0 Helpful?

How do I balance a Zehnder Comfoair 350?

I recently installed this model Zehnder HRV, and now need to learn how to balance it. The manufacturer's installer manual is too brief on this procedure to be helpful. Is there anyone out there who can anyone give me the detailed procedure on how to balance this HRV?

My main concern is to ensure the intake/exhaust is balanced and that I am not pushing too many CFM's into/out of the house. I don't care too much about getting each room's cfm perfect at this point - since I'm going to be continuing to renovate the house. I just don't want to be pushing moisture into the walls right now.

I am working with an old fashioned, two-tube Magnehelic Pressure Gauge.

Thanks in advance !

Asked by Matthew Robinson
Posted Aug 27, 2014 10:13 AM ET
Edited Aug 27, 2014 10:40 AM ET


2 Answers

Select your preferred way to display the comments and click "Save settings" to activate your changes.

Step 1: Read this blog by Alex Wilson: Commissioning Our Heat-Recovery Ventilator.

Step 2: For any remaining questions, call up Barry Stephens (603-422-6700) at Zehnder America.

Answered by Martin Holladay, GBA Advisor
Posted Aug 27, 2014 10:42 AM ET
Edited Aug 27, 2014 10:46 AM ET.



Thank you for directing me to these useful sources. Having read through the article, I understand that I will need a hood-format anemometer if I want to ensure precisely the right CFM's at each distribution / return grill. I might end up doing this step in the end, if I can find a relatively inexpensive option for this tool.

As for the other step (the 1st step?), where the whole house intake is balanced to the whole house exhaust, I would like to know:

1) if my analog two-tube Magnehelic Pressure Gauge (0" - .5" of water) will work for this purpose, and if so, exactly how,
i.e. 2) where do I position each of the two tubes,
3) at what level (low, med, high) do I run the Zhender unit during the balancing,
3) what specification chart do I use for the balancing,
4) how do I actually adjust the intake/exhaust in the unit - are there adjustable dampers, for instance, and
5) what is the order in which I run through the various steps?

I'm basically looking for the equivalent of a Hanes manual (for vehicles) - style explanation of the procedure. The article to which you direct me makes the point that there will be alot of back-and-forth adjustments on the room-by-room cfm balancing. This makes sense to me intuitively.

I have called Zhender, but learned that Barry Stephens is away from the office this week. I will try him next week, but if anyone can answer some of these q.'s in the meantime, I would be most appreciative.

Thank you,


Answered by Matthew Robinson
Posted Aug 27, 2014 3:25 PM ET

Other Questions in Mechanicals

Previous code for unvented cathederal ceiling insulation

In Building Code Questions | Asked by Steve Gabrielidi | Nov 25, 15

Split system location

In Mechanicals | Asked by A Lange | Nov 24, 15

Humidity control other than plug in De/humidifier

In GBA Pro help | Asked by Terry Sharpe | Nov 27, 15

Can pex pipe be reused after a fitting is removed?

In GBA Pro help | Asked by K C | Nov 27, 15

Solar array positioning in Charleston, SC

In Green building techniques | Asked by F White | Nov 24, 15
Register for a free account and join the conversation

Get a free account and join the conversation!
Become a GBA PRO!