Furnace filter


Old 11-17-18, 11:41 AM
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Furnace filter

big box stores have electrostatic and non-electrostatic filters. Are they interchangeable? The electro ones are twice the price and everything Iíve read says to check your furnace before using an electro version. Iím talking about the disposable filters.

Also so any risk using a MERV 12? My unit has a MERV 8 right now. First time Iím changing it.

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Old 11-17-18, 04:14 PM
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According to ASHRAE tests, there are 4 general tiers or categories of MERV ratings:
  • MERV 1–4 (decent): A filter in this MERV range is your typical disposable fiberglass filter. These can pick up particles that are 10 microns or larger, which include pollen, regular standing dust.
  • MERV 5–8 (good): These filters are better at catching small particles (3–10 microns) like mold spores, hair spray, dust mites and animal dander.
  • MERV 9–12 (better): The best option for residential use. These air filters can remove pollutants as small as 1–3 microns, which includes particles like humidifier dust, auto emissions and legionella.
  • MERV 13–16 (best): These filters are usually only found in hospitals because they can capture particles as small as 1–0.03 microns in size. Particles this small include bacteria, tobacco smoke and even the contaminants in sneezes.

So obviously the higher the number the better the filtering but at a cost. The better the filtering the more restriction to airflow. So too high a filter value will reduce airflow, can cause an A/C evaporator to freeze over and a gas furnace to overheat. A restriction can also cause a blower motor to run hot thus shortening its life.

I don't normally recommend going higher then a Merv 8 in a typical home system. If you really want to consider better filtering..... bring in an HVAC tech who can measure your airflow with better filters.
Old 11-17-18, 05:38 PM
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Thanks PJ. Was leaning towards the 8. No smokers here and a small non-shedding dog.

Any comment about the electro vs. Non filters?

Is it the actual air handler which makes the electrostatic filter work? Or will an electrostatic filter charge the particles in any air handler?

Iíve read info that an electrostatic filter might not be safe in all furanaces.

Having trouble finding a non-electro MERV 8 at the big boxes.
Old 11-19-18, 05:04 AM
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stick with the $5 filter from your local hardware store. Everything else is to restrictive if it hasen't been designed into the system.
Old 11-19-18, 05:14 AM
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....more like $20-$45 where I am. Size is 16x25x4.

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