A precise sheet-metal adaptation to preserve airflow in a particularly challenging space
At Saint-Théodore-d’Acton, we completed an installation of a FRIEDRICH ZoneAire® Premier PTAC distinguished by an immediately visible constraint: the unit’s upper air outlet was located beneath a long structure running along the wall. Installing the PTAC without modifying the air distribution would have directed a significant portion of the conditioned air toward this surface rather than into the room.
The solution therefore did not simply consist of inserting the unit into an existing wall opening. We incorporated a custom-fabricated supply plenum, positioned directly above the PTAC. This metal box captures the air at the unit’s outlet and redirects it toward an unobstructed front grille.
This adaptation allows air to be directed into the room while keeping the unit in its original location, near the floor. It also avoids a much more invasive modification to the wall, built-in furniture, and installations surrounding the system.
The photograph shows several important features of this project:
- a unit installed at a low height on an existing base;
- a hardwood floor that had to be protected from condensate;
- a long white enclosure located behind and to the right of the PTAC;
- an electric baseboard heater nearby;
- limited clearance for movement due to the carpet and furniture;
- a metal air-distribution box mounted above the unit;
- a horizontal grille directing the airflow toward the center of the room.
In this type of project, a few inches can determine whether the installation works properly. We must preserve airflow, access to the filters, possible chassis removal, and the ability to perform HVAC maintenance without dismantling the entire structure.
Why the original air outlet could not be left as it was
A PTAC generally draws room air through its large front grille, then discharges conditioned or heated air through an opening located on top. This configuration works very well when the upper outlet is completely unobstructed.
In Saint-Théodore-d’Acton, the room’s geometry complicated this airflow. The horizontal structure running along the wall was located directly in the natural path of the supply air. Without an adaptation, several problems could have arisen:
- immediate return of treated air to the front return;
- heat buildup around the unit;
- uneven cooling or heating of the room;
- increased airflow noise;
- extended compressor operation;
- inaccurate temperature readings around the PTAC;
- discomfort in areas far from the unit.
We therefore designed the enclosure to extend the air outlet and move the distribution point forward. The grille visible on the front of the plenum has horizontal louvers that promote more even distribution throughout the room.
A plenum that would add as little resistance as possible
A sheet-metal adaptation should not be merely aesthetic. Its interior shape must limit abrupt changes in direction and constrictions.
A duct that was too narrow would have increased the static pressure experienced by the fan. An angle that was too sharp would have created turbulence and noticeable whistling. A misaligned plenum would have allowed some of the air to escape behind the enclosure.
We therefore paid particular attention to several elements:
- the width of the PTAC outlet;
- the available height beneath the existing structure;
- the free area of the supply grille;
- the continuity between the unit and the plenum;
- the tightness of the metal joints;
- the possibility of removing the front panel;
- the mechanical stability of the enclosure.
The visible result in the photo is a compact assembly that follows the line of the wall. The plenum does not extend in front of the PTAC’s large return grille and does not block the main access to the unit.
FRIEDRICH ZoneAire Premier: a range available in several capacities
The name ZoneAire® Premier refers to a family of PTAC units, not a single capacity. According to current FRIEDRICH documentation, this range is available in electric-heating and heat-pump versions, with nominal capacities covering approximately the 7,000 to 15,000 BTU/h category.
The nameplate of the photographed unit is not legible. We therefore cannot honestly assign this installation an exact capacity of 9,000, 12,000, or 15,000 BTU/h. The complete model number must be recorded directly from the chassis label.
This verification confirms:
- actual cooling capacity;
- the presence of a heat pump or electric heating only;
- voltage;
- heating element capacity;
- circuit amperage;
- refrigerant type;
- energy performance;
- compatibility with the existing sleeve.
Technical reference points for the current range
In the current documentation for ZoneAire Premier models using R-32, the published cooling capacities range approximately from 7,200 to 14,800 BTU/h, depending on the model and voltage. The listed EER values range from approximately 10.4 to 13.3. For heat pump versions, the published heating capacities range approximately from 5,800 to 13,800 BTU/h, with COPs reaching approximately 3.6 for certain lower capacities.
These figures help illustrate the scope of the range, but they should not be automatically applied to the unit in Saint-Théodore-d’Acton. A product's exterior design may remain similar for several generations, while the refrigerant, controls, and performance change.
The current range notably includes electric models identified by the PDE prefix and heat pump models identified by the PDH prefix. The manufacturer's documentation also distinguishes between 208/230-volt and 265-volt versions.
A standard format that does not eliminate the need for verification
Current models are designed around a sleeve 42 inches wide and 16 inches high, with a published sleeve depth of 13 3/4 inches. With the front installed, the stated total depth reaches approximately 21 1/2 inches.
This widely used format facilitates certain PTAC replacements, but a similar dimension never guarantees complete compatibility.
During our inspection, we must also consider:
- the actual wall depth;
- the condition of the sleeve;
- the location of the exterior grille;
- the outward slope;
- the mounting points;
- condenser ventilation;
- condensate drainage;
- the available space behind the front panel;
- the position of the electrical outlet.
In this project, the presence of the plenum added an additional constraint. The PTAC had to be able to slide in and out of its sleeve without destroying all the wall finish. We therefore arranged the adaptation to preserve reasonable mechanical access.
The front return grille had to remain completely unobstructed
The large louvered section on the lower front is the main air-return area. It must not be obstructed by the rug, furniture, or a decorative panel.
In the photograph, the rug stops at a sufficient distance from the PTAC. This detail is important because a thick floor covering placed too close could hinder the panel’s opening or cause dust to accumulate in front of the filters.
We recommend keeping a clear area in front of the unit and avoiding placing the following there:
- a sofa;
- an armchair;
- a coffee table;
- boxes;
- heavy curtains;
- a basket;
- a storage cabinet.
The fan must be able to draw in the necessary volume of air before passing it over the coil. An obstructed return often leads to reduced capacity, increased noise, and faster filter fouling.
Flooring protection and condensate management
The visible wood flooring beneath the PTAC made water management particularly important. A slow leak can go unnoticed for several weeks before causing discoloration, swelling of the flooring, or a damp smell.
In particular, we check:
- the sleeve’s slope toward the exterior;
- the condition of the metal bottom;
- the absence of perforating corrosion;
- the free flow of water;
- the joints around the opening;
- the exterior wall’s watertightness;
- the absence of condensation on cold surfaces.
Current ZoneAire Premier units use a condensate management system that can spray water onto the outdoor coil to improve heat exchange, then drain the excess. The manufacturer also offers drainage accessories for certain configurations.
An incorrect slope or a deformed sleeve can direct this water back indoors. That is why we check the chassis position before commissioning, even when the opening has existed for several years.
Coordination with the electric baseboard and visible wiring
An electric baseboard heater is visible near the floor on the left side of the installation. Its proximity required careful cable routing to prevent a wire from being placed against a heated surface or in an area where it could be damaged.
A PTAC can be equipped with an electric heating element rated at several kilowatts. In the current documentation for the product line, FRIEDRICH specifies different cord and circuit configurations of 15, 20, or 30 amps, depending on the voltage and heating capacity.
Before making any connection, we therefore check:
- voltage indicated on the nameplate;
- circuit capacity;
- circuit breaker;
- outlet configuration;
- condition of the cord;
- grounding;
- compatibility between the power cord and the heating element.
It is not enough for the plug to fit the outlet. An older installation may have been modified, and two PTACs of identical dimensions may require different power supplies.
Commissioning adapted to the custom plenum
After installation, we could not limit ourselves to confirming that the unit started. Its operation had to be evaluated with the redirection cabinet in place.
We paid attention to the following elements:
- airflow at the plenum grille;
- absence of leaks between the PTAC and the cabinet;
- noise at the metal joints;
- plenum vibration;
- supply air uniformity;
- fan operation;
- control response;
- cooling output;
- heating operation, depending on the version;
- drainage;
- front panel stability.
We also checked that the cabinet did not create resonance. A large sheet-metal surface with insufficient reinforcement can amplify fan noise or vibrate when the compressor starts. The fasteners must support the plenum without unnecessarily transmitting vibrations to the wall.
This project in Saint-Théodore-d’Acton shows why a PTAC requires genuine HVAC expertise
The main mistakes to avoid when adapting a supply air outlet
Build a cabinet that is too narrow
Reducing the passage area can create a compact finish, but it can also severely restrict airflow. The fan then operates under conditions different from those for which it was designed.
Direct the air toward the return
When the supply grille is too close to the façade, the conditioned air can immediately return to the unit. The temperature measured near the PTAC then no longer represents the room temperature.
Secure the plenum permanently to the chassis
The PTAC must remain removable for cleaning, repair, or replacement. An adaptation that traps the unit turns every service call into demolition work.
Neglecting vibrations
Metal can produce intermittent noises that are difficult to reproduce during a short visit. The connections, supports, and panels must be sufficiently rigid.
Blocking the control panel
Depending on the ZoneAire Premier version, the controls may be integrated into the top of the unit. The adaptation must preserve access to them or provide for a compatible wall thermostat.
Ignoring the heat from the nearby baseboard heater
A heat source that is too close can affect a sensor's reading, damage a cable, or create an artificially high-temperature zone.
BTU capacity: why floor area is not enough
The capacity must be matched to the room's actual load. To select a PTAC, we consider, among other things:
- floor area;
- ceiling height;
- the number and size of windows;
- solar orientation;
- insulation;
- air infiltration;
- the room's use;
- the number of occupants;
- the electrical appliances present;
- the desired temperature;
- the presence of supplemental heating.
An oversized unit may run very short cycles and remove humidity less effectively. An undersized model may run continuously on the hottest days without reaching the setpoint.
In an installation with a plenum, we must also ensure that the adaptation does not reduce the capacity actually delivered to the room.
LogisVert grant: the product line name is not enough
A heat pump version of the FRIEDRICH ZoneAire Premier should not automatically be presented as eligible for financial assistance. Hydro-Québec requires searching for the equipment using the ENERGY STAR model number or AHRI number and specifies that the official list of eligible heat pumps takes precedence. The application should normally be submitted within nine months of installation.
The LogisVert incentive for multifamily buildings applies specifically to cold-climate wall-mounted heat pumps when all conditions are met. A PTAC should therefore not be confused with a qualifying wall-mounted ductless air conditioner covered by this particular incentive.
Before quoting an amount, we need several pieces of information:
- full model number;
- AHRI number, when available;
- installation date;
- building category;
- applicable certification;
- LogisVert list corresponding to the date of the work.
This check prevents a purchasing decision from being based on an uncertain subsidy.
Recommended maintenance for this configuration
The custom plenum does not replace the unit’s regular maintenance. It even adds an area that must be inspected to ensure that significant dust does not accumulate in the transition.
We recommend:
- inspect the filters monthly during periods of intensive use;
- clean the return grille;
- dust the plenum grille;
- watch for any new metallic noise;
- keep the carpet and furniture at a distance;
- check that there is no water on the hardwood floor;
- do not place liquid on the cabinet;
- have the sleeve and exterior grille inspected periodically.
Current FRIEDRICH documentation indicates that ZoneAire Premier units have washable filters accessible from the front and diagnostic functions on models with digital controls.
A result adapted to the building rather than a forced standard installation
This installation in Saint-Théodore-d’Acton illustrates how we approach less conventional projects. The existing space, horizontal structure, electric baseboard heater, hardwood flooring, and furniture required a solution adapted to the room.
The FRIEDRICH ZoneAire® Premier PTAC was integrated with a supply-air plenum that performs three essential functions:
- draw in air from the top outlet of the unit;
- bypass the obstruction created by the existing structure;
- direct the conditioned air toward the occupied space.
This adaptation makes it possible to maintain a compact solution without a central duct network while improving air distribution throughout the room. It also demonstrates the importance of combining expertise in air conditioning, heating, electrical work, sealing, and sheet metal work when installing a PTAC.
At AirGreen, we carry out HVAC installation, replacement, and HVAC maintenance projects in Montreal, Laval, Longueuil, the North Shore, the South Shore, and several surrounding municipalities. When a standard installation is not suitable for the building’s architecture, we assess airflow, technical access, and site constraints before fabricating a customized solution.