HVAC Air Conditioning 3 — Questions and Answers
Question 1: What condition is indicated when a technician measures frost forming uniformly across the entire evaporator coil surface?
- Normal operation
- Low airflow across the coil (Correct answer)
- Overcharge of refrigerant
- TXV stuck open
Correct answer: Low airflow across the coil
Uniform frost across the entire evaporator typically indicates insufficient airflow, causing the coil temperature to drop below 32°F across its full face.
Question 2: Which refrigerant replaced R-22 as the standard for residential air conditioning in the United States?
- R-410A (Correct answer)
- R-134a
- R-407C
- R-32
Correct answer: R-410A
R-410A (sold under brand names like Puron) became the replacement for R-22 in residential AC systems due to its zero ozone depletion potential.
Question 3: What is the function of a crankcase heater on a compressor?
- Preheat suction gas before compression
- Prevent refrigerant migration and dilution of oil during the off cycle (Correct answer)
- Increase compression ratio
- Protect motor windings from overvoltage
Correct answer: Prevent refrigerant migration and dilution of oil during the off cycle
A crankcase heater keeps the compressor oil warm during the off cycle to prevent liquid refrigerant from migrating into the crankcase and diluting the lubricant.
Question 4: A technician measures a temperature split of 14°F across the evaporator (return air 75°F, supply air 61°F). What does this suggest?
- Normal operation for a properly sized system (Correct answer)
- System is significantly underperforming
- Refrigerant overcharge
- Condenser is fouled
Correct answer: Normal operation for a properly sized system
A temperature split of 14-22°F across the evaporator coil is generally considered normal for a properly operating air conditioning system.
Question 5: What is the purpose of the filter-drier in an air conditioning system?
- Reduce refrigerant pressure
- Remove moisture and contaminants from the refrigerant (Correct answer)
- Separate oil from refrigerant
- Meter refrigerant flow to the evaporator
Correct answer: Remove moisture and contaminants from the refrigerant
The filter-drier removes moisture (which can cause acid and freeze-ups) and solid contaminants from the refrigerant circuit.
Question 6: Which EPA section governs the handling and recovery of refrigerants?
- Section 404
- Section 608 (Correct answer)
- Section 609
- Section 612
Correct answer: Section 608
EPA Section 608 regulates the servicing, maintenance, repair, and disposal of stationary refrigeration and air conditioning equipment to prevent refrigerant venting.
Question 7: What does the term 'ton of refrigeration' refer to?
- The weight of the condensing unit
- 12,000 BTU/hr of cooling capacity (Correct answer)
- The refrigerant charge weight in the system
- 1 ton = 1,000 watts of electrical consumption
Correct answer: 12,000 BTU/hr of cooling capacity
One ton of refrigeration equals 12,000 BTU/hr, originally based on the heat needed to melt one ton of ice in 24 hours.
HVAC Air Conditioning 3
What condition is indicated when a technician measures frost forming uniformly across the entire evaporator coil surface?