Vacuum Gauge for HVAC Filter Replacement?

[Raizinman]

My home furnace/Air Conditioner unit utilizes a Spaceguard 20x25x6 Merv 11 filter for filtration in the home. They cost around $25 to $35 each but last about a year. Because of the cost, I don’t like to replace these filters too early and if I leave them in too long, they start to restrict the flow of air inside the house. So, I’ve been pondering what is the best way to determine when to replace these filters? Inspecting them does not really work, as after a month or so, they get a layer of dust that is not really that much different visually than what they look like in 12 months. Time is not really a good basis, as sometimes depending on the weather (dry & dusty) causes the filter to clog faster than wet and humid weather. So I’ve been thinking for a more definitive way to determine when to replace the furnace filter. I thought if I added a vacuum gauge (can be found on ebay for less than $5 with free shipping) and mounted it between the blower motor and furnace filter, then as the filter clogged this should cause a restriction and show a reading on the vacuum gauge. Has anyone else tried this? Is this theory sound?

 

[pcgeek11]

Yes your thoughts are valid, this is common in industrial environments.

This is what you need.

http://www.amazon.com/General-G-99-Air-Filter-Gauge/dp/B005ES5IRI

or

https://www.everythingtruckparts.co...ogleshopping&gclid=CJbWgu2hhswCFYSDaQoddYYKyA

 

[bamx2]

also know as manometer

 

[boomerang]

Just for informational purposes I have a Carrier Infinity system that runs a pressure test every day at 1 PM and let's me know when the filter needs to be changed.

 

[mindless1]

Any furnace of that type is going to have a thermal sensor for the overheat shutdown circuit, that you can just read with a multimeter to see how hot it's getting and judge airflow from that, BUT it won't help during A/C months (though you could put another sensor after the A/C coil solely for your own reading of low temperature rather than high) and at some point even with a filter, you may find that the filter is less and less dirty each time and the temperature rise (or drop with A/C) is due to other portions like the fan squirrel cage or coil getting dirty. Of course those should be cleaned as needed, but a lot of people wait till it becomes a problem.