10 exam-style questions with answers and explanations, straight from our 1,050-question bank. Tap an answer to check yourself. When you're ready, take the scored version in the free practice test.
A contractor completes a Manual J load calculation for a residence and arrives at a design cooling load of 28,400 Btu/h. Concerned about an unusually hot summer, he adds a 15% safety factor before selecting equipment. This practice is:
Correct answer: D - Incorrect, since Manual J procedures are already conservative
Why does Manual J specify outdoor design conditions using a percentile value rather than the record extreme temperature for a location?
Correct answer: B - Sizing to a rare extreme oversizes the system for nearly all operating hours
A technician selects a condensing unit with a nameplate rating of 36,000 Btu/h for a residence with a design cooling load of 34,100 Btu/h. Before finalizing the selection, what must be verified?
Correct answer: A - Capacity at the job's design conditions meets both sensible and latent loads
A designer calculating available static pressure uses the filter's pressure drop as published for a clean filter. What is the consequence?
Correct answer: C - Available static pressure is overstated, producing ducts undersized in service
Two homes each report an indoor relative humidity of 50%. Home A is maintained at 70°F and Home B at 78°F. Which statement is correct?
Correct answer: D - Home B contains more moisture per pound of dry air
An instructor tells a class that infiltration only needs to be considered when calculating the heating load. This statement is:
Correct answer: C - Incorrect, since infiltration adds both sensible and latent cooling load
A duct system requires 1,150 CFM. The designer determines an available static pressure of 0.36 in. w.c. and a total effective length of 240 feet. What is the design friction rate, in in. w.c. per 100 ft?
Correct answer: B - 0.15
A heat pump's balance point for a particular residence is 34°F. At an outdoor temperature of 28°F, what is true?
Correct answer: D - Heat pump capacity is below the building load, so supplemental heat is needed
A residential duct system has 14 supply runs. To determine total effective length, the designer should use:
Correct answer: C - The effective length of the longest supply run plus the longest return run
A designer completes a whole-house block load calculation showing 32,000 Btu/h of cooling, and intends to size the duct system from this result. What is the problem?
Correct answer: A - The block load carries no room-level detail, so airflow per room is unknown
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