Condensing boilers are heating systems designed recover heat from exhaust gases. This process, known as condensing, allows these boilers to achieve efficiencies exceeding 90%, far surpassing the 70-80% efficiency typical of older, non-condensing boilers.
How Do Condensing Boilers Work?

Our Team Installing A Condensing Crest Boiler At A University
Condensing boilers are specifically designed to heat water for hydronic systems, which distribute hot water to radiators, underfloor heating, and other heating components. While they don’t purposely generate steam, small amounts of steam are naturally produced during the combustion process as a byproduct of burning fuel.
In older boilers, this steam, along with other hot exhaust gases were sent up the chimney, wasting valuable heat. Condensing boilers, however, are designed to capture this wasted heat. They cool the exhaust gases, causing the steam to condense into water. The heat released during this condensation process (called “latent heat”) is then reused to warm the water in the system. This makes condensing boilers far more efficient than older designs!
The resulting condensate, is slightly acidic, and needs to be run through a neutralization kit to prevent damage to plumbing and the environment.
Advantages and Things To Consider
Advantages
- High Energy Efficiency Condensing boilers achieve efficiency levels between 90% and 98.5% by extracting additional heat from exhaust gases through a secondary heat exchanger. This process reduces fuel consumption and lowers energy bills.
- Reduced Environmental Impact By utilizing more energy from the combustion process, they emit fewer greenhouse gases, contributing to a lower carbon footprint.
- Sealed Combustion Sealed combustion systems draw air directly from the outside and exhaust flue gases directly outdoors. This varies from traditional systems that draw air from the indoor space. This new design improves efficiency by preventing conditioned indoor air from being used in the combustion process.
Disadvantages
- Complex Installation and Integration Retrofitting condensing boilers into existing heating systems can be challenging. They often require modifications to the current setup, including the installation of a condensate drain and ensuring compatibility with low-temperature return water systems. A study done by ASHRAE Philadelphia goes on to say; “Designing an energy-efficient design for a heating system using condensing boilers is completely different than designing a conventional boiler system. The goal in a conventional system design is to keep the boiler return water temperature above 140˚F (60˚C) . The goal for a condensing boiler system is to return 80˚F (27˚C) to the boilers to maximize efficiency. This difference in the optimal boiler EWT results in significant differences in systems. These differences include distribution piping design, operating system delta-T, coil selection, boiler sequencing, and system control. Given the cost premium of a condensing boiler, the designer’s goal is to make the system operate as efficiently as possible.”
- Higher Initial Costs The upfront cost of condensing boilers is typically higher than that of traditional boilers. However, the increased efficiency will lead to cost savings over time.
- Maintenance Requirements Due to their complex systems, condensing boilers may require more frequent maintenance. Components like the condensate drain can be prone to issues such as freezing in cold weather, which can lead to system shutdowns.
- Potential for Corrosion The acidic nature of the condensate produced can lead to corrosion if not properly managed. It’s essential to use corrosion-resistant materials and ensure regular maintenance to mitigate this risk.
Maintenance Requirements
Regular maintenance is critical to ensure the longevity and performance. Key tasks include:
- Heat Exchanger Cleaning: Prevents scale buildup and ensures efficient heat transfer.
- Condensate Neutralizer Monitoring: Keeps the pH of drained condensate at safe levels.
- System Pressure Checks: Ensures the boiler operates within recommended pressure ranges.
- Annual Professional Inspections: Includes combustion analysis, cleaning, and system tuning for peak efficiency.
Are They Worth It for Industrial Applications?
The answer depends on your specific needs. For industries focused on reducing operating costs and minimizing emissions, condensing boilers can be an excellent choice. However, success hinges on proper system design, professional installation, and regular maintenance to ensure peak performance.
Final Thoughts On Condensing Boilers
Condensing boilers are a highly efficient heating solution, achieving efficiencies over 90% by reclaiming wasted heat from exhaust gases. This reduces fuel consumption and greenhouse gas emissions, making them an environmentally friendly choice.
However, they require precise system design with low return water temperatures and corrosion-resistant materials. Retrofitting into older systems can be challenging, and the higher upfront costs must be weighed against long-term savings.
For industries focused on energy efficiency and sustainability, condensing boilers are an excellent option when properly installed and maintained. Give us a call at 1-800-237-3141 or schedule an appointment if you would like to see if a condensing boiler makes sense in your facility.