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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
L-0952 Introduction
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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