"gapping" filter and airflow (plz read for clarification)

[dave1234]

Dont know if "gapping" is the word im looking for but read on. Consider the following; a filter rack with 2 oh say 18X18X1 filters. The return size is pinched down for what ever reason through the wall where the filter rack is. With the filters in place it makes a whisiling noise (yes all that said is a whole issue in itself but one question at a time) bothers the gal in the adjacent office so the staff routinley pulls the filters up to relieve the noise leaving about a 5-6" "gap" between the bottom of the rack and the bottom of the filter. My question is in theroy would (aside from the obvious reduction in return size) this also reduce the airflow since the air would enter in through the 5-6 inch gap of un-filtered space by virtue of the fact that its taking the path of least resistance as opposed to having the filters totally in place? Does that make sense what im trying to say here? Thoughts?

[dlove]

That gap over time will dirty a coil pretty fast. The whisiling noise could be coming from the air sucking between the filters like wax paper over a comb. In some cases i will use a link filter so you would have a 18 x 36. But you are correct that its not good to restrict return air. I would check the pressure drop with a clean filter and again with out a filter. that will tell you pretty quick you have issues.

[dave1234]

Much agreed but the partial removal of the filters stops the whistle. My question is does the majority of the air just use that clear unfiltered space say 6x36 since it'll naturally seek path of least resistance rather then using the whole 36x36 return path does that make sense?

[james mo]

you reduce the return static pressure by pulling the filters up. if you are using pleated filters try using standard filters. proper air flow is more important then filtered air

[Joehvac25]

If your stacking 2 together and pleated that's not good, try a single 2" thick filter.


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[dave1234]

you reduce the return static pressure by pulling the filters up. if you are using pleated filters try using standard filters. proper air flow is more important then filtered air

Interesting could you please expand on that

[beenthere]

It increases air flow.

[dave1234]

How does increasing airflow reduce static pressure?

[jdblack]

How does increasing airflow reduce static pressure?

They are one in the same. The filters restrict airflow which increases your static pressure because the blower is working harder to pull air through the filters.



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[dsprice]

Static measures resistance against airflow. The lower the number, the less resistance.

[Joehvac25]

They are one in the same. The filters restrict airflow which increases your static pressure because the blower is working harder to pull air through the filters.



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I thought Learned on here it works the same just runs hot from low air flow.


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