The Red Seal current-exam information lists quantity of heat = CFM × 1.08 × temperature difference among the formulas supplied at the sitting. A candidate still has to recognize the quantities, keep the units straight and decide what the result means. This original example practises that reasoning; it is not a recalled exam question.
What does each number mean?
Sensible heat (Btuh) = 1.08 × airflow (CFM) × dry-bulb temperature difference (°F). CFM is cubic feet of air per minute, and Btuh is British thermal units per hour. For cooling, use the difference between entering and leaving dry-bulb temperatures as a positive magnitude. The Red Seal sheet lists 1.08 as its specific-heat-of-air factor; keep its imperial units with this equation. A Celsius difference cannot simply be inserted without the appropriate conversion.
This is a sensible heat calculation: it tracks the air-temperature change. It does not calculate moisture removal or total cooling capacity. The Red Seal sheet separately lists an enthalpy-change formula for total airside heat.
What does the worked example give?
Suppose a study problem gives 800 CFM and dry-bulb temperatures of 75 °F entering and 55 °F leaving a cooling coil. The difference is 20 °F. Substitute: 1.08 × 800 × 20 = 17,280 Btuh of sensible heat transfer. The numbers are chosen for arithmetic practice, not as a target temperature split or a field diagnosis.
Check the direction: warmer entering air and cooler leaving air mean sensible heat was removed from the airstream. If the answer choices are near each other, write the temperature difference and units before multiplying.
What if airflow is the unknown?
Rearrange the same equation: CFM = sensible Btuh ÷ (1.08 × ΔT). For a stated sensible load of 16,200 Btuh and a stated 15 °F temperature difference, the arithmetic gives 16,200 ÷ 16.2 = 1,000 CFM. Reinsert the result: 1.08 × 1,000 × 15 = 16,200 Btuh. That reverse check catches a misplaced decimal.
First ask whether the problem gives a sensible load. Using total cooling Btuh in this rearrangement can overstate the airflow when the coil is also removing moisture.
When is this formula the wrong tool?
Use the formula only for the stated airside sensible-heat problem. Moisture removal needs enthalpy or other latent-load information. The 1.08 factor is an approximation tied to air properties; real air density varies with conditions. Trane's design guidance uses an air-density and specific-heat factor that can differ from the common rounded value. For real commissioning, measure airflow properly and follow the equipment maker's procedure before drawing a fault conclusion from a temperature split.
This is distinct from refrigerant-side superheat and subcooling. To practise a different measurement sequence, see the pressure-control example. You can start with the free original sample; its draft questions do not reproduce Red Seal exam items.
Sources
- Red Seal: Refrigeration and Air Conditioning Mechanic exam information and mathematical formulasCurrent-exam counts and supplied formula list; checked 2026-09-25
- Red Seal: Refrigeration and Air Conditioning Mechanic trade pageCurrent-exam standard status; checked 2026-09-25
- Trane: design psychrometricsAir-density specific-heat factor varies; checked 2026-09-25
Examen Studio is independent and not affiliated with the Red Seal Program or Skilled Trades Ontario. This article is a study aid; on the job, follow current codes, regulations and manufacturer instructions.