Archive Monthly Archives: November 2016

Winter Experiment: Heat Recovery Ventilator (HRV) to Energy Recovery Ventilator (ERV)

November 24, 2016

On November 18, 2016 we did some maintenance. The Zehnder ComfoAir 350 ventilation system is the heart of our Passive House (Passivhaus in German). It continuously provides pre-warmed filtered fresh air to  different rooms and exhausts stale air from kitchen and bathrooms. The heat recovery ventilator (HRV) was originally installed four years ago and commissioned in January 2013. In addition to cleaning out the filters couple of times a year, we were supposed to clean out the HRV core annually. This was the first time we pulled out our HRV core and it was quite dirty.

​We also pulled out the bypass duct. Our system is configured as ComfoAir 350 LEFT where the fan on the right side move the air in and out of the house (through ComfoPipes) and the fan on the left move the air within the house (through ComfoDucts.) In the LEFT version the bypass duct (black hexagonal foam) is installed behind the core. 

The body of the ComfoAir 350, the casing that housed the core, was dirty too. Our first task was to clean out the dust, dirt, and dead bugs. We didn't have a vacuum cleaner handy, so we simply wiped down the surface with damp paper towels. 

There are two fans: one of the right and another on the left. We pulled out the fan on the right side, opened it up, cleaned it, and replaced it. Then repeated the procedure with the  left. We took care to not pull on the power cables attached to the fan.  

Now that everything is clean again, it's time to replace the core. Instead of re-installing the HRV core we chose to install the ERV core (enthalpy exchanger). Note that the ERV core is blue. The color of the HRV core was teal. This will help redistribute the moisture extracted from the kitchen and bathrooms to the other rooms. We are doing this because we live in a dry climate. In the winter the air outside is so dry. When the dry air is brought into the house  the relative humidity in some of the rooms drop below 30 percent. So, to avoid dry skin and chapped lips, we are doing an experiment this winter.

We replaced the front covers and the filters. We use the red F7 filter (MERV 13) on the right (towards ComfoPipe) and the black G4 filter (MERV 7/8)  on the left (towards ComfoDuct).

We will be collecting the temperature and humidity data through our WELserver. While our sophisticated body sensors (skin and lungs) will tell us whether our experiment was a success or not, the measurements of relative humidity will convey them in numbers. Stay tuned.​