Lennox 38M78 Low Ambient Pressure Switch, 450 PSI In / 250 PSI Out

Description

Lennox 38M78 Low Ambient Pressure Switch Overview

The Lennox 38M78 is an OEM low ambient pressure switch engineered to protect refrigeration circuits during cold-weather operation. By monitoring system pressures and interrupting operation when conditions fall outside safe parameters, this switch helps prevent compressor damage and ensures reliable performance year-round.

Key Specifications

• SKU / Part Number: 38M78
• Cut-In (Make) Pressure: 450 PSI
• Cut-Out (Break) Pressure: 250 PSI
• Function: Low Ambient Pressure Switch
• OEM Lennox Replacement Part

How It Works

The low ambient switch senses refrigerant-side pressure and opens the circuit when pressure drops to the cut-out setpoint (250 PSI), preventing the system from operating under dangerously low-pressure conditions common in cold ambient temperatures. The switch automatically resets and closes the circuit once pressure recovers to the cut-in setpoint (450 PSI), restoring normal system operation without manual intervention.

Features & Benefits

• Protects compressor from low-pressure damage during cold ambient conditions
• Automatic reset — closes at 450 PSI cut-in, opens at 250 PSI cut-out
• Direct OEM Lennox replacement for accurate fit and reliable performance
• Helps maintain system efficiency and extend equipment service life
• Suitable for use in residential and light commercial Lennox refrigeration and air conditioning systems

Application

Designed as a direct OEM replacement for compatible Lennox air conditioning and heat pump systems. Always verify compatibility with your specific Lennox equipment model before installation. Consult Lennox documentation or a qualified HVAC technician for proper installation and wiring procedures.