Johnson Controls MR4DR24-12 Defrost Control

The Johnson Controls MR4DR24-12 is a professional-grade electronic temperature control designed for precise defrost management and multi-stage HVACR applications. Operating on 24 Vac, this four-stage controller provides exceptional reliability with a ± 1.8 degree accuracy, ensuring tight setpoint maintenance in critical refrigeration environments. The unit features built-in alarm management and is packaged with two A99BB-200C sensors, allowing for immediate deployment. Designed for efficiency, the MR4DR24-12 DIN rail mount configuration simplifies installation within standard electrical panels. This model is technically identical to the MR4DR24-12C, offering full compatibility for contractors seeking a direct replacement. By integrating temperature and defrost control into a single module, it eliminates the need for redundant hardware, streamlining commercial refrigeration servicing and system troubleshooting. The intuitive interface allows for fast parameter adjustments, making it a staple for technicians managing complex cooling cycles and evaporator coil maintenance.

• Multi-Stage Precision: Four stages of control allow for complex sequencing of compressors, fans, or defrost heaters.
• Integrated Alarm Logic: Provides dedicated temperature and system alarm management to prevent stock loss and equipment failure.
• High Accuracy Sensing: Includes two A99BB-200C thermistor sensors for reliable feedback across a wide operating range.
• Mounting Versatility: Standard 35mm DIN rail mounting ensures a secure fit and organized wiring in control cabinets.

Common Questions

Is the MR4DR24-12 compatible with older Johnson Controls A99 series sensors?
Yes, this controller is designed to work seamlessly with A99 series PTC silicon temperature sensors, specifically the included A99BB-200C models.

Can I use this model to replace the MR4DR24-12C?
Yes, the MR4DR24-12 and the MR4DR24-12C are identical units with the same technical specifications and performance characteristics.

What is the primary benefit of the four-stage control in defrost applications?
The four stages allow for more granular control over the refrigeration cycle, such as managing multiple fans or tiered heating elements to optimize energy use during defrost.

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.