When the air exchanger no longer breathes properly: a revealing HVAC service call in Montreal
In a mechanical room located in Montreal, our AirGreen team was called to inspect an Aldes air exchanger suspended from the ceiling, connected to a network of metal ducts serving several interior zones. The client reported a marked decrease in ventilation, a feeling of stagnant air in some rooms, and irregular noise coming from the unit, especially when the system was running at higher flow rates. At first glance, the installation seemed clean and accessible, but several visual clues indicated that a full diagnosis was necessary: closely spaced ducts, limited access around the device, presence of connections under the unit, and a mechanical environment shared with other HVAC equipment.
At AirGreen, we know that an air exchanger is not just an accessory. It is an essential element of indoor air quality. In a residential, multi-unit, or light commercial property in Montreal, Laval, Longueuil, on the North Shore or the South Shore, poor ventilation can quickly cause discomfort: excessive humidity, persistent odors, condensation, airborne dust, a feeling of heavy air, and reduced performance of other heating, ventilation, and air conditioning systems.
An Aldes unit suspended in a complex mechanical space
The device observed on site was an Aldes air exchanger, installed high up, suspended on a metal structure and connected to several rigid ducts. This type of installation is common in buildings where ventilation is centralized while keeping the floor space clear. The Aldes unit was positioned near the ceiling, above other mechanical components, which required a methodical approach to avoid disturbing adjacent ducts or damaging existing connections.
The Aldes brand is well known in the ventilation field. It is often used for air renewal systems, heat recovery, or controlled air distribution. In this specific case, the model number was not clearly visible in the photo provided, but the configuration allowed identification of a central ventilation unit of the air exchanger type, integrated into a duct network.
Symptoms reported before our arrival
The client did not report a complete failure, but rather unstable operation. This is often what makes service calls on air exchangers more delicate: the unit may still start but no longer provide the expected airflow, balance, or reliability.
The reported symptoms were as follows:
- Less effective ventilation in certain areas.
- Unusual noise coming from the unit or ducts.
- Feeling of humid or stagnant air.
- Intermittent operation depending on speed or demand.
- Concern about the condition of the ducts and connections.
- Need to check if the unit could be repaired rather than replaced.
This type of situation requires more than just a quick cleaning. A well-executed HVAC service call should help determine if the problem comes from the motor, the fan, the filters, the duct network, a stuck damper, a drain, an electrical control, or a pressure imbalance.
Initial inspection: access, safety, and general condition
Our first step was to secure the work area. A suspended unit like this requires careful inspection, especially when it is above other equipment. Before touching the unit, we checked:
- Apparent sturdiness of supports.
- Condition of ducts connected to the unit.
- Signs of vibration or displacement.
- Presence of condensation around the unit.
- Condition of visible electrical connections.
- Accessibility to service panels.
- General cleanliness around air intakes and outlets.
One of the important elements in this type of intervention is not to draw conclusions too quickly. A noise in an Aldes air exchanger can come from a worn-out motor, but also from a poorly fixed panel, a stressed duct, a support transmitting vibrations, a clogged filter, or an unbalanced airflow.
HVAC Diagnosis: Understanding the Air Path Before Replacing Parts
A common mistake in air exchanger repairs is to replace a part without checking the entire network. At AirGreen, we always proceed following the system logic: air enters, passes through the unit, goes through the filters, fans, internal exchanger, then exits through the ducts. If a single section is blocked, poorly connected, or unbalanced, the device may seem defective when the problem lies elsewhere.
In this case, our diagnosis focused on four main elements: airflow, internal mechanics, moisture evacuation, and electrical control.
Filter and internal dirt check
We first inspected the filters and the accessible interior of the device. On an air exchanger, saturated filters can significantly reduce flow. This forces the fans to work harder, increases noise, and can create the impression of a breakdown even though the device is still working.
A filter that is too dirty can also cause an imbalance between the extracted air and the introduced air. In a well-insulated building, this can cause excessive negative or positive pressure, which affects comfort, odors, humidity, and even the performance of a central heat pump or another air conditioning system.
Fan and motor inspection
We then checked the operation of the fans. The noise reported by the client could correspond to dust accumulation on a turbine, misalignment, a worn bearing, or vibration transmitted by the box.
On site, one of the important points was to distinguish an internal mechanical noise from a noise amplified by the ducts. A metal duct can sometimes act as a resonance box. That’s why we listened to the device at different points: near the Aldes box, near the ducts, at the supports, and near accessible outlets.
Duct connection inspection
The image showed a dense installation, with several rigid ducts around the unit. In such a configuration, the connections must be well sealed to avoid air leaks. A leak on a supply or exhaust duct can reduce the efficiency of air renewal and give the impression that the air exchanger is no longer working properly.
We paid special attention to metal transitions, joints, collars, and sections where the duct changes direction. Air leaks in a mechanical room can go unnoticed, but they have a real impact on overall performance.
Drain and condensation check
An air exchanger can generate condensation depending on the season, indoor humidity, and outdoor temperature. If the drain is partially blocked, poorly sloped, or poorly connected, water can accumulate, cause odors, create corrosion, or trigger intermittent problems.
During our intervention, we checked the connections under the device, visible lines, and signs of moisture around the unit. This point is particularly important in Montreal, where seasonal variations are marked: cold winters, humid spring periods, and summer heat episodes heavily stress ventilation systems.
A targeted repair to restore ventilation and reassure the client
After inspection, our team carried out targeted restoration of the unit and its accessible elements. The goal was not to replace the device unnecessarily but to restore reliable, quiet, and balanced operation.
Cleaning of accessible components
We started by cleaning the accessible areas inside the device. This step often helps reduce operating noise and improve airflow. Filters, accessible internal surfaces, dust accumulation points, and certain areas around the fans were inspected and cleaned within safe access limits.
Cleaning an air exchanger should not be improvised. Some components are sensitive, and it is important to avoid forcing the panels, moving cables, or damaging the seals. On a suspended unit like this one, the intervention must also consider the working position and the risks related to working at height.
Adjustment and securing of the panels
The Aldes casing had a configuration where the service panels must be properly closed to avoid vibrations. We checked the visible fastenings and contact points that could transmit metallic noise. A slightly loose panel can create disproportionate noise, especially when the fan increases its speed.
After adjustment, the operation was more stable, and the noise perceived around the unit was significantly reduced.
Checking the device's airflow and response
Once the components were cleaned and the connections inspected, we tested the device at different speeds. This step confirms that the air exchanger responds correctly to the control and that the symptoms do not return as soon as the system changes speed.
We also observed the duct network's reaction: no excessive vibration, more regular airflow, better-controlled noise, and improved operational stability.
Advice given to the client after the intervention
At the end of the service call, we explained to the client the observed points and recommended measures to prevent recurrence. For an Aldes air exchanger installed at height, preventive maintenance is especially important because the device is less visible daily. When equipment is out of sight, filters, drains, and panels can be neglected longer than expected.
We recommended:
- A regular schedule for filter checks.
- Annual inspection of the unit and accessible ducts.
- Monitoring new noises or vibrations.
- Checking the drain before periods of high humidity.
- Special attention to odors, condensation, and flow changes.
- Professional intervention as soon as intermittent operation appears.
Why air exchangers are essential in modern buildings
Modern buildings are often more airtight than older constructions. This is good for energy efficiency, but it makes mechanical ventilation essential. Without a functional air exchanger, indoor air can quickly become loaded with humidity, odors, particles, and pollutants.
In Greater Montreal, we frequently see ventilation problems related to:
- Filters forgotten for several seasons.
- Poorly balanced ducts.
- Clogged drains.
- Motors at the end of their life.
- Stuck dampers.
- Poorly sealed connections.
- Devices installed in hard-to-reach places.
- Systems that have never been adjusted after renovations.
Good HVAC maintenance helps extend the device's lifespan and improve comfort without necessarily replacing the entire system.
Mistakes to avoid with an Aldes air exchanger
During this type of call, some mistakes often recur. The first is turning off the air exchanger for long periods to reduce noise or save energy. This can worsen humidity problems and make indoor air less healthy.
The second mistake is changing the settings without understanding the system's balance. An air exchanger operates with precise air volumes. Too much extraction or too much air supply can create discomfort and harm the overall performance of the building.
The third mistake is to confuse cleaning with repair. Cleaning can improve the situation, but if the motor, fan, control board, or drain has a defect, a proper diagnosis is still necessary.
Finally, vibrations should never be overlooked. A minor vibration can become a more serious problem if it affects the supports, ducts, or panels of the unit.
Result of the service call in Montreal
After our intervention, the Aldes air exchanger operated more steadily, with better ventilation felt and reduced noise. The client was able to understand the likely cause of the symptoms and the steps to take to keep the device in good condition.
This type of service clearly illustrates the AirGreen approach: inspect before replacing, diagnose the entire system rather than just one part, and offer a clear, durable solution adapted to the actual installation.
Whether it’s for an air exchanger, a wall-mounted heat pump, a central heat pump, a wall air conditioner, a MultiZone unit, a VRF system, a PTAC / VTAC, a humidifier, or a dehumidifier, our team works with the same rigor in Montreal, Laval, Longueuil, on the North Shore and the South Shore.
AirGreen: HVAC repair, maintenance, and diagnostics in Greater Montreal
A service call for an air exchanger should provide more than just an observation. It should allow the client to know if the device is safe, efficient, repairable, and well suited to its use. At AirGreen, we take the time to analyze the symptoms, installation, accessibility, ducts, and internal components before recommending the best solution.
For owners, building managers, condominium associations, and occupants who want to improve indoor air quality, professional service on an Aldes air exchanger can make an immediate difference: fresher air, better humidity control, reduced noise, and more consistent comfort.