Do I need a new HVAC system?

Here’s a simple DIY trick to see if your HVAC system is literally burning money.

Check out the size of your ducts.

Ducts can only hold so much air. That won’t stop the unit from trying to meet the demand of the thermostat,and it’ll run as hard as it can until the thermostat shuts it off.

When a duct is undersized, it’s like trying to blow out a candle through your kid’s juice box straw. You blow as hard as you can and only so much air will pass through. Just like your furnace’s blower motor, you’re working way harder than necessary for flickering results.

A typical 2500-square-foot home should have an 80,000 to 100,000 BTU furnace. This information is sometimes visible on labels inside the faceplate, which usually lift off without any tools needed. The furnace includes the fan, aka blower motor, and is what moves air through your home.

However, even if you can decipher the BTUs—older units may have no label or the writing has long since faded—it may make little difference in how well it operates. And it would be hard to tell if the ducts are undersized.

Properly sized ducting means your furnace has a better chance for working at peak efficiency. This 8×12-inch ducting shown below is grossly undersized for the 2500 square foot home it services. It should start at a 8-inch-by-24-inch size.

Under-sized ducts is a common problem in both old and new construction. A quality HVAC contractor will spot this from a mile away and be able to recommend ways to save your furnace and save you some cash.

Happy birthday to me.

Mark

A licensed contractor, tool expert, wood and outdoor enthusiast, and elite Spartan Race competitor, he writes about home improvement and tools for national magazines and websites, and teaches hands-on clinics for other remodeling professionals. Check out his book, The Carpenter's Notebook.

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