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Community and Q&A

How exactly does this Carrier ERV work? Is it any good?

Zach_SF | Posted in Mechanicals on

Hello, I’m working with a contractor putting together a plan for air sealing, insulation and a new furnace. For ventilation, he is suggesting a Carrier “comfort” series ERV. This unit has no separate control panel, it simply runs whenever the furnace fan is running, and it connects ONLY to the return trunk of the furnace system, either directly to the furnace cabinet or the return plenum/duct.

I found the install manual here:

It’s described as a simpler 2-duct system. I guess the triangle cut outs are in place of the 3rd and 4th duct connections found on most HRV’s/ERV’s. There are three different motor speeds that can be selected (hard-wired), as well as a dampers to balance the the supply and exhaust ducts.

I am confused how the ERV can be supplying fresh air and exhausting stale air into the return portion of the system at seemingly the exact same spot (the two triangle cut-outs)? Can someone give me a good explanation of how this is possible. Also, has anyone here had experience with this model and how well it works? Thanks for bearing with my lack of knowledge as I learn more building science.

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  1. GBA Editor
    Martin Holladay | | #1

    This type of ventilation system uses much more electricity than a system with dedicated ventilation ducts. The key to the system's inefficiency can be found in the installation instructions: "In order to meet required ventilation airflows, it is recommended that the furnace blower run in a low speed continuous operation mode at all times." It seems clear from the installation instructions that the ERV also has its own fans, and that these ERV fans are "designed to run whenever the furnace blower is running."

    This ERV doesn't pull stale air from bathrooms or laundry rooms the way an ordinary ERV does; instead, it pulls "stale air" from the return air duct of the furnace. This is just a percentage of the indoor air circulating through the furnace; it isn't "stale air" at all.

    In my mind, if you are going to the trouble of installing an ERV, you should install a real ERV, with real ventilation ductwork, not this compromise appliance.

    Note as well that this ERV will get ice buildup in its heat-exchange core if it is installed in Climate Zones 6, 7, or 8. It is only suitable for Climate Zones 5 and warmer areas.

  2. Reid Baldwin | | #2

    A patent application, available at provides some additional explanation. The jist seems to be that there is a steady flow past the two ports, which are side by side, so you don't get cross-flow. It is like trying to get from a highway entrance ramp on the right side of the road to an exit ramp on the left side of the road at the same interchange.

    It also looks like they intentionally make the exhaust fan stronger than the supply fan such that they get balanced airflow when the return duct is depressurized.

    If the furnace fan runs only when heating or cooling is required, then you only get ventilation at those times. Ensuring that you get enough ventilation would require something like a CFIS fan cycler control. Ensuring that you don't get excessive ventilation would require something like a CFIS damper control.

  3. Zach_SF | | #3

    Thanks Reid & Martin for the additional information. I'm in northern California, so pretty mild climate, zone 3 I believe. Martin: After reading the details of BSC's Central Fan Integrated Supply Ventilation, maybe this is my best option and easier/more affordable than a full blown independently ducted HRV/ERV. What do you think of that vs. something like the Lunos?

  4. GBA Editor
    Martin Holladay | | #4

    Assuming you have a furnace with an ECM blower -- that is, a blower with an energy-efficient motor -- then a central-fan integrated supply ventilation system makes sense. The Lunos approach only makes sense (in my opinion) for small apartments or retrofit jobs.

    For more information on the advantages and disadvantages of various types of ventilation systems, see Designing a Good Ventilation System.

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