NCCER Case Analysis & Practical Application 3 — Questions and Answers
Question 1: You are asked to install a ceiling fan where only a standard light fixture box exists. The box is rated for 35 lbs. The fan weighs 28 lbs. What is the correct action?
- Proceed with installation since the fan is under the box weight limit
- Replace the box with a fan-rated brace bar assembly before installation (Correct answer)
- Secure the existing box with additional screws to the joist
- Hang the fan using a safety cable attached to the joist
Correct answer: Replace the box with a fan-rated brace bar assembly before installation
Ceiling fans require fan-rated boxes because of dynamic load and vibration; a standard light box rated for weight alone is not approved for fan use.
Question 2: A customer reports intermittent flickering of lights throughout the house, not just on one circuit. What is the most likely cause?
- Multiple failing light switches throughout the home
- A loose neutral connection at the main panel or utility connection (Correct answer)
- Too many LED bulbs on dimmer switches
- A failing HVAC blower motor drawing excess current
Correct answer: A loose neutral connection at the main panel or utility connection
Whole-house intermittent flickering typically points to a loose main neutral, which can cause voltage fluctuations across all circuits.
Question 3: While caulking the joint between a bathtub and tile wall, you notice the existing caulk has black mold underneath. What is the correct remediation sequence?
- Apply new caulk directly over the old caulk after a surface cleaning
- Remove all old caulk, treat with mold-killing solution, allow to fully dry, then re-caulk (Correct answer)
- Apply mold-resistant paint over the area before caulking
- Re-grout the joint instead of caulking since grout resists mold better
Correct answer: Remove all old caulk, treat with mold-killing solution, allow to fully dry, then re-caulk
Removing all old caulk, killing existing mold spores, and ensuring complete dryness before re-caulking prevents mold from growing under the new application.
Question 4: A homeowner wants to convert a 3-prong dryer outlet (NEMA 10-30) to a 4-prong outlet (NEMA 14-30) for a new dryer. What does this conversion require?
- Only a new outlet receptacle since the wiring is compatible
- Running a new 4-wire cable (two hots, neutral, and ground) from the panel to the outlet (Correct answer)
- Adding a ground wire from the outlet box to the nearest water pipe
- Upgrading the circuit breaker to 50 amps for the 4-wire configuration
Correct answer: Running a new 4-wire cable (two hots, neutral, and ground) from the panel to the outlet
A NEMA 14-30 requires a separate equipment ground wire; the old 3-wire circuit lacks this, so new 4-wire cable must be run from the panel.
Question 5: You discover that a toilet is rocking slightly and has a soft floor around the base. What is the most important first step?
- Tighten the closet bolts to stabilize the toilet
- Turn off the water supply and inspect for subfloor damage before any other repair (Correct answer)
- Replace the wax ring immediately to stop any leaks
- Reinforce the toilet base with silicone caulk
Correct answer: Turn off the water supply and inspect for subfloor damage before any other repair
A soft floor around a rocking toilet suggests subfloor water damage that must be assessed before making any repairs, since the scope of work may be much larger.
Question 6: A sliding patio door is difficult to open and close. After cleaning the track, it still drags. What is the next most likely fix?
- Replace the entire door frame
- Adjust or replace the door's roller assemblies at the bottom of the door panel (Correct answer)
- Lubricate the top guide channel with silicone spray
- Add weatherstripping to reduce friction on the sides
Correct answer: Adjust or replace the door's roller assemblies at the bottom of the door panel
Worn or damaged roller assemblies are the most common cause of a hard-to-slide patio door after the track has been cleaned.
Question 7: You are patching a 6-inch hole in drywall. Which method provides the most structurally sound repair?
- Fill the hole with joint compound in multiple layers without backing
- Use a self-adhesive mesh patch kit rated for holes up to 6 inches
- Cut a clean square, install backing clips or a backer board, then install a cut patch piece (Correct answer)
- Glue a piece of drywall over the hole using construction adhesive
Correct answer: Cut a clean square, install backing clips or a backer board, then install a cut patch piece
For holes larger than 4–5 inches, a California patch or backer-clip method with a properly fitted drywall piece provides solid backing and a flush, durable repair.
NCCER Case Analysis & Practical Application 3
You are asked to install a ceiling fan where only a standard light fixture box exists.
The box is rated for 35 lbs.
The fan weighs 28 lbs.
What is the correct action?