For contractors servicing HVACR systems, the Johnson Controls A19AAF-21 Temperature Control provides a dependable mechanical solution for high-accuracy thermal regulation. This single-stage, remote bulb temperature control is specifically engineered for precision in heating or cooling applications, featuring a 40 to 90 degree F setpoint range and a tight 1.5 degree F fixed differential. As the A19AGF-23 direct replacement, this unit integrates seamlessly into existing setups using its 6-foot capillary and 3/8" x 5-3/4" sensing bulb. The liquid-filled element ensures the A19 series mechanical thermostat is unaffected by barometric pressure or cross-ambient conditions, maintaining consistent calibration. Utilizing SPDT switch action, the control supports 24 to 277Vac electrical loads with an automatic reset function. The screwdriver slot range adjuster allows for secure setpoint configuration, preventing accidental adjustments in high-traffic equipment rooms. Whether used in refrigeration display cases or industrial heating, this Penn A19 control delivers the rugged reliability expected in professional mechanical installations. Key Benefits Direct Replacement Compatibility: Fully replaces the legacy A19AGF-23 model without requiring mounting modifications. High Switch Versatility: The SPDT (Single-Pole, Double-Throw) contacts allow for use in both heating and cooling circuits. Precision Sensing: Features a 1.5 degree F fixed differential for minimal temperature swing and tighter process control. Robust Construction: Equipped with a 6' copper capillary and a liquid-filled bulb designed for ambient temperature protection. Secure Adjustment: Includes a concealed screwdriver slot to ensure setpoints are protected from unauthorized tampering. Common Questions Is the A19AAF-21 suitable for direct immersion applications? Yes, but it requires a bulb well (such as the WEL14A series) to protect the sensing element and allow for removal without draining the system tank. Does this control require a power source to operate the sensing mechanism? No, this is a mechanical thermostat that relies on the physical expansion of liquid in the capillary to trigger the switch, though the terminals must be wired to your 24-277Vac circuit. Can I use this model to replace a manual reset limit control? No, the A19AAF-21 features an automatic reset mechanism. If your application requires a safety cutout that stays off until manually cleared, you must use an occupant-safe manual reset model. 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.
