- Energy-saving opportunities exist through proper operation and maintenance practices, and through energy-efficient retrofits.
- Replacing a 15-year-old model could save you more than 20% or more on your fuel bills.
- Heat exchangers save energy by pre-heating the makeup water and cooling the blow-down water before discharge.
A significant amount of fuel is burned by U.S. commercial and industrial facilities to power boilers for raising steam. This steam is used for space heating, process heating, and to produce electricity. Despite the fact that boilers have been available for decades, many of today's boiler technologies and practices are not very efficient. Thus, potential energy-saving opportunities exist through proper operation and maintenance practices, and through energy-efficient retrofits.
The following guidelines and suggestions can help increase boiler efficiency and save on your natural gas fuel bill.
Operation and Maintenance Practices
- High, excess oxygen levels in your boiler will result in wasted heat and lower boiler efficiency. Excess oxygen levels should not exceed 6%. Periodically monitor flue gas levels and adjust boilers to maintain excess air at optimum levels. Inexpensive flue gas analyzers and oxygen trim systems can help to monitor and adjust excess air levels.
- Examine both shutdown and idle options during low demand periods. The article, Nights and Weekends: Boiler Load Management Strategies, identifies some factors to consider.
- Monitor flue gas temperature. If the flue gas temperature rises, it is an indication of scale or deposit formation on boiler tubes.
- Mechanically, or chemically, clean scale buildup off boiler tubes on a regular basis. Scale buildup will inhibit heat transfer and force the boiler to burn additional fuel to meet the hot water and steam requirements of the system.
- Make sure that excess carbon monoxide levels are within acceptable limits of 200 ppm. High, excess carbon monoxide levels are a sign that combustion is incomplete and fuel is being wasted.
- Inspect boiler insulation on a regular basis, and repair or replace any damaged or missing insulation.
- Check steam traps periodically for leaks. A leaking steam trap can result in additional natural gas consumption and increase annual energy bills by hundreds, or even thousands, of dollars. Excessive steam emanating from the feed water tank vent is an indication that there may be an internal steam leak.
Replace older boilers with new, more efficient models—Replacing a 15-year old model could save you over 20% on your fuel bills, around 32% if you are installing a condensing boiler, and up to 40% if you also install good heating controls. See the U.S. Department of Energy fact sheet How to Buy an Energy-Efficient Commercial Boiler.
Install a boiler economizer—Economizers pre-heat the feed water and increase boiler efficiency by 2% to 3%. Good candidates for economizer retrofits are boilers that exceed 100 hp and operate at pressures over 75 psig. For more information, see Use Feedwater Economizers for Waste Heat Recovery.
On larger boilers, install a blow-down heat exchanger—Heat exchangers save energy by pre-heating the makeup water and cooling the blow-down water before discharge. Boilers with continuous blow-down exceeding 5% are good candidates for heat recovery. For more information, see Recover Heat from Boiler Blowdown.
Consider installing a condensate return system to your boiler—Returned condensate saves on fuel, makeup water, and chemical treatment costs. Less condensate discharged into the sewer system can also save on disposal costs. For more information, see the U.S. Department of Energy fact sheet, Return Condensate to the Boiler.
Upgrade your boiler system with energy-efficient burners—The burner is designed to maintain the proper air-to-fuel mixture that will maximize combustion efficiency and minimize air emission. An efficient burner requires no more than 2% to 3% excess air. Replacing an older burner with a new, more energy-efficient model can result in significant energy savings and a quick payback. For more information see Upgrade Boilers with Energy-Efficient Burners.