Installation of a FORESTAIR PTAC under a window in Léry, on Montreal’s South Shore

Thorough commissioning for a PTAC integrated into an existing opening

At Léry, on Montreal's South Shore, we worked on a FORESTAIR PTAC installation built directly beneath a large window. The configuration presented several important considerations: an existing wall opening, significant exposure to outdoor light, an upper area used as a shelf, and a unit whose controls needed to remain easily accessible.

In the photo taken during our service visit, the PTAC control panel is open and the unit is operating in cooling mode. The display shows a setpoint of 71 °F, or approximately 21.7 °C, while an infrared thermometer shows a reading of 17.6 °C in the area being checked in front of the supply grille.

This verification was part of the commissioning process. Our goal was not simply to confirm that the fan was running, but to ensure that the unit responded to the controls, produced perceptible cooling, and distributed the air properly throughout the room.

Why a FORESTAIR PTAC was suitable for this installation in Léry

A PTAC, or packaged terminal air conditioner, combines the main air-conditioning components in a single cabinet. Depending on the exact model, it may also include a heat-pump heating function, an auxiliary electric heating element, or a combination of these technologies.

Unlike a ductless wall-mounted heat pump, a PTAC generally does not require:

• for a separate outdoor unit;
• for exposed refrigerant lines;
• for a pipe cover on the façade;
• for a drain running through several rooms;
• for electrical connections between two separate units.

The unit passes directly through the wall inside a sleeve. Its interior section handles the room air, while its rear section exchanges heat with the outdoors.

At this property in Léry, the location beneath the window made it possible to keep the main walls available for furnishing. This arrangement is common in apartments, residences, hotels, offices, and some multi-unit buildings where each room or dwelling must have independent control.

What the photo reveals about our inspection method

The image shows several significant elements of this HVAC installation.

The control cover is raised, providing direct access to:

• the mode selection;
• the temperature setting;
• the fan speed;
• the automatic functions;
• the operating indicators;
• the settings accessible to the user.

The 71 °F setpoint is a reasonable indoor temperature for checking the unit’s response in cooling mode. The indicator lights show that the selected functions are active.

We also used an infrared thermometer to obtain a quick indication of the temperature near the air outlet. The visible reading of 17.6 °C confirms that an area noticeably cooler than the setpoint was present in front of the grille at the time of the photo.

An infrared reading does not replace a complete diagnosis

An infrared thermometer primarily measures the temperature of a targeted surface. It should not be confused with an air probe inserted directly into the supply airflow.

To assess a PTAC’s performance more precisely, we can compare:

1. the return-air temperature;
2. the supply-air temperature;
3. the actual room temperature;
4. the time elapsed since the compressor started;
5. the fan speed;
6. the humidity level;
7. the stability of the operating cycle.

A single reading is therefore not enough to establish the unit’s actual capacity. However, it remains useful during startup for quickly detecting a lack of cooling, an obstruction, or an obvious malfunction.

An installation directly beneath a large window

The selected location offers a practical advantage, but it also requires several checks.

A window is often an area where heat gains are higher in summer. Solar radiation passes through the glazing, warms the sill, and increases the cooling load in the room. In winter, this same area can become a source of heat loss if the seal is inadequate.

The PTAC must therefore offset part of this heat load without its airflow being blocked.

In this installation in Léry, the supply grille is located directly beneath the window ledge. We must ensure that cool air can move into the room rather than remain trapped beneath the ledge.

Objects placed on the unit can interfere with its operation

A piece of fabric is visible on the upper ledge near the window. Although it does not appear to completely block the grille in the photo, this situation illustrates an important recommendation: no curtain, item of clothing, cushion, or decorative object should be able to fall in front of the air intake or outlet.

A textile pulled against the grille can cause:

• reduced airflow;
• reduced efficiency;
• ice formation on the evaporator;
• increased noise;
• longer cycles;
• premature wear of the ventilation motor;
• poor dehumidification of the room.

We also recommend keeping the front area of the FORESTAIR PTAC completely clear. A sofa, bed, or piece of furniture placed too close can redirect the cold air directly toward the unit and distort the reading from its temperature sensor.

The wall sleeve: the most important component behind the unit

The interior appearance of a PTAC alone cannot determine the quality of the installation. Much of the work is located around the sleeve passing through the wall.

This sleeve must fulfill several functions:

• support the weight of the unit;
• keep the PTAC stable;
• separate indoor air from outdoor air;
• prevent water infiltration;
• promote condensation drainage;
• limit vibrations;
• withstand temperature variations.

In Léry and on the South Shore, wind-driven rain, snow, ice, and freeze-thaw cycles place considerable stress on exterior seals. A small opening around the sleeve can let cold air in even when the PTAC is turned off.

The slope must promote drainage toward the outside

A PTAC produces condensation when it removes moisture from the indoor air. The sleeve must follow the slope specified by the manufacturer so that this water remains directed outside or toward the drainage system designed for the unit.

An inverted slope can cause:

• water accumulation in the sleeve;
• blowing noises produced by the fan;
• odors;
• corrosion;
• marks on the interior wall;
• damage to the flooring;
• deterioration of the materials around the window.

During a PTAC installation or replacement, we never assume that the existing sleeve is suitable simply because the new appliance can be inserted into it.

Replacing an old PTAC does not automatically mean keeping the old sleeve

The exterior dimensions of several PTACs may appear similar, but the units are not necessarily interchangeable.

The differences may involve:

• the cabinet depth;
• the location of the rear openings;
• the type of exterior grille;
• the drainage method;
• the position of the seals;
• condenser airflow;
• the fastening system;
• the sleeve’s load-bearing capacity.

An appliance installed in an incompatible sleeve may recirculate its own hot air at the rear. The compressor then operates under poor conditions, and cooling capacity decreases.

Before proceeding, we therefore check the sleeve model, its condition, slope, fastening, and compatibility with the selected FORESTAIR PTAC.

The technical details that ensure the PTAC’s comfort and reliability

The FORESTAIR brand and appliance type were confirmed for this project. However, the complete model number, nominal BTU capacity, voltage, and efficiency ratings are not visible in the photo.

We avoid assigning a capacity to a PTAC solely based on its appearance. Two units with similar cabinets may offer very different capacities, such as 9,000, 12,000, or 15,000 BTU/h, depending on the product line and configuration.

The nameplate remains the reference for confirming:

• the model number;
• the serial number;
• cooling capacity;
• heating capacity;
• the refrigerant type;
• the voltage;
• the minimum circuit ampacity;
• the maximum permitted protection;
• the power of the electrical element, if applicable;
• applicable certifications.

Sizing must correspond to the room’s actual load

Capacity selection should not be based solely on floor area.

To determine the needs of a room in Léry, we must also consider:

• the size and orientation of the window;
• the quality of the glazing;
• sun exposure;
• wall insulation;
• the ceiling height;
• the number of occupants;
• air infiltration;
• the floor where the room is located;
• the presence of electrical appliances;
• the residential or commercial use of the space.

The large window visible above the PTAC can represent a significant heat load. A room with extensive glazing exposed to the sun may require more cooling than a room of the same size with small, shaded windows.

Consequences of an undersized unit

An undersized PTAC may run almost continuously during hot days. The set temperature becomes difficult to reach, the compressor runs longer, and comfort remains uneven.

Consequences of an oversized unit

An oversized unit can lower the temperature quickly, then shut off before removing enough moisture. The room feels cold near the unit but retains a damp sensation.

Proper sizing promotes more stable cycles, better dehumidification, and a more consistent noise level.

The power supply must match the exact model

PTACs are available in several electrical configurations. Some operate on a power supply different from a conventional household outlet and require a dedicated circuit.

Before commissioning, we check in particular:

• the voltage indicated on the nameplate;
• the plug type;
• the circuit capacity;
• the wiring gauge;
• the protection at the electrical panel;
• the grounding;
• the condition of the outlet;
• the absence of overheating or damage.

We do not use an extension cord, power strip, or improvised adapter to power a PTAC. The current required by the compressor and any heating element may be too high for this type of accessory.

Noise level also depends on the installation

A PTAC contains the compressor in the same unit as the indoor grille. It is therefore generally more audible in the room than a wall-mounted heat pump, whose compressor is installed outside.

However, noise may be worsened by:

• an improperly secured sleeve;
• a vibrating front panel;
• a damaged outdoor grille;
• a dirty fan;
• a clogged filter;
• a cabinet in contact with the structure;
• a loose finishing piece;
• an object placed on top.

During commissioning in Léry, we pay attention to the compressor sound, fan operation, and vibrations transmitted to the wall or windowsill.

Maintaining a FORESTAIR PTAC

The front filter must be cleaned regularly. The frequency varies depending on room use, the presence of pets, dust, and operating time.

A clogged filter reduces airflow and can lead to decreased performance. It can also cause ice to form on the indoor coil.

A more comprehensive HVAC maintenance service may include:

• cleaning the filter;
• inspecting the evaporator;
• cleaning the fan;
• inspecting the outdoor condenser;
• checking the condensate pan;
• clearing the water drainage paths;
• inspecting the sleeve seals;
• checking the outdoor grille;
• testing the controls;
• comparing inlet and outlet temperatures.

We recommend a professional inspection when a PTAC has a water leak, a persistent odor, reduced airflow, unusual noise, or an inability to maintain the requested temperature.

Subsidies and energy eligibility

Eligibility for financial assistance cannot be confirmed based on the unit’s appearance. It depends on the exact model, its certifications, the type of project, the building, and the program criteria in effect at the time of the application.

A PTAC should not be assumed to qualify for the same programs as a cold-climate wall-mounted heat pump. Before recommending a unit based on a subsidy, we always verify its technical specifications and the applicable requirements.

The result of our work in Léry

This installation demonstrates the importance of structured commissioning. The FORESTAIR PTAC responded to the controls, the setpoint was adjusted to 71 °F, and a reading of 17.6 °C was observed in the controlled area near the supply outlet.

Beyond these figures, we paid attention to access to the controls, airflow, the space beneath the window, and conditions that could affect long-term operation.

At AirGreen, we treat a PTAC installation as a true heating, ventilation, and air conditioning project. We inspect the unit, as well as its integration with the building, its electrical supply, drainage, and accessibility for maintenance.

We offer our HVAC services in Léry, Châteauguay, Longueuil, Montréal, Laval, on the North Shore, and throughout the South Shore. Our approach focuses on reliable operation, clean workmanship, and equipment suited to the actual needs of each room.