EngiMetric
HVAC & Services Calculation guide Understand a concept

Sensible load versus latent load, and why the split decides the equipment

Separating the heat you feel from the moisture you remove, and why a humid climate shifts the balance sharply.

The engineering question

A cooling load number does not tell you what to buy. How much of it is heat and how much is moisture?

Worked example

The figures below were produced by running the Sensible & Latent Heat Calculator with the same inputs — during the build, from its authoritative engine.

Results
Sensible load 43200 Btu/h
Latent load 40800 Btu/h
Total load 84000 Btu/h
Equivalent capacity 7 tons
Basis Constants assume standard air (0.075 lb/ft³); the latent transfer uses 0.68 Btu·min/(lb·grain).
  1. Sensible load is 1.08 × CFM × ΔT for standard air.
  2. Latent load is 0.68 × CFM × ΔW in grains per pound.
  3. In humid climates the latent share is commonly half the total duty.

Sanity check

A coil selected on the sensible load alone will not control humidity. Add the latent component before choosing capacity.

Tools for this problem

These are the EngiMetric calculators that compute the numbers in this topic. Each one shows its formula, its units and its limits rather than returning a bare result.

References & standards

  • ASHRAE Handbook — Fundamentals, load processes
  • ACCA Manual J — load calculation

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