313D Safety and Regulations 3 — Questions and Answers
Question 1: What does the ASHRAE Standard 15 primarily govern in HVAC applications?
- Energy efficiency ratings for air conditioners
- Safety code for mechanical refrigeration systems (Correct answer)
- Indoor air quality ventilation rates
- Refrigerant leak detection alarm thresholds only
Correct answer: Safety code for mechanical refrigeration systems
ASHRAE Standard 15 is the Safety Standard for Refrigeration Systems, covering safe design, construction, installation, and operation of refrigerating systems.
Question 2: Under the NEC, which article specifically addresses wiring methods and equipment for air conditioning and refrigerating equipment?
- Article 210
- Article 230
- Article 440 (Correct answer)
- Article 460
Correct answer: Article 440
NEC Article 440 covers air conditioning and refrigerating equipment, including motor circuits and overcurrent protection requirements specific to hermetic refrigerant motor compressors.
Question 3: A residential split system's outdoor disconnect must be located within sight of and within how many feet of the equipment?
- 25 feet
- 50 feet (Correct answer)
- 75 feet
- 100 feet
Correct answer: 50 feet
The NEC requires the disconnecting means to be within sight of and within 50 feet of the air conditioning equipment it serves.
Question 4: Which refrigerant classification under ASHRAE 34 indicates the highest flammability level?
- Class 1
- Class 2L
- Class 2
- Class 3 (Correct answer)
Correct answer: Class 3
ASHRAE 34 Class 3 refrigerants are highly flammable, with a flame propagation rate greater than 10 cm/s and heat of combustion ≥19 kJ/g.
Question 5: What is the purpose of a relief valve on a refrigerant receiver or storage tank?
- To regulate operating pressure during normal use
- To vent refrigerant when pressure exceeds safe limits (Correct answer)
- To prevent refrigerant from migrating to the compressor
- To equalize pressure between high and low sides
Correct answer: To vent refrigerant when pressure exceeds safe limits
Relief valves are safety devices that open to release refrigerant when pressure exceeds a preset limit, preventing vessel rupture.
Question 6: According to OSHA, what is the permissible exposure limit (PEL) for R-22 (chlorodifluoromethane) over an 8-hour workday?
- 500 ppm
- 1,000 ppm
- 1,000 mg/m³
- There is no established OSHA PEL for R-22 (Correct answer)
Correct answer: There is no established OSHA PEL for R-22
OSHA has not established a specific PEL for R-22; however, ACGIH has a TLV of 1,000 ppm and manufacturers recommend limiting exposure based on SDS data.
Question 7: When brazing copper refrigerant lines in a residential system, which safety practice is specifically required to prevent refrigerant decomposition into toxic by-products?
- Pressure-test the system before brazing
- Purge lines with dry nitrogen during brazing (Correct answer)
- Wear a full-face shield instead of safety glasses
- Use a self-igniting torch to minimize sparks
Correct answer: Purge lines with dry nitrogen during brazing
Purging with dry nitrogen during brazing prevents oxidation scale formation inside the tubing and prevents residual refrigerant from decomposing into toxic gases like phosgene.
313D Safety and Regulations 3
What does the ASHRAE Standard 15 primarily govern in HVAC applications?