Installation of a Broan-NuTone V130H80RT air exchanger (AI series, Virtuo technology) in Vaudreuil-sur-le-Lac, in Vaudreuil-Soulanges

SELF CHECK on the screen: the unit checks itself, and here is what it looks at

Vaudreuil-sur-le-Lac is one of the smallest villages in the Montérégie: a little over one thousand residents, a wooded enclave tucked between Vaudreuil-Dorion and Lake of Two Mountains, a few minutes from L'Île-Cadieux. The village began as a vacation destination — summer cottages beneath the towering trees, occupied from June to September — and then, home by home, transformed into a year-round municipality.

That past leaves two traces we find on almost all our projects in the area: buildings expanded in stages, with heterogeneous envelopes and limited mechanical space, and a dense forest canopy that directly influences the placement of exterior components.

The assignment

The residence is a converted former vacation home, with approximately 1,800 sq. ft. of living space on two levels, three bedrooms, heated by a central heat pump with electric backup. The basement is partially finished.

The homeowners contacted us after a difficult winter: heavy condensation on the windows facing the lake, an odor that settled in the basement starting in February, and a general feeling of stale air on days when no one opened a door.

Readings before the work, in April:

• 55% relative humidity on the main floor, 60% in the basement.
• No continuous mechanical ventilation.
• Three bathroom fans on switches, one of them disconnected.
• There are no combustion appliances in the home.

Selected unit: Broan-NuTone V130H80RT

Airflow calculation for this house:

• Using the formula: 0.01 × 1,800 = 18, plus 7.5 × (3 + 1) = 30. Total: 48 CFM.
• Using the reference table (1,501 to 3,000 sq. ft., 2 to 3 bedrooms): 60 CFM.

Selected setpoints: 60 CFM in continuous mode and 105 CFM at high speed—approximately 88% of the certified maximum at actual pressure, leaving the reserve needed for normal buildup in the ductwork.

SELF CHECK: the mode no one knows how to interpret

The photo of this job site shows the wall control displaying SELF CHECK, with the house icon in solid mode and no airflow arrows. This is the unit’s self-diagnostic, and it is a normal state—not a malfunction.

What the unit checks during this self-diagnostic

The AI series includes an internal verification routine that checks, within a few minutes:

• The response of the two motors—supply and exhaust—and their ability to reach the programmed setpoints.
• The readings from the airflow sensors integrated into each circuit.
• The operation of the motorized dampers, which must open and close completely.
• Communication with the wall control and connected sensors.
• The consistency of the configuration parameters saved during commissioning.

During this test, the unit does not ventilate normally: it runs its motors according to a defined sequence. That is why the display shows no airflow arrows.

When it starts

Three main situations:

1. When power is turned on, especially after a power outage or unplugging.
2. At the technician’s request, during commissioning or maintenance.
3. Automatically, when the electronics detect an inconsistency between what they command and what they measure.

What to do—and, above all, what not to do

Do not unplug the unit. This is the most common reaction, and the most counterproductive one: cutting the power during a self-diagnostic simply restarts the sequence when the unit is plugged back in.

Let the test finish. The unit will return to its normal mode on its own once the check is complete, and the screen will display the ventilation mode and airflow rates again.

If the mode persists for more than a few minutes or keeps coming back, the unit is signaling a real problem. This is the time to call. It is not the time to cover the screen or turn off the circuit breaker.

A detail we always explain: the humidistat is paused

In the photo, the screen shows 51% measured against a 45% setpoint. During normal operation, this excess would switch the unit to high speed.

During the self-diagnostic, this logic is suspended. The unit runs its test sequence, not its humidity setpoint. A homeowner who sees their screen in this state often concludes that the humidistat is not working. It is working — it is simply waiting for the test to finish.

The outdoor temperature sensor, and what a dash means

In the upper-right corner of the screen, “–°C ext.” replaces a numerical value. No outdoor temperature is displayed at that moment.

What this reading is used for

The outdoor temperature is not decorative on a ventilation control. It controls two functions:

• Defrosting logic, whose activation and duration depend directly on the outdoor cold.
• Help with seasonal adjustment, by giving the homeowner the information needed to adjust their humidity setpoint.

What a dash means

Three possible causes, in order of frequency:

1. The unit has just been powered on and does not yet have a stabilized reading. That is the case here, since it is running a self-diagnostic. This is normal and temporary.
2. The sensor has not yet been connected, a situation we encounter on installations taken over from others where the previous installer had skipped this step.
3. The sensor is defective or its wiring is interrupted.

If the dash remains for several hours after normal operation, it needs to be addressed. A unit that does not know the outdoor temperature applies a default defrosting logic, which is less suitable than logic controlled by the actual measurement.

Defrosting: what happens in the core at -25 °C

It is the least-explained mechanism in residential ventilation, and the one that determines the actual performance of an air exchanger in Quebec.

Why an HRV frosts

The heat-recovery core brings two separate air streams into thermal contact: the warm, humid air leaving the house and the cold, dry air entering from outdoors.

In winter, outgoing air gradually cools as it passes through the core. It first reaches its dew point—moisture condenses, forming the condensate the unit drains. Then, at the coldest end of the core, this condensation freezes.

Frost accumulates, blocks the passages, and reduces airflow and efficiency. Without a defrost mechanism, an HRV would gradually become blocked during a prolonged cold spell.

The two strategies

Recirculation defrosting. The unit closes the outdoor-air intake damper and circulates warm indoor air through the core to melt the frost. During the cycle, the house continues to receive air, and no negative pressure is created. This strategy requires motorized dampers, which the AI series includes as standard.

Exhaust-only defrosting. The supply fan stops while stale air continues to pass through the core and warm it. It is mechanically simpler, but during the cycle, the house expels air without bringing any in: it becomes slightly depressurized. In a building with a wood stove, fireplace, or combustion appliance, this difference is not insignificant.

Preheating. A third approach is to install an electric preheater on the intake duct so that incoming air never reaches the temperature at which frost forms. This is effective, but it adds direct electrical consumption, and we recommend it only when the configuration genuinely requires it.

What this changes for the homeowner

Three concrete points:

• Defrost cycles are normal. Hearing the unit change operating modes in very cold weather is not a sign of failure.
• The published efficiency in extreme cold—67% at actual pressure on this unit—already takes into account the energy used for defrosting. That is exactly why this figure is lower than the 77% measured at 0°C.
• A frosted or blocked intake hood makes everything worse. That is why winter inspection of exterior hoods is not optional.

The project: a wooded village, façades to preserve

Positioning the outdoor hoods

Vaudreuil-sur-le-Lac is a village where the appearance of properties matters and where mature tree cover is a defining feature of the surroundings. The placement of the outdoor components was therefore discussed with the owners before the first hole was drilled.

Our rules, applied here as everywhere else:

• At least 1.8 m of separation between the fresh-air intake and stale-air exhaust.
• The least exposed façade to views from the street, without compromising operation.
• Sufficient height above the ground to remain clear in the event of snow accumulation.
• Away from the dryer vent and any other exhaust outlet.
• Gust-resistant intake hood with fine-mesh grille, essential beneath a tree canopy.

What mature trees require

An intake hood located beneath maple and pine trees receives leaves, needles, and samaras every autumn, and large amounts of pollen every spring. A clogged grille reduces fresh-air intake, unbalances the unit, and worsens frost formation in winter.

We therefore scheduled two mandatory annual inspections with the client instead of the usual general recommendation: one in November, after the leaves have fallen, and one in June, after pollen season.

Two-stage commissioning

On this project, as with all our ventilation installations in recent years, commissioning takes place over two visits.

First visit, on the day of installation. Setting the setpoints, starting the self-diagnostic, checking that the two airflow rates converge, priming the trap, and explaining the wall control to the client.

Second visit, two to four weeks later. The system has had time to stabilize, and the house has gone through its normal cycle. We take the airflow readings again, check the measured humidity against the setpoint, confirm that the outdoor sensor is reporting correctly, and adjust whatever needs adjusting.

It is this second visit that distinguishes a delivered installation from a verified one. Nearly all the adjustments we make happen at that point.

Errors to avoid

1. Unplugging the unit during a self-diagnostic only restarts the sequence.
2. Conclude that the dehumidistat is defective because the measured humidity exceeds the setpoint during a SELF CHECK mode.
3. Ignore a persistent dash in place of the outdoor temperature and let the unit defrost according to a default logic.
4. Interpret defrost cycles as a malfunction and turn the unit off in the middle of winter.
5. Compare efficiency measured at 0°C with efficiency in extreme cold and conclude that the unit is underperforming.
6. Place an intake hood beneath mature trees without fine-mesh screening or seasonal inspection.
7. Consider commissioning complete on the day of installation, without a verification visit.
8. Connect the clothes dryer or range hood to the air exchanger's network. Dedicated exhaust, without exception.

What we take away for vacation homes that have become primary residences

Six months after commissioning, relative humidity had stabilized around 38 % on the main level during cold weather, compared with 55% before the work, and around 42 % in the basement versus 60%. No condensation reappeared on the lake-facing windows.

What homeowners appreciated most was not a number. It was understanding what their unit was displaying. A wall control you know how to read becomes a diagnostic tool; a control you do not understand becomes a source of concern, then a button you eventually stop using.

Applicable grants

The Québec government's Rénoclimat program provides financial assistance of approximately $500 for installing or replacing an HRV or ERV, provided that the unit is listed in the Home Ventilating Institute (HVI) certified product directory. The model number shown on the unit's nameplate lets you verify the listing in a few seconds.

Two decisive procedural conditions:

• The initial energy assessment must take place before the work. An assessment carried out afterward makes the application ineligible.
• A post-work assessment is required to trigger payment.

Amounts and eligibility criteria are reviewed periodically. We verify eligibility at the time of submission rather than providing a figure that may have changed.

Maintenance

• Every 3 months: clean or replace the interior filters, then check that the displayed airflow rates have returned to their setpoints.
• Once a year: rinse the recovery core, reprime the drain trap, and check that the outdoor temperature is displayed correctly.
• In November and June: clean the exterior hoods. In tree-covered areas, these two deadlines are firm.
• Twice each winter: adjust the humidistat setting according to the outdoor temperature.
• In very cold weather: let the unit run its defrost cycles without interfering.

Why entrust your ventilation to AirGreen

We design, install, and maintain heating, ventilation, and air conditioning systems in Greater Montreal with more than fifteen teams on the road. Our service area covers Montreal, Laval, Longueuil, the North Shore, the South Shore, and all of Montérégie, including Vaudreuil-Soulanges: Vaudreuil-sur-le-Lac, Vaudreuil-Dorion, L'Île-Cadieux, Hudson, Saint-Lazare, and Pincourt.

What we bring to a residential ventilation HVAC installation:

• A measurement-based diagnosis before any recommendation, level by level.
• Sizing calculated at actual pressure, with a programmed reserve below the certified maximum.
• A defrosting strategy adapted to the building, taking into account whether or not combustion appliances are present.
• Hood placement discussed with the client, based on the surroundings and the property's appearance.
• Commissioning in two visits, with written readings taken at each visit.
• Training for the homeowner on how to read their wall control, because a system you understand is a system you maintain.
• A team holding an RBQ licence, along with comprehensive support for subsidy applications.

If your wall control displays a message that no one has explained to you, or if your air exchanger behaves differently in very cold weather without you knowing why, contact AirGreen. We take readings, we measure, and we take the time to show you what your system is doing.