CBC Mechanical, Electrical & Plumbing (MEP) Systems 2 — Questions and Answers
Question 1: What is the purpose of a backflow preventer in a building's plumbing system?
- To increase water pressure throughout the system
- To prevent contaminated water from flowing back into the potable water supply (Correct answer)
- To reduce water hammer in the pipes
- To regulate domestic hot water temperature
Correct answer: To prevent contaminated water from flowing back into the potable water supply
A backflow preventer stops non-potable water from reversing direction into the clean drinking water supply, protecting public health.
Question 2: Which wiring method is typically required for exposed electrical installations in commercial construction?
- NM cable (Romex)
- Underground feeder cable (UF)
- Electrical metallic tubing (EMT) conduit (Correct answer)
- Service entrance cable (SE)
Correct answer: Electrical metallic tubing (EMT) conduit
EMT conduit is required for exposed wiring in commercial occupancies because NM (nonmetallic-sheathed) cable is not permitted in commercial construction.
Question 3: Which HVAC component is responsible for removing excess moisture from indoor air during the cooling process?
- Furnace heat exchanger
- Condenser fan motor
- Evaporator coil (Correct answer)
- Expansion valve only
Correct answer: Evaporator coil
The evaporator coil chills air below its dew point, causing water vapor to condense onto the coil surface and drain away, dehumidifying the space.
Question 4: What does the SEER (Seasonal Energy Efficiency Ratio) rating measure on air conditioning equipment?
- Maximum sound output level of the compressor in decibels
- Cooling efficiency over an entire cooling season relative to energy consumed (Correct answer)
- Peak cooling capacity expressed in BTUs per hour
- Airflow speed of the air handler blower in CFM
Correct answer: Cooling efficiency over an entire cooling season relative to energy consumed
SEER is total seasonal cooling output (BTU) divided by total electrical energy consumed (watt-hours), indicating overall seasonal efficiency.
Question 5: What is the purpose of a GFCI (Ground Fault Circuit Interrupter) outlet in a building?
- To provide surge protection against lightning strikes
- To detect small ground faults and cut power within milliseconds to prevent electrocution (Correct answer)
- To prevent electrical overloads from damaging connected appliances
- To regulate voltage fluctuations on the circuit
Correct answer: To detect small ground faults and cut power within milliseconds to prevent electrocution
GFCI devices detect current imbalances as small as 5 milliamps caused by ground faults and interrupt power within 1/40th of a second to prevent electrocution.
Question 6: Where is a service entrance located in a residential electrical system?
- At each individual branch circuit outlet
- At the main connection point where utility power enters the building (Correct answer)
- Inside the sub-panel that feeds a detached garage
- At the grounding electrode system buried in the yard
Correct answer: At the main connection point where utility power enters the building
The service entrance is where utility conductors connect to the building's electrical system, typically consisting of the service drop or lateral, meter socket, and main disconnect.
Question 7: What is the minimum clearance required between a gas water heater and combustible materials per standard codes?
- 1 inch
- 3 inches
- 6 inches (Correct answer)
- 12 inches
Correct answer: 6 inches
Most building codes and appliance manufacturer requirements mandate a minimum 6-inch clearance between gas-fired water heaters and combustible materials to prevent fire hazards.
CBC Mechanical, Electrical & Plumbing (MEP) Systems 2
What is the purpose of a backflow preventer in a building's plumbing system?