CRC CRC Electrical, Plumbing & Mechanical Systems 2 — Questions and Answers
Question 1: A residential contractor is installing a 200-amp service panel. What minimum wire gauge is required for aluminum service entrance conductors at this ampacity?
- 2/0 AWG aluminum (Correct answer)
- 4 AWG aluminum
- 1/0 AWG aluminum
- 2 AWG aluminum
Correct answer: 2/0 AWG aluminum
For a 200-amp service, 2/0 AWG (double-ought) aluminum conductors are the NEC-approved minimum size for service entrance cables.
Question 2: What is the purpose of a 'expansion tank' in a closed-loop residential water heater system?
- To absorb thermal expansion of heated water and prevent pressure buildup (Correct answer)
- To store extra hot water for peak demand
- To filter sediment from the water supply
- To reduce water hammer in supply lines
Correct answer: To absorb thermal expansion of heated water and prevent pressure buildup
When a backflow preventer creates a closed system, an expansion tank absorbs the volume increase from heated water, preventing unsafe pressure spikes in the plumbing.
Question 3: Which type of duct insulation is required when supply ducts pass through an unconditioned attic space?
- Minimum R-8 insulation per the IECC (Correct answer)
- No insulation is required in attic spaces
- Minimum R-4 insulation
- Minimum R-13 insulation
Correct answer: Minimum R-8 insulation per the IECC
The International Energy Conservation Code (IECC) requires supply ducts in unconditioned attics to be insulated to at least R-8 to minimize heating and cooling losses.
Question 4: A homeowner complains of a 'water hammer' — loud banging pipes when a faucet is turned off. What is the best remedy?
- Install water hammer arrestors near the affected fixtures (Correct answer)
- Increase water pressure
- Replace all copper pipes with PEX
- Install a pressure-reducing valve at the main
Correct answer: Install water hammer arrestors near the affected fixtures
Water hammer arrestors contain a chamber with an air cushion that absorbs the pressure wave created when water flow is suddenly stopped, eliminating pipe banging.
Question 5: When sizing a residential HVAC system, what is the primary calculation method used to determine heating and cooling loads?
- Manual J load calculation (Correct answer)
- Rule-of-thumb square footage method
- Manual D duct design
- Energy Star rating system
Correct answer: Manual J load calculation
ACCA Manual J is the industry-standard protocol for calculating residential heating and cooling loads based on climate, insulation, windows, occupancy, and other factors.
Question 6: In residential electrical work, what is the purpose of a grounding electrode system (GES)?
- To provide a low-impedance path to earth that stabilizes voltage and dissipates fault current (Correct answer)
- To protect against arc faults in branch circuits
- To increase the ampacity of the service panel
- To balance loads across hot legs
Correct answer: To provide a low-impedance path to earth that stabilizes voltage and dissipates fault current
The GES connects the electrical system to the earth, providing a reference voltage, dissipating lightning surges, and offering a fault current path that activates overcurrent protection.
CRC CRC Electrical, Plumbing & Mechanical Systems 2
A residential contractor is installing a 200-amp service panel.
What minimum wire gauge is required for aluminum service entrance conductors at this ampacity?