By Eamonn Ryan

CAREL, on 2 December 2025, hosted a live webinar on the topic ‘How STone Virtual Loop can streamline the developer’s working life in the HVAC/R industry’ presented by Matteo Galenda, CAREL application specialist HVAC residential group solution marketing, and Simone Armano, CAREL SSD HVAC and food retail manager – digital department. This is part two of a three-part series.

The conversation underscored the importance of understanding context in refrigeration design.

The conversation underscored the importance of understanding context in refrigeration design. Freepik.com

…continued from part one.

 

  1. Far fewer lab hours

Traditionally, developers must physically book a laboratory slot, wait for unit availability, and run tests on a prototype. With the Virtual Loop, most of this can be done from a laptop significantly reducing:

  • Energy consumption
  • Laboratory technician time
  • Prototype wear
  • Debugging cycles

This is particularly valuable when new team members or junior developers need time to learn HVAC behaviour: the software becomes a safe thermodynamics playground.

 

  1. Automatic and repeatable testing

The tool supports:

  • Continuous integration testing
  • Regression testing
  • Unique validation sequences
  • Scripted automated tests

Developers can re-run identical scenarios repeatedly – something almost impossible on a physical unit due to drift, ambient variations, or mechanical wear.

 

  1. Software debugging without physical risk

STone Virtual Loop can emulate:

  • Mechanical failures
  • Stuck expansion valve
  • Fan failure
  • Refrigerant leakage
  • Blocked coils
  • Incorrect control logic
  • PID instability
  • Defrost routines failing
  • Protection logic not triggering

This is invaluable because software protection routines are meant to prevent damage before it happens. The Virtual Loop lets developers test such conditions safely, without risking compressors, valves or heat exchangers.

 

  1. Faster onboarding for new engineers

HVAC/R developers are often great programmers but lack hands-on thermodynamics experience. The Virtual Loop visualises system behaviour – pressures, temperatures, superheat, subcooling – in real time, enabling ‘learning by doing’ in a risk-free environment.

 

  1. Built-In cybersecurity compliance

With rising cybersecurity requirements (IEC 62443, UL 2900), every software change must be validated. STone streamlines this by allowing rapid patch testing without needing a lab prototype each time – an increasingly important capability for manufacturers scaling global fleets of connected HVAC/R units.

 

How it works: A developer’s workflow

The typical setup follows four simple steps:

  • Unit configuration: Select refrigerant, heat-source type (air/water), flowrates, component sizes, etc.
  • Virtual wiring: Bind virtual sensors, actuators and thermodynamic variables to the controller’s I/O.
  • Boundary conditions: Define environmental conditions: temperature cycles, humidity profiles, seasonal defrost patterns.
  • Run simulation: The virtual system operates exactly like a unit under test – compressor ramps up, superheat shifts, fans start, alarms trigger, etc.

Within seconds, developers can see:

  • Pressure differentials
  • Compressor envelope behaviour
  • Defrost sequences
  • DHW cycles
  • Humidity control
  • Alarm cascades

This granular transparency is invaluable when validating control logic.

 

What STone Virtual Loop is not

CAREL emphasises that this is not a performance modelling tool. It does not aim to:

  • Provide precise COP/EER values
  • Design heat exchangers
  • Match an exact refrigerant charge
  • Size piping or compressors

Its primary purpose is software logic validation, not unit design.

For engineering departments that require accurate performance prediction, traditional simulation tools (such as Modelica, TRNSYS and ANSYS) remain necessary.

Continue to part three…

 

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