Ask Kaptain Kool: Unit Tons & Air Filters

Kaptain Kool here, ready to answer all of your HVAC questions. Have a question? Send me an email, and I’ll take a crack at it.

Kaptain Kool – What does it mean when my house has a ‘three-ton’ unit?

 — Andy, in Mesta Park

There’s funny story that circulates from time to time – a homeowner, upon hearing he’s to have a four-ton a/c unit installed, asks “How on earth are you going to fit that in my back yard?”

Your question is a fair one, one I’ve heard a number of times. Three tons of what, exactly? Like many things associated with older technology, this term has a bit of a funny origin. A ton refers to how much heat it would take to melt one ton of ice in 24 hours. It turns out that it takes 288,000 British Thermal Units (what we commonly call BTUs) to melt that much ice. Your a/c system tonnage is measured in BTU/hour, so we divide 288,000 by 24, and a one-ton unit is 12,000 BTU per hour, and your three-ton unit is rated at 36,000 BTU per hour.

If all that math isn’t your cup of tea, just know that the larger the tonnage, the more square footage the unit can cool. Resist the urge to oversize your unit by too much, though – an oversized unit comes at a cost of efficiency and can create humidity problems inside your home.

I keep hearing I should change my air filters every month. Is that really necessary?

— Doug, in Del City

The short answer is ‘maybe’. I definitely recommend checking your air filter every month, and making an assessment of how dirty it’s gotten in the past 30 days. It’s possible that you’re using a high-efficiency pleated air filter that can go a couple of months between changes. But for most folks, changing your air filter every month is the cheapest insurance against early breakdowns you can have. Set a reminder on your calendar and on the first of every month, pull your air filter out. If it’s dirty, go ahead and make the swap. It’s as simple as that, and your preventive maintenance is done.

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This post was written by Air Conditioning Service, Inc.