View Full Version : "time to change filter" Meter ?
03-09-2005, 12:38 PM
I'm a homeowner. I've seen some kind of an inexpensive "meter" for sale for about $15 that you place in the return air stream/system that you 'zero' when you place a new filter(s).When the resistance/negative air pressure increases to a certain spot on the meter, It lets you 'know' it's time to change the filter(s) for your central hvac system...Are these bunk or are these worth fooling with? I'm trying to use the thicker pleated filters that last longer rather than the cheap monthly filters.
Thanks in advance, Mike
03-09-2005, 01:01 PM
I'm not sure this is helpful as I'm not familiar with that particular device. But in general, anything that helps remind a homeowner to change the filter in a meaningfull way would be good. We all tend to forget the maintenance required for the things we own inluding our bodies.
Some Thermostat systems have such a device built in such as the Honeywell Perfect Climate control system.
How that unit works is it keeps track of the actual time the blower is on and therefore the filter is used.
This is in contrast to the time honored tradition of marking the date of a filter change on the furnace and changing it at a certain time interval. The problem with the traditional method is that it does not keep track of actual use and doesnt compensate for vactions or hot or cold spells.
The device appears to use pressure drop. Pressure drop could be another way, but though the concept is problaby the best engineering wise, there could be a number if areas where the detailed implementatin of the concept causes problems. My beleif is that a well desinged pressure drop system is expensive and may not get you much more than an "ON time" indicator.
How much is the unit?
I'd also want to understand the installation issues in
Maybe someone else is familiar with the details
[Edited by hoffa on 03-09-2005 at 01:22 PM]
03-09-2005, 01:37 PM
You can just pull the filter out and see if it's dirty once a month and replace when needed. That doesn't cost anything and would probably be more effective.
03-09-2005, 01:41 PM
It costs time
03-09-2005, 01:55 PM
So does going down stairs to look at the meter that will probably be located in the r/a drop
03-09-2005, 02:11 PM
There is an area in the central part of my home (a partitioned off back of a colset) about 1 1/2' X 4 1/2' which houses the 20 X 25 filters ( X 2 filters) and has duct work in the top of this space that goes to the return plenum to the horizontal hvac unit in my attic. I considered puting this 'change filter meter thing' in this area where the filters are housed. Mike
03-09-2005, 02:12 PM
Agree - so the question is which takes less time, removing and inspecting the filter or looking at the meter.
The other option is the on-time alerts built into the Thermostats. There a red indicator comes on - no isntepction required.
03-09-2005, 03:16 PM
You probably should still change the filter monthly.
Good ones have smaller holes, and will restrict airflow quicker than the cheap ones.
I haven't seen the device you are talking about, but it certainly should work.
Large commercial systems use something similar.
Some window units have a little "tattle-tale".
Both of these are visual indicators.
A better device would shut the system down, if the filter gets dirty, or sound an alarm.
What is the name & model of this little gadget?
Where did you see it?
03-09-2005, 03:32 PM
probably talking about the "whistler"
round disk you stick to the filter when you change it, filter gets dirty and causes this to annoy you
most people put them on their dryer after the first change
03-09-2005, 03:33 PM
I think bwal is on to something. The reason pros use a pressure drop system is that at that price point of commercial units, adding a quality pressure drop system is attractive.
My concern remains whether a quality after market pressure drop system can be done. And if it can be done is this such a unit.
Interval replacement does not necessarily relate to useage - but it is the most common residential method.
If you just change filters on a fixed number of days, you have to pick a number based on worst case conditions. If your thermostat measures the hours the central fan runs, that will certainly be more in proportion to how much life the filter has left.
It is my understanding that commercial systems often use a manometer permanently connected, to tell when the pressure drop gets higher (i.e. when the filter loads up and should be changed). The following link is a cheapie meter that will do that:
This link has a clearer picture:
To actually say a homeowner can "look at" the filter and know when it needs changing... how is that not inferior to having a meter to actually measure pressure drop? How can it be easier to expose the filter, than to look at a wall mounted meter? I am simply not understanding how a measurement is anything but the best answer.
Unless it is a Carrier Infinity system which both measures and interprets the data, i.e. tells the homeowner how much filter life is left. Great if you have it, but of course the Infinity will cost somewhat more than $15.
Hope this helps -- P.Student
03-09-2005, 05:09 PM
P. Student posted links to the exact "gauge" I was asking about.
03-09-2005, 05:46 PM
It definately looks simple
03-09-2005, 06:26 PM
Originally posted by mikebean
P. Student posted links to the exact "gauge" I was asking about.
A Dwyer Magnegelic is a better device, really, as it doesn't require a fluid to operate.
You'd be looking for a low-range Magnehelic.
03-09-2005, 06:37 PM
The best way tom remember when to change your filter is the day your electric bill comes change filter.Or if you are online as much of us are; set your calender to remind you when every month or every other month..
03-09-2005, 07:34 PM
I have been installing the General media filters on all furnaces we install for years and they all come with this gauge. We installed them at first but now throw them away. You turn the fan on and then adjust a screw which opens and closes a air flow opening until you get the ball in the green area. The slightest turn of the screw will move the ball to much and its hard to get it to stay in the green zone. You end up coming back in a week because its in the red and then you have to explain to the customer why they should not pay any attention to this good looking gauge.
03-09-2005, 07:56 PM
Hey, it's a gimmick.
An expensive gimmick at that.
Look, man, just check the filter on a regular basis & change as needed.
03-10-2005, 09:36 AM
I like the idea of the Dwyer Gauge. What pressure range would be best for a home sysyem? 0 - 1, 0 - 2 ? Also, I wanted to use the High dollar ($20 -$30) 4 or 5 inch pleated filters (I need 2)because I thought they would last longer than the $2 monthly filters and I beleived they would do a fine job of filtering. I don't want to spend $50 a month to change them every time the electric bill comes. I could spend $4 a month for 2 crappy filters at $2 each and chance them with every electric bill. Are the 4 or 5 or 6 inch deep filters worth fooling with? My goal is to keep stuff off of my evap coils at a reasonable cost. Thanks, Mike
03-10-2005, 12:40 PM
well i dont know anything about these little "meters" but i have a dual RA and have to 2 filters.I went an bought the WATCH DOG which has A CO detector & a ANNOYING alarm that beeps to tell me to clean them ( washable) only thing is damn winter is here and it takes 2 days for them to dry so i have to make 2 trips to the basement to change the filters :)
I just tell my customers to check the filter when theier int he basement doing laundry any how;)
It seems there have been problems with this $15 gauge due to its cheapness and imprecision. Sad to hear if this is just not quality enough to do the job. For a techy kind of homeowner, you might consider a solution which does not have those quality drawbacks.
The Magnehelic gauge is a great idea but it's a little expensive isn't it?
Shopping on Ebay you can buy a Dwyer Model 25 in the $15-25 range. For example:
They seem to be pretty common, it's the red-oil type which has been made for decades. Screw it onto the wall somewhere, using the hardware that comes with. You can locate a 1/4-inch tube takeoff in the return plenum and basically measure the pressure drop across the filter. Note what it is when a new filter is installed, and the filter will need changing when you see maybe 0.1 inch w.c. difference from the new filter.
It seems to me that changing every 30 days is analogous to changing your car engine oil every 3000 miles. Virtuous but not necessarily what the equipment needs. And having a meter to measure pressure drop, is analogous to having a BMW with an internal computer to actually *calculate* when the oil needs to be changed. Of course if someone critiques this who really understands filtration, I may have to change my analogy some <g>.
Hope this helps -- P.Student
03-11-2005, 09:58 PM
I have the dwyer incline tube manometer, about $30. You could install that and mark the acceptable range with the included arrows- hi and low airflow limits. You would connect to supply and return to get the ESP reading.
Esp will indicate the excact airflow- dirty filter, too many registers closed or dirty coil. After all, its airflow that kills the equipment, whether filter or closed registers.
I came up with a simple unit that would use ESP to cut on the "check" light that many tstats have, about $60 for parts out of grainger catalog. Apparently that's too much and some people would not be able to wire it in, so its in drawer now.
The one you are looking at,works just fine,read the instructions and install it in the correct place.TTt
03-15-2005, 01:42 PM
Originally posted by hoffa
It costs time Thats the most ridicoulus(yeah,yeah) statement I`ve heard off. It takes time to wipe your ass off every time you take a **** but we still do it, right. It only takes 3 seconds: take it out, check it, put it back in if its clean. Now go back to being a couch potato.
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