Air Filters

Tim Carter, of http://AsktheBuilder.com, tells us why using air filters in our homes is so important.

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• air
• filters
• filter
• furnace
• fibers
• protection
• dust
• pollutants
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• tim
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[MRFoxMulder]

Electrostatic & pleated filters are a death sentence to system performance beause they increase static press. which reduces air flow. This can cause a furnace to overheat and the A/C to freeze up. Unlerss the system was designed them Contact a quailfied contractor who understands airflow performance and static pressures. Upgrading to a high efficiency air filter without any other considerations is costly.

[AsktheBuilder]

Correct. Dirty filters can dramatically increase static pressure.

[aznpride1979]

what is the merve rating on the electrostatic filter?

[AsktheBuilder]

I believe it's the same as its coefficient of continuity.

[dma3754]

You're right - 0.5"wc is the "target" TESP - this will allow 400 cfm/ton give or take 10% - just right! BUT exactly HOW is the homeowner supposed to verify that the new "high performance" air filter won't reduce air flow and end up causing more problems than help?

[AsktheBuilder]

Without a gauge, I suspect they should check the filter regularly and change it when they see visible dirt buildup. They should also follow all written instructions from the filter and HVAC equipment manufacturers.

[LanceTruett]

@jteamaz it does sound like the unit needs more area to breathe. The two and four inch filters will be stronger to resist the bowing you describe, but residential AC systems are designed to use 1" filters. Two cheaper suggestions than upsizing the return: change the filter monthly, sometimes dirt and grime increase resistance to airflow, and two try a polyester media form filter. Poly loads evenly and does not restrict airflow like traditional pleated filters do.

[LanceTruett]

@MRFoxMulder I agree. Most filters, especially highly Merv rated pleated filters, are SO efficient that the air is slowed down and wear and tear increases on the unit.

We use Merv rated polyester that captures particulate throughout the depth of the loft as opposed to just on the surface.

[jteamaz]

I want good filtration without excess restriction, the pleated filters in my unit are bowing when I remove them because they're pulling so hard. Fiberglass filters are useless, should I upsize the cold air return from 20 x 25, or have it modified to hold a thicker filter, say 2" to 4" ??

[sonitx]

In 5 years of cleaning electrostatics we've found the following - Electrostatic filters start up with about 25% higher resistance than standard pleated filters, but as they fill up they depth load while the pleated filter face loads. The result is, during the second half of the filter life, the electrostatic remains fairly constant in flow while the flow of the pleated is reduced significantly and quickly.