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Old 02-12-2011, 01:50 PM   #16
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what is best furnace filter to buy?


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Originally Posted by Jackofall1
In a nut shell, yes

Mark
So that's like a Merv 11

Pleat Spacing on Filtrete® Micro Allergen Reduction Filter
The Filtrete® Micro Allergen Reduction Filter carries a 3M Microparticle Performance Rating (MPR) of 1000 - roughly equivalent to a MERV 11 rating

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Old 02-12-2011, 01:53 PM   #17
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what is best furnace filter to buy?


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Filters except 3m are rated in MERV (google that for more info). The higher the merv the more air is restricted and the harder it is for your furnace fan to move it. This can result in an overheated and damaged furnace or frozen and damaged AC. Only way to know for sure is to try it and check the temp rise thru the furnace after is has run for 5 minutes. Stick a thermometer in the supply duct downstream a foot away from the plenum and subtract the house temp from it and check the temp rise specs on the model # sticker inside the furnace. ie:35-65degF. I recommend a Merv 8 filter and unless you have a newer furnace with an ECM motor and large ductwork you can have problems with the more restrictive types. AC needs checking by a Pro to see if it has enough airflow.

http://www.furnacefiltercare.com/merv-ratings.php
So I should get this one?

http://www.filtrete.com/wps/portal/3...gl85WZKW2WB2bl
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Old 02-12-2011, 02:00 PM   #18
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what is best furnace filter to buy?


You could try that, but, again do you have a meat thermometer? With one of those filter in place and the furnace running for about 5 min put the thermometer in the plenum above the heat exchanger and see what temp you are getting, then look at the thermostat and subtract that temp from the one you measured.

Take that and look at the tag in the furnace, are you in spec? If you are no problem if you aren't then change the filter to a lesser grade.

Heres a complete list that I have found, I mispoke I though a rating of 1000 was closer to MERV 8 it not and MERV 8 is what you furnace heat exchanger was designed for.

Here are some of the Filtrete filters offered by 3M:
Dust & Pollen Filter, Microparticle Performance Rating 600,
MERV rating of 8
Micro Allergen Filter, Microparticle Performance Rating 1000,
MERV rating of 11
Ultra Allergen Filter, Microparticle Performance Rating 1250,
MERV rating of 11
Advanced Allegen Filter, Microparticle Performance Rating 1500,
MERV rating not available

Good Luck,

Mark
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Old 02-12-2011, 02:00 PM   #19
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what is best furnace filter to buy?


Those red ones are not too bad and don't seem to cause problems where I am but for some reason we have larger ductwork than a lot of what is commonly used in the US. I prefer filters with a Merv rating stamped on them like the True Blue kind from HDepot. The other guys are a bit vague in their info. Irregardless of what you use the temp rise should be checked thru the furnace and airflow and freon pressures check in the summer by a Pro.
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Old 02-12-2011, 02:02 PM   #20
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When checking temp rise it is important the thermometer be a foot downstream from the plenum/bonnet and not be able to "see" the heat exchanger as radiant heat from it will give a false reading.
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Old 02-12-2011, 02:04 PM   #21
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what is best furnace filter to buy?


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Originally Posted by yuri
Those red ones are not too bad and don't seem to cause problems where I am but for some reason we have larger ductwork than a lot of what is commonly used in the US. I prefer filters with a Merv rating stamped on them like the True Blue kind from HDepot. The other guys are a bit vague in their info. Irregardless of what you use the temp rise should be checked thru the furnace and airflow and freon pressures check in the summer by a Pro.
The 700-1085? I think 600 sounds like the way to go.
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Old 02-12-2011, 02:06 PM   #22
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I would start with it. May want to buy one of the higher grade but get the temps and freon pressures checked normal preventative maintenance that needs to be done) and ask the tech whether it is safe to use. No way to verify that over the net.
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Old 02-12-2011, 02:10 PM   #23
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what is best furnace filter to buy?


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Originally Posted by yuri
I would start with it. May want to buy one of the higher grade but get the temps and freon pressures checked normal preventative maintenance that needs to be done) and ask the tech whether it is safe to use. No way to verify that over the net.
You would start with 700-1085 vs 600? Wouldn't 600 be safer to start with?
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Old 02-12-2011, 02:13 PM   #24
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Start with the lowest grade (600)which is safer, and work your way up one grade if you find it is not doing as good a job as you like. If you want a REALLY good filter system which has very little resistance/pressure drop we install these on 95% of our jobs. 5" pleated filter. Need a contractor to install it if you have room in your ductwork or when you get a new furnace.
http://www.lennox.com/products/indoo...-systems/HC10/
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Old 02-12-2011, 02:14 PM   #25
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Its all based a heat exchanger performance, if you are not going to check that performance than yes for sure stick with the 600.

If you are going to measure the perfomance then you can experiment.

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Old 02-12-2011, 03:07 PM   #26
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Weird thing is consumer reports rates the 3M 2200 the highest. 600 the lowest.
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Old 02-13-2011, 05:40 AM   #27
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what is best furnace filter to buy?


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temps and freon pressures checked normal preventative maintenance that needs to be done) and ask the tech....
That's really the key: find an HVAC contractor who knows how to measure actually performance, and understands what the measurements mean. This is common in the commercial HVAC world, but at least here in Chicago such contractors are far in the minority at residential work - a few percent of the total.

(I know this because these tests leave physical evidence they have been performed, and I almost never see such evidence at home inspections).

There are reasons why this is so: such testing it takes time, it's hard to get customers to pay for this sort of investigation, it's hard to get customers to understand the result, and it's really hard to get customers to pay to fix the problems that are found - both because it's often expensive to do so, and because "it seems to be running fine as it is...".

But... these are the contractors who will find the furnaces that are running at far below potential efficiency because of poor design and incorrect installation, and the ones who can achieve additional efficiency at existing installations.
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Old 02-13-2011, 05:51 AM   #28
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what is best furnace filter to buy?


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Weird thing is consumer reports rates the 3M 2200 the highest. 600 the lowest.
They are testing in a very narrow context, not in terms of overall system performance.

Also, the situation is complicated.

For example, a filter that traps a greater percentage of the airborne particulate matter should in theory decrease the amount of material trapped on the AC coil, which should slow the rate at which such material decreases system performance - however the rate at which material sticks at the coil also depends on particulate size, and as a filter traps increasingly smaller particles, it has decreasingly less effect on how material is deposited at the coil... it makes a difference whether you are filtering out cat hair or pollen.

____________

As noted above, one way to both increase capture and reduce back pressure at the filter is to use a thicker pleated filter, which has greater surface area.
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Old 02-13-2011, 07:00 AM   #29
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what is best furnace filter to buy?


Use a standard pleated air filter. And a bypass HEPA filter.
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Old 02-13-2011, 08:02 AM   #30
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Like this one:

http://www.lennox.com/products/indoo...-systems/HEPA/

There are other brands (Lifebreath makes one). They can be expensive to maintain as a HEPA filter kit may be $200 or more. Great for people with allergies, asthma etc.

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