Startup, Troubleshooting & Maintenance — California C-10 Practice Questions

36 questions · 16% of the C-10 Electrical Trade exam

Worked questions

1. A 24-volt control coil measures 0 volts while its controller is calling for operation. What should be verified next?

AReplace the branch-circuit breaker with a larger one
Trace the complete series control path
CBypass every safety switch
DIncrease the equipment grounding conductor size

Why B is correct

Zero volts at a commanded coil points to a loss in the control-power path or an open safety/control. Tracing the circuit safely identifies the open point; bypassing safeties or changing unrelated power components is improper.

2. A breaker trips immediately each time a circuit is energized. What should occur before resetting it again?

De-energize and find the fault
BReset repeatedly until it stays on
CHold the handle closed
DInstall a larger breaker

Why A is correct

Repeated immediate tripping can indicate a short circuit or ground fault. Defeating or upsizing protection without diagnosing conductor and load conditions can cause fire or equipment damage.

3. What should be verified before first energizing a switchboard?

AOnly paint color
Pre-energization assembly, grounding, settings, and clearance checks
CTools left inside for adjustment
DOnly utility bill

Why B is correct

Pre-energization inspection catches mechanical, wiring, contamination, and setting errors without exposing personnel to avoidable energized work.

4. A newly installed personnel-protection device does not trip with its integral TEST control. What conclusion is justified?

AThe equipment grounding conductor should be removed for the described C-10 installation and documented operating conditions
BThe branch circuit is proven overloaded
The protective function was not demonstrated and the device or circuit needs evaluation
DReverse phase sequence is proven

Why C is correct

The best answer is: The protective function was not demonstrated and the device or circuit needs evaluation. Failure of the prescribed test means protection has not been verified; it does not by itself diagnose overload or phase sequence. The device and its supply/line-load connections should be evaluated. This transferred field condition tests the same installation or safety principle in a different project context. The other choices conflict with the cited rule, listing, safe-work process, or necessary diagnostic sequence.

5. Current is normal, but a newly coupled motor vibrates excessively. Which mechanical checks should be made?

AReverse neutral polarity for the described C-10 installation and documented operating conditions
BRemove overloads
CIncrease breaker rating
Alignment, mounting, bearings, balance, and load

Why D is correct

The best answer is: Alignment, mounting, bearings, balance, and load. Mechanical problems can damage a motor even when electrical current appears normal. Alignment and load checks should precede electrical protection changes. This transferred field condition tests the same installation or safety principle in a different project context. The other choices conflict with the cited rule, listing, safe-work process, or necessary diagnostic sequence.

31 more in the bank

Answers and explanations for these are in the app.

A battery energy-storage enclosure shows swelling cells and an unusual odor. What should the technician do first?
A battery system reports high temperature and abnormal odor. What is the first response?
A breaker trips only after a load runs for twenty minutes. What should be investigated?
A contactor coil receives rated voltage but chatters. What should be evaluated?
A GFCI device will not trip using its integral test function. What is the appropriate conclusion?
A motor has normal current but excessive vibration after coupling. What should be checked?
A PV array produces expected open-circuit voltage but nearly zero current under adequate irradiance when connected to the inverter. What is a reasonable next check?
A standby transfer switch transfers but fails to retransfer after normal power returns. What should be checked?
A three-phase motor has markedly unbalanced phase currents and is overheating. What should be checked before changing overload settings?
A three-phase pump runs backward after startup. What is the appropriate correction?
An insulation-resistance reading is unexpectedly low. What should be checked before condemning the feeder?
Before first energizing a new panel, what is the best sequence?
One PV string has normal open-circuit voltage but low operating current. What should be checked?
What should an electrical commissioning record contain?
Why should sensitive electronic equipment be isolated as directed before megohmmeter testing?
A breaker holds initially but opens after twenty minutes at steady load. Which conditions should troubleshooting examine?
A commissioned battery system reports high temperature and an abnormal odor. What action comes before routine diagnostic work?
A contactor has rated coil voltage yet chatters and will not seat consistently. What should be evaluated?
A controller calls for a relay, but zero volts are measured across its 24-volt coil. Which portion of the circuit should be traced next?
A feeder's insulation-resistance value is unexpectedly low after a rainy installation period. What should be ruled out before replacement is ordered?
A loaded three-phase motor overheats while its phase currents differ greatly. What should be investigated before raising overload settings?
A megohmmeter test is planned on wiring connected to electronic controls. Why must equipment be isolated according to instructions?
A new switchboard is mechanically complete and ready for first energization. Which sequence best controls the startup?
A newly energized circuit trips instantaneously twice. What should occur instead of another immediate reset?
A three-phase fan rotates backward on initial startup. What is the safe corrective method?
A transfer switch moves to standby but remains there after normal power is stable. Which control sequence elements should be tested?
An ESS cabinet has bulging cells, elevated temperature, and a chemical odor. What is the first defensible technician response?
Before a new switchboard is energized, which assembly, grounding, setting, and workspace checks belong in the record?
One PV string has normal open-circuit voltage but lower operating current than parallel strings. Which causes should be investigated?
The commissioning binder lists equipment but contains no measured results or open deficiencies. What information should be added?
Under full sun, a PV input has expected open-circuit voltage but almost no operating current. Which checks should come next?

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