03 - Determining Air Conditioning System Capacity

Learn BTU capacity concepts, ACCA Manual J/S basics, sizing tolerances, and the risks of under- or over-sized cooling systems.

Show Notes:

Episode Overview:
Inspectors are not required to confirm exact BTU capacity but should understand capacity concepts to assess potential sizing issues. Learn ACCA Manual J (load calculation) and Manual S (equipment selection), ideal sizing tolerance (within ~½ ton), and risks of improper sizing. Includes rules of thumb and geographic variability cautions.

What You'll Learn: • ACCA Manual J (loads) and Manual S (capacity) workflow • Ideal sizing tolerance: within ~½ ton of calculated capacity • Risks of under-sizing (insufficient cooling, high energy use) • Risks of over-sizing (short cycling, poor humidity control, discomfort) • Common rules of thumb (400-800 BTU per 1,000 ft²) and their limitations • Geographic and climate variability

Key Takeaways: ✓ Understand capacity concepts without performing Manual J calculations ✓ Recognize signs of over-sized or under-sized systems ✓ Use rules of thumb cautiously and understand their limitations

IRC Code References: ACCA Manual J & S; IRC 2018 Chapter 14

Study Tips: Practice estimating capacity for sample homes using rules of thumb, then compare to actual installed capacity.

Intro

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This episode is hosted by Charlie Bellefontaine of Chicagoland Home Inspectors

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