Johnson Controls A11D-4 Temperature Control

The Johnson Controls A11D-4 Temperature Control is a heavy-duty low temperature cutout freezestat engineered specifically to protect hydronic coils, cooling coils, and liquid-handling pipes from icing and over-cooling. This mechanical temperature control utilizes a 20-foot sensing element to detect the coldest point along its entire length, ensuring that localized freezing triggers the safety response. With a SPDT switch and manual reset functionality, the A11D-4 provides a trip-free mechanism that requires physical intervention before operation can resume, maintaining strict safety protocols for critical HVACR systems. The 1/8-inch diameter sensing element is connected by a 4-foot capillary, with precision repeat accuracy that remains unaffected by ambient temperature fluctuations at the control diaphragm cup. Designed for versatile integration, it supports 24 to 277Vac configurations and features a setpoint cutout range of 2 to 7 degrees Celsius (35 to 45 degrees Fahrenheit) with a 6.7 degree C fixed differential. The dust-protected enclosure and direct reading scale allow for reliable HVAC freeze protection and easy field adjustments from both the top and bottom of the rugged galvanized steel case.

Key Benefits

• Sensing Coverage: The 20-foot bulb ensures comprehensive monitoring of large coil surfaces to prevent localized freeze-ups.
• Fail-Safe Design: The trip-free manual reset lever prevents automatic system restarts until a technician has inspected the equipment.
• Environmental Stability: The design ensures the diaphragm cup and capillary are not influenced by the surrounding ambient temperature, providing consistent trip points.
• Wide Voltage Support: Compatible with 24 to 277Vac, making it a universal fit for various commercial and industrial control circuits.
• Internal Durability: Equipped with precision snap-acting contacts housed in a dust-protected enclosure for long-term switching reliability.

Common Questions

How does the manual reset function on the A11D-4?
The unit features a trip-free manual reset. If the temperature drops to the cutout setpoint, the contacts trip. You must wait for the temperature to rise at least 12°F (6.7°C) above the cutout point before the lever can be manually depressed and released to resume operation.

Can the sensing element be shortened or cut?
No, the 20-foot vapor-actuated sensing element cannot be cut or kinked. To provide accurate coil freeze protection, the entire length should be distributed across the face of the coil to ensure the coldest spot is always detected.

Where can I adjust the temperature setpoint?
The A11D-4 features a direct reading scale. Adjustments to the cutout range can be made via a screw accessible from either the bottom of the housing or the top when the cover is removed.

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.