Hey Ed, What Is the Correct AF on a Fire-Fueled Furnace?

In this edition of "Hey Ed," Ed talks about the correct air flow for a fire-fueled furnace.

Hey Ed, what is the correct AF on a fire-fueled furnace? The correct AF on a furnace, and hey, I know what you’re thinking. Air flow, I think everybody knows that’s what that stands for. Air flow on a fuel-fired furnace. Every manufacturer puts out a furnace, whether it’s an oil furnace or a gas propane natural furnace, on the data plate. And I’m dating myself when I say data plate. They’re not plates. They probably haven't been plates for 25 years. They’re stickers. But on that sticker, it will tell you a range, making up numbers. I’m going to say 25 to 50 is what’s published inside of a furnace. We’re going to take the 25 and the 50. We’re going to add them together. We’re going to divide by two. And our target temperature rise on that furnace, based on the guidance that you’ll find in manuals, is in the middle of that temperature rise. And that’s the way I see it.