Johnson Controls A350AA-3 Temperature Control

The Johnson Controls A350AA-3 is a specialized on/off electronic temperature control designed for modular integration within the System 350 platform. Operating on 24Vac, this unit features a broad setpoint range of -30 to 130°F, making it a versatile choice for both heating and cooling applications in commercial refrigeration. The inclusion of an A99BC-25 silicon sensor ensures high-accuracy thermal sensing with excellent linear response across the entire operating range. Technicians can fine-tune system cycling using the adjustable differential (1 to 30°F), while the concealed setpoint adjustment prevents unauthorized tampering in high-traffic mechanical rooms. This SPDT relay output controller allows for seamless multi-stage configurations when paired with S350 stage modules. The offset adjustment capability further enhances precision by allowing the sensor reading to be calibrated against a secondary reference, ensuring tight tolerance in temperature-sensitive environments. Built for DIN rail or surface mounting, this electronic temperature control is a dependable solution for commercial HVACR technicians requiring modular flexibility.

Key Benefits for the Contractor:

• Precise Switching: The SPDT relay provides reliable on/off control for compressors, fans, or heating elements.
• Modular Compatibility: Designed to snap together with other System 350 modules via a 5-pin connector for expanded functionality.
• Field Calibration: Features an integrated adjustable differential to prevent short-cycling and protect equipment longevity.
• Reliable Sensing: Utilizes A99 Series silicon sensors which are interchangeable without requiring recalibration of the control.
• Secure Setup: Internal setpoint dial and concealed adjustment prevent end-user interference with programmed parameters.

Commonly Asked Questions:

How do I wire the A350AA-3 for a cooling application?
For cooling, wire the compressor or contactor coil to the Normally Open (N.O.) and Common (COM) terminals of the SPDT relay output. The relay will close when the temperature rises to the setpoint plus the differential.

Can the A99 sensor lead be extended?
Yes, the A99BC-25 silicon sensor leads can be extended using standard 18 AWG shielded cable. Ensure connections are secure to avoid introducing resistance that could skew temperature readings.

What is the purpose of the 1 to 30 degree F offset?
The offset adjustment allows you to shift the control's calibration to match a known accurate thermometer or to compensate for sensor placement variances in a large walk-in box or plenum.

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.