After how many hours should a filter be changed

[Kooshball]

All the pleated filters that I buy recommend changing every three months. In NC June, July & Aug have much more HVAC activity than Sep, Oct, Nov so why not specify an interval based on hours instead of time?

I have been tracking my hours and I have 200 on a MERV7 pleat installed in my ceiling which has been there for 6 weeks. The filter looks fine but that seems like a lot of hours.

Any hour based recommendations for filter changes?

Thanks

[david8370]

In the paperwork I received with my White-Rodgers thermostat, it says that 200 hours is typically about 30 days....unless you run your fan constantly.

[fixitguy]

Got 6 kids running around outside in the dirt?? 3 dogs with long hair??
Live at the intersection of two gravel roads....

the house keeper comes 3 times a week.. Theres the contrast,
so changing by the HOUR doesnt make sense does it??

Sensing the air pressure changes would show how dirty the filter is.
but that setup is more than you want to spend... So how about when it
looks dirty????

[pstu]

All the pleated filters that I buy recommend changing every three months. In NC June, July & Aug have much more HVAC activity than Sep, Oct, Nov so why not specify an interval based on hours instead of time?

I have been tracking my hours and I have 200 on a MERV7 pleat installed in my ceiling which has been there for 6 weeks. The filter looks fine but that seems like a lot of hours.

Any hour based recommendations for filter changes?

Thanks
You might take a look at this product, "GeneralAire G99 Air Filter Gage":

http://www.iaqsource.com/product.php?p=generalaire_g99&product=112063

Useful background information might be found in this publication relating to schools. Look especially in the section titled "Monitoring Pressure" as it relates to changing air filters.

http://www.epa.gov/iaq/schooldesign/hvac.html#Monitoring%20Pressure

Hope this helps -- Pstu

[jerryd_2008]

You might take a look at this product, "GeneralAire G99 Air Filter Gage":

http://www.iaqsource.com/product.php?p=generalaire_g99&product=112063

...

My new 5" filter came with a gauge like this on it. Need to calibrate it when a new filter is put in. Involves just turning gauge needle to clean filter setting with screw driver.

Are these pretty reliable and accurate enough?

[Henry1]

I bought one of those GeneralAire G99 Gages and mounted it in the return air plenum. It sometime sticks.

In the meantime, I bought a great Magnehelic (0"-.50" W.C.) on Ebay for only 15 or 20 dollars.

Run a 1/8" tube from the Magnehelic over to your return plenum (downstream of your filter) and you can get a much better idea when to change your filter based on watching the needle creep higher over a period of several months.

Stick to a good filter (I use a 4" thick Nordic Pure--best price, free shiping, best quality). Most filter manufacturers have a table that shows the range their filter operates at.

[HVAC9900]

Are using 4" pleats at work on the few rtu's we have, get 3000 hours between changes.