CSLB C-20 HVAC ContractorPlanning and LayoutMedium
A load calculation determines a home's total cooling requirement to be 42,000 Btu/hr. How many tons of cooling capacity should the equipment be sized for?
- A3.5 tons
- B4.0 tons
- C4.5 tons
- D3.0 tons
Show answer & explanationAnswer & explanation
Correct answer: A. 3.5 tons
One ton of cooling equals 12,000 Btu/hr. Dividing 42,000 by 12,000 gives 3.5 tons, so a 3.5-ton unit matches the calculated load.
Why the other options are wrong
- B. This oversizes the unit beyond the Manual J load.
- C. This significantly oversizes the equipment, risking short cycling.
- D. This undersizes the equipment relative to the calculated load.
Ton of Cooling Conversion
One ton of air conditioning capacity equals 12,000 Btu/hr, used to convert calculated loads into standard equipment sizes.
- 1 ton = 12,000 Btu/hr
- Manual S matches equipment tonnage to Manual J load
- Oversizing by more than 15% can cause poor humidity control
Memory trick: Twelve thousand Btu makes one ton — remember the golden conversion.