On Sun, 15 Nov 2015 15:54:46 -0800 (PST), DerbyDad03
wrote:

On Sunday, November 15, 2015 at 6:44:05 PM UTC-5, Chicago Bob wrote:
I don't need a complex programmable thermostat. All I want is to know how

The programmable thermostat is meant for someone who leaves the house
empty when he goes to work, and/or who wants to save on heat or AC
when he's sleeping. In order to save money and conserve fuel.

many hours that fan has run so I know when to change the air filter. The
fan runs frequently in the summer and winter, but very infrequently in
the spring and fall. How often the fan runs is determined by temperature.
You can go weeks - or months - without the fan running at all.

All you need to do is keep track of the fan hours while checking the filter every
now and then.

I like your idea but I'd make it even simpler than this. Just keep
track of the weeks or months while checking the filter every now and
then.

Once you notice that it needs to be changed, you'll know how
many hours of fan operation it takes.

Once you notice it needs to be changed, you'll know how many months of
operation it takes.

From then on, all you need to do is keep
the amount of dust in your house exactly the same over those hours of operation

I think you were sarcastic here, but I still like your idea.

and you can change the filter based on run time.

Good luck with that.