Repair of a Midea VRF system in Côte-des-Neiges

A technical intervention in the middle of Montreal winter

At AirGreen , weather conditions never stop our teams. This winter, we were called to work on a Midea VRF system installed on the roof of a commercial building in Côte-des-Neiges . The client reported a complete heating failure , a critical problem at -10°C. The system, composed of a multi-branch outdoor condenser and several indoor units, ensured the comfort of offices spread over two floors.

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Diagnosis: System shutdown and error code E6

Upon our arrival on the snowy roof, our technicians noticed that the outdoor unit was completely shut down , although the power supply was active. The control screen showed an error code E6 , typical of a communication problem between the indoor units and the main module .
Removing the cover from the control panel quickly revealed the cause: frozen condensation around the communications bus connector, combined with oxidation on some wires.

Our diagnostic steps included:

• Checking the 230V and 24V power supplies on the main board.

• Continuity check between communication terminals A/B.

• Thermal inspection of electronic boards with infrared camera to detect cold spots.

• Reading of the refrigeration pressures , confirming that the circuit was not at fault.

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Repair: deoxidation, wiring and recommissioning

Once the diagnosis was made, we proceeded with a complete repair of the communication circuit .
Here are the steps followed:

1. Complete disconnection of the control unit.

2. Clean the terminals with a specialized dielectric cleaner to remove moisture and residue.

3. Replacement of oxidized wires with new shielded conductors , better insulated against frost.

4. Application of a protective dielectric grease to prevent future water infiltration.

5. Soft restart of the system after checking the voltage and resistances.

After these operations, the VRF restarted normally. The communication lights stabilized, and the indoor units resumed heating mode in less than five minutes. The customer immediately noticed an increase in the ambient temperature in the offices.

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Post-repair performance checks

To ensure long-lasting performance, our technicians performed a series of post-repair checks :

• Suction and discharge pressure : 145 psi and 360 psi respectively, perfect for outdoor conditions.

• Compressor discharge temperature : 64°C, stable.

• Power consumption : within the nameplate standards.

• Communication between modules : no delay, stable signal at constant 5 V.

We also installed a rigid insulation cover on the electrical panel to better protect the system against melting snow and frost, common on Montreal's flat roofs.

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AirGreen Expertise: When Technical Rigor Makes All the Difference

Repairing a VRF requires specific expertise. These systems are more complex than a standard residential heat pump:
They use digital communication cards , electronic expansion valves and interconnected master modules .
At AirGreen, our qualified technicians work on most brands , which allows us to:

• Read and interpret proprietary Midea, Gree, Fujitsu, Daikin and Trane error codes .

• Handle VRF diagnostic tools accurately.

• Repair while respecting the factory settings.

In this specific case, our intervention made it possible to avoid the complete replacement of the main module , a saving of more than $3,000 for the customer.

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Prevention and recommended maintenance

To prevent this type of breakdown from happening again, we offered the customer annual VRF preventive maintenance , including:

• Checking the wiring and communication connections.

• Inspection of cold insulation to prevent condensation.

• Cleaning the coils with biodegradable products.

• Cold start test to detect communication problems before winter.

Regular maintenance helps maintain the reliability of these complex systems, which are essential for occupant comfort.

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Result: comfort restored and customer satisfied

At the end of the visit, the heating was fully functional in all areas of the building.
The relieved customer particularly appreciated the speed of our diagnosis and our ability to repair on site, without waiting time for parts.

Once again, AirGreen demonstrates that its expertise in commercial HVAC and VRF systems is unmatched in Greater Montreal.
Regardless of the brand, complexity or outside temperature, our teams are ready to intervene quickly to ensure continued comfort .

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AirGreen — Specialists in HVAC and VRF systems in Montreal, Laval, Longueuil, North Shore and South Shore.
Your performance, our priority.