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How Kriwan Modules and PTC Sensors Work Together
How Kriwan Modules and PTC Sensors Work Together
A Kriwan motor protector (such as the industry-standard Kriwan INT69 and INT369) is the electronic control module that reads, processes, and acts upon the signals sent by PTC thermistor safety sensors embedded inside a commercial refrigeration compressor.
If the PTC thermistors are the “eyes” sensing the compressor’s temperature, the Kriwan module is the “brain” that instantly cuts power if the system gets too hot.
Commercial compressors from brands like Bitzer, Copeland, and Carlyle rely on this exact combination to prevent catastrophic motor meltdowns:
Functions of Kriwan Modules are as follows:
- Continuous Monitoring: The Kriwan module feeds a small electrical sensing current through the Kriwan PTC winding sensors embedded in the compressor’s motor.
- The Series Chain: Kriwan modules can monitor up to nine PTC sensors wired in a single series loop. These sensors track distinct danger zones simultaneously, including the three separate motor winding coils, the oil sump temperature, and the hot cylinder head discharge.
- The Trip Event: Under normal conditions, all PTC sensors maintain a very low electrical resistance, keeping the loop closed. However, if even one area overheats, its specific PTC thermistor’s resistance spikes drastically.
- Instant Shutdown: The Kriwan electronic module instantly detects this overall resistance spike, opens its internal relay, breaks the safety control circuit, and shuts down the compressor contactor before any permanent insulation damage occurs.
Why Commercial Refrigeration Uses This Pairing
- Fail-Safe Design: Kriwan modules operate on the closed-circuit principle. If a sensor wire breaks or disconnects, the loop is broken, and the Kriwan module will shut down the system immediately to prevent unmonitored operation. []
- Fast Response Times: Kriwan’s custom PTC sensors feature an engineered Resistance-to-Temperature (R/T) curve that is significantly steeper than standard industrial specifications. This minimizes thermal delay, triggering safety shutdowns much faster than external bimetal clickson overloads.
- Smart Diagnostics: Modern Kriwan modules (like the INT69 and INT369 Diagnose series) don’t just trip; they store flash codes that tell technicians exactly whether the shutdown was triggered by a PTC thermal overload, a phase failure, or an asymmetrical power supply fault.
