How to inspect furnace filters?

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Everybody says to inspect your furnace filters, but they don't say what to look for. On the TV news they always say it, then show a filter that is completely clogged. Obviously they should be replaced before that. So what should I look for to decide if I need to replace them. I have been replacing them every 3 months, but when I do I can barely tell the difference between the old ones and the new ones.
Bill
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On Wednesday, September 30, 2015 at 2:15:43 PM UTC-4, Bill Gill wrote:

If they are conventional filters, you can see dirt, they look darker than a new one. Mine can easily go more than a year. It depends how dusty your environment is, if you have pets, etc. If you can barely tell the difference, you're probably changing them too often. The typical 1" thick fiberglass type is almost worthless. It will hopefully stop some stuff, but to do any kind of reasonable trapping, you need one of the 4" thick ones or an electrostatic.
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On Wednesday, September 30, 2015 at 2:40:36 PM UTC-4, trader_4 wrote:

I don't know if 4" filter would fit on my furnace. At a minimum, some tin snips would be required.
I have something very similar to this, where the filter slips into a 1" slot in that space just above the left hand edge of the red & white label.
http://strandlund.com/wp-content/uploads/2014/02/62.jpg
The old furnace had a huge blower on the right hand side of the unit so that is where the cold air returns are. When the new furnace was installed, the cold air returns were just extended down to the floor and branched over to the furnace, just like in that picture. It would take some duct-work work to get a bigger filter in there someplace.
I use a 3 layered, reusable, washable filter that I blow out with a leaf blower about once a month. I blast it with the blower in the opposite direction of the air-flow arrow and watch the dust fly. I also take it apart and wash the foam sheets at least once a year.
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I listen for the sound to change.
As the filter loads up and air resistance increases, the sound from the return area gets higher pitched. Then I change them.
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On Wednesday, September 30, 2015 at 3:44:57 PM UTC-4, DerbyDad03 wrote:

The 4" type go into a filter holder that's between the return plenum and the furnace and it's designed to accept them. It's similar idea to where an electrostatic type filter would go. You couldn't put a 4" one into my furnace either, all it will accept is the minimal 1" type. Not sure if it's 4" or maybe 5", but whatever it's the larger, pleated type.
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On Wednesday, September 30, 2015 at 5:44:25 PM UTC-4, trader_4 wrote:

That was my point. If I want to "upgrade" to a 4" filter, I would have to design my own filter holder. It could be done (it's just duct-work work) but I'm not going to do it.
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On Wednesday, September 30, 2015 at 8:35:59 PM UTC-4, DerbyDad03 wrote:

You don't need to design the filter holder, they are available in standard sizes that mate with furnaces:
https://www.nationalairwarehouse.com/rheem-air-handler-media-air-filtration-system-21-wide-cabinet.html
I put one in when I replaced my furnace 4 years ago. But it would require some duct work.
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On Thursday, October 1, 2015 at 8:02:37 AM UTC-4, trader_4 wrote:

Oh, sorry...I'll re-phrase...
"If I want to "upgrade" to a 4" filter, I would have to design my own filter holder *holder*."

Why does that sound so familiar?
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trader_4 wrote:

In my house. actually original filter was Honeywell electronic. 16x25x5 pleated fit perfect in it's place. I alternate between pleated, or electronic one.(cleaned in DW)
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On 9/30/2015 11:15 AM, Bill Gill wrote:

We buy the cheap(est) -- DIRT cheapest! -- filters and try to replace them monthly. We tend to have a fair bit of dust/dirt from the climate in which we live so they get "visibly dirty" pretty quickly.
Our thinking is that it's easier to remember to do something (trivial) every month than to keep track of N month intervals.
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On Wednesday, September 30, 2015 at 2:12:01 PM UTC-5, Don Y wrote:

I write on my kitchen calendar to check and change filters every 3 months. No problem keeping track of when to do this.
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On 9/30/2015 1:32 PM, ItsJoanNotJoann wrote:

And when to fertilize the citrus trees, when to change the batteries in the smoke detectors, when the roof needs to be repainted, when the swamp cooler pads need to be serviced, etc.
We find it easier to just put things in very regular schedules: e.g., instead of fertilizing three times/year (as recommended), we fertilize monthly; cooler gets serviced at end of season with pads replaced (instead of waiting for the pads to *need* to be replaced); smoke detector batteries on New Years Eve; roof gets 20% serviced each year -- instead of once every 5 years; etc.
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On Wednesday, September 30, 2015 at 3:53:26 PM UTC-5, Don Y wrote:

I don't have any fruit trees. The smoke alarms 'tweets' when the batteries needs to be changed. You paint your roof??? No swamp cooler here, just central heat & air.

The cat does get his flea drop medication the first day of _every_ month. And the rechargeable tooth brush is run down completely and recharged the first day of every month.
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On 9/30/2015 10:12 PM, ItsJoanNotJoann wrote:

We have 6 citrus. Ensuring regular watering and fertilizing ensures large, tastey fruit (we just finished LAST year's OJ... now we have to wait until January for the next crop -- though the lemons will come due before then)

We don't wait until it starts it's INCESSANT chirping. Do you want to listen to it for an hour, day, week before you get around to replacing the battery? Easier to be proactive and replace it before it complains.

Yes. Common practice is ~every 7 years. If you *wait* 7 years, chances are you will end up with problems -- things that have "gone south" at year #3 and become problems long before #7.
So, *planning* on doing a portion of it every year reduces the effort required for "year #7 (or, year #5, in our case) AND ensures the roof gets looked at often enough that any problems get caught before they become "trouble". E.g., our roof is over 20 years old (25+) and still "intact". All neighbors have had theirs replaced in that time.

Heat, air and cooler. As cooler is on roof, it requires maintenance (make sure water line doesn't freeze in winter, make sure it is cleaned out -- mold, etc. -- at end of season, etc.) each season.

We try to do everything on a predefined schedule instead of having to be "reactive" -- or, remember more "complex" schedules. The effort is more expensive than the cost.
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On Thursday, October 1, 2015 at 12:40:13 AM UTC-5, Don Y wrote:

Yippee Skippee

I change it immediately upon hearing it tweet.

You live in a trailer? That's the only people I know who 'paint" their roofs.

Ummm, ok.

My central heat and air unit sits on a concrete pad in the yard next to my house.

Whatever works for YOU, my uncomplicated schedule works for ME.
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On 10/1/2015 2:54 AM, ItsJoanNotJoann wrote:

We watch neighbors with fruit trees that fail to produce "useful" fruit -- simply because they don't invest the effort beyond "token waterings". Or, let the fruit rot on the tree because they aren't inclined to pick it.
We deliver ~400 (large) limes to the laundry at one of the local hospitals for the (primarily Mexican) help there to enjoy (else, we would discard them -- our yearly lime needs are met with just a few dozen limes!). This year, we'll probably give the excess Navels to the food bank. The lemons will end up in my tea...

We don't keep "spare batteries" (for anything) on hand. I suspect this is true of many folks as it seems common for people to UNPLUG their smoke detectors when they start chirping. Then, forget to buy the battery and end up operating with no smoke detectors in place (at least, we hear of homes lost to fire wherein the smoke detectors had no batteries in them -- this seems like a logical explanation of what transpired).

I suspect 60-70% of the homes, here, are "frontier style" -- flat roofs. A small percentage are shallow peaked with asphalt shingles (which don't fare well in the heat/sun. Another group are ceramic tile (which are expensive to maintain).
Those with flat roofs regularly paint their roofs -- *not* to "seal" the roof (which is what most folks think) but, rather, to keep the sun's rays from degrading the underlying felt. There is also some benefit as it helps reflect heat off the roof instead of letting it soak through the roof to the living space immediately below.

At $5-8K, it's an expense you'd rather avoid!

Our furnace is indoors. The ACcompressor on a concrete pad outside. Swamp cooler is on the roof. Folks with heat pumps tend to have the entire unit located on the roof. Some folks will install AC compressor on roof as well (esp for a retrofit where it is not practical to route refrigerant lines to a pad adjacent to the house *from* the furnace which is typically centrally located.
Some folks have two or three AC units (very large homes).

Experience has taught us that *this* is what works best for us. We don't "discover" the filter needs to be replaced and then "discover" we don't have a replacement on hand. Instead, we treat it like any other "scheduled maintenance" item and replace it on *our* schedule (instead of *its* schedule) so we always know when we will *need* replacements.
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On Thursday, October 1, 2015 at 12:40:49 PM UTC-4, Don Y wrote:

Not even for flashlights? That seems risky. Do you change them on a regular schedule whether they need them or not? Do you not have any battery operated flashlights? That seems risky too.

How "common" do you think this is?
Yes, you hear about the homes/lives that were lost to those fires, but you don't hear as much about the people whose homes and/or lives were saved because their detectors worked. The good news doesn't often make the headlines because it doesn't sell.
"Family doesn't die in house fire. House saved. More at 11."
My guess is that "common" is not the right word to apply to the sad situations.
Just FYI...
Many new-ish battery operated smoke and/or CO detectors are designed such that they cannot be (easily) mounted if they don't have batteries installed. A spring loaded tab extends in such a way as to prevent either mounting or (with some older models) from closing the battery door.
Obviously, making the mounting impossible/very difficult is the best method to help prevent the "use' of a detector without batteries. The user would have to physically put the detector someplace else (hopefully not in a drawer) while they run out and buy batteries.
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On 10/1/2015 10:04 AM, DerbyDad03 wrote:

We have two or three of the larger "maglites", a couple of small "pen-light" style with rechargeable batteries, and numerous of the "disposable" HF offerings (again, with rechargeable cells).
We also have several "crank" flashlights and shake-lights.
In an outage, we use CFL's powered by any of the ~13 UPS's scattered around the house.
Most "batteries" here are AA or AAA (or, the larger gelled electrolyte/AGM batteries in the UPS's) -- all these small flashlights, remote controls, electronic magnifiers, etc. So, we keep 4 spares in a charger and swap them out with <whatever> needs them when the time comes.
Aside from the CO/smoke detectors, *nothing* uses 9V batteries so no reason to keep them on hand.

It do4esn't matter how common it is to the folks who failed to replace their batteries! :> It's not common for folks to get struck by lightning -- yet I don't run outside and stand under a tree when we have an electrical storm! :>

Of course! But, they were saved because they *did* replace their batteries. As *we* do! The difference is, we don't wait for the detectors to chirp to prompt us to do so.
When detector 1 chirps, do you JUST replace it's battery? What about the other detectors? Should you anticipate that they will be needing replacement soon? Or, wait for them to start chirping as well? (How is being proactive in that case different from my approach of anticipating detector 1's failure?!)

Note that modern smoke/CO detectors *acknowledge* this practice by requiring 110VAC operation (with battery for "backup") *or* having 10 year batteries, etc.
So, obviously "enough" people died because they (effectively) disabled their detectors to merit changes in the way those detectors are designed/made. That suggests *someone* thought it enough of a problem to address it!

Most detectors are *easily* removed. Ours require a twist to unlock the detector from the base, then unplug the three conductor cable assembly. Thereafter, where you put the detector is up to you -- the *house* won't complain that the detector is "missing"!
What *will* get complaints is a detector that chirps every few minutes until you "feed it". Given how easily it can be disconnected, it's obvious why so many *do* get disconnected -- "while I remember to run out and buy batteries" (which I suspect is rarely done "right now")
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On Thursday, October 1, 2015 at 1:22:05 PM UTC-4, Don Y wrote:

You're changing the subject instead of answering my question. I didn't ask how about terrible it is for those that have been impacted by their mistake, I asked you how "common" you think it is.
You said it was "common" for people to remove the batteries and leave them out. I say it isn't. A tragedy, yes, but common? I think not.

10 year batteries are not required nor do all "modern" battery operated detectors have 10 year batteries. "Modern" detectors that use standard batteries are readily available on the consumer market.
Scroll down past the 10 year battery section here:
http://www.kidde.com/home-safety/en/us/products/fire-safety/smoke-alarms/

Addressed it by offering options, but not by *requiring* it.
A problem doesn't have to be "common" for it to be addressed. It is not "common" for people to be killed by the Takata air bag inflator ripping through their necks, yet over 23 million inflators have been recalled.
My only objection is to your use of the word "common". In terms of the number of detectors installed, the practice of taking the batteries out, and leaving them out, is not "common". An issue worth addressing? Absolutely. Common? Until I see the numbers, I'll vote No.

I didn't say anything about detectors be hard to *remove*, I said that the newer ones are difficult to *install* without batteries - as a safety feature. Let me explain:
In the old days, you could twist the detector off the base, remove the batteries from the back, and simply twist the detector back on, saying to yourself "I'll pick up some batteries tomorrow". On some models, you could open the front panel, take the batteries out and close the door. Tomorrow comes and goes, as does the next day and the next, until that detector is forgotten about and people die.
These days, most detectors will not allow the user to twist the detector back onto the base without batteries installed. This adds a layer of safety because the detector will (hopefully) be left out in the open as a reminder that it has no batteries.

See my paragraph above. A detector that can't be remounted without batteries being installed first is much safer than the old style. Yes, you can still disconnect it, but hopefully people will now say "I'll pick up some batteries tomorrow. Since I can't reinstall this detector until I do, I'll put it right "here" as a reminder."
When my basement CO detector came to the end of it's 7 year lifespan, I took the batteries out to stop the chirping. I could not reinstall the unit. I brought it upstairs, put it on the kitchen table and then put my cars keys on top of it. I doubt that *I* would have reinstalled it without the batteries anyway, but I'm sure that some folks would have. I'm sure many lives have been saved because of that feature.
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On 10/1/2015 12:23 PM, DerbyDad03 wrote:

How long is "leave them out" to satisfy you? If they are "out" for an hour, a day, a week? The time when they are not installed represents the time when the detector is inoperative. The period of time when the occupants are not protected.
Do people leave them out *forever*? Doubtful. Do they leave them out for weeks at a time? Probably. How many things do you "drop everything" to address the instant they draw attention to themselves (chirp, chirp)? Or, do you put it on the shopping list for "next week"? Or, hope to remember it??
From a 9/2015 NFPA report:
Smoke Alarm Power Sources Hardwired smoke alarms were present in 48% of reported home fires with smoke alarms. Alarms powered by battery only were present in in 46% of reported home fires.
In reported home fires in which the fire was large enough to activate the alarm, - Hardwired smoke alarms operated 94% of the time. - Battery-powered smoke alarms operated in four out of five (80%) fires.
Reasons that Smoke Alarms Did Not Operate when Present in Large Enough Fires --------------------------^^^^^^^^^^^^^^^ In fires in which the smoke alarms were present but did not operate, - Almost half (46%) of the smoke alarms had missing or disconnected batteries. Nuisance alarms were the leading reason for disconnected smoke alarms. - Dead batteries caused one-quarter (24%) of the smoke alarm failures. - Only 7% of the failures were due to hardwired power source problems, including disconnected smoke alarms, power outages, and power shut-offs.
So, in response to your comment, below: "Common? Until I see the numbers, I'll vote No." I vote *yes* (70% of the fires!) -- unless you'd care to offer some OTHER numbers?

And for new homes, they must have an AC primary power source! This implicitly acknowledges the fact that batteries DON'T get replaced and that this leads to loss of life (see above)

See above. Or, do your own research if you distrust mine.

Having a bit of clutter around the house is not an effective deterrent. If the device was the size of a dishwasher, it might be ("Bob, will you PLEASE get some batteries so we can get this damn dishwasher-sized device out of the middle of the living room??"). I have the old smoke detector for the bedroom hallway sitting on a box of CAT5 wire, here -- has probably been here for months (as long as the box of wire!) since the time when I replaced it's *partner* (and opted to replace both to ensure they were electrically compatible with each other instead of risking an incompatibility)
I could just as easily have put it in a drawer, cabinet, garage shelf, etc.

Like the old detector that's been sitting here, by me?

You can't legislate or design-in common sense. I can put a dead battery in a detector and reinstall it "so I know where I've stored it". I can put a detector in a drawer, garage, etc.
I designed a "marine" autopilot many years ago. I wanted to install an annunciator to alert the "skipper" that we were approaching the programmed destination (otherwise, he would likely go aft or below deck to work on something *else* now that the autopilot had freed him from the tedium of steering the boat.
Boss laughed and said, "The first thing they'll do is cut the wires to your alarm. *THEN* what will you do?? (to protect them from themselves)"
IIRC, our current AC/DC detectors will let you silence the "chirp" for some period of time (hours??). But, it won't go away indefinitely. Despite the fact that AC power is ensuring the detector continues to provide its protective function.
So, when it becomes annoying, we *will* unplug it and set it aside (counting on the next unit to protect us). As we *rarely* buy batteries, its not likely that this detector will be put back into service in short order. Hence our practice of simply replacing batteries yearly. The expense isn't going to bankrupt us. And, doing so annually on New Year's (instead of August 19th or May 27th) makes it a memorable task.
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