Boiler Energy Code Rules: Input Size and Return Water Temperature
"Boiler Energy Code Rules: Input Size and Return Water Temperature" is lesson 6 of 7 in the Boiler and Steam Fitting (C-4) Learning Hub. It opens with "What Counts as a Commercial Boiler" and works through 5 short steps, then a worked example you can check yourself against.
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Steps in this lesson
What Counts as a Commercial Boiler
Mandatory Features: Section 120.9
Hydronic System Measures: Section 140.4(k)
High-Capacity Gas Boiler Systems: Section 140.4(k)8
How This Meets the Mechanical Code
The worked example in the course applies this lesson to a realistic job in 6 steps, starting with "Weighted efficiency".
What you'll be able to do
Explain the main idea of "Boiler Energy Code Rules: Input Size and Return Water Temperature" in plain language you can use on the exam.
Apply this step with confidence: "Hydronic System Measures: Section 140.4(k)".
Apply this step with confidence: "High-Capacity Gas Boiler Systems: Section 140.4(k)8".
Apply this step with confidence: "How This Meets the Mechanical Code".
Test yourself on the worked example and the quick-check quiz inside the classroom.
The diagram for this lesson, exactly as it appears in the Learning Hub.
The first steps of this lesson
Step 1: What Counts as a Commercial Boiler
2025 Energy Code §100.1 defines a commercial boiler as a boiler with a capacity (rated maximum input) of 300,000 Btu/h or more serving a space heating or water heating load in a commercial building, and a boiler system as one or more boilers with their piping and controls that supply steam or hot water to heat output devices remote from the boiler. The mandatory and prescriptive boiler rules below key off the input rating, so the first job on any boiler plant is to total the input of the boilers and note how many share a stack.
Step 2: Mandatory Features: Section 120.9
On newly installed commercial boilers, §120.9(a) requires combustion air positive shut-off on all boilers of 2.5 MMBtu/h (2,500,000 Btu/h) and above that are designed to operate with a nonpositive vent static pressure, and on all boilers where one stack serves two or more boilers with a total combined input of 2.5 MMBtu/h per stack. A flue damper or vent damper is a positive shut-off device (§100.1). Per §120.9(b), combustion air fans with motors of 10 hp or larger must use a variable speed drive or controls that limit the fan to no more than 30 percent of design wattage at 50 percent of design air volume. Per §120.9(c), boilers of 5 MMBtu/h and greater must hold stack-gas oxygen at 5.0 percent or less (dry basis) over firing rates of 20 to 100 percent, controlling combustion air with firing rate or flue gas oxygen, with common linkage or jackshaft prohibited; boilers with a steady-state full-load combustion efficiency of 90 percent or higher are excepted.
The remaining 3 steps, the worked example and the quiz are in the course. This is a preview. The full lesson, with the step-by-step explanations, a worked example and a quick-check quiz, is inside the classroom.
Independent exam preparation. Contractors Classroom is not affiliated with the Contractors State License Board, and no course can guarantee a passing result.
