Load Calc & Design

Manual J load calculation in plain terms — sensible vs. latent, design temps, equipment sizing and why oversizing hurts comfort.

5 guides

• Design Temperatures and What They Mean
  Design temperatures are the worst-case-but-not-freak conditions a system is sized to handle. What the outdoor and indoor design temps mean, why they're percentile-based, and how the temperature difference drives the load.
• Equipment Sizing: The Manual S Concept
  The load calc tells you the BTU/h; Manual S is how you pick actual equipment to match it. Why nameplate tonnage isn't the whole story and how rated capacity shifts with conditions.
• Manual J in Plain Terms: What a Load Calc Is and Why It Matters
  A load calculation in plain language — what it measures, why it beats rules of thumb, and what goes into figuring out how much heating and cooling a building actually needs.
• Sensible vs. Latent Load: Temperature vs. Moisture
  Cooling does two jobs — lowering temperature (sensible) and removing moisture (latent). Understanding the split explains why a house can be cold and clammy, and why equipment selection has to account for both.
• Why Oversizing Equipment Hurts Comfort and Humidity
  Bigger isn't safer — an oversized system short-cycles, leaves the house humid, creates hot and cold spots, and wears out faster. Here's the mechanism and how to talk a customer out of upsizing.

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