Johnson Controls A19AAC-4 Temperature Control

The Johnson Controls A19AAC-4 is a heavy-duty, mechanical temperature control engineered for precision in HVACR applications. Built with a Single-Pole Double-Throw (SPDT) switch, this line-voltage controller acts as a versatile solution for both heating and cooling equipment setups. The unit features a setpoint range of 0 to 80?F, specifically designed for low-to-medium temperature monitoring where a 5 degree F fixed differential is required for consistent cycling. The case compensated design ensures that ambient temperature changes around the control housing do not drift the 0 to 80?F setpoint, providing high accuracy regardless of the installation environment.

For contractors needing a reliable remote bulb temperature control, the A19AAC-4 includes a 6-foot capillary connected to a 3/8" x 4" copper sensing bulb. The automatic reset functionality ensures the system resumes operation immediately once the temperature returns to the setpoint. Adjustments are made via a secure screwdriver slot, preventing accidental tampering in high-traffic mechanical rooms. This SPDT temperature control is rated for 24 to 277Vac, making it compatible with a wide array of commercial fan coils, refrigeration units, and space heaters.

Key Benefits for HVACR Techs

• Universal Voltage Compatibility: Rated for 24 to 277Vac, simplifying truck stock by covering multiple application voltages with one line voltage thermostat.
• Environmental Stability: The ambient compensation feature prevents setpoint drift, ensuring the 0 to 80?F range remains accurate in unconditioned spaces.
• Flexible Mounting: A 6-foot capillary allows for remote sensing in ducts, tanks, or walk-in boxes while keeping the controller accessible.
• Durable Construction: Features a rugged NEMA 1 enclosure and a liquid-filled sensing element for long-term responsiveness in demanding environments.

Common Questions & Contractor Insights

How do I wire the A19AAC-4 for cooling versus heating?
As an SPDT controller, use the Red (Common) and Yellow terminals to open the circuit on temperature rise (heating), or the Red and Blue terminals to close the circuit on temperature rise (cooling/fan).

Can this control be used for direct immersion in water tanks?
Yes, but it requires a compatible bulb well to protect the copper sensing bulb from corrosion and to allow for replacement without draining the system.

What is the benefit of a screwdriver slot adjuster over a knob?
In commercial environments, the screwdriver slot prevents unauthorized personnel from altering the setpoints, maintaining system balance and reducing callback frequency.

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.