20 Safety Practice Questions & Answers

1. 1. In the hierarchy of controls used on a solar job site, which type of measure is the least effective and is relied on only after the others have been applied?

   • A.Substitution of the process with a less hazardous one
   • B.Personal protective equipment worn by the worker✓ Answer
   • C.Elimination of the hazard from the work task
   • D.Engineering controls built into the equipment

   PPE is placed last because it does nothing to the hazard itself: it protects only the individual wearing it, and it stops working the moment it is worn incorrectly, damaged, or taken off. Elimination, substitution and engineering controls change the job so the hazard is smaller or absent for everyone on site, which is why they come first.

   Source: OSHA hierarchy of controls (elimination, substitution, engineering controls, administrative controls, PPE)Report a problem with this question

2. 2. During daylight a crew opens the inverter's AC disconnect and its DC disconnect before opening a combiner box. How should the PV source-circuit conductors running from the modules to that combiner be treated?

   • A.As energized, because the modules keep producing voltage in daylight✓ Answer
   • B.As de-energized, because the DC disconnect has been opened
   • C.As de-energized, because no current can flow in an open circuit
   • D.As energized only while the inverter is still drawing power from them

   A module generates voltage whenever light falls on its cells, and there is no switch at the cell to stop that. Opening a downstream disconnect interrupts current flow but leaves the full open-circuit voltage of the string standing on the conductors between the modules and the open point, so those conductors are treated as live at all times.

   Source: OSHA guidance on solar photovoltaic hazards — direct-current circuits energized by daylightReport a problem with this question

3. 3. A service crew must open a combiner box on an operating array at midday. Besides opening the disconnects, what step does OSHA's solar work guidance recommend to reduce the DC hazard?

   • A.Covering the modules with opaque material to block light✓ Answer
   • B.Shorting the module leads together to drain the charge
   • C.Removing the string fuses so the strings read zero volts
   • D.Waiting ten minutes for the module capacitance to bleed off

   Since the array cannot be switched off at the source, the only way to reduce its output is to take away the light. An opaque cover stops the cells generating, which is why OSHA pairs covering the modules with circuit isolation rather than treating isolation alone as sufficient.

   Source: OSHA guidance on solar photovoltaic work — covering modules during servicingReport a problem with this question

4. 4. Why does a fault arc in an array's DC circuit tend to be harder to extinguish than an arc in an AC circuit at similar voltage?

   • A.DC current reverses direction faster, which feeds the arc plasma
   • B.DC current never crosses zero, so the arc is not interrupted✓ Answer
   • C.DC circuits always carry more current than AC circuits do
   • D.DC conductors have higher impedance, which heats the arc further

   Alternating current passes through zero twice in every cycle, and each of those instants gives the arc a natural chance to die out. Direct current is continuous, so once an arc is struck nothing in the waveform helps to quench it and it must be forced out by separation, cooling or an arc chute.

   Source: Physics of direct-current arcing; OSHA and NFPA guidance on direct-current arc hazardsReport a problem with this question

5. 5. A trainee says that once locks and tags are applied to the array disconnects, the entire DC side of the system is safe to work on. Which statement corrects him?

   • A.The shock hazard is removed but an arc-flash hazard still remains present
   • B.The locks take effect only after the inverter finishes its shutdown cycle
   • C.The modules ahead of the locked disconnect still produce voltage in daylight✓ Answer
   • D.The whole DC side becomes safe as soon as the tags are signed and dated

   Lockout/tagout controls the specific point that is locked open; it cannot stop sunlight from making the cells generate. Everything electrically upstream of the locked disconnect, back to the modules themselves, stays energized and must still be treated as live and tested before contact.

   Source: OSHA control of hazardous energy (lockout/tagout), 29 CFR 1910.147, applied to photovoltaic direct-current circuitsReport a problem with this question

6. 6. While mounting an AC disconnect beside the utility meter, an associate looks at the meter enclosure and the conductors feeding it. What is true of that equipment?

   • A.The utility conductors are protected by the building's main breaker
   • B.The meter enclosure is de-energized once the main breaker is opened
   • C.Pulling the meter de-energizes both sides of the meter socket safely
   • D.Conductors on the utility side of the meter are always energized✓ Answer

   The service conductors and the line side of the meter socket are fed directly from the utility transformer, and the building's main breaker sits downstream of them. Nothing a crew can switch on the premises will de-energize that equipment, and it is also unfused at that point, so only the utility may work on it.

   Source: OSHA electrical safety-related work practices for construction, 29 CFR 1926.416 — energized utility-side conductorsReport a problem with this question

7. 7. Why does a solar crew working near energized electrical equipment wear arc-rated shirts rather than ordinary polyester ones?

   • A.Synthetic fabric builds static that can start an arc by itself
   • B.Arc-rated fabric conducts heat away from the body during a fault
   • C.Polyester blocks radiant heat but not the pressure wave of an arc
   • D.Untreated synthetic fabric melts onto the skin and worsens a burn✓ Answer

   An arc releases intense radiant heat in a few thousandths of a second. Untreated synthetics soften at those temperatures, melt and adhere to skin, so the burn continues after the arc is over, whereas arc-rated fabric chars and self-extinguishes instead of melting.

   Source: OSHA personal protective equipment requirements for construction, 29 CFR 1926.95; arc-rated clothing practice for electrical workReport a problem with this question

8. 8. A qualified person must take a reading inside an enclosure that cannot be de-energized. Why is the one-hand technique used?

   • A.It keeps contact area small enough to stay below let-go current
   • B.It leaves the free hand available to hold a work light
   • C.It allows a faster retreat if the equipment starts to arc
   • D.It keeps current from crossing the chest between both hands✓ Answer

   Current takes the path between the two points of contact with the body. If both hands are in the enclosure, that path runs hand to hand straight across the chest and through the heart, which is the most dangerous route; keeping one hand out of the circuit removes that path.

   Source: OSHA safety-related work practices for work on or near energized equipment, 29 CFR 1926.416Report a problem with this question

9. 9. An installer clips a fall arrest lanyard to a plumbing vent pipe on the roof. Why is that unacceptable?

   • A.Vent pipes cannot be bonded to the array's grounding system
   • B.Lanyards may be anchored only at the ridge line of a roof
   • C.The vent is not an anchorage rated for fall arrest forces✓ Answer
   • D.A vent anchor may be used only with a second worker watching

   An anchorage for personal fall arrest must support 5,000 pounds for each attached worker, or be part of a system designed and supervised by a qualified person with a safety factor of at least two. A vent pipe is a thin plumbing component fastened for drainage, not engineered or tested for arrest loads, and it will tear out.

   Source: OSHA personal fall arrest system criteria, 29 CFR 1926.502 — anchorage strengthReport a problem with this question

10. 10. On a low-slope commercial roof a warning line is set back from the edge. What does that line establish?

    • A.The separation between the electrical and mechanical work zones
    • B.The limit inside which work may proceed without fall arrest✓ Answer
    • C.The limit of the crane's swing radius during module hoisting
    • D.The area where module pallets may be staged on the deck

    The warning line fences off the strip nearest the edge, where the fall exposure is greatest. Work carried out inside the line, away from the edge, may proceed without conventional fall protection, while anyone who crosses the line toward the edge must be protected by guardrails, nets or a personal fall arrest system.

    Source: OSHA fall protection for low-slope roofs, 29 CFR 1926.501 — warning line systemsReport a problem with this question

11. 11. Modules are being set along a roof edge while the homeowners and a delivery van use the driveway directly below. What is the correct control for the ground area?

    • A.Barricade the area below the work and keep tools tethered or secured✓ Answer
    • B.Post a sign at the front door asking people to watch overhead
    • C.Move the ladder to the far end so the driveway stays open
    • D.Assign one worker to shout a warning whenever something drops

    The hazard below rooftop work is falling tools, fasteners and glass, and a dropped object reaches the ground far faster than a shouted warning travels. Physically excluding people from the drop zone and preventing the drop in the first place by tethering tools controls the hazard instead of relying on someone reacting in time.

    Source: OSHA construction housekeeping, 29 CFR 1926.25, and falling object protection, 29 CFR 1926.501Report a problem with this question

12. 12. A straight ladder is set so that its working length from the base to the point of support is 16 feet. Applying the four-to-one setup rule, how far out from the wall should the base sit?

    • A.8 feet
    • B.4 feet✓ Answer
    • C.16 feet
    • D.2 feet

    The four-to-one rule places the base one foot out for every four feet of working length, so 16 divided by 4 gives 4 feet. Setting the base too close makes the ladder likely to tip backward as the climber nears the top, and setting it too far out lets the feet slide out.

    Source: OSHA ladder standard, 29 CFR 1926.1053 — four-to-one setup ratioReport a problem with this question

13. 13. A ladder must be set beside a service entrance where energized conductors are exposed. Which ladder is required?

    • A.One of aluminum bonded to the grounding electrode
    • B.One of aluminum fitted with rubber feet and shoes
    • C.One with nonconductive rails, such as fiberglass✓ Answer
    • D.Any ladder, provided a spotter watches the top of it

    Where the ladder or the worker on it could contact exposed energized parts, nonconductive side rails are required, not merely preferred. Aluminum rails conduct, so brushing a live service conductor puts the whole ladder and the climber into the circuit, and rubber feet do not interrupt that path because the current returns through the worker's body.

    Source: OSHA ladder standard, 29 CFR 1926.1053 — nonconductive side rails near exposed energized equipmentReport a problem with this question

14. 14. A large, heavy commercial module has to reach a flat roof two storeys up. What is the correct way to move it?

    • A.Raise it with a hoist, conveyor, or crane rather than carrying it up a ladder✓ Answer
    • B.Strap it to the worker's harness so both hands stay free for climbing
    • C.Have two workers pass it up while standing on separate ladders
    • D.Carry it up the ladder under one arm with the other hand on a rail

    Climbing requires both hands on the ladder, and a module is heavy, wide and catches wind, so carrying one destroys three-point contact and shifts the climber's centre of gravity away from the rails. OSHA's solar guidance is explicit that modules are raised by hoist, conveyor or crane and never carried up a ladder.

    Source: OSHA guidance on solar photovoltaic material handling — hoisting modules to the roofReport a problem with this question

15. 15. Why is handling a module on a roof especially hazardous when the wind is gusting?

    • A.Moving air builds static on the glass, causing an involuntary jerk
    • B.Wind pressure makes the glass crack inside the frame more easily
    • C.Its large flat face catches the wind and can unbalance the worker✓ Answer
    • D.Wind loosens the mounting clamps faster than they can be torqued

    A module presents a large flat area to the wind and behaves like a sail, so a gust turns into a sudden sideways force that the worker must resist while standing near an edge. That is why modules are carried low, kept edge-on to the wind where possible, handled by two people, and set down and secured when gusts build.

    Source: OSHA guidance on solar photovoltaic work — handling modules in windy conditionsReport a problem with this question

16. 16. A crew is working on a dark commercial roof during a heat advisory. Which practice best controls heat illness?

    • A.Drink water on a schedule and rest in shaded breaks✓ Answer
    • B.Drink a large volume of water only once thirst sets in hard
    • C.Take salt tablets and work through the hottest hours
    • D.Wear an extra layer so sweat stays close to the skin

    Thirst lags well behind actual fluid loss, so a worker who drinks only when thirsty is already dehydrated. Small drinks at regular intervals plus scheduled rest in shade let the body shed heat before core temperature climbs, and a dark roof radiates heat that makes the working surface hotter than the air temperature suggests.

    Source: OSHA heat illness prevention guidance for outdoor work — water, rest, shadeReport a problem with this question

17. 17. A crew is on a roof when rain begins and thunder is heard nearby. What is the correct decision?

    • A.Shift to the shaded side, away from the edge, and keep working
    • B.Keep working if everyone is tied off to a certified anchorage
    • C.Switch to rubber-soled boots and keep working on the wet deck
    • D.Leave the roof and stop work until conditions become safe again✓ Answer

    A wet roof loses the friction that footing depends on, and no harness or boot protects anyone from lightning, which strikes the highest point on a structure and can travel through metal racking and conductors. Inclement weather is a stop-work condition; the crew descends, secures loose material, and waits until the roof is safe and dry.

    Source: OSHA construction fall protection and roof work practice — slippery surfaces and lightning as stop-work conditionsReport a problem with this question

18. 18. A worker is in contact with an energized conductor and cannot let go. What should a co-worker do first?

    • A.Start chest compressions immediately where the worker lies
    • B.Cut power at the source before anyone touches the worker✓ Answer
    • C.Push the worker off with an aluminum conduit that is nearby
    • D.Pull the worker clear by the clothing to break the contact

    A person still in contact with a live conductor is part of the circuit, and anyone who grabs them becomes part of it too, which is how single incidents turn into multiple casualties. The circuit is opened or the source isolated first; only then is the victim moved, emergency services called and care given.

    Source: OSHA electrical safety guidance — rescue from contact with energized conductorsReport a problem with this question

19. 19. A worker's fall arrest system has stopped a fall and the worker now hangs in the harness, conscious but unable to reach the roof. What must happen?

    • A.The crew should photograph the anchorage first, before moving the worker
    • B.The worker should be left in place until the arrest equipment can be inspected
    • C.The crew should rescue the worker promptly, since suspension soon turns dangerous✓ Answer
    • D.The worker should stay suspended until emergency personnel can arrive

    Hanging motionless in a harness lets blood pool in the legs because the leg straps compress the veins, and that can cause collapse in a short time even in an uninjured person. The employer must plan for prompt rescue or self-rescue before anyone is exposed to a fall, so the rescue plan is executed immediately rather than waiting.

    Source: OSHA fall protection systems criteria, 29 CFR 1926.502 — prompt rescue of a fallen workerReport a problem with this question

20. 20. The racking, modules and AC disconnect are installed, and only the final connection into the building's main service panel remains. Who should perform it?

    • A.Any crew member who holds a current first aid and CPR certificate
    • B.The associate, since the main breaker will be left in the off position
    • C.A licensed electrician or qualified person, per the jurisdiction✓ Answer
    • D.The associate, with the homeowner present as a second observer

    Terminating into a service panel is licensed electrical work, and the busbar and line-side lugs there stay energized regardless of breaker position, so it sits outside an associate-level scope. Recognising where a task passes to a licensed electrician, a qualified person or a structural professional, and referring it, is itself part of working safely.

    Source: NABCEP PV Associate scope of practice — recognize and refer; state and local electrical licensing under the authority having jurisdictionReport a problem with this question

Practice questions based on the published knowledge domains of the NABCEP PV Associate Job Task Analysis and on standard photovoltaic engineering and safety references. NABCEP is not affiliated with this site and does not endorse it. Answers here deliberately avoid code dimensions, manufacturer specifications, incentive rules and prices, all of which change and vary by jurisdiction — always apply the electrical and building codes adopted by the authority having jurisdiction, the equipment manufacturer's instructions, and your employer's safety program. Confirm current exam requirements with NABCEP before testing. About the NABCEP Associate program →