Controls & Refrigerant Distributors


Each cooling unit (or evaporating unit) in a modulating system requires its own control. There are two options: The SMX II microprocessor system or three-knob electromechanical switch assembly.

The SMX II microprocessor control system consists of a PLHMX-HV power/logic module, SMXir keypad/display (one for each evaporating unit), CXP cable, and a TSEP temperature sensor.

The PLHMX-HV power/logic module includes a 3 ft (0.9 m) wire harness that connects to the evaporating unit’s junction box. The CXP cable, available in many different lengths, connects the SMXir keypad/display to the PLHMX-HV. The TSEP temperature sensor, also available in different lengths, plugs into the PLHMX-HV. The TSEP’s sensor bulb is installed in the return air path.

The SMXir keypad/display has an attractive, compact housing available in black or white. The display includes a mounting plate for easy surface-mount installation. A large, easy-to-read LED shows cabin temperature, set point, programming prompts, and fault code warnings. Small LEDs and backlit text indicate system status. Under a decorative hinged door is the membrane-sealed SMX 10-button keypad with clearly labeled keys for single-keystroke operation. Internal electronics have an anti-corrosion coating. An optional infrared remote control is available. For more information about the SMXir keypad/display, including dimensions, please refer to specification sheet L-2088.

The three-knob electromechanical switch assembly is available in two varieties: The SA1 for cooling only systems, and the MS5 for units with electric heat. Knobs control mode, fan speed, and a thermostat. These controls come with a 10 ft. (3 m) capillary tube, 3 ft. (0.9 m) wire harness, and color-coded terminal strip. For more information, please refer to specification sheet L-0243.

Electromechanical controls with rotary switches are available for Cruisair DX modulating units.

Key Benefits

  • SMX II features: Automatic or manual fan-speed control, inside temperature display, auxiliary heat control, auto dehumidification, nonvolatile memory, fault display, brightness control
  • SMX II programmable functions: Fahrenheit/Celsius display, low- and highspeed fan adjustment, compressor time delay, compressor response differential, fan response differential, continuous/ intermittent fan, line voltage calibration, temperature sensing calibration, factory memory reset, dehumidification cycle parameters
  • Optional remote control for SMXir keypad/display
  • 3-knob electromechanical control features: Knobs for mode, fan speed, and thermostat, available with electric heat control (MS5 model)