Expert intervention by AirGreen to restart a heat pump installed on an exterior metal structure
At AirGreen , we were recently called upon for a residential HVAC service call in Sainte-Julie , on the South Shore of Montreal. The customer contacted us after noticing that their Midea wall-mounted heat pump had suddenly stopped producing heat, accompanied by an unusual metallic noise coming from the outdoor unit.
The installation of this unit was unusual: attached to a metal stair structure at the rear of a multi-family building, exposed to the elements and vibrations. This type of configuration, while practical for freeing up floor space, can lead to resonance, drainage, and long-term thermal stability issues .
Diagnosis: Vibrations, Obstruction, and Frosted Sensor
Upon our arrival, our technicians undertook a complete inspection of the Midea system , starting with the following three areas:
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Mechanical observation : The outdoor unit vibrated abnormally when the compressor started.
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Electrical Check : The supply voltages were correct, but the control relay showed signs of wear.
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Airflow Analysis : The outdoor fan was running, but circulation appeared to be reduced.
Further inspection revealed that the metal bracket was acting as a resonance chamber , amplifying compressor vibrations. Additionally, debris and dust were partially blocking the exhaust grille. Finally, a frosted temperature sensor was preventing the automatic defrost from activating, resulting in incomplete thermal cycling.
Repair steps: precision and optimization
1. Securing and partial dismantling of the unit
Before any handling, we secured the outdoor unit mounted on the steel structure using straps and a temporary AirGreen support . This ensured the technician's safety while avoiding misalignment of the refrigeration lines.
2. Deep cleaning and controlled defrosting
Using AirGreen biodegradable cleaner and a low-pressure rinse, we removed dust and pollen buildup from the grille.
The frosted sensor was gently defrosted and replaced correctly to ensure a reliable thermal reading.
3. Checking the refrigeration circuit
We performed a nitrogen pressure test to confirm that no leaks were present. The R410A refrigerant charge was slightly low (approximately 15% loss), likely due to a historical microleak sealed during a previous service. A calibrated partial recharge restored the optimal pressure.
4. Reduced noise and vibration
To correct the resonance problem, we installed industrial rubber anti-vibration pads between the mounting legs and the metal platform. This measure reduced audible vibrations by more than 70% , ensuring significantly quieter operation.
5. Replacing the control relay
The compressor start relay , showing signs of corrosion, was replaced with an original Midea part. This replacement stabilized the start cycle, eliminating untimely shutdowns.
Results: Restored comfort and improved performance
After restarting the system, the Midea heat pump immediately returned to normal performance:
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Indoor blowing temperature : 11°C in air conditioning mode.
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Stabilized pressure : 130 psi.
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Noise level : reduced to a slight constant hum, without metallic resonance.
The customer was able to see that the air circulation had become fluid again , and that the ambient temperature of the accommodation was regulated effectively without excess energy consumption.
AirGreen advice for installations on metal structures
Heat pump installations on stairs, balconies or suspended structures require special precautions :
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Always use vibration dampers between the compressor base and the structure.
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Avoid accumulations of snow and debris around the unit, as they affect defrosting.
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Check metal supports regularly to prevent corrosion.
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Schedule an annual professional maintenance including cleaning and pressure checks.
These practices not only extend the life of the heat pump, but also reduce noise pollution for occupants and neighbors.
AirGreen: the HVAC benchmark on the South Shore and throughout Greater Montreal
This repair service in Sainte-Julie perfectly illustrates AirGreen's philosophy:
intervene quickly, diagnose accurately and restore full system performance without compromising durability.
Our technicians, specialized in Midea, Fujitsu, Gree, Lennox, Sharp, and Bosch systems, master all possible configurations, whether residential, multi-family, or commercial.
Each AirGreen intervention combines technology, experience and attention to detail , guaranteeing optimal performance and lasting comfort, whether you are in Montreal, Laval, Longueuil, on the North Shore or the South Shore .
AirGreen — your trusted partner for the repair, maintenance and installation of high-performance HVAC systems throughout Greater Montreal.