Installation of a GREE FreeMatch R32 multi-zone wall-mounted heat pump with 4 heads in Calixa-Lavallée (Marguerite-D'Youville RCM, Montérégie)

Four heads, one compressor: the thing quotes never explain

A 4-head multi-zone system is easy to sell. Four rooms, four remote controls, four temperatures. This is how most quotes present it, and this is what the client understands.

The physical reality is different, and it deserves to be explained before the work rather than during the first winter: the four heads share a single compressor, a single refrigeration circuit, and a single reversing valve. This constraint determines the sizing, the system's behaviour under simultaneous demand, whether or not one room can be heated while another is being cooled, and even the subsidy code the client may be able to use.

Here is how we approached this installation in Calixa-Lavallée, and what we explained to the homeowner before drilling the first wall.

Calixa-Lavallée: 500 residents, no duct network, no natural gas

Calixa-Lavallée is the smallest municipality in the Marguerite-D'Youville RCM, in Montérégie, between Verchères and Contrecoeur. About five hundred people, a predominantly agricultural territory, a modest village core, and a name borrowed from the composer of the national anthem.

For an HVAC contractor, this rural profile creates very consistent conditions:

• No natural gas network. Heating is electric, oil-fired, or wood-burning.
• Few homes equipped with a duct network. Homes heated with electric baseboards have never had ductwork, and installing it afterward often costs more than the equipment itself.
• Very different needs from one room to another. A country home with a large south-facing open area, two upstairs bedrooms, and an office added in a former sunroom cannot be heated with a single setpoint.
• Distances. The condenser is not always installed three metres from the living room.

This is the natural setting for multi-zone systems. Not because they are trendy, but because the central solution would require ductwork that does not exist.

Selected equipment: GREE FreeMatch R32, GWHD(36)ND6MO condenser

We selected the GWHD(36)ND6MO condenser, which supports 2 to 4 indoor units. This is the exact configuration for the project: four heads, with no room for any future additions. This point was discussed with the client because it is not insignificant.

Installed condenser specification sheet

The rule no one explains: head capacities do not add up

This is the core of sizing a multi-zone system, and this is where customer satisfaction and the contractor's reputation are determined.

The combination ratio

On a 4-head system, the sum of the indoor units' nominal capacities almost always exceeds the condenser's capacity. Four heads rated at 9,000, 9,000, 12,000, and 12,000 BTU/h total 42,000 nominal BTU/h on a condenser certified at 36,000 BTU/h, or approximately 117 %.

This is not a design error: it is the design. It relies on load diversity—the four rooms never reach their peak at the same time. A north-facing bedroom reaches its maximum demand at five in the morning in January; the south-facing living room reaches its own at three in the afternoon in July. The condenser modulates between 8,870 and 40,900 BTU/h in cooling and between 8,870 and 51,180 BTU/h in heating to follow the actual total, not the theoretical total.

This limitation must be clearly explained to the customer: at maximum simultaneous demand, each head receives less than its nominal capacity. On the coldest morning of the year, with four heads calling for heat, the distribution is proportional, and no room receives its full heating output. A combination ratio chosen without calculating the load for each room produces exactly this situation, and the customer concludes—in error—that the unit is defective.

The modulation floor: the trap of an undersized head

The other end of the range is just as important and much less well known. The condenser does not go below 8,870 BTU/h. That is its floor, regardless of the number of heads operating.

Direct consequence: if a single 9,000 BTU/h head operates alone one evening in October, the system is already at its minimum. It cannot modulate any lower. It reaches the setpoint, stops, and restarts—this is short cycling, with the resulting discomfort, compressor wear, and actual efficiency below the displayed SEER2.

We derive two design rules from this:

1. Never connect a single small head to a large condenser hoping to add more later. The system will operate poorly throughout the interim period.
2. Group zones that call for the same mode. Two upstairs bedrooms facing the same direction behave as a single load and keep the compressor above its minimum operating level.

One mode at a time: heating OR cooling

This is the most misunderstood feature of all multi-zone systems of this type. The four heads share a single refrigeration circuit with one reversing valve. The unit can therefore heat all four rooms or cool all four rooms. It cannot do both at the same time.

In practice, the first head to call determines the mode; a head requesting the opposite mode goes into standby or fan-only operation. In Calixa-Lavallée, as everywhere in Quebec, the critical period is the shoulder season: late April and early October, when a south-facing room with large windows overheats while a north-facing bedroom remains cool.

We discussed this with the client before signing, and this is the kind of conversation that distinguishes a properly designed HVAC installation from equipment sold by tonnage. Possible strategies:

• Group zones by orientation and use, so contradictory demands are rare.
• Accept the constraint with full awareness, which is the case in the vast majority of homes.
• Physically separate a room with very different thermal behavior—a computer-equipped office or a glass-enclosed sunroom—on an independent system when the budget and intended use justify it.

One useful detail here: the cooling range extends down to an outdoor temperature of -30 °C. This is not a typo. A room with high internal heat gains—a home office, a home server room, or a room next to a wood stove—can be cooled in the middle of winter, which most systems refuse to do below 0 °C.

A single electrical circuit for the entire system

One feature of the FreeMatch R32 concretely changes the cost of the work: the indoor units are powered by the outdoor unit. There is no dedicated circuit or outlet to install in each room.

The electrical summary is therefore:

• One circuit to the condenser, sized according to MCA 30 A and protected according to MOCP 45 A.
• One interconnection cable to each indoor unit, routed with the refrigerant piping and condensate drain in the same conduit.

In an older house in Calixa-Lavallée—with lath-and-plaster walls, no vertical service cavities, and an electrical panel often already heavily loaded by baseboard heating—this design avoids four electrical penetrations and four panel circuits. It is a technical argument, but also a building-preservation argument.

The piping: where the real cost of a four-indoor-unit system lies

The condenser is factory-charged for 40 metres of total piping, across all circuits. The maximum total length is 80 metres, with a maximum elevation difference of 25 metres. Beyond the 40 metres included in the factory charge, 20 grams of R32 per additional metre must be added.

On a four-indoor-unit system, this calculation is not merely theoretical. Let us take a realistic layout for a two-storey country house:

The total of 58 m remains below the 80 m limit but exceeds the 40 m factory charge by 18 m. The additional charge is therefore 18 × 20 g = 360 g, bringing the system charge to approximately 3,060 g of R32.

Three consequences that we document systematically:

1. The additional charge must be weighed, not estimated from pressure readings. An electronic scale, a written record, and a signature.
2. The actual length of each branch must be measured, not inferred from a plan. Routing around joists and columns can easily add two or three metres per branch.
3. The total charge, not that of a single indoor unit, governs the A2L requirements. We will get to that.

R32, A2L classification, and minimum room area: what changes with a multi-zone system

R32 is classified as A2L, mildly flammable, and the FreeMatch range comes standard with a refrigerant leak detection sensor. So far, there is nothing different from a standard wall-mounted air conditioner.

The difference is in the numbers. A 9,000 BTU/h single-zone mini-split contains a few hundred grams. This system contains more than three kilograms, and all that refrigerant circulates through a single circuit. If a leak occurs at one indoor unit, it is not the fraction assigned to that unit that can be released there: it is the circuit's full charge.

This distinction governs the minimum room area required by the applicable standard for each head. A small 8 m² bedroom poses no problem on a single-split system; on a high-load multi-zone system, it requires an explicit check against the installation manual's table and sometimes choosing a different location for the head or a different type of indoor unit.

We perform this calculation during the design stage, not at the time of installation. An entirely installed system whose head is located in a room that is too small cannot be corrected with a screwdriver.

The wall-mounted head: what the photo shows and what it implies

The visible wall-mounted unit is a GREE head installed high on a light-coloured wall in a finished room.

The display shows 74: a settings issue, not a malfunction

The digital display shows 74, meaning a setpoint in degrees Fahrenheit—approximately 23.3 °C. Units leave the factory with the imperial display, and many Quebec customers spend weeks reading a value that means nothing to them.

The switch to degrees Celsius is made using the remote control. We set it systematically during commissioning and show the customer how to do it, because an occupant who does not understand the display on their unit eventually adjusts it by trial and error—that is, incorrectly.

In the same conversation, we explain the remote control's remote sensor function, often called I Feel: the setpoint is then measured at the height of the remote control rather than at the head, two metres below the ceiling. In a room with a high ceiling, the difference between the two readings can easily reach two degrees.

Ceiling clearance and wall position

The head is installed near the ceiling, as it should be, but the clearance above the casing is not merely an aesthetic detail: it determines the return-air intake. A head pressed beneath molding or wedged under a poorly assessed cathedral ceiling recirculates its own discharged air and loses a measurable portion of its capacity.

We apply three positioning criteria, in this order:

1. The return-air clearance above and on the sides, as specified in the manual.
2. The path of the air jet, which must not sweep across a nearby side wall or blow directly onto a seated person.
3. The condensate drain outlet with a continuous slope, which very often determines which side of the wall the head can be installed on.

Wall marks: a real, predictable, and avoidable problem

Marks can be seen on the wall beneath the head. This phenomenon is known and has nothing to do with a leak: the air jet carries suspended dust along the surface, and the deposits settle in the turbulence zones beneath and beside the unit.

The aggravating factors are identifiable: a dirty filter, a head installed too close to a perpendicular wall, louvers fixed in a downward position, and above all, a lack of regular HVAC maintenance. Cleaning the filters every four to eight weeks during the operating season resolves most of the problem. We leave this instruction in writing and show the customer how to remove the filters before leaving the job site.

The most costly design mistakes on a four-head multi-zone system

We are regularly called in as a second option for multi-zone systems installed elsewhere, in Montreal, Laval, Longueuil, on the North Shore, and on the South Shore. The same mistakes keep recurring, and almost all of them are made before the first hole is drilled.

• No room-by-room load calculation. The heads are selected based on floor area, which consistently results in oversized bedrooms and undersized open areas.
• An excessive combination ratio, promising the customer performance the condenser cannot deliver under simultaneous demand.
• A single small head on a large condenser, with short cycling guaranteed outside peak season.
• The single-mode constraint never explained, resulting in a service call in October and a customer convinced they were misled.
• The total piping length not added up. On a four-head system, it is easy to exceed the 40 m of pre-charged piping without realizing it, resulting in a system that is undercharged by several hundred grams.
• The additional charge estimated from pressure readings rather than weighed.
• The minimum room area not verified for the head installed in the smallest bedroom.
• The condensate drain installed with a reverse slope, or connected to a pump when a gravity drain was possible—each added pump is another failure point, multiplied by four.
• Unsealed wall penetrations on the interior side, allowing outdoor air to pass behind the drywall and causing condensation in winter.
• The condenser installed on the ground without clearance for defrosting, which matters twice as much on a multi-zone system operating for more hours per season.

Rebates: three AHRI codes for a single condenser

This system has an administrative peculiarity that deserves the full attention of owners and contractors.

The GWHD(36)ND6MO condenser has three distinct AHRI reference codes, depending on the type of indoor units connected to it:

In other words, adding a single ducted unit to a set of three wall-mounted heads changes the system from code 214931589 to code 214931599. The condenser is physically the same. The subsidy application is not.

We have seen applications denied or delayed for this very reason: a file prepared with the “non-ducted” code even though the installed system included a ducted unit. We therefore provide the code corresponding to the configuration actually installed, along with the list of indoor units.

Systems with this level of efficiency—SEER2 21, HSPF2 10, and ENERGY STAR certification—are generally eligible for financial assistance programs offered in Quebec, subject to the criteria in effect when the application is submitted. These criteria change faster than brochures do, so we recommend verifying them before signing the contract rather than after the work is completed.

What the customer received at the end of the project

• The complete list of indoor units, with their capacity and location.
• The AHRI code corresponding to the configuration actually installed.
• The measured length of each branch, the total, and the additional charge weighed in grams.
• Commissioning readings for each head: incoming and outgoing air temperatures, current draw, and pressures.
• Confirmation that the minimum room size requirement was verified for each of the four heads.
• The display switched to degrees Celsius and a demonstration of the remote sensor function.
• Instructions for cleaning the filters and the recommended HVAC maintenance schedule.

AirGreen in Calixa-Lavallée and Greater Montreal

Multi-zone systems account for an increasing share of our work, particularly in the rural municipalities of Montérégie where ductwork does not exist and natural gas is unavailable. We serve Calixa-Lavallée and the entire MRC de Marguerite-D'Youville, as well as Montréal, Laval, Longueuil, the North Shore, and the South Shore.

If you are considering a wall-mounted heat pump, a two-, three-, or four-head system, a central heat pump, or replacing an existing unit, our team performs a room-by-room load calculation before recommending a model. With a multi-zone system, this calculation—not the total tonnage—determines whether the system will deliver on its promises in January.