Furnace filters

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I’ve read so much about which furnace filter to use...Yada yada...

MERV over 11 too restrictive. Repair guys use those flimsy filter things at $1 each. Electrostatic is the way to go. Get a lifetime filter and never replace again.

Does anybody definitively know? Experts please reply.
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Im not an expert by any means but i think it depends on how easy the filter is to change and how much stuff you are filtering.

I change my mothers every 3 months or so and its absolutely filthy. If i use the high dollar filters they clog and suck themselves inward bypassing, the cheapos seem to do the best trapping everything on one side and not imploding.

So my vote would be to try the cheapo blue glass media filter and check on it every month..if its not that bad then move up to a better one and check on it every few months.
 
I use the least expensive pleated filter, on the recommendation of the HVAC tech at work. Works for me.
 
I compromise with MERV 7 or 8 pleated filters. They catch more than the fiberglass cheapies and have more surface area. Mine are both in ceiling grills and I run my blower continuously and just change them when they look dirty which ends up being about every two months or so. I get them cheap because I work for Lennox and our filters are made specifically for us. If my unit in the attic had the space I would add a housing for a 5" filter, throw a MERV 10 or 11 in there, and just change it annually. I did add self adhesive door weatherstripping inside my grills so the filters are held in place and bypass is more or less eliminated.

There really isn't ONE right filter setup for every situation I'm afraid.
 
DBMaster, believe it or not, I’m still using a Pulse. Installed in 1994. Never changed plug. Only cleaned and replaced that filter. Which one of your filters should I use?
 
Originally Posted By: DBMaster

There really isn't ONE right filter setup for every situation I'm afraid.


Probably why they make various grades.

Like oil...
 
As I said, there isn't ONE correct filter. Regardless of the furnace type, the rest of the system can be very different from one installation to another (I'm talking about different plenums, return air setups, geography and weather conditions affecting what kind and how much dust you have, etc.). but, with that said, what size and how many filters does your house use?

MAYBE if I actually saw your system I could make a recommendation, but I'm no expert. I'm a supply planner and I manage inventories of various commodities. I'm not a tech, though, I have done some work on my own system and I've picked up a fair amount of knowledge over the years.

If your filter is turning into a dish there's too much restriction, period. My house was built with only ONE return air grill. When the system ran it sounded like a vacuum cleaner and the filter immediately looked like an inverted bowl. I built a return air plenum and added a second filter grill and return duct - much better.

Oh, and yes, those Pulse furnaces were very efficient for their time and durable as nails. One of the items out of the thousands I buy was the spark plugs, from Federal Mogul. Lennox discontinued them six years ago after FM decided to cut off our credit due to a single late payment of $1,200.
 
I have 3 return ducts upstairs and 2 return ducts downstairs. I currently have the downstairs ducts sealed off. If I open them, they pull "all" the air. I was wondering if there was someway to utilize them better? In the summer, I have to close off the finished basement blower ducts because it gets too cold. I open them up in the winter to keep it a little warmer. I'll send you some pics PM style. If you have time to comment, ok. If you don't, no big.


I'm using a Lennox Electronic Filter EAC-12 and the only other filter I use is a 1 inch 20x25 right beside the motor. Yep, it does sometimes dish....not good....

I was thinking about getting a 1 inch BOAIR 20x25.
 
My brother is a HVAC guy by profession. He put in a Goodman 90+ furance and an evaporating coil at cost for $1200 about 15 years ago. The air filter box takes a 16X20X5 filter.
A 5" thick air filter. I started out using the cheap 1" filters which the next owner of the house can is so desired. I switched to using MERV 13 filters and the dust is much less vs the cheap filters. Guess what? The blower motor went out.
It is a two stage motor and it cost me $600 for the motor! I'm not sure if the MERV 13 filter caused that or not.
 
I just read a review of this on CR. 4" deep filters performed the best. Unfortunately, I'm not set up for one.

Of the 1" thick types, Filtrete Healthy Living Ultimate Allergen Reduction 1900 MPR air filter scored excellent with minimal resistance. It's about $20 though.

You'll only get the best performance from such a filter if both supply & return air ducts are sealed.
 
I like electrostatic, but the collection plates are a hassle to clean and contacts can
break or bend.

I have a pleated filter first, then the electrostatic! Best combo ever, installer
of the new furnace didn't want to do the duct work for it, but I paid extra to get it!

Then I got the cold air return grills that have filter too as a DIY install, nice!

I'll never "need" duct cleaners again LOL
 
Just from my own personal reading when HEPA shopping, it seemed most common suggestion to avoid HVAC filters above MERV 8. It was the best middle ground for air filtering without excessive restriction causing cooling issues.

I run filtrete simply because I like lowes better than Home Depot, and try to get the MPR (600/800) closest 6/8 MERV, but it goes as high as 2800 MPR.

It's important to keep in mind that MPR is a rating only for small particles, and doesn't take small/large like MERV does. There's no real MPR = MERV chart I could find.

Run a MERV 6-8, and then a HEPA for the tiny stuff.
 
Almost all the pleated 1 inch filters have the problem of quickly restricting airflow. The higher the rating (MERV, etc.) the faster the filter will load up.
The washable filters can also be too restrictive. Although systems with ECM motors can compensate for restriction there is a limit and long term restrictions can cause coil icing when cooling, heat exchanger cracks on gas furnaces, and high pressure problems on heat pumps.

If you want to have high efficiency media filters I recommend you go as thick as possible and then select a high MERV rating.

I had a Carrier electronic air cleaner that finally failed, it was never as good as promised, I removed the cells and measured the space for a media filter.

I found a company the makes custom filters send me an 18 x 24 x 6 MERV 11 filter, $24 each minimum order of 4.

They last me about a year, fan running almost continuously, and no dust accumulating on blower.
 
Originally Posted By: dschultz
Almost all the pleated 1 inch filters have the problem of quickly restricting airflow. The higher the rating (MERV, etc.) the faster the filter will load up.
The washable filters can also be too restrictive. Although systems with ECM motors can compensate for restriction there is a limit and long term restrictions can cause coil icing when cooling, heat exchanger cracks on gas furnaces, and high pressure problems on heat pumps.

If you want to have high efficiency media filters I recommend you go as thick as possible and then select a high MERV rating.

I had a Carrier electronic air cleaner that finally failed, it was never as good as promised, I removed the cells and measured the space for a media filter.

I found a company the makes custom filters send me an 18 x 24 x 6 MERV 11 filter, $24 each minimum order of 4.

They last me about a year, fan running almost continuously, and no dust accumulating on blower.


I just found out what you did. My Lennox Electronic Filter is dead. It is a 16X25x5 on the inside. I'm gonna do just what you did and stick a Lennox filter in the empty slot. Wonderful! Thanks!
 
Originally Posted By: sleddriver
I just read a review of this on CR. 4" deep filters performed the best. Unfortunately, I'm not set up for one.

Of the 1" thick types, Filtrete Healthy Living Ultimate Allergen Reduction 1900 MPR air filter scored excellent with minimal resistance. It's about $20 though.

You'll only get the best performance from such a filter if both supply & return air ducts are sealed.
4 Pack of Filtrete 1900's at Sam's Club for $50.00. Order online.
 
I'm by no means an expert, only a homeowner.

I didn't want to waste money on changing filters to soon.
Or abuse the furnace blower and efficiency.

The furnace Co. shows a maximum static pressure of .50" of water column.
This info. is found on a sticker inside your furnace.

I then installed a Differential Pressure Gauge that reads the air pressure on each side of the filter.
You only need one gauge, I have two just to confirm accuracy.
NO filter - gauge reads 0
New filter - gauge reads .34
After 1 year, the gauge is reading .38 / filter is only slightly gray color with NO visual dirt
I could go longer, but will now change after 1 year.
Filter Co. says to change every 3 Months, so I'm saving money and not hurting the furnace efficiency.



Sorry the photos are turned, that's just the way they downloaded.

If anyone wants to order these gauges, I bought them on E-Bay (along with the mounting brackets).
 
DBMaster,

Same principal BUT, you need to measure the air pressure before & after the filter.
Look at the 1st photo to see where the tubing goes.

My gauges read in Inches of Water Column.
 
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