Johnson Controls MR4PMUHV-12 Control

The Johnson Controls MR4PMUHV-12 is a professional-grade, multi-function refrigeration defrost control designed for precise temperature management in commercial walk-in coolers and freezers. As a primary digital defrost timer replacement, this unit integrates four critical functions into a single HVACR control module: a high-accuracy thermostat, a defrost cycle timer, a digital readout, and a defrost termination switch. It supports both electric heat defrost and hot gas defrost strategies, utilizing time-based or temperature-based termination to optimize system efficiency. The included relay pack provides heavy-duty switching for compressors up to 2 HP, 20A heater loads, and evaporator fans, effectively eliminating the need for external contactors in many applications. Equipped with dual A99BB-200C sensors, the MR4PMUHV-12 ensures ±1.8°F accuracy. Its nonvolatile memory protects programmed defrost schedules during power interruptions, while the integrated alarm management system alerts technicians to sensor failures or high-temperature excursions via local codes or remote relay triggers.

Key Benefits

• Consolidated Control: Replaces separate electromechanical timers, thermostats, and termination switches with one digital microprocessor-based control.
• Enhanced System Reliability: Built-in short-cycling delay protects the compressor from premature wear during rapid thermal fluctuations.
• Flexible Installation: The modular design allows the control and relay pack to be mounted together or up to 50 feet apart for easier wiring access.
• Evaporator Fan Management: Programmable fan delays and temperature-based fan startups maximize cooling efficiency post-defrost.
• High-Load Capacity: Direct control of inductive loads up to 16 FLA and non-inductive loads up to 20A reduces the footprint of the control panel.

Common Questions

Can the MR4PMUHV-12 replace a standard Paragon timer?
Yes, this unit is a common digital upgrade for Paragon 8145-00 and 8145-20 models, offering more precise digital control and integrated fan/alarm management.

How far can the sensors be extended?
The included A99 sensors support wiring runs up to 300 feet (91 meters) when using appropriate gauge wire, with a programmable offset to maintain calibration accuracy.

Does this control support manual defrost initiation?
Yes, technicians can manually trigger an immediate defrost cycle or a "deep freeze" cycle directly from the front keypad to assist in system commissioning or troubleshooting.

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.