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Tool and Procedure Name for calibrating stale air collection ports?

mikeysp | Posted in General Questions on

Hi. I am in zone 4a and have about finished installation of my ERV. 

I have a ductless mini split heat pump, so the ducting I have is only for the ERV. I have one 6″ main fresh air supply duct into the house and five 4″ stale air out ducts from the house. 

As I understand it, if I leave it as is, I will have most of my CFM out happening at the stale air out duct closest to the ERV and very little getting extracted at the farthest point form the ERV. 

So, I am going to utilize an adjustable duct cover to limit air flow in the five stale air out duct points. 

What is the tool and procedure called for adjusting the CFM at each stale-air out duct port?

Since one room has two people sleeping in it and another has one person, I will be adjusting my CFM accordingly.

Once I get this info, I will get the tool if I do not have it already and watch how-to videos to finalize my installation. 

Thank you.


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  1. Expert Member
    Akos | | #1

    You can use an anemometer. Lot of times the velocity is pretty low so it won't read all that well, in that case put a duct reducer over the register to increase the velocity.

    Getting any decent accuracy is not easy no matter what you do, the only thing I have ever done for an ERV is hold my hand in front and roughly adjust. Close enough.

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