SENVILLE LETO Mini-Split | 24000 BTU | Montréal, Laval, South Shore

A 24,000 BTU unit that truly makes sense in large open areas, provided you look well beyond the nominal capacity

The SENVILLE LETO 24,000 BTU R454B Mini Split is intended for an entirely different type of project than a small bedroom heat pump. With a nominal capacity of 24,000 BTU/h, an airflow rate approaching 730 CFM, and an indoor unit more than 42 inches wide, this is an appliance designed to move enough air to condition a large living area, an open floor, a loft, a small commercial space, or certain residential spaces that are difficult to cool with a smaller unit.

For our wall-mounted heat pump installations in Montreal, Laval, Longueuil, the South Shore, the North Shore, and Montérégie, we nevertheless emphasize one point: buying a 24,000 BTU unit because a space “seems large” is not a sizing method. This model can be highly effective when installed in the right building, but it can also be oversized in a better-insulated property or in an area where air circulation is restricted by several partitions.

The model pairing in question is specific:

• Outdoor unit: SENL-24CD-OL
• Indoor unit: SENL-24CD-ILL
• AHRI reference: 215735291
• Refrigerant: R454B
• Power supply: 208/230 V
• Nominal capacity: 24,000 BTU/h

The current AHRI certificate confirms that this combination is active, is sold in Canada, and lists a nominal cooling capacity of 24,000 BTU/h, an SEER2 of 18.7, an EER2 of 10.0, a nominal heating capacity of 24,000 BTU/h, and an HSPF2 of 9.3 for Region IV.

The technical specifications that truly define the 24,000 BTU LETO

Senville’s official brochure presents the SENL-24CD as a mini-split air conditioner with heat pump, rated at 24,000 BTU, offering a seasonal efficiency rating of 18.7 SEER2 and a heating capacity advertised down to approximately -15 °C.

The technical sheet on page 4 provides especially useful information: the system does not operate constantly at 24,000 BTU. Its Inverter technology allows it to modulate its capacity across a wide range.

In air conditioning:

• nominal capacity: 24,000 BTU/h;
• modulation range: 5,500 to 24,200 BTU/h;
• listed power consumption: 480 to 2,590 W;
• published operating current: 2.1 to 11.3 A.

In heating mode:

• nominal capacity: 24,000 BTU/h;
• modulation range: 6,300 to 27,000 BTU/h;
• listed power consumption: 410 to 2,690 W;
• published current: 2.2 to 11.8 A;
• Manufacturer-stated nominal COP: 3,31.

This modulation range matters greatly in a real HVAC installation. When a large room needs only a fraction of the maximum capacity, the compressor can slow down rather than continually cycling on and off. This promotes a more stable temperature and better energy management.

18.7 SEER2: solid efficiency, but it must be interpreted correctly

An SEER2 of 18.7 represents good efficiency for a 24,000 BTU mini-split in this category.

However, this does not mean that a homeowner will automatically achieve a specific percentage of savings on their Hydro-Québec bill. Senville states that its DC inverter technology can reduce consumption by up to 48% in certain comparison scenarios, but this figure necessarily depends on the system being replaced and the operating conditions. The brochure describes this technology as automatically modulating power according to demand.

At AirGreen, we prefer to explain the mechanism rather than promise universal savings.

An inverter compressor can reduce its speed as the temperature approaches the setpoint. In a properly insulated home in Boucherville, for example, the system can operate for much of a summer day without reaching its maximum capacity.

In an older house in Montreal with several large south-facing windows, the same heat pump might have to work much harder.

The unit’s efficiency is therefore important, but you must also consider:

• insulation;
• the building’s airtightness;
• solar exposure;
• the window area;
• the ceiling height;
• the layout of the rooms;
• the number of occupants;
• the actual heat load;
• the requested temperature.

What maximum area can a 24,000 BTU unit serve?

The Senville brochure presents this model as suitable for approximately 1,000 to 1,250 sq. ft.

This statement warrants an important nuance.

A wall-mounted unit does not distribute air like a central system equipped with ductwork. Even if the cooling capacity is sufficient for 1,200 sq. ft., the cool or warm air must physically reach the different zones.

We can therefore have two very different situations.

Example 1: Open-concept area on the South Shore

A 1,050 sq. ft. open-concept ground floor with a kitchen, dining room, and living room may be suitable for a 24,000 BTU unit if the load calculation confirms it. The indoor unit can project air over a long distance and effectively condition a large volume.

Example 2: Partitioned floor in Montreal

A 1,000 sq. ft. floor comprising four closed bedrooms and a long corridor may be much less suitable for a single wall-mounted unit. Even with 24,000 BTU available, air cannot pass through doors and walls.

This is an error we strive to avoid at AirGreen: increasing the BTU capacity does not solve an air distribution problem.

Still-solid heating capacity at -8 °C and -15 °C

This is one of the most interesting features of the SENL-24CD-OL / SENL-24CD-ILL.

The certification data associated with this pairing indicate:

• 24,000 BTU/h at approximately 8 °C;
• 20,800 BTU/h at approximately -8 °C;
• 17,000 BTU/h at approximately -15 °C;
• COP of 2.14 at approximately -15 °C.

In other words, at -15 °C, the unit retains approximately 71% of its rated heating capacity. The ENERGY STAR data currently published for this pairing also lists it as an ENERGY STAR certified cold-climate model.

This latter figure should be distinguished from the commercial brochure, which only advertises heating down to -15 °C. The certification applies to the specific pairing SENL-24CD-OL + SENL-24CD-ILL, not simply to the name “LETO”.

For homeowners in Greater Montreal, this means that this model can provide a significant amount of heating during a good part of the winter.

However, we do not position it in the same way as a heat pump whose manufacturer explicitly advertises operation down to -25 °C or -30 °C. In a property that relies heavily on the heat pump as its primary heating source, we always verify the building’s balance point and whether supplemental heating is available.

The $2,496 LogisVert rebate: how the calculation works

The capacity at -8 °C is particularly important in Quebec because Hydro-Québec uses this data to calculate the Heat Pump measure of its LogisVert program.

For an ENERGY STAR-certified cold-climate heat pump, Hydro-Québec currently offers $120 per 1,000 BTU/h at -8 °C when all program conditions are met.

The certified capacity of the Senville LETO in question is 20,800 BTU/h at -8 °C.

The calculation is therefore:

20.8 × $120 = $2,496

This explains the amount of 2 496 $ indicated for this unit.

For some eligible multi-unit residential buildings, the situation can become even more attractive. Since June 15, 2026, a bonus may increase the assistance to $220 per 1,000 BTU/h at -8 °C when an ENERGY STAR – Cold Climate wall-mounted heat pump is installed in a building meeting Hydro-Québec’s specific criteria.

At 20,800 BTU/h, this would theoretically represent:

20.8 × $220 = $4,576

This amount applies only if all conditions of the multi-unit residential building component are met. At AirGreen, we always verify the exact model, address, building type, and program criteria before presenting financial assistance as guaranteed.

What we look at on site before installing a 24,000-BTU LETO

Airflow completely changes the unit’s behavior

The Senville LETO 24,000 BTU can provide an indoor airflow of approximately:

• 329.6 CFM at low speed;
• 400.2 CFM;
• 529.7 CFM;
• up to 729.9 CFM in Turbo mode.

Sound level naturally follows airflow: approximately 27 dB(A) at low speed, then 41.5, 45, and up to 54 dB(A) in Turbo mode.

The 27 dB(A) figure is particularly interesting during moderate operation. But in a large room that constantly forces the unit to operate in Turbo mode, the acoustic experience will obviously not be the same.

This is another reason to size the heat pump properly.

An indoor unit significantly larger than a 9,000- or 12,000-BTU unit

The indoor unit measures approximately:

42.52 in. × 8.90 in. × 13.19 in.

and weighs approximately 30.64 lb.

The outdoor condenser measures approximately:

35.04 in. × 13.46 in. × 26.50 in.

for a weight of approximately 94.58 lb.

These dimensions directly affect our site preparation.

In some Montréal duplexes, the available wall space between a window and a door simply does not allow an indoor unit larger than 42 in. to be installed properly while maintaining the necessary clearances.

On the South Shore or in Laval, the outdoor unit may also need to be positioned between a window, a fence, and a side passage. We must then maintain sufficient clearance around the heat exchanger and preserve future access for servicing.

3/8 in – 5/8 in piping: an essential detail when replacing a system

The SENL-24CD-ILL uses 3/8 in piping for the liquid line and 5/8 in for the suction line. Senville confirms this combination for its 24,000 BTU units.

This is particularly important when replacing an older mini-split.

We regularly meet customers who wish to keep the existing piping because it runs through a finished ceiling, a renovated basement, or a difficult-to-access façade.

The answer cannot be determined solely by looking at the length.

We check:

• the actual diameter of both lines;
• their condition;
• compatibility with the new refrigerant;
• the absence of contamination;
• the quality of the insulation;
• the route;
• the connections;
• the total length.

An older line set of 1/4 in × 1/2 in, for example, is not equivalent to the 3/8 in × 5/8 in piping specified for this 24,000 BTU unit.

25 ft precharge: beware of long installations

The system is precharged with R454B for a length of up to 25 ft. The brochure specifies that an installation with a 50 ft kit requires additional refrigerant to be added on site by the installer.

Senville also confirms that single-zone systems are precharged for 25 ft and that adding refrigerant becomes necessary when the total length exceeds the specified charge.

This is a detail we take very seriously at AirGreen.

An installation where the outdoor unit is placed on a rear balcony while the indoor unit is located on the opposite façade can quickly exceed a short standard line length. The charge adjustment must then be calculated and carried out correctly.

R454B: a new generation of refrigerant

This version uses R454B rather than the R410A used in older generations of LETO. The brochure and manufacturer confirm this refrigerant for the current SENL-24CD-L.

This distinction is important when comparing products online.

Older Senville LETO 24,000 BTU product sheets can still be found online stating:

• R410A;
• approximately 15 SEER;
• older dimensions;
• older model numbers;
• different warranty;
• Optional Wi-Fi.

This information concerns previous generations and must not be confused with the SENL-24CD-OL / SENL-24CD-ILL R454B pairing.

For us, the exact model number is always more reliable than the simple series name.

Electrical supply: a circuit to be verified before the installation date

The brochure specifies a 208/230 V single-phase, 60 Hz power supply, with:

• voltage range: 187 to 253 V;
• MCA: 19 A;
• maximum protection: 20 A;
• indicated interconnection wiring: 14/4 AWG.

The fact that a 24,000 BTU unit can operate with maximum 20 A protection is useful for electrical planning, but we never consider these few figures authorization to automatically reuse an existing circuit.

The panel, wiring, run length, and applicable requirements must be verified for each installation.

Wi-Fi and Alexa: convenient for a large living area or commercial space

The LETO is compatible with Alexa, and its smart control allows users to adjust the temperature, create routines, and manage the system remotely. The brochure explicitly indicates this integration.

In a small commercial space or a secondary residence, this feature becomes especially useful.

For example, a homeowner can adjust the setpoint before arriving or check the system’s operation without being physically in front of the remote control.

An AirGreen project in Montreal that clearly illustrates the choice of location

We have already completed a Senville LETO installation in Montreal in which our team paid particular attention to the positioning of the condenser and indoor unit.

The condenser had been mounted on a bracket to limit vibrations and maintain sufficient clearance around the heat exchanger. The indoor unit had been positioned to distribute air toward the central part of the living space rather than toward a nearby wall.

Although this documented project involved another capacity in the LETO range, the lesson applies directly to the 24,000 BTU model: the greater the airflow, the more the unit’s orientation matters.

We have also worked with LETO units in apartments in Rosemont–La Petite-Patrie, where the challenge was not only capacity, but also the available space and the need to maintain a discreet installation in a Montreal plex.

Errors we seek to avoid with a 24,000 BTU unit

Choosing 24,000 BTU simply because “bigger heats better”

An oversized heat pump can quickly reach the requested temperature and then reduce or stop operating too often. In cooling mode, this can also impair humidity control.

Installing the indoor unit in an enclosed hallway

A high capacity cannot make up for poor placement. The airflow must reach the areas that need heating or cooling directly.

Neglecting pipe size

The 24,000 BTU LETO requires 3/8 in × 5/8 in piping. An existing line of another size does not become compatible simply because it is already installed in the wall.

Confusing the older and newer LETO generations

R410A, R454B, 15 SEER, 18.7 SEER2, older warranties: several versions are still circulating online. We always verify SENL-24CD-OL + SENL-24CD-ILL.

Placing the condenser too low

In the Montreal region, snow and ice must be taken into account from the design stage. A condenser surrounded by snow in mid-January no longer has the airflow conditions specified by the manufacturer.

Warranty: clearly distinguish the manufacturer’s documentation from the protection offered to the customer

The current Senville brochure indicates a 5-year manufacturer’s warranty on the compressor and 5 years on parts. This same coverage appears on the manufacturer’s current page.

The AirGreen product information sheet provided for this product, for its part, mentions coverage 10-10-0 with the possibility of additional warranty coverage. It is therefore important that the final quotation clearly specify which protection applies to the project: the basic manufacturer’s warranty, a promotional program, distributor protection, or additional AirGreen coverage.

For the customer, the contractual document provided with the installation remains the reference document to keep with the serial numbers and invoice.

LETO 24,000 BTU maintenance: airflow must remain unobstructed

A unit capable of moving nearly 730 CFM must have clean coils and filters.

We particularly recommend:

1. to clean the filters regularly;
2. to monitor dust buildup on the evaporator;
3. to keep the outdoor condenser clear of leaves, snow, and vegetation;
4. to verify that the drain is properly removing water;
5. to have the system inspected if its capacity appears to be declining;
6. to schedule a deep cleaning of the wall-mounted heat pump when the indoor coil becomes visibly dirty.

A dirty filter does not only reduce airflow. It can also alter the system’s internal operating temperatures and reduce the heat pump’s actual capacity.

Which customer do we primarily recommend this model for?

The 24,000 BTU SENVILLE LETO is particularly well suited to a homeowner looking for:

• high cooling capacity;
• a relatively open area;
• an Inverter unit;
• an efficiency rating of 18.7 SEER2;
• significant heating capacity down to approximately -15 °C;
• a system R454B;
• Wi-Fi/Alexa compatibility;
• a heat pump eligible for LogisVert assistance when the program conditions are met;
• a generally more accessible budget than a high-end unit designed to provide heating down to -30 °C.

For a property where the main goal is to replace nearly all electric baseboards, even during extreme cold, we can also compare the LETO with wall-mounted heat pump models designed for lower outdoor temperatures.

Why have this Senville installed by AirGreen?

At AirGreen, our work goes beyond simply supplying the SENVILLE LETO 24,000 BTU.

We check the required capacity, unit placement, air distribution, electrical circuit, and piping 3/8 – 5/8, drainage, the total length of the refrigerant line, the R454B charge, and service clearances.

We install wall-mounted heat pumps throughout Greater Montreal, Montreal, Laval, Longueuil, Boucherville, the South Shore, the North Shore, and Montérégie, where buildings vary enormously: century-old plexes, newer condos, single-family homes, businesses, apartments, and complete renovations.

It is precisely this diversity that has taught us that choosing the right heat pump never depends on a single value in a table.

Request a quote for your 24,000 BTU SENVILLE LETO

Are you considering the SENVILLE LETO 24,000 BTU R454B Mini Split for a house, condo, plex, or commercial space in Montreal, Laval, Longueuil, the South Shore, or the North Shore?

Contact AirGreen for a quote. We can confirm sizing, check your electrical installation and piping, plan the location of the units, and verify the LogisVert financial assistance applicable to your project.