CRC CRC Electrical, Plumbing & Mechanical Systems 1 — Questions and Answers
Question 1: In residential wiring, what is the maximum number of 20-ampere branch circuits required to serve kitchen counter receptacles per the NEC?
- At least two small-appliance circuits (Correct answer)
- One dedicated 15-amp circuit
- Three 20-amp circuits minimum
- A single 30-amp circuit
Correct answer: At least two small-appliance circuits
The NEC requires a minimum of two 20-ampere small-appliance branch circuits to supply all receptacles serving countertop surfaces in the kitchen.
Question 2: A residential plumber installs a P-trap below a lavatory sink. What is the P-trap's primary function?
- To hold water that blocks sewer gases from entering the home (Correct answer)
- To increase water pressure at the fixture
- To filter debris from the drain line
- To regulate hot and cold water mixing
Correct answer: To hold water that blocks sewer gases from entering the home
The water retained in the P-trap creates a seal that prevents hazardous sewer gases (like hydrogen sulfide and methane) from traveling back through the drain into the living space.
Question 3: What type of HVAC system circulates conditioned air through a network of ducts to multiple rooms in a home?
- Forced-air system (Correct answer)
- Radiant heating system
- Mini-split (ductless) system
- Baseboard hydronic system
Correct answer: Forced-air system
A forced-air system uses a furnace or air handler to move conditioned air through supply and return ducts, distributing heating or cooling throughout the home.
Question 4: When installing electrical outlets in a bathroom, the NEC requires them to be protected by which device?
- Ground Fault Circuit Interrupter (GFCI) (Correct answer)
- Arc Fault Circuit Interrupter (AFCI)
- Surge protector
- Double-pole breaker
Correct answer: Ground Fault Circuit Interrupter (GFCI)
The NEC mandates GFCI protection for all receptacles in bathrooms because water proximity creates an elevated shock hazard; GFCI devices cut power within milliseconds of detecting a ground fault.
Question 5: What is the minimum slope required for a residential drain pipe to ensure proper drainage per most plumbing codes?
- 1/4 inch per foot (2% grade) (Correct answer)
- 1/8 inch per foot (1% grade)
- 1/2 inch per foot (4% grade)
- 1 inch per foot (8% grade)
Correct answer: 1/4 inch per foot (2% grade)
A minimum slope of 1/4 inch per foot (approximately 2%) is required for drain lines 3 inches or smaller to maintain adequate flow velocity and prevent solids from settling.
Question 6: Which refrigerant is most commonly used in modern residential air conditioning systems due to lower ozone depletion potential?
- R-410A (Correct answer)
- R-22 (Freon)
- R-12
- R-502
Correct answer: R-410A
R-410A replaced R-22 as the standard residential AC refrigerant because it contains no chlorine and does not deplete the ozone layer, in compliance with EPA regulations.
CRC CRC Electrical, Plumbing & Mechanical Systems 1
In residential wiring, what is the maximum number of 20-ampere branch circuits required to serve kitchen counter receptacles per the NEC?