June 1, 2021

Condensing Vs. Non-Condensing Boilers

As the weather starts to warm up, you’re probably not thinking about your heating equipment or about anything having to do with condensing, but the best time to plan a replacement for your old boiler is when it’s not in high demand – aka during the warmer months of the year.

When it comes to having a new boiler installed, you have a few choices to make – what size do I need, what brand, and should I choose a condensing or non-condensing heating system. If you have an old boiler or furnace, it’s probably non-condensing since condensing type heaters are fairly new.

A boiler works by drawing heat from fuel as it burns. In both condenser and non-condenser boilers, that heat is sent through a heat exchanger, which transfers heat to the water that will eventually run through your radiators or baseboards. The problem is no fuel-burning system operates at 100 percent efficiency; some of the heat produced will be lost along the way, including through exhaust.

When it comes to choosing between condensing and non-condensing, how do you make the right choice? Let’s look at the differences between the two.

Non-condensing boilers

The heating temperatures are kept high enough to prevent water vapor in the flue gas from condensing. If it does condense, this condensate causes corrosion due to its acidity. But operating a boiler or furnace to prevent condensate also means that precious heat is lost to the atmosphere as the water vapor is released. This limits efficiencies to the 70-80% range.

Condensing boilers

In a condensing boiler the exhaust from the fuel burning process is routed to a secondary heat exchanger, which extracts more heat and diverts it back into your heating system (this process is skipped in a non-condensing boiler). By pulling more heat from the fuel burning process, your condensing boiler typically improves operating efficiency by 10 percent more, which means lower bills for you.

So why aren’t all boilers condensing?

Two reasons: First, non-condensing boilers are cheaper to manufacture – primarily because they don’t use the upgraded parts needed to handle exhaust during the second heat exchanger phase. The second reason? Because it requires an expert to install a condensing boiler in a way that ensures you’ll spend less on fuel than with a non-condensing boiler.

So which one is better?

From an energy perspective, condensing boilers are more desirable, even with a higher initial cost. However, there are other considerations for these systems.

Discharging the condensate

One consideration is that the acid in the condensate needs to be neutralized before it can be discharged to the drainage system. This is accomplished by a condensate neutralization kit, which is a key component of condensing systems.

Operating temperature

Because the operating temperature of a condensing system is lower, this affects the performance of the heat emitters and distribution system for boilers. You may need to change radiators and piping if you are replacing a non-condensing boiler with a condensing boiler.

Venting requirements

Venting for the two systems is different. Because of the non-condensing boiler’s higher operating temperatures, a metal type B vent with a vertical termination is required. Condensing boilers are vented with fan powered plastic (PVC) pipes that can be terminated through a side wall. The combustion air for condensing burners is taken directly from outdoors, unlike non-condensing systems that take air from the room.

Both condensing boilers, with Annual Fuel Utilization Efficiencies (AFUE) in the 95% range, and mid-efficiency boilers, with AFUEs in the mid-80% range, have their place depending on the home and homeowner’s goals when purchasing a new boiler.

If maintained properly both condensing and non-condensing boilers can provide many years of efficient, reliable home heating. However, as a general statement, non-condensing boilers tend to have slightly longer life spans in the 20 year or longer range where condensing products typically have lifespans of 15 years or longer. This, of course, is often dependent on proper care and maintenance.

If you’re purchasing a new boiler for your home and you don’t know which one to choose, give us a call and we can help you make the right decision.

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