Please review our FAQs below and don’t hesitate to contact us if you have any additional questions.

At what temperature is my HRV/ERV going to shut down?

There are several variables that influence the point at which the fans are shut off, such as outdoor air temperature, return air temperature, whether the unit is an HRV or ERV, system size and cfm, use of boost mode, etc. The unit is programmed to monitor all of these variables, and depending on the combination of factors it’s possible for the fans to be shut off anytime the outdoor temperature is below freezing. But in general, an HRV with an internal pre-heater can function normally down into the 20’s (F) and an ERV down into the teens. It’s possible for the units to function at even lower temperatures depending on the variables mentioned earlier.

Zehnder offers more robust pre-heater options for customers in especially cold climates. Please contact your Zehnder technical sales representative for more information.

Why do I have an A7 error code on my controller?

The most common source of an A7 error code is when a unit with an internal pre-heater turns off the fans because the temperature has dropped below the safe operating limit. This is exactly what we want the unit to do in these conditions so that the HRV or ERV core doesn’t freeze. The pre-heater works to avoid or delay a necessary shut-down, but if the temperature gets cold enough even the pre-heater isn’t enough to protect the core, so the fans will be turned off. Because this is the desired function, the A7 isn’t so much an error code as it is a notification. The unit is programmed to periodically check the air temperatures and resume normal operation when it’s safe to run. But even after the fans are running again the A7 notification will remain on the controller to alert the user that there has been a shut-down. To clear the code, simply unplug the HRV/ERV for a minute or so and plug it back in.

There may be other, less common reasons for an A7 code, so if the code persists be sure to contact your Zehnder service technician.

What Is the warranty policy of Zehnder America?

Zehnder America, Inc. Limited Warranty

When installed according to the applicable Zehnder America, Inc. Installation instructions and the applicable local, state, and federal building codes and unless specified otherwise, all Zehnder America, Inc. products sold in North America carry a two (2) year LIMITED WARRANTY (from the original date of shipment by Zehnder America, Inc.) covering defects in the original manufacturer.  The warranty does not apply to damage from accident, misuse or alteration; or where the equipment has been improperly installed, improperly wired, improperly maintained or connected to an improper voltage in violation of the product’s installation and operating instructions.   This warranty is null and void if the product was improperly installed or operated incorrectly at any time.  All claims for warranty work must be sent by certified mail and must be accompanied by proof of the date of purchase.

The customer shall be responsible for all costs incurred in the removal or reinstallation of products, including labor costs and shipping costs incurred in the return of products to Zehnder America, Inc.  The existence of a warranted defect shall be determined solely by Zehnder America, Inc., or by its authorized representative.  Zehnder America, Inc. may, at its election, determine to repair or replace the product if under warranty.  It is agreed that such repair or replacement is the exclusive remedy available from Zehnder America, Inc.


Can the ERV/HRV system be use in both retrofits and new construction applications?

Yes, Zehnder’s Comfosystems are ideal for both applications to provide optimal indoor air quality.

How easy is the ERV/HRV system to install?

Because Zehnder designs whole-house ventilation systems, components easily fit together. This integrated functionality allows for a more rapid system installation saving both time and money for both the installer and the end user.

Why should I install a ventilation system?

A user-independent supply of fresh air is necessary as buildings become increasingly air-tight. Today’s new builds and refurbishments demand ventilation concepts for protection against moisture, which prevents mildew formation and helps retain the value of the property. Advantages include energy savings of up to 50%, pollen-free air for allergy sufferers and generally improved comfort.

Does a ventilation system increase energy consumption?

A ventilation system with heat recovery considerably reduces your energy consumption. The energy won from the extract air is approximately 15 – 20 times greater than the energy consumed by the highly efficient DC motors of the ventilation device.

Can the air in a ventilation system become too dry in winter?

When cold outside air is heated to room temperature its relative humidity drops and the air feels dry. The same applies to window ventilation. Zehnder has the enthalpy heat exchanger for this application. It provides heat recovery and recovers moisture from the extract air.

Can I hear noises from neighboring rooms through my ventilation system?

Zehnder air distributors are designed such that there is no direct connection between rooms. All air ducts lead directly from the manifold to the respective rooms. Noise transmission via the air distribution network does not occur.

How can dust in the air pipes be prevented?

Dirt particles in the outside air are removed by the filter in the ventilation device. In addition, extract air filters and the special, smooth internal walls in the air ducts prevent dirt deposits. The distribution system is designed to allow easy cleaning of the air ducts.

Can the HRV/ERV unit be tied into a central HVAC ducting system?

No, it will cause an extreme imbalance between the fresh and extract air. The unit will not be able to function as designed and will greatly decrease transfer efficiency. Novus units are an exception, but still not recommended. It will only provide adequate ventilation to all rooms when the large central HVAC fan is running which is generally only a portion of the year.

Can the system with Geothermal Heat Exchanger (comfofond) be used to heat and cool my home?

No, it will preheat or precool the incoming air keeping the core from freezing and making the unit more efficient. For a 2000 sf house, the amount of cooling it can provide is usually less than 2000 BTUs (for humid climates this will slightly dehumidify the air). It will, however, help redistribute the conditioned air for an evener household temperature. For additional heating options, check out our sister site RuntalElectric.com here.

How do I connect the wireless boost switch to my HRV?

1) Install the battery being careful to not bend the prongs (that go up the side of the battery and wrap to the top side, not bent down under the battery). 2) Unplug the HRV unit from the outlet and then plug it back in. This action now gives you a 10-minute window where the HRV is open to switch synchronization. 3) Simultaneously press the “1” button and the clock button on the boost switch. You will need to hold these for 10-15 seconds. During this time you will see the indicator lights on the switch blink on and off in random-seeming patterns. Once the switch is synched both indicator lights will come on green for about a second and then you can release the buttons. 4) Test the switch to ensure that the synchronization worked. 5) If you need to synch another switch, do these steps again for the second switch (and third, fourth, however many you need).

Can I heat my house by adding a post heater to the HRV/ERV?

When used as a post heater, the ComfoInline Heater is intended to only temper the air and not to be used as the building’s primary heating source. For more information, check out this blog post.