Johnson Controls A19EAF-2 Temperature Control

The Johnson Controls A19EAF-2 Temperature Control is a heavy-duty mechanical duct thermostat designed for precision air temperature regulation in HVAC systems. Featuring a Single Pole Double Throw (SPDT) snap-action switch, this flange-mounted duct control provides reliable operation for heating, cooling, or ventilation applications such as rooftop units and make-up air heaters. The unit covers a wide 30 to 110 degree F setpoint range with a tight 2 degree F fixed differential, ensuring consistent cycling and preventing excessive equipment wear. Its liquid-filled sensing element and air coil bulb are specifically engineered for high-velocity air streams, remaining unaffected by barometric pressure or cross-ambient conditions. Built with a rugged NEMA 1 cold-rolled steel enclosure and an integrated automatic reset, the A19EAF-2 supports 120Vac to 240Vac line voltage switching. The external knob allows for rapid field adjustments, while the adjustable flange enables various insertion depths to locate the sensing bulb in the optimal portion of the air duct.

Key Benefits

• Versatile Application: The SPDT switch allows the control to be wired to open or close a circuit on temperature rise, making it suitable for both heating and cooling equipment.
• Durable Construction: Features a gray baked enamel steel cover and case to withstand the demands of commercial mechanical rooms and industrial environments.
• Accurate Sensing: The liquid-filled sensing bulb ensures "repeat" accuracy regardless of ambient temperature fluctuations outside the duct.
• Ease of Installation: The flange mounting system facilitates quick mounting on flat surfaces, and the screw-type terminals simplify field wiring for HVAC contractors.
• Adjustable Depth: The flange-mounted design allows for repositioning the sensing element within the air stream for the most accurate average temperature readings.

Common Questions

Can the A19EAF-2 be used to control a duct heater?
Yes, the A19EAF-2 is frequently used as an operating control for duct heaters. By using the SPDT contacts, you can wire the unit to energize the heating circuit when the temperature drops below the setpoint.

How do I wire this control for a cooling application?
For cooling (close on rise), wire to the Red (Common) and Yellow terminals. For heating (open on rise), utilize the Red and Blue terminals. Always use copper conductors and follow local electrical codes during installation.

What is the purpose of the 2 degree fixed differential?
A fixed 2 degree F differential ensures the system does not "short cycle." Once the setpoint is reached, the temperature must change by 2 degrees before the switch returns to its original state, protecting the motor and contactors.

Disclaimer: While we strive for 100% accuracy, product data and specifications are subject to change. Please contact our team to confirm compatibility or technical details before purchasing.