What this photo really shows: a central heat pump installed, but not yet in service
In the image, the unit has been in place for two hours. It is level, bolted to its base, electrically connected, and will not operate for several more hours. A manifold gauge set is hanging from the fan grille, a digital vacuum gauge is screwed onto the service port, a nitrogen cylinder and torch are waiting on the floor, and the copper tubing has not even been insulated yet.
This is precisely the part of the work that separates a central heat pump that will last fifteen years from one that will begin losing capacity in its third winter. It is not visible in any final project photo, it does not appear on any itemized quote, and it accounts for a considerable portion of the day.
We installed a three-ton GREE FLEXX R32 system in La Présentation, in the Maskoutains RCM in Montérégie: GUD36W2/NhE-D(U) outdoor unit and GUD36AH2/G-D(U) indoor unit. Here is the commissioning process, step by step.
La Présentation: an agricultural village at the gates of Saint-Hyacinthe
La Présentation borders the Salvail River, northeast of Saint-Hyacinthe, at the heart of one of Quebec's most active agricultural areas. Two local realities influence our technical decisions:
- Homes are often isolated or located in small village clusters, with real travel times for a service call. A system that requires three corrective visits is costly for everyone. Doing things right the first time is not a matter of appearances; it is an economic necessity.
- Seasonal agricultural dust is carried by the air. The outdoor coil of a heat pump installed in a rural area becomes dirty faster than that of a unit in Longueuil or Laval, which changes the recommended HVAC maintenance schedule.
The installed pairing
| Data | Value |
|---|---|
| Rated cooling capacity | 34,000 BTU/h |
| Rated heating capacity | 34,000 BTU/h |
| Modulation range | 18,000–37,000 BTU/h |
| SEER2 | 18 |
| HSPF2 | 10 |
| EER2 | 12 |
| COP | 3,2 |
| AHRI number | 217120760 |
| Refrigerant | R32, 2.9 lb (102.3 oz) |
| Outdoor unit | 990 × 960 × 370 mm, 187.5 lb, 61 dB(A) |
| Electrical (outdoor) | MCA 27.7 A / MOCP 30 A |
| Factory charge / maximum length | 24.6 ft (7.5 m) / 98.4 ft (30 m) |
The hours we never bill enough for
Step 1: brazing under nitrogen
Copper heated with a torch in the presence of air produces copper oxide inside the tube. This oxide later flakes off and circulates through the system. Destination: the electronic expansion valve, the strainers, and the compressor.
The solution is simple and visible in the photo through the presence of the cylinder: a slight flow of dry nitrogen circulates through the piping throughout the brazing process. The flow must be low—enough to displace the oxygen, but not enough to cool the joint or blow away the brazing alloy.
What we regularly find when correcting previous installation work: systems brazed in open air, with blackened tube interiors. The damage is invisible and irreversible.
Step 2: nitrogen pressure testing
Once the joints are complete, the piping is pressurized with nitrogen to the value specified in the manual and left under observation.
The detail that distinguishes a serious test from a symbolic one: the ambient temperature must be recorded at the same time as the pressure. A difference of a few degrees between the beginning and end of the test can shift the pressure by several psi, which may lead you to conclude that a nonexistent leak is present—or conceal a real leak. We record the starting pressure, the starting temperature, and the same values at the end.
A nitrogen pressure test is performed before evacuation, never afterward. Searching for a leak with refrigerant in the system is both ineffective and contrary to good environmental practices.
Step 3: evacuation, and why analog gauges are not enough
The two manifold gauges visible in the photo are essential for reading operating pressures. They are incapable of measuring a vacuum accurately. Their lowest graduations stop at values that, when converted, represent thousands of microns. A system that appears to be “pegged in the red” on an analog gauge may contain enough moisture to form acids in the compressor oil.
This is the role of the small digital vacuum gauge screwed onto the side of the unit, on the right in the photo. It reads in microns, and it is the only measurement that matters.
Our rules for this step:
- Remove the Schrader cores with pressurized extraction tools. A core left in place restricts evacuation and can triple the evacuation time.
- Use large-diameter hoses that are as short as possible. Pressure loss in a standard charging hose is the most common bottleneck.
- Evacuate both sides of the circuit, liquid and gas.
- Place the vacuum gauge far from the pump, ideally at the opposite end of the system. A gauge installed at the manifold measures the pump's performance, not the system's condition.
- Pull below 500 microns, then continue for a while.
Step 4: The rise test
This is the decisive step, and also the one most often skipped for lack of time.
The pump is isolated from the system with a valve—not simply turned off—and the gauge is observed. Three possible behaviors, each telling a different story:
- The value remains stable below 500 microns. The system is dry and leak-tight. The valves can be opened.
- The value rises, then stabilizes around a higher value. Moisture remains and continues to evaporate. Continue evacuation, possibly with a dry nitrogen break to help remove the residual water.
- The value rises and never stops rising. There is a leak. Repeat the pressure test.
This reading is the true signature of a job well done. It takes time, impresses no one, and determines the compressor's service life.
Step 5: Opening the valves and weighing the charge
The three-ton FLEXX contains 2.9 lb (102.3 oz) of R32 as a factory charge, intended for 24.6 ft (7.5 m) of piping. Beyond that, add 0.32 oz per foot (30 g/m) for this configuration—a value that is not the same as on the four- and five-ton models, which regularly catches people out.
The addition is done using an electronic scale, not by estimation. The added amount is recorded on the commissioning sheet and on a label affixed to the unit. The next technician to work on this system will know exactly how much refrigerant it contains—information that would otherwise be lost forever.
Why R32 makes this rigor non-negotiable
The orange label visible on the casing bears the wording A2L R32. The R32 is a mildly flammable refrigerant, with a global warming potential significantly lower than that of R-410A. It imposes specific requirements:
- No recovery or transfer with equipment not intended for A2L. Recovery pumps, hoses, detectors: the equipment must be rated for this refrigerant.
- No drilling into pressurized piping, as explicitly stated by the warning affixed to the unit.
- Service by qualified personnel only. This is not administrative wording: recovery and charging procedures differ from those for R-410A.
- An A2L leak-detection sensor, included and factory-installed on the indoor unit, which must remain powered at all times.
Residual moisture and brazing residue have the same consequences in an R32 system as in an R-410A system. The difference is that the entire handling protocol is more strictly controlled, and a shortcut taken along the way becomes a shortcut documented by the label affixed to the unit.
The support, slabs, and fence
The unit rests on an aluminum base set on concrete slabs, in a side area bordered by a wooden lattice fence. Three checks were carried out before placing the unit:
- The stability of the slabs. A slab that rocks under 187 lb puts the piping under tension and eventually fatigues the fittings.
- Clearance from the lattice. A lattice allows air to pass through, which is a real advantage over a solid fence, but it does not eliminate the need to respect the minimum distance specified in the manual. A panel added later to “hide the unit” cancels out this benefit.
- The level, checked again after installation. Oil return to the compressor and drainage from the base pan depend on it.
What we record at the end of commissioning
Before leaving a job site, we record a series of values that become the reference for any future service:
- suction and discharge pressure and temperature;
- calculated superheat and subcooling;
- delta T return air / supply air;
- external static pressure of the ductwork;
- compressor and fan amperage, compared with the 27.7 A MCA;
- total charge, factory charge plus weighed-in addition;
- final reading of the rise test.
A client who has these figures can know, five years from now, whether their system has drifted. A client who does not have them will have to pay for a complete diagnosis to answer the same question.
What this La Présentation project reminds us
Mistakes to avoid
- Brazing without nitrogen. The damage is internal, invisible, and cannot be corrected.
- Judging a vacuum with an analog gauge. These dials do not measure microns.
- Leaving the Schrader cores in place during evacuation. The time lost encourages shortening the step.
- Placing the vacuum gauge on the manifold, next to the pump. This measures the pump, not the system.
- Stopping the pump without isolating the system for the rise test. Pump oil can migrate back into the circuit.
- Charging by estimation rather than by weight. On a variable-speed system, an approximate charge reduces efficiency without triggering an error code.
- Documenting nothing. Information lost during commissioning can never be recovered.
Rebates and eligibility
The installed combination is ENERGY STAR-certified and bears AHRI number 217120760. This number, specific to the exact combination of the indoor and outdoor units, is what government programs and local rebates verify—not the product line name. Criteria and amounts change from year to year and depend in part on the heating source being replaced, an important variable in agricultural areas where propane and heating oil are still used. We verify eligibility with the client before signing.
Our coverage
We carry out these HVAC installations in Montréal, Laval, Longueuil, the North Shore, the South Shore, and throughout Montérégie, including La Présentation, Saint-Hyacinthe, Saint-Damase, Sainte-Madeleine, and Saint-Barnabé-Sud. Every project includes documented commissioning, provided to the client—not just a simple start-up followed by a handshake.
If you are shopping for a central heat pump, ask every bidder: What vacuum level are you targeting, and will you provide me with the commissioning readings? The answer will tell you more than any brochure.