Mechanical, Electrical & Plumbing (MEP) Systems Flashcards

What is the standard residential electrical service voltage in the United States?

Answer: 120/240 volts, single-phase

Standard US residential service provides 120/240-volt single-phase power, delivering 120V for outlets and lighting and 240V for large appliances.

Which pipe material is most commonly used for residential drain, waste, and vent (DWV) systems in the US?

Answer: PVC Schedule 40

PVC Schedule 40 is the dominant DWV pipe material in residential construction due to its low cost, ease of installation, and corrosion resistance.

What is the minimum wire gauge (AWG) required for a 20-amp branch circuit per the NEC?

Answer: 12 AWG

The NEC requires 12 AWG copper conductors for 20-amp circuits; using 14 AWG (rated 15 amps) on a 20-amp breaker creates an overheating and fire risk.

In a split-system air conditioner, which component is located outdoors?

Answer: Condenser unit

The condenser unit, containing the compressor, condenser coil, and condenser fan, is installed outdoors to reject heat absorbed from inside the building.

What is the function of a condensate drain in an air conditioning system?

Answer: To remove moisture collected by the evaporator coil during cooling

During cooling, moisture from indoor air condenses on the evaporator coil; the condensate drain removes this water to prevent overflow and property damage.

Which type of valve allows fluid flow in only one direction and prevents backflow?

Answer: Check valve

A check valve automatically closes when flow attempts to reverse direction, allowing passage in only one intended direction and preventing backflow.

Which code requires arc-fault circuit interrupter (AFCI) protection in residential sleeping areas and most living spaces?

Answer: National Electrical Code (NEC)

The NEC mandates AFCI protection in bedrooms and most rooms of dwelling units to detect and interrupt dangerous electrical arcs that can ignite fires.