Lennox 18J74 Low Ambient Pressure Switch Low Ambient Pressure Switch

Low Ambient Pressure Switch

The Low Ambient Pressure Switch is designed for use with all 18JA and 18JB Geothermal units. The pressure switch turns the outdoor unit on when the temperature drops below 45-50°F and off when the temperature rises above 60-65°F. This prevents short cycling of the compressor and increases the life of the compressor. The Low Ambient Pressure Switch must be used with a temperature sensor to properly control the thermostat.

The Lennox Low Ambient Pressure Switch (Model 18J74) is designed for use with rooftop-mounted packaged air conditioning and heat pump systems. This switch permits control of your heating, ventilating, and cooling system in warmer, humid climates. The unit primarily decrease the compressor speed, but no coolant flow is permitted through the valve to the evaporator. This switch provides significant energy savings during the summer months .

The Lennox Low Ambient Pressure Switch is designed for the air conditioner or heat pump that requires a temperature setting different than normal, but the thermostat cannot compensate to achieve this due to low ambient temperatures. The 18J74 is pre-programmed for normal and low ambient -20°F settings.

The LOW AMBIENT PRESSURE SWITCH (LAPS) is designed to provide extra protection and support for in-house home comfort systems.  The LAPS will cycle on and off in low ambient pressure situations to protect equipment, preventing costly repairs and minimize downtime. This 78-Volt Low Ambient Pressure Switch features a built in damper actuator, which replaces an external switch box and wiring.

The same Lennox-developed low ambient pressure switch that's been protecting customers' equipment for over 30 years. It senses negative pressure changes in the return air duct before the blower starts and helps shut off the furnace or air handler to protect it from damage. Plus, it offers added assurance with a visual alarm!

The Lennox Heating Low Ambient Pressure Switch is designed for systems designed for heating and air conditioning applications. It has the flexibility to connect and disconnect at three points and accepts up to 1/2" tubing.

The Genuine 18J74 is a solid state low-ambient pressure switch that responds to pressure changes without varying resistance.