Replacing A/C filter by hours


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Old 09-06-07, 10:04 AM
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Question Replacing A/C filter by hours

I just installed a programmable thermostat. It has a feature that keeps track of the hours the A/C and heater run and will alert me to change filters at a set interval. I've been changing the filters every 30 days or so and have no idea how many hours of actual run time that is. I'm using 3M Filtrete filters (20x25x1 & 14x25x1). The house is about 2500 square feet. Is there some spec for actual hours of use? Thanks.
 
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Old 09-06-07, 12:52 PM
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Buy the hour! No! But if you are using the 3m filters Id keep changing them every 30 days so you don't do any damage to your system. Most other filters can go 90 days with out ant problems.
 
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Old 09-06-07, 03:44 PM
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park19, Welcome to our forums!

You don't say which Filtrete filter you have but the higher the filtration the more you have to pay attention to how often you change it.

Seasonal filter changes was pretty much the norm when everybody used simple throw away fiberglass filters but todays high filtration ones have to be monitored a bit more closely.
The greater the filtration, the more restriction it causes which in turn can cause problems with your furnace from being starved of air.

If you are using expensive higher filtration filters I would suggest you not go on a time basis but rather just remove the filter periodically and look at it.
You then can at least get some idea on what to expect for a lifespan.

I shudder when I see discarded filters that look almost as good as new which often happens when time is used.

Which Filtrete filter do you use?
 
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Old 09-06-07, 05:11 PM
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Originally Posted by GregH
You don't say which Filtrete filter you have but the higher the filtration the more you have to pay attention to how often you change it.

Seasonal filter changes was pretty much the norm when everybody used simple throw away fiberglass filters but todays high filtration ones have to be monitored a bit more closely.
The greater the filtration, the more restriction it causes which in turn can cause problems with your furnace from being starved of air.

If you are using expensive higher filtration filters I would suggest you not go on a time basis but rather just remove the filter periodically and look at it.
You then can at least get some idea on what to expect for a lifespan.

I shudder when I see discarded filters that look almost as good as new which often happens when time is used.

Which Filtrete filter do you use?
I buy their mid-quality, 1085 filters. They say on the wrapper, good for up to 3 months, but they are plenty dirty after 30 days. I used to buy the super cheap ones, but my wife suffers from allergies and asthma and the 3M filters seem to keep the dust down a bit.

I guess the timer feature on the new thermostat isn't that useful then. It does seem to count the total time the system is running, so that might be an interesting statistic. Thanks for the advice.
 
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Old 09-06-07, 07:17 PM
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Which is more efficient?

I'm playing with this new programmable thermostat and I'm wondering, what is more efficient; turning it up to 80 during the day when no one is here and then turning it down to 75 OR leaving it at around 77 during the day. I had it at 80 today and set it to 75 at around 4:30 and it took a good 3 hours of solid running to get back down to 75 degrees. It is summer in Texas after all.
 
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Old 09-06-07, 08:55 PM
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Max efficiency is reached after 30 minutes of runtime. So if you leave the unit off for a full eight hour day, minus the three to bring the temp down, so five hours of off time. It's kind of a toss-up. Run it one way for a month, then try the other way. Compare to average high temp for both months. It might give you a clue.

My unit also times actual unit run time. It does it in days however. With standard 40% pleats I change the filter after 30 days of runtime, or 720 hours. I arrived at this number by closely monitoring the amount of noise at the filter (using a db meter) and checking the actual filter condition. The filter wasn't plugged, but the noise level was becoming noticeable. As a start, try half that for the higher efficiency filters.
 
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Old 09-08-07, 09:17 PM
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Wink

We try and tell people to not use over a MERV 5 filter . Over that seems to be to hard on the blower.
 
 

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