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Réparation d’une thermopompe murale Lennox à Saint-Constant
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Repair of a Lennox wall-mounted heat pump in Saint-Constant

Flat roof intervention for a system with reduced performance

At AirGreen , we were recently called to repair a Lennox wall-mounted heat pump installed on the roof of a small commercial building in Saint-Constant , on the South Shore of Montreal . The client had noticed that their system was no longer producing enough cold air, despite the compressor running continuously. This situation was leading to excess energy consumption and insufficient indoor comfort.

Step One: Diagnosis of Performance and Pressures

Upon arriving on site, our technician found that the Lennox unit appeared to be running normally, but the refrigeration lines were warm to the touch—a clear sign of low refrigerant or a charge imbalance .

Using our digital manifold and a calibrated refrigerant cylinder , we undertook a static pressure test. The measured values ​​confirmed a refrigerant level significantly below the manufacturer's specifications :

  • Suction pressure: 60 psi (instead of the expected 115 psi).

  • Discharge pressure: 180 psi (instead of 340 psi).

These data indicated a slow leak in the refrigeration circuit.

Leak location: precision and AirGreen method

To locate the leak, we applied a three-step method:

  1. Injection of a fluorescent tracer into the refrigerant circuit.

  2. Using a UV lamp and an electronic leak detector .

  3. Targeted application of a foaming solution to flare fittings and welds.

The leak was identified on a brazing of the discharge tube , slightly cracked due to repeated mechanical vibrations caused by the compressor.

Complete repair: soldering, leak test and refill

Once the leak was confirmed, we proceeded to completely repair the circuit :

  • Safe purge of residual gas.

  • Silver solder on the damaged area, with thermocouple temperature control.

  • Leak test at 350 psi for 20 minutes, no drop observed.

  • High vacuum down to 500 microns to remove all moisture.

  • Accurate charging of R-410A refrigerant on the electronic scale, according to Lennox data.

Once the system was put back into service, the pressures were stable again:

  • Suction: 120 psi

  • Discharge: 360 psi

  • Discharge temperature: 7.5°C

Interior cooling was restored within minutes , with a temperature difference of more than 12°C between the intake and exhaust air.

System optimization and maintenance tips

Before leaving the premises, we checked several elements to ensure the durability of the HVAC system :

  • Tighten the fasteners to limit compressor vibrations.

  • Cleaning the outdoor condenser using a mild biodegradable solution.

  • Checking the condensate drain .

  • Calibrating the indoor temperature sensor .

We also recommended annual AirGreen preventative maintenance to the customer, which helps detect micro-leaks and prevent future yield losses.

Result: Restored Lennox performance and comfort regained

The customer immediately noticed an improvement in indoor comfort , while appreciating the reduction in overall system operating noise. Thanks to precise recharging and durable sealing, the Lennox heat pump now regains its original energy efficiency .

This intervention, carried out in demanding outdoor conditions on a roof exposed to the sun, demonstrates the technical rigor and versatility of our AirGreen technicians, capable of working on both residential and commercial installations.

AirGreen: Your HVAC Partner on the South Shore and Beyond

At AirGreen , we provide diagnostics, repairs, and complete maintenance for Lennox, Midea, Fujitsu, Gree, Zephyr, and many other HVAC systems. Our services cover Montreal, Laval, Longueuil, the North Shore, and the South Shore , with one constant goal: to optimize your comfort while reducing your energy costs .

Tips to prevent refrigerant leaks on your Lennox heat pump:

  • Check that the outdoor unit is securely mounted and free from vibrations.

  • Prevent debris from accumulating near the condenser.

  • Have the system pressures tested annually .

  • Never delay reporting an unusual noise or decreased performance .

Conclusion

Thanks to a quick and precise intervention, our AirGreen team gave a second life to this Lennox heat pump in Saint-Constant . The combination of a meticulous diagnosis, a durable repair and a calibrated recharge helped restore the system to full efficiency and occupant comfort.