CBC Mechanical, Electrical & Plumbing (MEP) Systems 1 — Questions and Answers
Question 1: What is the primary purpose of a pressure relief valve (PRV) on a hot water heater?
- To prevent excessive pressure buildup that could cause an explosion (Correct answer)
- To regulate water temperature at the fixture
- To control the flow rate of hot water
- To filter sediment from the water supply
Correct answer: To prevent excessive pressure buildup that could cause an explosion
A pressure relief valve opens automatically when tank pressure exceeds safe limits, preventing catastrophic failure or explosion of the water heater.
Question 2: What is the minimum slope required for horizontal drain pipes in residential plumbing per the IPC?
- 1/8 inch per foot
- 1/4 inch per foot (Correct answer)
- 1/2 inch per foot
- 1 inch per foot
Correct answer: 1/4 inch per foot
The International Plumbing Code requires a minimum slope of 1/4 inch per foot for horizontal drain pipes to ensure adequate gravity flow.
Question 3: Which electrical circuit type does the NEC require for kitchen countertop receptacles?
- 15-amp, 120-volt general purpose circuit
- 20-amp, 120-volt small appliance branch circuit (Correct answer)
- 30-amp, 240-volt dedicated circuit
- 50-amp, 240-volt appliance circuit
Correct answer: 20-amp, 120-volt small appliance branch circuit
The NEC requires at least two 20-amp, 120-volt small appliance branch circuits to serve kitchen countertop receptacles.
Question 4: What is the primary function of a P-trap in a plumbing drain system?
- To prevent pipes from freezing in cold climates
- To maintain a water seal that blocks sewer gases from entering the building (Correct answer)
- To reduce water pressure at the fixture
- To filter debris from drain water
Correct answer: To maintain a water seal that blocks sewer gases from entering the building
The P-trap holds a water seal that acts as a barrier, preventing toxic and flammable sewer gases from traveling up through drain openings into occupied spaces.
Question 5: Which HVAC system type can provide both heating and cooling using a single piece of equipment?
- Boiler with baseboard radiators
- Heat pump (Correct answer)
- Evaporative cooler
- Steam radiator system
Correct answer: Heat pump
A heat pump transfers heat in both directions by reversing refrigerant flow, providing heating in winter and cooling in summer from one system.
Question 6: Which pipe material is approved for natural gas distribution inside residential buildings?
- PVC (polyvinyl chloride)
- CPVC (chlorinated polyvinyl chloride)
- Black steel pipe or corrugated stainless steel tubing (CSST) (Correct answer)
- Type M copper tubing
Correct answer: Black steel pipe or corrugated stainless steel tubing (CSST)
Black steel pipe and CSST are the code-approved materials for interior natural gas distribution; plastic pipe is prohibited for gas service inside buildings.
Question 7: What is the function of a circuit breaker in a residential electrical panel?
- To convert AC power to DC for sensitive electronics
- To increase voltage for high-demand appliances
- To automatically disconnect a circuit when current exceeds safe limits (Correct answer)
- To evenly distribute load across all circuits
Correct answer: To automatically disconnect a circuit when current exceeds safe limits
A circuit breaker trips (disconnects) automatically when current exceeds its rated amperage, protecting wiring and equipment from overheating and fire.
CBC Mechanical, Electrical & Plumbing (MEP) Systems 1
What is the primary purpose of a pressure relief valve (PRV) on a hot water heater?