Condensing boiler
What it is
Condensing boilers reclaim that latent heat by condensing the water vapor and transferring that heat to the incoming return water.
The combination of a gas-fired, modulating condensing boiler with baseboard convectors has become a common energy-efficient solution for space heating in cold climates.
The reason condensing boilers achieve such high efficiencies is that they have the ability to recapture the latent energy from the moisture in the combustion gases when those gases condense.
Hot water boilers include both condensing and non-condensing varieties. Condensing boilers are able to extract heat from water vapor in the combustion gases for use in producing hot water, and are typically more efficient than non-condensing models.
Its parts
- Outdoor reset
- If your existing standard boiler still works, you can reduce your annual energy use by adding a small modulating condensing boiler to your system. On the coldest winter days, the standard boiler will operate, and on milder days the more efficient condensing boiler will take over when lower boiler supply and return water temperatures can be initiated by the outdoor reset controls (see Figure 7 and Figure 8 below.)
- PVC vent
- The secondary heat exchanger extracts more heat from the combustion gas, cooling it to the point where there is condensation – hence these types of heaters are called “gas condensing.” These gas condensing tankless water heaters, like gas condensing furnaces, require venting through a vertical PVC pipe and a condensate drain.
Related pages
- Glossary: Condensing boiler
Its entry, and the guide's pages that use it.
- Hot-water heat
How hot-water boilers and radiators work, bleeding, pressure and efficiency
Sources
- U.S. Department of Energy. Boiler Replacement Package Performance Requirements, Savings and Costs (DOE Building Technologies Office).
- U.S. Department of Energy. Measure Guideline: Condensing Boilers - Optimizing Efficiency and Response Time.
- U.S. Department of Energy. Purchasing Energy-Efficient Boilers (DOE Federal Energy Management Program).
- ENERGY STAR. ENERGY STAR Commercial Boiler Design Guide.
- ENERGY STAR. How It Works - Whole-Home Gas Tankless Water Heaters.
- U.S. Department of Energy. Steam System Balancing for Multifamily Existing Buildings.