
• Rotate blower in the direction of the duct run if possible.
• Install flexible ducting tightly and smoothly, with as few
bends as possible.
• Keep duct runs as short as possible.
• Support ducting to prevent sagging during boat operation.
• Trim excess ducting before attaching to transition adapt-
ers.
• Make sure ducting is not crushed or kinked.
• Use a flexible transition duct between blower and any
built-in ducting.
Discharge Air Grill
Location of the discharge grill should be as high as possible
in the cabin (minimum three feet (1m) above the floor), and
oriented so that airflow between the discharge and return
encompasses as great an area as possible. Care should be
taken to avoid “short cycling,” a situation where the condi-
tioned air is blown directly back to the evaporator coil without
being substantially mixed with the cabin air.
A grill plenum should be incorporated behind the grill to
provide a chamber for the air to expand and flow quietly into
the living area. The plenum also provides a hose connector
to attach the flexible duct behind the grill. (See Figure 8.)
Installing the Cooling Unit Control
Each independent cooling unit in the modulating system will
have its own control. Refer to the wiring diagrams in the back
of this manual.
SMX II Control System
The SMX II control system consists of:
Power/Logic (P/L) module - Monitors and controls all
functions of the cooling unit.
Keypad/Display - The SMXir is a 10-button user interface
touch pad with a digital readout and LED indicators.
Temperature-Sensing Element - Air temperature is
monitored by a temperature-sensing element (TSEP) that
plugs into the power/logic board.
Connecting Cable - The keypad/display connects to the P/L
board with a CXP connecting cable.
Warning
Make sure all power is off before opening any electrical
box. Failure to do so may result in injury or death.
Installing the Power/Logic Box
The Power/Logic box has a 3 ft (.9m) wire harness that must
be connected to the air handler junction box. These wires
can be extended if needed. Refer to installation diagrams in
back of this manual.
• It is very important that the P/L box is mounted in an
accessible location.
• The SMX P/L board is ignition protected, enclosed, and
operates in ambient temperatures up to 130°F (54°C).
• The P/L box may be installed in any position.
• The P/L board dissipates heat when operating, and must
be installed in a ventilated location.
• The P/L box is NOT waterproof and must be placed where
it will NOT get wet.
Installing the SMXir Keypad/Display
The SMXir keyboard/display should be installed so it is both
visible and accessible. It should be placed in plain view and
within easy reach of the operator.
Select a spot on an interior, vertical surface. This can be an
inside wall, partition or other permanent structure with rear
access for wiring. The SMXir control operates on low voltage
DC and is certified ignition-protected. The space behind the
SMXir control does not have to be ventilated since the
control components do not produce heat.
The SMXir keypad is surface mounted, and only requires a
hole for the CXP cable. Refer to Figure 10 in the back of this
manual for installation instructions. Plug the interconnect
cable in and route it to the Power/Logic (P/L) box.
SMX Interconnect Cable
Connection between the SMXir keypad and the Power/Logic
board should be made with a CXP cable. This is a shielded
cable with RJ12 (phone-type) 6-pin plugs on each end.
CXP cables are available in different lengths, from 2 feet
(.6m) to 80 feet (24m). Route the cable from the power/logic
board to the keypad. Cable runs should be as short as
possible and should not be bundled with high voltabe or
antenna cables. Plug the cable in at both ends, and secure
per low DC voltage standards.
Caution
The CXP interconnect cable transmits low voltage DC
signals. It can be affected by outside interference from
high voltage cables or other sources. Do not route the
SMX interconnect cable beside AC power cables or
other high voltage wiring.

12 English
L-0952 Installation
Installing the Temperature Sensor
The TSEP temperature sensor measures the cabin air
temperature and relays the information to the power/logic
board. The sensor is 1" long by ¼” diameter (25mm x 7mm
diameter) and is attached to a length of flat, 4-conductor
cable with an RJ-11 (phone-type) plug at the end. Different
lengths of TSEP cables are available, from 2 feet to 80 feet
(.6m to 24m).
For best results, the sensor should be placed in the return air
path, in front of the system evaporator coil. Directly behind
the return air grill is often a good location. The sensor must
not touch the evaporator coil, or be placed in the discharge
air.
With the TSEP in the return air path, use the default mode of
continuous fan operation for the most accurate temperature
control. If intermittent fan operation is desired (fan on and off
with the setpoint), the sensor must be wall mounted on an
INSIDE surface not subject to any influence from heat
outside of the area (including direct sunlight). Thermistor
covers are available from Cruisair for wall mounting.
The TSEP cable plugs into the RJ-11 jack on the P/L board
marked “INSIDE TSE”. Coil up any excess cable, and tie out
of the way.
Installing the Pump Relay
The following instructions apply to systems that have
multiple condensing units served by a single seawater pump.
If there is only one condensing unit on the vessel, or if each
unit has its own seawater pump, then skip to the next
section.
Location
The pump relay is generally located in the engine room near
the seawater pump, but it can be mounted anywhere that is
convenient and accessible. It must be mounted in a dry
location, away from any possible water spray, with room for
some heat dissipation.
Ignition Protection Warning
PR3X and PR8X pump relays are certified ignition
protected. However, pump relays with electromechanical
relays or contactors (such as 3-phase pump relays) are
not ignition protected and must never be installed in
spaces containing gasoline engines, tanks, LPG/CPG
cylinders, regulators, valves or fuel line fittings. Failure to
comply may result in injury or death.
Operation
PR3X and PR8X pump relays are identical in operation.
When any condensing unit turns on, the pump relay will turn
the seawater pump on, and the pump will stay on until the
last condensing unit shuts down. The PR3X can serve up to
three condensing units, and the PR8X can serve up to eight
condensing units. Both can operate either 115V or 230V,
single phase pumps, with a maximum current of 15 amps.
Voltage and Triggers
Triggers are used in the pump relays to isolate the pump
signal from each condensing unit. Some pump relays come
with pre-installed triggers, or you can buy triggers separately.
Triggers come in 115V and 230V, and must match the
control voltage of the condensing unit. Both 115V and 230V
triggers can be used together in a single pump relay if the
system requires it. The trigger is simply a relay that closes
when the condensing unit turns on. Because each trigger is
isolated, the polarity of the signals from the condensing units
does not matter.
Electrical Connections
Warning
Make sure all power is off before opening any electrical
box. Failure to comply may result in injury or death.
General Electrical Notes
• Failure to properly ground and bond the system will void
the warranty, and may result in a dangerous installation.
• All electrical connections should be made within the
electrical junction boxes supplied with the units. Most units
have terminal strips that are labeled or have color-coded
wiring. Open terminal strips (such as supplied with switch
assemblies) require that the included terminal strip cover
be installed over the terminal strip and the back of the
switch after installation is complete.
• Wiring diagrams are included in the back of this manual
and under the cover of the electrical boxes on all units.
Contact Dometic if you have any questions about the
wiring diagrams.
• Each A/C condensing unit requires its own dedicated
circuit breaker of the appropriate size. See data plate on
the unit for suggested breaker and wire sizes.
• If there is only one A/C unit, the seawater pump can be
wired in parallel with the compressor and doesn’t require
it’s own circuit breaker (make sure the breaker is large
enough for both the compressor and pump). If multiple A/
C units are served by a single pump, then a pump relay is
needed, and will require a separate circuit breaker.

13 English
L-0952 Installation
• Each cooling unit that has electric heat should have its
own separate circuit breaker. Cooling-only cooling units
have only a blower and solenoid that require electrical
power and draw very low current. If desired, multiple
cooling-only cooling units can be run on one breaker.
• The wiring from the cooling unit control to the condensing
unit compressor relay is for signal power only. However,
this control power is line voltage (230VAC).
• All units must be grounded to minimize the potential
hazard of electrical shock and personal injury.
• The condensing unit must be connected to the ship’s
bonding system to prevent corrosion due to stray electri-
cal current. All pumps, metallic valves and fittings in the
seawater system that are isolated from the condensing
unit by rubber hose or PVC plastic must be individually
bonded also.
• Use ring or locking fork type wire connection terminals.
• Field wiring must comply with ABYC or local electrical
codes.
• Power to the unit must be within the operating voltage
range indicated on the data plate.
Three Phase Power
Three phase motors will run forward or backward depending
on the arrangement of the three wire connections. The scroll
compressors used on Cruisair Modulating condensing units
are direction sensitive. If the wire sequence is incorrect, the
compressor will run backwards and not cool properly. It will
also make unpleasant noises. Centrifugal pumps are also
direction sensitive. Make sure 3-phase motors are running in
the correct direction.
Safety Warning
To prevent a possible electrical shock in the event a
component has an electrical breakdown, which could
result in serious injury or death, always ground the
system in the following manner:
• Use proper wire size with a ground to feed power from the
ship’s electrical panel to each cooling unit junction box.
Make sure the ground wire is properly connected to the
ground buss in the ship’s service distribution panel and to
the ground lug in the cooling unit’s junction box.
• Connect the junction box ground lug to the P/L box green
wire (or to the switch assembly terminal strip).
• Use proper wire size with a ground to feed the power from
the ship’s electrical panel to the condensing unit’s junction
box. Make sure the ground wire is properly connected to
the ground buss in the ship’s service distribution panel
and to the condensing unit’s ground lug.
• Ground the seawater pump, and pump relay (if used) to
the condensing unit’s ground lug.
• Bond the ground lug on the condensing unit to the ship’s
grounding system.
• Check the continuity of the ground system before the
system is energized.
Note
Always follow ABYC guidelines or local codes when selecting
breakers and wire sizes. ABYC standards are available from:
American Boat and Yacht Council, 3069 Solomon’s Island Rd.,
Edgewater, MD 21036, Telephone: [phone]
Final Inspection
Prior to charging or energizing the system, conduct a final
inspection using the following checklist.
Inspecting the Seawater Cooling System
• Is the seawater pump properly sized for the system?
• Is the pump oriented correctly and mounted securely with
the pump outlet above the inlet?
• Is the centrifugal seawater pump located so it is below the
water line at all times?
• Are the inlet and outlet through-hulls secure, properly
sealed and properly oriented?
• Are all hose clamps tight?
• Are seawater hoses double/reverse clamped?
• Are there any loops or dips in the seawater plumbing that
might cause the system to become air-locked?
• Is the strainer located between the seacock and the
pump, and is it correctly oriented?
• Are all metallic seawater fittings, the pump, condenser
and manifold properly bonded?
Inspecting the Condensing Unit
• Is the condensing unit mounted securely?
• Are the fasteners accessible for future service?
Inspecting the Cooling/Heating Unit
• Is the unit securely mounted?
• Are condensate drains properly routed to an overboard
discharge or sump?
• If only one condensate drain is used, have any other drain
holes in the drip tray been plugged?
Inspecting the Refrigerant Connections
• Are flare joints made with forged flare nuts and properly
tightened?
• Are flare joints and tees properly insulated?
• Are all suction lines individually insulated?
• Are tubes fastened securely to the boat every three feet or
as needed throughout their length?

14 English
L-0952 Installation
Inspecting the Air Distribution System
• Is there unobstructed airflow from the return air grill to the
coil?
• Is there a lint screen or filter in the return air path where it
is accessible for regular cleaning?
• Have flexible ducts been pulled tight to remove bends and
constrictions?
• Are grills correctly sized for the system?
Inspecting the Control and Electrical Wiring
• Is the thermostat sensor or thermistor properly located
and secured in the return air path and not in direct contact
with any metal objects?
• Are all wiring harnesses properly secured?
• Are wiring connections made, color-to-color, correctly at
terminal strips?
• Are all components properly grounded and bonded?
• Are proper sized circuit breakers installed?
• Are terminal strips located in a dry, safe place and
properly covered?
Charging the System with Refrigerant
Special considerations when charging the
Modulating system
All cooling units must be turned on and running (solenoid
valve open) in the cool mode before evacuating the system
or adjusting the refrigerant charge. To ensure that all
evaporators are on in the cooling mode, and the solenoid
valves are open, set each cabin control’s set point down to
the lowest temperature setting. There is no need for the
compressor to run while evacuating the system, so turn the
condensing unit’s circuit breaker off before turning the
cooling units on.
The modulating unit is different from a standard DX condens-
ing unit in that it has two special refrigerant valves that allow
partial loads to run safely: the hot gas bypass valve and the
“de-superheat” valve. These valves are factory set and do
not require any field adjustment. Any field adjustments could
cause the valves to operate incorrectly, causing damage to
the compressor or compromising the performance of the
system.
As cooling units in the system shut down, the suction
pressure at the modulating condensing unit will drop. The hot
gas bypass valve senses the suction pressure and will open
to allow discharge gas to flow into the accumulator if the
suction pressure drops below 55 psi. This will raise the
suction pressure and prevent liquid refrigerant from reaching
the compressor.
As more hot (high-pressure) gas is dumped into the suction
line (due to cooling units shutting down), the superheat
(suction gas temperature going into the compressor) can rise
to unsafe levels. A thermal expansion (TX) valve is installed
which acts as a “de-superheat” valve. It senses the super-
heat and will flash liquid refrigerant into the accumulator to
cool the suction gas.
This process automatically balances the system as the load
from the evaporators changes. This is why it is important to
have all cooling units on and operating while charging the
system. If one or two are off line, it will cause the refrigerant
circuit to alter and make it impossible to correctly charge the
system.
The following instructions should be followed in evacuating
and charging a Cruisair modulating condensing system with
R-22. Some special-order units may contain refrigerant other
than R-22. Please follow the special charging procedures
included with the unit.
Notice
US federal law prohibits the intentional release of refrigerant
gases into the environment, including the R-22 refrigerant
used in most Cruisair systems. Special care must be taken
when installing, charging, and servicing Cruisair equipment
to prevent any loss of refrigerant. Only EPA certified techni-
cians with the proper equipment should perform service on
the refrigerant circuit.
Initial Charging, New System
There are three refrigerant circuit components in a Cruisair
Modulating System: the condensing unit, the cooling/heating
unit (evaporator) and the copper refrigerant line-sets. The
condensing unit is shipped from the factory charged with
refrigerant gas.
It will be necessary to properly evacuate the cooling units
and line-sets before releasing the refrigerant from the
condensing unit into the system. To facilitate this evacuation
procedure, there is a special vacuum port (aka: purge port,
access port, evacuation port or service port) located on the
condensing unit’s discharge base valve. This vacuum port
has a red cap and a schrader valve, and is located at the
2:00 position on the base valve.
Required tools to charge a modulating system:
1. R-22 container (typically the disposable-type container
color-coded green for R-22).
2. Gauge manifold with self-closing fittings on the charging
hoses.
3. Vacuum pump.
4. Base valve wrench and hand tools.

15 English
L-0952 Installation
5. Accurate thermometer.
6. Thermometer to measure superheat.
Proceed as follows:
1. Turn the condensing unit’s circuit breaker OFF so the
compressor will not run while the system is being
evacuated.
2. Do not touch the condensing unit base valve stem
covers or white port caps. Remove the red cap from the
vacuum port on the discharge base valve (right side of
unit, 2:00 position on base valve).
3. Connect the low side pressure gauge hose to the
vacuum port on the base valve. Connect the vacuum
pump hose from the center position on the gauge
manifold to the vacuum pump. The high side hose is not
used at this time.
4. Close all gauge manifold valves.
5. Energize (open) all cooling unit solenoid valves by
turning each control on and setting the lowest possible
set point.
6. Energize the vacuum pump. Open the manifold valves to
the vacuum pump and the base valve vacuum port.
7. As the pump operates, the low-pressure gauge needle
will fall to a vacuum. When the vacuum reaches 28
inches Hg close the vacuum pump valve and turn the
vacuum pump off. Let the system sit untouched for 15
minutes and then observe the gauge. If any vacuum has
been lost, look for leaks, especially at flare joints. Repair
all leaks. Then return to step #4 above and evacuate the
system again. Once the vacuum has been held at 28
inches Hg for at least 15 minutes, proceed to the next
step.
8. Open the vacuum pump valve and leave the vacuum
pump operating for at least six hours, and until a vacuum
of at least 29 inches Hg is achieved. Close the vacuum
pump valve and turn the vacuum pump off. Wait one
hour. If no vacuum is lost, proceed with charging. If any
leaks are indicated, inspect flare joints again. Repair all
leaks. Then return to step #4 above and evacuate the
system again. Once the vacuum has been held at 29
inches Hg for at least one hour, proceed to the next step.
9. Remove the low pressure gauge hose from the vacuum
port, replace and tighten the red cap.
10. Turn off vacuum pump and disconnect that line from
gauge manifold.
11. Remove both condensing unit base valve stem caps
from top of base valves. Ensure that both white gauge
port caps, and the red vacuum port cap, are in place and
tight. Open both base valves fully by turning the valve
stems fully counter-clockwise. This will allow the refriger-
ant in the condensing unit to enter the system. Replace
and tighten the valve stem caps.
12. Turn all cooling units OFF.
The system is now partially charged and is ready for final
adjustment.
Adjusting the Charge
After the system has been evacuated and is partially
charged, the final charge must be added and adjusted. To
correctly adjust the charge in a modulating system, the
superheat must be measured.
1. At this time, all cooling units should be OFF. Turn the
condensing unit’s circuit breaker ON.
2. Remove the discharge port base valve stem cap, and
make sure that the valve is in the back-seated (fully
counter-clockwise) position.
3. Make sure the gauge manifold valves are closed.
4. Remove the white gauge port cap from the discharge
base valve and connect the gauge manifold high side
hose. Remove the port cap from the suction port near
the low-pressure switch and connect the gauge manifold
suction hose. Connect the refrigerant tank to the gauge
manifold.
5. Attach the thermometer or temperature sensor to the
suction line near the low-pressure switch. Wrap insula-
tion over the sensor so that the ambient temperature
does not affect it.
6. Open the discharge base valve to the test position by
rotating the stem one turn clockwise. The high side
gauge should now register a pressure reading.
7. Set all the cooling units to cooling, and the set points as
low as possible to ensure that the solenoid valves are
energized (open) and the blowers are on high speed. If
need be, open exterior doors to ensure that the rooms
do not achieve set point before charging is complete. The
compressor should start as soon as the first unit is
turned on.
NOTE: All the cooling units must be on so both the hot
gas bypass valve and de-superheat (TX) valve do not
open. The system cannot be charged properly if either
valve is open.

16 English
L-0952 Installation
8. At this point the system is under-charged and may go
into a low-pressure situation in which the hot gas bypass
valve may open. To test if that valve is open, touch the
lines leading in and out of the valve. If both are the same
temperature then the valve is open. If the valve is open
then slowly add refrigerant in small increments until the
hot gas bypass valve closes and the incoming and
outgoing lines have different temperatures.
9. Allow the system to run for five to ten minutes so the
refrigerant pressures will stabilize. Measure the super-
heat.
NOTE: There is no ideal super heat temperature, but it
should be anywhere from 10° - 20°F (5.6° - 11.1°C),
depending on the load on the cooling units. On cool
days, it will be lower, and on hot days it will be higher.
10. Add refrigerant to reduce the superheat, or remove gas
to increase it. Do this in very small increments and allow
the system to stabilize before taking another superheat
reading.
11. Once the superheat is set properly, close the manifold
gauge valves, and backseat the discharge base valve.
Torque the stem-packing nut (gland nut) to 8 ft. lbs. or 96
in. lbs. Remove the manifold gauge hoses and replace
the service port caps.
Removing Refrigerant from the System
When adjusting the charge in the refrigerant system, some
refrigerant gas may need to be removed. It is a violation of
federal law to vent (release) refrigerant into the atmosphere,
and it is necessary to capture any refrigerant that is removed
from the system. There are two methods of doing this:
1. Use an approved refrigerant recovery unit and refillable
refrigerant container.
2. Allow refrigerant to escape from the high-pressure side
into a refillable refrigerant container.
Initial Start Up
1. Open the seacock (seawater inlet valve).
2. Turn on all circuit breakers for the air conditioning
system: condensing unit, cooling units, and pump (pump
may or may not have its own c/b).
3. Set the system for cooling at the SMXir keypad, and
adjust temperature setting so the unit will turn on.
4. Verify that water is flowing from the overboard
discharge.
5. Allow unit to run for 10 minutes at high fan speed. Check
the temperature differential between discharge and
return air by placing an accurate thermometer in front of
the discharge grill and then in front of the return air grill.
In cooling, the difference between the discharge and
return should 15 - 20°F (8.3 - 11.1°C).

17 English
L-0952 Operation
Operating Instructions - SMX II Control
Systems
The SMX Keypad/Display
The SMXir and SMX II keypad/displays are arranged for
logical operation. The button layouts on the SMXir and the
SMX II are similar, and the buttons perform the same
respective functions.
1. Data Display
Large LED readout that provides indication of current
setpoint, temperatures, programmed values and error
messages.
2. Cooling Indicator
Lights when system is running in cooling mode (solenoid
valve open and compressor running).
3. Heating Indicator
Lights when unit is operating in the electric heat mode.
4. Setpoint Indicator (SMX II Display Only)
Lights when setpoint is displayed. Off when inside
temperature is displayed.
5. SET Key
Press the SET key to display your currently selected
setpoint (the temperature you wish to maintain in the
cabin). The SET key also is used to dim the data display
readout.
6. UP-DOWN Keys
Press UP or DOWN to raise or lower the setpoint. Press
and hold keys for large changes. Note: if inside tempera-
ture is displayed, touching the UP or DOWN key will
cause the setpoint to be displayed.
7. TEMP Key
Press once to display inside temperature. Press TEMP
twice, and the display will alternate between inside
temperature and setpoint. Press again to return to inside
temperature only.
Hint
You can display temperature in degrees Fahrenheit or
Celsius.
8. OFF Key
Turns system off. Note that the data display remains on.
You can continue to adjust setpoint, display temperature
readings and activate the manual fan to circulate air
while the system is in the OFF mode.
9. Cool Mode Indicator
Lights when you press the COOL key to select the
cooling mode.
10. Heat Mode Indicator
Lights when you press the HEAT key to select the
heating mode.
11. COOL Key
Turns the system on in the cooling mode.
12. HEAT Key
Turns the system on in the electric heat mode.
Hint
Press both HEAT and COOL at the same time, and the
system will automatically switch between cooling and
heating mode. When in the automatic switchover mode, both
the COOL and HEAT indicators are lit.
13. Manual Fan Indicator
Lights when fan is running in manual mode.
14. SLOW-FAST Keys
Control fan speed when the fan is in the manual mode.
Pressing SLOW or FAST key when in automatic fan
mode will change the system into manual mode.
15. FAN Key
Selects manual or automatic fan control mode. Press
once to select manual control. Press FAN again to select
automatic fan speed control. In this mode, the fan speed
is controlled by the microprocessor as a function of the
difference between setpoint and inside temperature.
16. Fan Speed Indicators
Row of five small LEDs below FAN key. Indicate the
current fan speed.
17. Inside Temperature Indicator (SMXir Display Only)
When illuminated, inside temperature is displayed.
When light is off, setpoint is displayed.
18. IR Receiver (SMXir Display Only)
Infrared remote receiver
19. Dehumid Key (Remote Control Only)
Changes system into the Humidity Control program.
20. Auto Switchover Key (Remote Control Only)
Places the system into automatic changeover mode, so
it will switch from cooling to heating as needed.
Definitions
LED - Light Emitting Diode. An indicator light is used to
denote mode or operating status.
Setpoint - The selected temperature you want to maintain in
the area being heated or cooled.
Modulating A/C Systems • Operation

18 English
L-0952 Operation
The SMXir Remote Control
The SMXir remote control keypad has the familiar layout of
the 10-button SMX keypad, and performs most of the same
functions. The remote can not be used to program settings.
Programming must be done at the keypad/display.
In addition to the standard keys, the SMXir remote also has
two quick-hit buttons that allow easy access to the humidity
control program and the automatic changeover mode.
The remote has three buttons that are not used on SMX II
systems. The Aux Heat, Aux Heat Auto Switchover, and the
Aux 1 buttons are for SMX Net systems only.
The SMXir remote control must be pointed at the SMXir
keypad/display, which has the IR remote receiver. The
remote will not work if the SMXir keypad/display has the
optional full coverage door and the door is closed.
See Figure 23 for SMXir Remote control angle and distance
range.
SMX II Keypad/Display
SMXir Keypad/Display
SMXir Remote Control

19 English
L-0952 Operation
Basic Operation
Power On
When AC power is applied to the system at the circuit breaker,
the SMX microprocessor retrieves from permanent memory
the last operating configuration. This process takes about four
seconds, after which the system will begin operating just as it
had been when power was last turned off.
System Off
Press the OFF key to turn the system off. Note that the data
display remains energized even when the system is off. The
fan can be turned on manually when the system is in the off
mode.
Note
The SMX has built-in protection against sudden power
interruptions. The system automatically stores the current
operating configuration in permanent memory every time you
make changes. (The new operation mode must be in affect
for 10 seconds before it is saved into permanent memory.)
When AC power is lost, the SMX system retains these
settings, and when AC power is restored it resumes opera-
tion using the same settings as before.
Selecting Setpoint
Press the SET key and the current setpoint will be displayed.
Press the UP or DOWN key to change the setpoint.
Displaying Temperature
To display cabin temperature, press the TEMP key. Press
TEMP twice for an alternating display of inside temperature
and setpoint. Press again to return to inside temperature
only.
Cool Mode
To enter the COOL mode, press the COOL key. The Cool
Mode Indicator will light to show that you have selected the
cooling mode.
The Cooling Indicator will be lit whenever the system is in the
cooling mode and the control is calling for cooling (solenoid
valve open and the compressor running). When the cabin
temperature is satisfied, the Cooling Indicator goes off
(solenoid valve is closed and the signal to the compressor
relay is off).
Heat Mode
Press the HEAT key to select HEAT Mode. The Heat Mode
Indicator will light to show that you have selected the heating
mode.
The Heating Indicator will be lit whenever the system is in the
heat mode and the electric heater is on. When the cabin
temperature is satisfied, the Heating Indicator goes off
(electric heater is off).
Automatic Changeover
Press the COOL and HEAT keys simultaneously for AUTO-
MATIC CHANGEOVER between COOL and HEAT Modes.
The mode indicators will light, indicating that the system is in
the automatic changeover mode.
For the SMXir Remote Control only - Press the Auto
Switchover key to enter automatic changeover mode.
Note that the Cooling or Heating Indicator will come on when
the compressor is running to show when the system is
running in the cooling or heating mode.
Manual Fan Speed Control
Press the FAN key to select manual fan control. The Manual
Fan Indicator will light to show that it is in the manual mode.
Then use the SLOW and FAST keys to select the desired fan
speed.
Note that the manual fan control may be used to circulate air
even when the system is in the OFF mode.
Automatic Fan Speed Control
If in manual fan mode, press FAN key to select automatic fan
control. The Manual Fan Indicator goes off, and the system
will automatically adjust fan speed as the actual cabin
temperature deviates from the setpoint. As setpoint is
approached, the fan speed automatically slows. Once
setpoint is reached, the compressor cycles off and the fan
keeps running on low speed.
Adjusting Brightness
Pressing the SET key repetitively will dim the LED display.
Keep pressing SET to return to full brightness.

20 English
L-0952 Operation
Using The Humidity
Control Routine
When engaged, the SMX humidity control routine automati-
cally turns the air conditioning system on at timed intervals to
remove moisture from the air. The system is programmed at
the factory for average values. To change the factory
settings, see "Humidity Control Program".
To start the dehumidification program:
• Press OFF.
• Press COOL, HEAT and FAN keys simultaneously.
For the SMXir Remote Control only - Press the Dehumid
key to enter dehumidification mode.
• The data display will flash HU, indicating that the program
is active.
• To halt the dehumidification program, press any key. The
HU message will stop flashing.
Programming the SMX II System
SMX control systems are programmed at the factory for
average values. For optimum performance, you may wish to
change these settings to suit your individual preferences.
All programming steps are entered by pressing the OFF key,
followed by the SET key, then simultaneously depressing the
two or three keys noted in the table below. Successful entry
into a programming mode is indicated by the presence of a
decimal point to the right of the two displayed characters. To
raise or lower a value, touch the UP or DOWN keys. To exit
the programming mode, touch the OFF key. (The SMXir
Remote Control cannot be used to program the system.)
Custom Programming Record
Use table below to keep track of any program changes. If a Factroy Memory Reset is performed, then all parameters will revert
back to factory default settings as outlined in the Programming Summary Table above.
Programming Summary Table
Programmable Function Keystroke Combination Factory Setting Range
Factory Memory Reset OFF & SET & FAN, then SET See table below before reset
Fahrenheit/Celsius DOWN & TEMP & UP F F or C
Auxiliary (Electric) Heat SET & HEAT – – or AH
Setpoint Differential SLOW & FAN 12 4 to 24
Fan Mode (Cont. or Int.) DOWN & FAN & UP C C or I
Low Fan Speed DOWN & SET 32 30 to 56
High Fan Speed SET & SLOW 60 41 to 90
Fan Response Differential COOL & SLOW 4 2 to 8
Temperature Calibration SET & UP – ± 1%
HU Precirculation TEMP & DOWN 10 Min. 10 Min.
HU Dehumidification TEMP & SET 30 Min.
HU Time Period TEMP & UP 12 Hrs.
See “Humidity
Control Program”
Unit Location (Cabin #, Salon, etc.)
Programmable Function Unit 1 Unit 2 Unit 3 Unit 4 Unit 5
Fahrenheit/Celsius
Auxiliary (Electric) Heat
Setpoint Differential
Fan Mode (Cont. or Int.)
Low Fan Speed
High Fan Speed
Fan Response Differential
HU Dehumidification
HU Time Period