Johnson Controls A11B-1 Freezestat

The Johnson Controls A11B-1 is a professional-grade low temperature cutout control, commonly referred to in the field as a freezestat. Engineered specifically for HVAC systems utilizing chilled water or steam coils, this mechanical temperature control protects against thermal damage by monitoring air duct temperatures. The unit features an SPST switch that opens on a temperature drop, effectively cutting power to the fan or closing dampers when localized temperatures reach the user-defined cutout range of 35°F to 45°F. With an automatic reset configuration and a fixed 12 degree differential, this control ensures the system resumes operation only after the sensing element reaches a safe 47°F to 57°F threshold. Its 20-foot sensing element provides a wide coverage area, detecting the coldest spot along any one-foot section of the capillary length to prevent coil rupture in stratified air conditions.

• Broad Electrical Compatibility: Rated for a wide voltage range from 24 to 277Vac, making it a versatile choice for various commercial control circuits.
• Precision Sensing: The 1/8" x 20' vapor-actuated capillary ensures reliable detection of localized freezing conditions across large air handler intake sections.
• Durable Construction: Built with a rugged enclosure designed to withstand the vibrations and environmental demands of mechanical rooms.
• Simplified Installation: Standard four-hole mounting and accessible terminal screws streamline the replacement of existing A11 Series controls.

How do I test the A11B-1 freezestat operation?
Technicians can verify functionality by exposing at least 12 inches of the capillary to temperatures below the setpoint (e.g., using an ice bath) and checking for continuity across the SPST terminals.

What is the difference between automatic and manual reset models?
The A11B-1 is an automatic reset control, meaning the switch closes automatically once the sensing element warms up by the fixed 12-degree differential. Manual reset models require a physical button press to restart the system.

Can this be used for both heating and cooling coils?
Yes, it is primarily used as a low-limit safety to protect any water-circulating coil exposed to outdoor air or low-temperature supply air streams.

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.