Hi All,

I am trying to figure out a good flow grid system to use for testing airflow in 2 to 5 ton forced air systems.

Any favorites?

Or, if you prefer a flow-hood, please tell my why.

The flow hoods I've used take up more space in my vehicle than I would like.

Thanks for your thoughts.


Tags: flow, hoods, tools

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I have 3 hoods - low flow ( 10-500 CFM)  Med flow (40-1500 CFM)  high flow (50-2000CFM) Open grid  for kitchen hoods. Plus hot wire plus presser plus other testing tools.   I test the air flow 3 ways  on each major job just to make my point or so I do not mess up.    Flow hoods have been used for 70 years and there's a lot of groups to help get it right.   look at http://www.trutechtools.com ,  www.nationalcomfortinstitute.com,  www.nebb.org,  https://www.aabc.com/www.tabbcertified.org.  I hope this helps some 80% air systems do not have the air flow to keep the unit on high limit.  

Thanks Eric!

Assuming that you're mainly interested in the total air handler flow, and you have access to the filter slots, I'd suggest looking at Energy Conservatory's TrueFlow.  It's a flat plate with openings; it has adapter plates for a variety of filter slot sizes. You'll also need to drill a hole in the supply plenum (or otherwise get a pressure tap in there).


I like the flat true flow plate when it fits-  if not the by pass is very very large.   Or if the presser is to high  its off some.   I have used 4 True flow plates  on a 2 ton spit system to find air flow.    Quick way is just use paper work that comes with the air handler ( you know the knee pad that come with the unit)  find the right unit using the right MO #  then total CFM reading the fan performance data at a constant speed chart.  to find Total SP use your blower door meter with a SP gauge both side of  motor, 3 of 10 will be off with high turbulence.  Have some fun with it and write about it I will be looking for your comments. 

If you wanted more information on the TrueFlow plate, the manufacturer is offering a webinar on it today: https://events-na11.adobeconnect.com/content/connect/c1/1097690081/...


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