Using the nominal 400 CFM per ton, how much airflow does a 3-ton air conditioner need?
Answer in CFM.
Show the answer
1200 CFM
Airflow = tons x 400 CFM per ton = 3 x 400 = 1,200 CFM.
Reference: Nominal airflow per ton of cooling
TradeExamPro › HVAC & Refrigeration
HVAC Fundamentals Practice Test
The refrigeration cycle, airflow, electrical and controls, heating and service practice, as tested on state HVAC licence exams and NATE-style certifications.
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Mixed practice test
10 questions, graded as you go, with the reason for every answer. No sign-up.
Timed mock exam
50 questions in 60 minutes, drawn from every topic. No answers shown until the end, then a score, your weakest topics and a review of what you missed.
Practise by topic
- Airflow psychrometrics 30 questions
- Electrical controls 35 questions
- Heating 30 questions
- Install service safety 30 questions
- Refrigeration cycle 35 questions
Sample questions
A heating element with a resistance of 12 ohms is connected to 240 V. How much current does it draw?
Answer in A.
Show the answer
20 A
I = E / R = 240 V / 12 ohms = 20 A.
Reference: Ohm's law
A furnace has 68°F return air and 125°F supply air. What is the temperature rise?
Answer in °F.
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57 °F
Temperature rise = supply air temperature - return air temperature = 125°F - 68°F = 57°F.
Reference: Furnace temperature rise
An air conditioner delivers 36,000 Btu/h while drawing 3,000 W at the rating condition. What is its EER?
Answer in Btu/Wh.
Show the answer
12 Btu/Wh
EER = cooling output in Btu/h / power input in watts = 36,000 / 3,000 = 12.
Reference: Energy efficiency ratio
What leaves the outlet of the metering device and enters the evaporator?
- A cold low-pressure vapor with several degrees of superheat
- A warm high-pressure liquid with several degrees of subcooling
- A cold low-pressure mix of liquid and some flash gas
- A cold low-pressure liquid with no vapor present at all
Show the answer
C. A cold low-pressure mix of liquid and some flash gas
The pressure drop across the metering device makes part of the liquid flash to vapor, which cools the rest to the evaporator saturation temperature, so a mostly liquid mixture enters the coil. It is not superheated vapor yet; superheat is only picked up near the evaporator outlet after all the liquid has boiled.
Reference: Metering devices; flash gas
Exams this helps with
| Exam | Who runs it | Where |
|---|---|---|
| HVAC / mechanical journeyman ready | State and local boards | United States (varies by state) |
| HVAC / mechanical contractor ready | State boards | United States (varies by state) |
| NATE Ready-to-Work and HVAC Support ready | NATE | United States |
| NATE air conditioning service and installation ready | NATE | United States |
| NATE heat pump service and installation ready | NATE | United States |
| NATE gas heating service and installation ready | NATE | United States |
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