Repair of a Panasonic heat pump on a flat roof in Ville-Marie (Montreal)

In several residential buildings in downtown Montreal, the outdoor units of wall-mounted heat pumps are installed on flat gravel roofs . This is convenient (less noise on the balcony, unobstructed access), but it also comes with very real challenges: exposure to wind, leaves and debris, temperature variations, UV radiation on the insulation, and sometimes supports that age faster than expected.

Recently, we worked on a project in Ville-Marie where the Panasonic outdoor unit (a wall-mounted inverter heat pump, HZ/Z series – the exact model isn't visible in the photo, but it's consistent with this unit size) was no longer able to maintain a stable indoor temperature. The client described the air conditioning as "inconsistent," with periods when the system seemed to work... then suddenly failing.

Context and visible clues on the installation

The photo shows several typical elements of a rooftop installation:

• Compact outdoor unit (mini-split format), with exposed coil on a large front surface.

• Elevated support placed on pieces of wood (type “sleepers”) to protect the roof membrane and limit vibrations.

• Electrical disconnect switch in the immediate vicinity (service box), essential for safe maintenance.

• Routing of connections (refrigeration piping + cable) along the roof, with insulation exposed to the elements.

This type of configuration is common in condominiums: the indoor (wall-mounted) unit is in the condo, and the outdoor unit is on the roof, sometimes quite far away, which increases the importance of a good installation (slopes, insulation, sealing, lengths, fasteners, etc.).

Reported symptoms: irregular performance and abnormal cycles

In this case, the symptoms were consistent with a problem combining insufficient heat exchange and disrupted operational control :

• Indoor air is less fresh (or heating is less efficient) despite normal demand;

• longer cycles, sometimes “strange” stops;

• Overall performance is down, especially on more demanding days.

On a roof, a simple detail can trigger this type of scenario: a clogged coil , a partial obstruction, or even an electrical component that is worn out due to temperature variations.

AirGreen diagnosis: field method, measurements and validation

At AirGreen, we avoid assumptions. On-site, our diagnosis always follows a logical process:

1. Complete visual inspection

   • condition of the coil (dust, leaves, deposits);

   • traces of corrosion, crushed fins, impacts;

   • stability of the support and unit level;

   • condition of pipe insulation (UV, cracks, humidity).

2. Electrical checks

   • check at the disconnector (tension, tightening, signs of overheating);

   • Wiring and continuity validation;

   • reading codes/states (depending on available access).

3. Functionality and parameter control

   • blowing temperatures inside;

   • start-up/variation behavior (Inverter);

   • pressures and superheating/subcooling (depending on conditions), to confirm whether the problem is more “airflow/exchange” or “refrigerant/control”.

What we found

The most telling aspect of this intervention was the impaired heat exchange at the outdoor unit, caused by a combination of debris (leaves/fine gravel) and restricted airflow through the coil. This often happens on flat roofs: the wind pushes the particles, and the coil gradually becomes blocked.

In parallel, we also noted signs of mechanical stress : slight instability of the support (micro-vibrations) and fasteners that need optimization. Even if it doesn't "break" the system overnight, it accelerates wear and tear (noise, component fatigue, and sometimes erratic behavior).

Repair: technical cleaning, restoration and securing

An effective repair isn't just a quick fix. On a Panasonic Inverter heat pump, a partially blocked coil can cause pressure fluctuations and force the unit to compensate, so it's essential to proceed properly:

1) Professional cleaning of the coil

• debris removal and controlled cleaning of the fins;

• local straightening of the fins if necessary;

• cleaning is appropriate so as not to damage the coating or further bend the coil.

Immediate result: the system regains its ability to reject/absorb heat correctly, which stabilizes the Inverter modulation.

2) Mechanical checks and adjustments

• securing the support and fixings;

• adding/optimizing anti-vibration elements as needed;

• validation of clearance all around the unit (essential for air).

On a roof, a poorly optimized support can transmit vibrations to the structure or cause gradual misalignment. We correct this before it becomes a recurring problem.

3) Electrical control at the disconnect switch

• checking the tightness and cleanliness of the connections;

• validation of power supply and startup behavior.

4) Complete performance test

Once the repairs are completed, we approve:

• stability of cycles;

• temperatures reached inside;

• machine response under load (cooling/heating depending on the season);

• noise/vibrations on the support.

Result: restored comfort and more stable operation

After the repair, the Panasonic heat pump returned to normal operation: more stable modulation, better ability to maintain the setpoint, and above all, more consistent performance. In practice, the customer observed:

• a feeling of comfort "that comes back quickly";

• less variation;

• a system that no longer forces unnecessarily.

In a downtown condo, this also translates into a better home work environment, less discomfort during peak periods, and peace of mind: you know the system is clean, safe, and back in working order.

Best practices (flat roof): what we systematically recommend

For installations like this one in Ville-Marie (and throughout Greater Montreal), our advice is simple and very worthwhile:

• Preventive cleaning of the coil (often once a year, sometimes twice depending on exposure).

• Protection and replacement of insulation exposed to UV radiation (otherwise losses, condensation, accelerated aging).

• Stable and elevated support to protect the roof and limit vibrations.

• Air clearance respected around the unit (unit “glued” = efficiency in drop).

• Pre-winter inspection : in heating, a dirty unit defrosts poorly and loses a lot of performance.

Why choose AirGreen for a Panasonic repair?

Because in practice, a heat pump that “seems to be working” may actually be losing 20 to 40% of its efficiency due to a single detail (coil, airflow, vibrations, insulation, power supply). Our approach aims to:

• diagnose accurately (no random testing);

• correct the cause, not just the symptom;

• Secure the installation to prevent returns.