Knowing the Basics of Setting Up Boilers, Furnaces Important in Making Them Last

Learning the importance of proper combustion in the modern home can go a long way in giving customers long-lasting products

Knowing the Basics of Setting Up Boilers, Furnaces Important in Making Them Last

Anthony Pacilla

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Shortly after the cave man made a fire in his cave, the first two combustion issues were realized. How do we get all this smoke out of the cave? And why are we suddenly so dizzy? Punching a hole in the top of the cave seemed to work well.

Later, when the tepee was erected, the understanding of exhaust and fresh air intake was recognized, as they had a smokestack penetrating the top and air openings in the skirt. Even though an actual open fire with no exhaust in your living area might be uncommon these days, we often overlook the importance of combustion within a tightly built modernized home.

It seems that we may have forgotten the combustion process because many of the houses we grew up in were older and “looser” homes — drafty single-pane windows, cracks in the basement window sills, old doors that didn’t shut all the way, spots where you can see daylight to the outdoors and uninsulated steel doors were the norm. These houses usually had very little insulation, large operational chimneys for old fireplaces, gable vents, space vents, vents to the outdoors in old boilers rooms and no vapor barriers.

The space heating and water heating equipment were unsealed open-burn chambers taking combustion air from the basement, which was an oxygen-rich environment because of how much fresh air could quickly be drawn in through this “loose” building structure. The result, most times, was an inefficient burn for each appliance as far as the utility bill was concerned. The combustion, on the other hand, made gas-fired appliances last a very long time because it was able to take the exact amount of air that is required for proper combustion. Because it was designed to operate this way, we routinely run into boilers or furnaces installed in the 1960s and 1970s that still work fine. This is what I call the “tepee effect” — air in, burn, exhaust out, repeat.

So why do many gas-fired units fail within a 10- or 20-year window while the predecessors lasted so much longer? You could argue that the quality of the material is inferior, but the combustion process is also an equally viable answer. Over the past few decades, we have decided to tighten up our houses to maximize energy efficiency. We’ve replaced those drafty windows with insulated, vacuum-tight windows, insulated the attic, insulated the walls, added vapor barriers, put spray foam in every crack, replaced those wooden or steel doors with high-insulation value doors and so on.

Well, guess what? Now your house is very tight — starving for fresh combustion air from the outside and lacking air to draft properly — and we are back to our cave man days to a certain extent. Unless you have a newer furnace or water heater that takes air from the outdoors directly through piping, you have a problem, especially with tank-type water heaters and 80% of furnaces.

Each Btu/h of gas burned requires about 50 cubic feet of air — that’s a lot of fresh air that your customer might not have available. So what happens? The customer will have incomplete and improper combustion. Improper combustion could potentially lead to all sorts of issues such as overfiring the unit, warping the metal, cracking the heat exchanger, burning recycled exhaust gas, setting off the carbon monoxide alarms and ultimately lead to premature unit failure.

Gas furnaces should be updated to the 90-plus high-efficiency units and piped to the outdoors. Too many times we have all seen the exhaust on these units piped outdoors but the fresh air intake is left taking air from the indoor space.

If the customer has a water heater that takes combustion air from the space it’s in, make sure you check your code book and installation manual to calculate how much fresh air it needs. Did the customer build a sealed room around their furnace and water heater with no way to get any fresh air? Especially in newer homes, this is standard practice. Can the problem be solved with installing a louvered door to that room to allow fresh air to enter the burn center?

If you have significant concerns after speaking with the customer about routine premature failures, you should do a few things. Check the gas pressure versus the rating tag allowances, do a proper combustion analysis with a combustion analyzer and compare it to the manufacturer’s allowances (even if that requires a phone call), and check the draft hoods (if applicable) with a match for back spillage.

We cannot allow builders and homeowners to trade a small percentage of utility or installation savings for a potentially life-threatening situation. Furthermore, we shouldn’t allow them to trade in these perceived savings for the cost of unnecessary and excessive repairs and replacement units due to improper combustion.  


Anthony Pacilla has been in the trades since he was 9 years old (family business). He started cleaning toilets, mopping floors and putting fittings away in the warehouse. As he picked up skills, he would add becoming a ground man and laborer. When he was ready, Pacilla became an apprentice and then a journeyman plumber. He graduated college with a business and economics degree and immediately wanted to come back to work in the family business. A few years ago, Pacilla become a licensed master plumber. To contact Pacilla, email


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