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Question DetailsAsked on 10/1/2013

air filters in HVAC systems--effective?

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2 Answers


You seem to have two identical posts on the same question - answers given at other post here -

Answered 6 years ago by LCD


The better efficiency rated filter has better filtration.The MERV is a standard rating and the higher MERV number (from 1-20) indicates the efficiency. A high filter rating is not practical if the filter is too small The filter will load too quickly. Then the system will suffer due to low air flow. The rule of thumb for filter surface that I use is 144 square inches per ton of air conditioning capacity. My 3.5 ton unit in So. Cal. has a 600 (20x30) square inch filter grille. I installed that size filter grille so I can use a high efficiency filter and the system air flow is at the recommended cubit feet per minute. The original filter grille would only accomodate a 20x20 inch filter.

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Answered 6 years ago by PoppyRoss

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