Choosing a new boiler for your home is an important decision. Making a knowledgeable choice can help you cut your home’s heating bill substantially. A high efficiency, gas-fired condensing boiler is one of the most economical and clean ways to heat your home, reduce your monthly heating bills, and lessen environmental impact. In most circumstances, a condensing boiler can be used to replace an existing boiler in an older heating system.
What makes a condensing gas boiler so efficient?
Condensing boilers produce heat by burning natural gas or propane fuel. The word “condensing” refers to the fact that these appliances are able to extract heat from the combustion process so efficiently that the flue gases leaving the boiler are at a much lower temperature than in a conventional boiler. The temperature of these flue gases is low enough that they actually condense inside the heat exchanger. That’s a good thing!
When fuel is burned in a boiler, it produces flue gas, similar to the exhaust from your car. This gas leaves the combustion chamber and enters the flue passages. The combustion chamber and flue passages (called the heat exchanger) are surrounded by water… the same water that is circulated throughout your home to deliver heat. By design, these flue passages harvest heat from the flue gas and transfer it to the water inside the heat exchanger. The more energy that the heat exchanger can harvest from the flue gas, the more value you get from every dollar you spend on fuel.
What is the Annualized Fuel Utilization Efficiency (AFUE) rating?
How much energy the heat exchanger extracts from the flue gas is referred to as the boiler’s Annualized Fuel Utilization Efficiency (AFUE) rating, and is often times described as an efficiency percentage. For example, a 30-year old boiler might be 70% efficient, meaning that for every dollar you spend on gas, 30 cents of heat escapes through the chimney or vent pipe. In comparison, a condensing boiler may provide up to 96% efficiency, which means that only 4 cents of heat escapes. That’s a big difference!
It may seem hard to believe, but upgrading from a typical 80% efficient boiler to any condensing boiler in U.S. Boiler Company’s extensive line can provide a 15-20% savings in energy. What this means for homeowners is that energy savings can be realized during the first year of operation, and every year thereafter!
A recognized symbol of energy efficiency is the ENERGY STAR® label. For a boiler to qualify for ENERGY STAR®, the product must meet or exceed the EPA’s minimum efficiency ratings. In U.S. Boiler Company’s line of condensing products, the Alpine, Aspen, K2 and K2 Combi boilers are ENERGY STAR rated.
Furthermore, condensing boilers are not just good for your wallet. They are also good for the environment. High efficiency boilers produce fewer emissions, which benefits everyone!
What is the difference between a condensing and a non-condensing gas boiler?
The biggest difference between condensing boilers and “conventional”, non-condensing boilers is “efficiency”. The most efficient boilers keep heat in the house rather than letting it escape through the chimney or vent pipe. An ultra-high efficiency boiler is able to keep more heat in the heating system, but the side effect is condensation.
So, back to the word “condensing.” As previously mentioned, the byproduct of harvesting more heat from the flue gas is the formation of condensate in the heat exchanger. Condensation begins when roughly 90% of the heat contained in flue gas is harvested. At this point, flue gas temperatures drop and as the flue gas cools, condensate forms in the heat exchanger.
Condensing boilers cool the exhaust gas so much that they can be vented with CPVC or Polypropylene (plastic) pipe, instead of the steel venting required by conventional boilers. They produce cooler exhaust because the extra heat has been harvested and transferred to the water in your heating system.
What happens to the liquid that is produced in the heat exchanger of a condensing boiler?
The condensate drains to the bottom of the heat exchanger and runs out of the boiler through a condensate drain. Because this fluid is a byproduct of combustion, it is acidic, typically between 3.2 and 4.0 pH (which is significantly less caustic than lemon juice or soda). The water from the condensate drain enters a device called a condensate neutralizer.
The neutralizer contains alkaline material (usually some form of Calcite), which is an environmentally friendly, chalk-like material that neutralizes the condensate. The condensate is then disposed of either down a drain or pumped out of the home.
Because this condensate is acidic, heat exchangers in a high-efficiency boiler need to withstand a low pH. All of U.S. Boiler’s high efficiency heat exchangers are made of stainless steel for long service life and reliability. The water produced in the condensation process can be destructive to conventional boilers, but condensing boilers are designed to operate under these conditions.
Is a condensing boiler the best choice for my home?
There are many factors to consider when determining the best choice for your home. The heating system in a home not only includes the boiler, but also all of the pipes, valves, pumps, and heat distribution as well. Your professional heating contractor will be able to determine what heating equipment will be best suited for your home heating system. You can browse our site for a heating contractor in your area.
Typically, condensing boilers operate most efficiently in homes with low system temperatures, such as those with radiant floor systems or in homes with high water volume cast iron radiators. In these applications, condensing boilers do not use indoor air for combustion and require a means to vent the boiler directly to the outside (not chimney venting). For high temperature systems, such as fin-tube style baseboard radiators, or in homes where it may be impractical to vent a boiler directly to outside air without using a chimney, a conventional cast iron gas boiler may be a more viable option. A consultation with a professional home heating contractor will provide the best answer.