Hvac air filters

[COcheesehead]

More pleats = less air flow right?

I just have to wonder about the efficiency of the more expensive "higher efficiency" filters. Don't they do the same thing a lower efficiency filter that is dirty does: reduce air flow?

Perhaps someone can explain to me what I am missing here.

I tend to think.you want to buy cheap filters and replace more often to get the greatest efficiency.

Density of the filter is different too. Traps smaller particles.

 

[ScoopKona]

I just finished changing all the hvac air filters in the house. I do it every 3 months like the package says. But they never really look dirty to me. I begin to wonder if I could change them less frequently. Do you change every 3 months?

Our house in Las Vegas has air conditioning. We don't use it. But we do use the furnace in the winter. So we need to clean our vents.

Buy the washable vents. They last a lifetime -- ours are nearly 20-years old. We take them into the shower quarterly. They have paid for themselves multiple times over. And our HVAC system is just as good today as the day we bought the house.

 

[mf15]

In addition to the furnace filter,there is the humidifier membrane and then
bulbs on the covid killer,UVC lamp.
Oldmike

 

[CardsFan]

More pleats = less air flow right?

I just have to wonder about the efficiency of the more expensive "higher efficiency" filters. Don't they do the same thing a lower efficiency filter that is dirty does: reduce air flow?

Perhaps someone can explain to me what I am missing here.

I tend to think.you want to buy cheap filters and replace more often to get the greatest efficiency.

Density of the filter is different too. Traps smaller particles.

The HE filters have will filter finer particles. That is what the MERV rating tries to show. They also have a much higher surface area (due to the deep pleats), so the pressure drop across them is not excessive, even though they are denser. They cost more to buy ($30-$50 a pop), but should not cost more to operate.

After seeing how dirty our filter was after one year, I will replace it more often. I have no doubt it was removing FAR more than the 1" filter we had before replacing the furnace and filter.

 

[Texas Proud]

I have a 5 inch 'whole house' filter that was advertised as a year long filter...


I change it around April 1st... use MERV 11 or 13...


Never saw a MERV 19

 

[Masquernom]

This information is from the AprilAire web site. Our house had the MERV 11 filter when we bought it. I changed to the MERV 13, and we have less dust now for sure. Had to buy a conversion kit for the filter housing to change filter type.


MERV 10, 11, and 13 filters should be changed annually; however, if you run your fan 24/7, check the filters at 6 months. All MERV 16, 213CBN, 413CBN, and 513CBN filters should be changed every 6 months.

These are just recommendations. Some filters may need to be changed more often and others less often.

How do I know when my filter is dirty and should be changed?
The color of the filter will change from a bright white to various degrees of dark gray. If you see dirt starting to cake on the outside of the filter, it should be changed immediately.

AprilAire air filters should typically be replaced every 6 to 12 months, saving you time and money compared to traditional 1-inch filters, which need to be replaced every 1 to 3 months.

 

[RetiredAndLovingIt]

Our house in Las Vegas has air conditioning. We don't use it. But we do use the furnace in the winter. So we need to clean our vents.

Buy the washable vents. They last a lifetime -- ours are nearly 20-years old. We take them into the shower quarterly. They have paid for themselves multiple times over. And our HVAC system is just as good today as the day we bought the house.

I've never heard of vent filters but it sounds like a good idea.
Are you talking about a foam type filter that goes inside your ceiling or floor air vents?
A link or photo of what you have would be helpful.

 

[ncbill]

Every few years I remember to replace the two filters I now have.

Since my idiot HVAC installers replaced a unit that only needed one filter with one that needs two.

When my current unit is replaced I'll make sure it goes back to only one filter needed...preferably 5" pleated instead of the 1" ones I have now.

 

[W2R]

I just finished changing all the hvac air filters in the house. I do it every 3 months like the package says. But they never really look dirty to me. I begin to wonder if I could change them less frequently. Do you change every 3 months?

Nope. I wait until they are really dirty and gross, due to LBYM instincts and the fact that I see no point in changing a mostly clean filter. Frank thinks I should, and sometimes he changes them for me earlier than I probably would change them, when he is over here.

 

[freedomatlast]

I change my Merv 8 filters once a year. After only 3 months, there is no significant increase in the amount of amps it takes to run the fan motor, which says the filter is still breathing fine. I do start to see an increase in month 11 and 12.

I tried the filters with a higher Merv rating, but didn't like the significant increase in amps that it took to run the fan motor with the higher restriction of air flow.

My personal opinion is that replacing furnace air filters every three months is analogous to changing motor oil in the car every 3000 miles. That is, in most situations, it's overkill, but greatly benefits the manufacturers of the products used.

 

[braumeister]

I'm very glad I saw this thread. I normally change our filter every three months, but I have often thought it was wasteful because it really doesn't look very dirty.

But with it on my mind I took a look yesterday, and noticed that it had been five months since my last change.

(I update a post-it note on the furnace when I change the filter.)

So I pulled it out yesterday and it was black. Those extra two months made an enormous difference, so I have now set a calendar reminder for the future.

 

[travelover]

I'm surprised that someone doesn't make a simple manometer to measure the air pressure loss across the filter. It seems like it would be a lot more objective than holding the filter up to the light.

 

[ScoopKona]

I've never heard of vent filters but it sounds like a good idea.
Are you talking about a foam type filter that goes inside your ceiling or floor air vents?
A link or photo of what you have would be helpful.

You can buy them on Amazon and the big box home stores like Lowe's. Just search for "washable air filter." The ones we bought 20 years ago are selling at Lowe's for $24. Frankly, I'm surprised people don't notice them when they go shopping for filters -- that's how we found them in the first place.

 

[RetiredAndLovingIt]

You can buy them on Amazon and the big box home stores like Lowe's. Just search for "washable air filter." The ones we bought 20 years ago are selling at Lowe's for $24. Frankly, I'm surprised people don't notice them when they go shopping for filters -- that's how we found them in the first place.

Got it, I was googling washable vent filter.
These washable ones look similar to the pad material used in my swamp cooler which can also last for years. I'll take a look next time I'm at Lowes or Home Depot.

 

[ScoopKona]

Got it, I was googling washable vent filter.
These washable ones look similar to the pad material used in my swamp cooler which can also last for years. I'll take a look next time I'm at Lowes or Home Depot.

I've had mine for 20 years and not only are they still in tip-top shape, so is my HVAC system. Best of all, one less worry.

 

[Montecfo]

I'm surprised that someone doesn't make a simple manometer to measure the air pressure loss across the filter. It seems like it would be a lot more objective than holding the filter up to the light.

Yes. And I'd like to use that to check the pressure loss from using expensive filters compared to cheap ones.

 

[Telly]

I'm surprised that someone doesn't make a simple manometer to measure the air pressure loss across the filter. It seems like it would be a lot more objective than holding the filter up to the light.

Well, somewhat like that...

The smaller furnace/AC I installed I used a Honeywell F200 media air cleaner with the remote status option. The front cover removes to access the 20" x 25" x 4" pleated media filter. In that cover there is a pressure differential sensor, and a low power transmitter powered by a CR123 battery. Mounting by the thermostat is a small remote indicator box with receiver and simple LCD display, also CR123 powered. If the pressure drop across the filter exceeds X inches of water column ("WC), the status changes. Also has a one-year timer in it, battery status, etc. I forgot what the "WC is to trigger it, it's in the manual. I usually use a MERV 11 or 12 filter in it. We've never gotten a filter in it dirty enough to trigger it.

I replace the filter every two years in the spring, on even-numbered years. The filter is large area-wise for the size of furnace. I chose it on purpose, as 20" x 25" x 4" is also the size of the Honeywell electrostatic precipitator I installed when I installed the big furnace/AC. If for some reason I should ever decide to quit using the precipitator, I can unplug its HV power supply cord, pull out its cells and pre and post filters, and slide in a same-size media filter.

A note to others... "Electrostatic Precipitator" was the original name for the concept, and I still use that name. Later it was changed to "Electronic Air Filter", as I guess E-P sounded too threatening.

Like Nuclear Magnetic Resonance, now "MRI" (Magnetic Resonance Imaging). Like "Computer Axial Tomography" shortened to CAT scan, replaced with "CT scan". Don't make people think they are being cut in half axially slice-by-slice

 

[target2019]

I've noticed that the used filters have less dirt since we acquired a Roomba vacuum. I change the cheap filter every 2-3 months.

 

[freedomatlast]

I'm surprised that someone doesn't make a simple manometer to measure the air pressure loss across the filter. It seems like it would be a lot more objective than holding the filter up to the light.

They do. See:

skip to about 3:30

But many people have the ability to measure amperes with a hand held DVOM that they already have. The more amps the fan motor is pulling the higher restriction of the filter.

 

[Steve s]

One winter had to replace Merc 8 after a couple months because furnace would shut down. That was the winter I purchased an ultrasonic humidifier. The humidifier would give out a white powder which plugged filter. Got rid of ultrasonic humidifier.

 

[Masquernom]

Yes. And I'd like to use that to check the pressure loss from using expensive filters compared to cheap ones.

Here you go, everything you need;

https://www.mcmaster.com/differential-pressure-gauges/

 

[kfsinc]

Way back when, I was an HVAC contractor. Sold hundreds of Aprilaire (HEPA) and GE (Electrostatic) filters. Moved on to another career and installed Aprilaire in several of my own homes. Wasn't a fan of the Electrostatic ones as they required power and were problematic.

My current home came with AirCare passive (non powered) Electrostatic filters. Even though we live in the 'woods' and have LOTS of Polen in the spring, they are noticeably better than anything I've had before.

They defiantly work as I have a noticeable reduction in airflow when they get dirty. The reduced airflow reduces the efficiency of my heat pumps. When they get dirty, every few months, I simply hose them off and re-install them.

 

[FIREarly]

Following the filter replacement instructions costs much less than the HVAC accidentally getting messed up and it'll be WAY more expensive.

 

[Murph]

Mine hardly get dirty, but I change them every 6 months whether they need it or not.

 

[Hermit]

Sounds like I am an outlier here. My furnace has a variable fan that speeds up when the filter gets dirty. I run the fan 24/7 during the heating season which is fairly long up here in the mountains. My wood stove is upstairs so I use the furnace fan to circulate the the air and keep the downstairs comfortable. It is also quite dusty here year round. I schedule the filter changes for once a month during the heating season. 45 days and they are really bad. In the summer I shut the furnace off. No air conditioning. BTW, once a month works out to about 720 hours between changes.