The Federal Energy Management Program (FEMP) provides acquisition guidance and Federal efficiency requirements for commercial boilers, which is a FEMP-designated product category. Federal laws and executive orders mandate that agencies meet these efficiency requirements in all procurement and acquisition actions that are not specifically exempted by law.
Meeting Energy Efficiency Requirements for Commercial Boilers
Table 1 displays the FEMP-designated minimum efficiency requirements for commercial boilers. All Federal purchases must meet or exceed the thermal efficiencies listed in Table 1. These efficiency levels can be voluntarily adopted by non-Federal organizations, institutions, and purchasers.
|Table 1. FEMP-Designated Efficiency Requirements for Commercial Boilers
(300,000–10,000,000 Btu/hour Rated Capacity)
|Boiler Type (Fuel)||Thermal Efficiency*|
|Hot Water (Gas)||94% or greater|
|Hot Water (Oil)||85.5% or greater|
|Steam (Gas)||80% or greater|
|Steam (Oil)||83.5% or greater|
|*Based on Hydronics Institute, Method to Determine Efficience of Commercial Space
Heating Boilers (HI BTS-2000, Rev. 06.07).
Defining the Product Category
These efficiency requirements and the associated guidance apply to gas- or oil-fired, low-pressure hot water or steam boilers used in commercial space heating applications with a rated capacity between 300,000 and 10,000,000 Btu/hour. High-pressure boilers (i.e., those used in industrial and cogeneration applications) and residential boilers (i.e., those with a capacity less than 300,000 Btu/hour) are excluded.
FEMP calculated that a product meeting FEMP-designated efficiency requirements saves money in lifetime energy costs if priced no more than $25,000 above the less efficient alternative. The most efficient level saves the average user more money: $30,000 in lifetime energy costs. The complete cost-effectiveness example and associated assumptions are provided in table 2 and can also be reproduced in FEMP's Energy Savings Calculator for Commercial Boilers.
|Table 2. Estimated Lifetime Energy Cost Savings for a Gas-Fired, Hot Water Boiler with a Capacity of 50,000 Btu/hour|
The performance of the base model in Table 2 is based on ASHRAE 90.1-2007 and the FEMP-designated minimum efficiency requirement is for a gas-fired, hot-water boiler. The performance of the best available model is from the AHRI Directory of Certified Products. To view the full results and assumptions for this scenario, use FEMP's commercial boiler calculator's default settings (choose "new," "water," and "gas").
Products meeting FEMP-designated efficiency requirements or ENERGY STAR performance specifications may not be life cycle cost-effective in certain low-use applications, such as when a device is being purchased for backup purposes and will remain in off mode for most of its useful life. For most other average or high-use applications, purchasers will find that energy-efficient products have the lowest life cycle cost.
Complying with Contracting Requirements
These requirements apply to all forms of procurement, including construction guide specifications and project specifications; renovation, repair, maintenance, and energy service contracts; lease agreements; acquisitions made using purchase cards; and solicitations for offers. Energy efficiency requirements should be included in both the evaluation criteria of solicitations and the evaluations of solicitation responses.
Federal Acquisition Regulation (FAR) Part 23.206 requires Federal agencies to insert the clause at FAR section 52.223-15 in solicitations and contracts that deliver, acquire, furnish, or specify energy-consuming products. FEMP recommends that agencies incorporate efficiency requirements into both the technical specification and evaluation sections of solicitations. Agencies may claim an exception to these requirements through a written finding that no ENERGY STAR-qualified or FEMP-designated product is available to meet the functional requirements, or that no such product is life cycle cost-effective for the specific application.
Buyer Tips: Choosing Efficient Products
A boiler system should be capable of meeting the building's peak heating demand and also operate efficiently at part-load conditions. Selecting the right system and properly sizing a boiler requires knowledge of both the peak demand and load profile. If building loads are highly variable, as is common in commercial buildings, designers should consider installing multiple small (modular) boilers in addition to boilers that have modulating burners. In periods of low demand, some of the boilers can be isolated from the other boilers and not incur any standby losses or cycling losses. They can also be automatically staged such that each boiler is running at its most efficient operating point without incurring additional cycling.
For guidance on boiler rightsizing and quality installation, consult the American National Standards Institute/Air Conditioning Contractors of America Standard 5: HVAC Quality Installations Specification (ANSI/ACCA 5 QI 2010).
Federal procurement officers and buyers should consider specifying boilers with the following features:
Water temperature reset: Hot water boilers should have the capability for water temperature reset. This is typically based on the outdoor air temperature or the return water temperature. When the heating load is reduced, the supply water is set to a lower temperature.
Modulating burners: It is recommended that boilers have the capability to vary their heating output by modulating the burner. Most of the time boilers operate at part load. To prevent excessive cycling and the losses that accompany them, specify boilers that have modulating capability. A minimum turndown ratio of 4:1 is recommended for gas-fired, hot-water boilers. This is particularly important in condensing boilers that run more efficiently at part load.
Low mass: Because boilers cycle on and off and it takes time to bring a high mass boiler up to operating temperature, using low-mass boilers will reduce energy consumption. In addition, some boilers can be brought online quickly, therefore avoiding the need to keep a boiler on hot standby.
Remote monitoring capability: Remote monitoring capability is useful to manage boiler operation and to detect any malfunctions in a timely manner.
Precise air-fuel ratio control: It is important to keep the air-fuel ratio at optimum levels at part-load operation as well as full-load operation. This is better accomplished by using sensor-driven servos rather than a mechanical linkage (e.g., jack shaft) between the gas input and the blower damper. Oxygen trim systems should be used on larger boilers. Oxygen trim systems monitor the oxygen in the flue gas and adjust the air-fuel ratio for optimum combustion efficiency.
Optimum start control: An optimum start control fires up a boiler so that it fires just in time to heat up a building before it is occupied in the morning.
Hybrid System: Conventional boilers are more efficient under full-load conditions, while condensing boilers are more efficient under part-load conditions. A hybrid system combines conventional and condensing boilers with controls that operate each type when optimal. This approach can be used in retrofit applications where new condensing boilers are integrated into an existing modular system with conventional boilers.
Other enhancements: Other options to increase efficiency of the heating system include reusing heat from blow down and return condensate for steam boilers, using electronic ignition devices, and increasing boiler and piping insulation.
User Tips: Using Products More Efficiently
Several diagnostic and maintenance procedures are important to maintain efficient boiler operation. Flue gas temperature monitoring is useful in detecting efficiency and operating problems. Maintaining steady excess air levels (with an oxygen trim sensor) ensures that burners will mix air and fuel properly. Low water levels can damage boilers so water levels should be checked frequently, as part of a regular maintenance program. Water treatment can prolong boiler life as well as increase its efficiency. Waterside and fireside surfaces should be cleaned annually.
The Boiler Efficiency Institute provides maintenance and operation manuals for boilers and boiler control systems. To encourage quality operations and maintenance, building engineers can also refer to ASHRAE/ACCA Standard 180: Standard Practice for Inspection and Maintenance of Commercial Building HVAC Systems. In addition, the FEMP O&M Best Practices Guide, Release 3.0, Chapter 9 provides valuable information on operation and maintenance of boiler systems.
Finding More Information
- Air Conditioning, Heating, and Refrigeration Institute (AHRI)
- American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE)
Updated January 2014