Replacing a 1993 air exchanger: what we found in the ducts before even taking the new unit out of the box
In Rivière-des-Prairies–Pointe-aux-Trembles, much of the residential housing stock was built between 1975 and 1995. Bungalows, semi-detached cottages, and single-story homes with finished basements: solid, often well-maintained homes, originally equipped with an air exchanger that is now approaching thirty years of service.
All these units reach the end of their service life at the same time. And in the vast majority of cases we see in the east end of the island, replacing the box solves only half the problem. The other half is in the walls.
The project described here is representative: a Pointe-aux-Trembles bungalow, built in the early 1990s, whose original unit had stopped working the previous fall. We installed a FANTECH ATMO 200H, an HRV with side ports, mounted on the mechanical-room wall. But the workday was divided approximately equally between the unit itself and restoring the condition of the duct network it inherited.
Repair or replace: our decision framework
We are regularly called to repair an air exchanger that no longer starts. We make repairs when they are justified—which is often the case for a motor, capacitor, or control board on a ten- or twelve-year-old unit. On a thirty-year-old unit, the conclusion almost always changes, and here are the five questions we ask, in order.
1. Are the parts still available? On a 1990s-generation unit, replacement motors are often obsolete or available only as an approximate equivalent. A poorly matched motor changes the airflow and throws off the balancing.
2. What condition is the recovery core in? An aluminum core clogged over thirty years and never rinsed may have lost a significant portion of its transfer efficiency. It may then be possible to get the unit running again without restoring its performance.
3. Is the cabinet still airtight? Door seals harden, internal partitions deform, and some stale air mixes with fresh air inside the appliance itself. This is invisible and negates the intended benefit.
4. What is the actual energy consumption? A thirty-year-old appliance running continuously consumes more than a current model for a lower airflow rate. With continuous operation, the difference becomes significant over an entire year.
5. Does the repair cost exceed one-third of the replacement cost? Beyond this threshold, on an appliance at the end of its service life, the repair amounts to investing in an asset that will fail again within two years.
In this case, four answers out of five pointed to replacement. We presented the client with the two costed options, and the decision was made in ten minutes.
The inherited network audit: the part no one charges for and everyone should do
A new air exchanger connected to a defective duct network produces a defective result. We therefore systematically inspect the entire existing network before confirming a replacement quote. Here is what this house had in store for us.
What we found
- Two insulated exterior ducts with split vapor barriers over approximately 60 cm. The insulation was saturated with water, and the joist above showed an old moisture mark. Cause: thirty winters of condensation through a tear that was never repaired.
- Collars sealed with cloth duct tape. The tape had hardened, the adhesive had crystallized, and three of the six collars could be pulled off by hand. Some of the fresh air therefore never reached the intended rooms: it spilled into the basement ceiling void.
- A flexible duct crushed to 40% of its cross-sectional area behind a plumbing enclosure added during the bathroom renovation, presumably about fifteen years earlier. The room served by this branch was precisely the one whose occupants were complaining.
- A partially obstructed outdoor intake hood blocked by an insect nest and the original insect screen, clogged with dryer lint — the dryer vent having been installed less than one metre from the intake hood.
- A painted bathroom exhaust grille, with louvers fused together by three coats of latex paint.
None of these defects is dramatic. Together, they explain why the house was ventilated poorly long before the unit failed.
What We Retained, Replaced, and Corrected
We do not replace an entire system as a matter of principle. We replace what is defective and retain what is sound, documenting it.
Retained: the main rigid sections, which were in good condition and whose diameter matched the intended airflow.
Replaced: the two insulated exterior ducts, the crushed section behind the plumbing cabinet, and all the interior grilles.
Corrected: all the collars, resealed according to the method described below; the fresh-air intake hood moved away from the dryer exhaust; the exterior grille replaced with a model having appropriately sized mesh.
This step accounted for about half a day of work. It also explains the difference in results between a properly performed installation and a simple box swap.
Why an ATMO with side ports instead of a HERO with top ports
It was the most concrete technical decision of the project, and it came down to inches.
The Clear-Height Calculation
The mechanical room of this bungalow had about 6 ft 10 in. of clear height beneath the joists, with a partial suspended ceiling. An HRV with top ports, such as the HERO line, requires space above the cabinet for the four collars plus the bend radius of the first elbows. In practice, this easily requires 12 to 16 in. of vertical clearance above the unit.
Combined with the height of a cabinet nearly 25 in. high and a mounting position high enough to clear the floor, the numbers did not add up—unless the first elbows were crushed, which would have imposed a permanent pressure drop on all branches.
The ATMO 200H has its four connections exiting through the sides. The ducts run horizontally, follow the wall, then rise where the available height permits. In the installation photo, this geometry is visible: the branches leave the unit laterally and extend on either side, without a single tight elbow at the cabinet outlet.
This is why both families coexist in the catalog. The choice between top ports and side ports is not a matter of preference; it depends on the room's geometry.
FANTECH ATMO 200H specifications
| Specification | Value |
|---|---|
| Airflow range | 60 to 200 CFM at 0.4 in. w.g. |
| Duct connections | 6 in, round, side-mounted |
| Power supply | 120 V / 1 phase, max. current 1.4 A |
| Power consumption | 50 W (low) / 168 W (high) |
| Fan efficiency | 1.3 CFM/W at 0 °C |
| Sensible recovery adjusted to 0 °C | 81 % |
| ERV at 0 °C | 75 % |
| ERV at –25 °C | 60 % |
| Defrost | Supply fan shutdown |
| Dimensions | 21 7/16 in H × 23 7/8 in W × 16 5/8 in D |
| Weight | 46 lb (21 kg) |
| Filtration | MERV 8 or MERV 13 optional |
The 50 W at low speed deserves emphasis in a replacement context. The outgoing unit, measured with a clamp meter before removal, drew noticeably more power for a lower airflow. In continuous operation twelve months a year, the difference in consumption is not insignificant—and it accumulates unnoticed, since the unit does not make a sound on the bill.
Collar sealing: what distinguishes an installation that lasts five years from one that lasts twenty-five years
Three products, three very different results
Cloth duct tape. Despite its name, it has no place on a permanent ventilation duct. Its adhesive deteriorates under thermal cycling, dries out, and fails. This is precisely what we removed from the original collars in this house. Its useful life is measured in years, not decades.
UL 181-approved aluminum tape. Suitable on a clean, flat, dry surface. It lasts much longer than cloth tape, but it does not conform well to the irregularities of a crimped collar or the overlaps of flexible duct.
Duct sealant. This is our default choice for HRV connections, and it is what the photo shows: a generous layer of sealant applied to the collars, intentionally extending onto the duct body and the sleeve. It remains flexible, fills irregularities, does not peel away, and withstands temperature cycles without cracking.
Our method for every connection:
- Duct fitted over the collar to a sufficient length.
- Mechanical hose clamp on the inner core of the flexible duct.
- Apply sealant around the entire circumference, covering the joint on both sides.
- Fold the outer vapor barrier over it, then add a second hose clamp.
- Aluminum tape over the vapor barrier to reseal the barrier against water vapor.
Five steps per connection, four connections to the unit, plus the branches. It is tedious. It is also the difference between an installation you never have to revisit and one that leaks into a finished ceiling.
Supply-fan-off defrost: the mandatory check before choosing this unit
The ATMO 200H uses supply-fan-off defrost. During the defrost cycle, the unit stops introducing fresh air and continues exhausting. This is a simple, robust mechanism, but it temporarily places the house under slight negative pressure.
This requires a check before making any recommendation, and we never skip it:
- Is there a natural-draft combustion appliance in the house? An older-generation gas furnace, a chimney-vented water heater, or a wood fireplace connected to a masonry chimney. If so, defrost behavior must be analyzed, and a model with recirculation defrost — equipped with an interlocked mechanical backdraft damper — becomes the appropriate choice.
- Is the wood stove or fireplace used? A decorative fireplace used three times per winter is not treated the same as a wood stove used daily.
- Which other exhaust fans operate simultaneously? A high-flow range hood, bathroom fan, clothes dryer: their combined effect matters.
In this Pointe-aux-Trembles house, heating was provided by a central heat pump with electric backup, and the water heater was electric. No combustion appliances, no fireplace in use. Fan-off defrost posed no restrictions, and the ATMO 200H was fully appropriate.
If the house had had a natural-draft gas furnace, our recommendation would have been different. This is the kind of check that takes five minutes and never appears in a phone quote.
The condensate drain in a replacement context
The existing drain descended toward a floor drain, but had a reverse slope over one metre and a trap that had long since lost its seal. We redid it completely: new tubing, a continuous slope toward the discharge point, a primed loop trap during commissioning, and fasteners every 60 cm to prevent low spots where water stagnates.
In the photo, the drain line is visible beneath the appliance, with its trap loop and attachment points. This part of the work takes twenty minutes and prevents the most frequent service call we received for air exchangers: water seeping from the bottom of the cabinet.
Errors to avoid during a replacement
- Replace the appliance without inspecting the system. The new appliance then inherits all the old one's defects, and the client concludes that the investment achieved nothing.
- Reuse collars sealed with cloth duct tape. They will come loose, and no one will know why the airflow dropped.
- Choose an appliance with top ports in a room with limited headroom. This crushes the first elbows, permanently penalizing the system.
- Ignore the defrost strategy when combustion appliances are present. This is the only item on this list that concerns safety.
- Leave the intake hood near the dryer exhaust. Lint settles on the grille and eventually gets into the core.
- Reuse the existing drain without checking it. An invisible reverse slope causes highly visible damage.
- Do not rebalance after replacement. The new appliance has different fan curves; the old settings do not apply.
Maintenance after a replacement
- Every 3 months — check and clean the filters. We recommend MERV 8 as standard and MERV 13 for occupants sensitive to particles, factoring in the additional pressure drop during balancing rather than afterward.
- Every 6 months — rinse the heat-recovery core, check the trap and drain line, and visually inspect the resealed collars.
- Annually — clear the exterior covers, check the condition of the vapor barrier on the exterior ducts, and revalidate the balancing at the pressure ports.
We systematically leave the client with the sheet recording the balancing values measured during commissioning. An appliance with documented reference airflows can be diagnosed in a few minutes, even five or ten years later.
Compliance, programs, and value for the home
For new homes covered by the Quebec Construction Code, balanced mechanical ventilation is required and is a condition of the Novoclimat program. For an existing home like this bungalow, replacing an HRV is generally not subsidized as such: energy-efficiency renovation programs primarily target insulation, air sealing, and heat pumps. Nevertheless, we verify eligibility and the order of the work with each customer before the project begins, because the sequence directly affects what can be recovered.
In the Rivière-des-Prairies–Pointe-aux-Trembles market, where buyers visit many homes of the same age, a recent, properly connected air exchanger accompanied by its balancing sheet stands out during a pre-purchase inspection. An original unit that is out of service also stands out, but in the opposite way.
For your replacement in the east end of the island or elsewhere
At AirGreen, we treat an air exchanger replacement as work on a complete system, not simply as replacing a unit. This involves inspecting the existing ductwork before preparing the quote, choosing the model based on the actual layout of the space and whether combustion appliances are present, resealing connections with sealant, reworking the drain, performing measured balancing, and providing the customer with a values sheet.
We carry out HVAC installations — air exchangers, wall-mounted and central heat pumps, air conditioners, and heating systems — in Rivière-des-Prairies–Pointe-aux-Trembles and throughout Montreal, Laval, Longueuil, the North Shore, and the South Shore. Licence RBQ # 5645-9605-01.
To have your current unit evaluated or to receive a quote for a FANTECH air exchanger, contact us at (514) 316-2973 or sales@airgreen.ca.