Heating, Air Conditioning, Fridge, HVAC/FILTER PRESSURE DROP


Good morning Jim, I hope it is a pleasant day for you. My question has to do with the math to figure the air flow of furnace/AC air filters  for example: filter xyz rated at PD 0.19" @ 295 fpm. Now it stands to reason that this filter in a 12" x 12" x 1" will let less air flow - than the same filter that is 25" x 30" x 1". How does one figure the math on this? I believe I might need more information for my equation? As you know, trying to get information on filters, is impossible from some companies and next to impossible from others. I have yet to find a company that gives all this information, except, for Flanders Pre-Pleat 40 on their home page under "industrial".    ( These filters can be used for residential apps) However even Flanders does not give out this info on all of their filters. I'm learning the hard-way that included in all bids should be a full External Pressure budget submitted and after install be tested and confirmed. Before my very expensive new change-out I had never even heard of it. When I questioned my contractor he had no idea of what ESP was.    Sincerely  Reg

I think you need to ask a Mechanical Engineer?
For my line of work I figure a 1" thick air filter allows 50% of the free area it covers pass through if the filter is new,
Every time air passes through the filter that 50% is reduced depending?

Heating, Air Conditioning, Fridge, HVAC

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Jim Barnhart


Fifty + years conditioning the air.


Answer questions about , residential and commercial. Answer questions about sheet metal fabrication. Fifty years plus experience. No answers for oil equipment, No answers for kitchen appliances, No answers for laundry appliances, I don't specialize in one particular area of the HVAC area, I'm more of a General Practitioner, Limited in refrigeration/

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