RE: How do you measure system airflow?

RE: How do you measure system airflow?

So much of what we do requires either measuring or approximating airflow measurement on the entire system (over the evaporator coil) what method or methods do you use?

If you absolutely had to get a system air measurement within 5% of reality on every call what method would you use?

BryanOrr Pretend Internet Professor Asked on March 3, 2018 in Residential HVAC.
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15 Answers

I’m currently using the Testo 410i vane anemometer and 405i hot wire anemometer for airflow measurement, along with a Dwyer Magnahelic 0 – 2″ W.C. for duct pressure testing.

However, I’m having a little bit of trouble getting semi-accurate readings on my Testo 405i, especially in radial flex duct systems employing a single plenum.  It’s impossible to do a proper traverse on a plenum full of take offs, or in a large flexible duct.  How can I get a true delivered CFM reading on these designs without using a flow hood or a timed register traverse on every return and supply termination?

Parts Changer Answered on March 5, 2018.

I think on those style systems you’re best to use TESP.  Where I’m at we’re 90% basements so I use my hot-wire in the return drop, as there’s typically enough straight duct to not affect the air flow readings.

It would be easier with proper plenum designs, however I understand that’s not always “real world”.


on March 5, 2018.
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