Electrical Components and Wiring Flashcards
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Read the first 7 Electrical Components and Wiring flashcards as text
Which electrical test would BEST confirm that a compressor motor winding has a ground fault?
Answer: Measure resistance between each winding terminal and the compressor shell/ground
A megohmmeter or ohmmeter reading between a winding terminal and the grounded shell detects insulation breakdown indicating a ground fault.
A residential condensing unit's nameplate lists MOCP as 35 amps. A technician installs a 40-amp breaker. This installation is:
Answer: A code violation because the breaker exceeds the maximum listed on the nameplate
Installing a breaker larger than the MOCP listed on the nameplate violates NEC 440.22 and the unit's listing, removing the equipment's certified overcurrent protection.
What is the purpose of the time-delay relay (TDR) found in some residential AC control circuits?
Answer: Prevents compressor short-cycling by enforcing a minimum off time between starts
A TDR enforces a compressor off-delay (typically 3–5 minutes) to allow pressures to equalize, preventing motor damage from trying to start against unequalized head pressure.
When installing low-voltage thermostat wire, what is the minimum recommended AWG size for runs up to 100 feet?
Answer: 18 AWG
18 AWG is the industry standard for thermostat wire runs up to approximately 100 feet, providing sufficient conductance to avoid excessive voltage drop in the 24V circuit.
A residential AC system trips the breaker repeatedly after running for 10–15 minutes. The MOST likely electrical cause is:
Answer: Compressor drawing excessive amperage due to a failing motor or refrigerant overcharge
Thermal trip after a short run time typically indicates the compressor is drawing above-normal current, which could be caused by a failing motor winding or an overcharged refrigerant system.
What does the 'W' terminal on a residential thermostat control?
Answer: Heating (furnace or heat pump) circuit
The W terminal carries the heat call signal, energizing the furnace burner, electric heat strips, or heat pump reversing valve depending on the system type.
A technician is connecting a new condenser fan motor and notices the motor has five leads. Which tool or resource should be used to determine the correct wiring configuration?
Answer: The motor manufacturer's wiring diagram printed on the motor label or data sheet
Multi-lead motors have specific wiring configurations for different voltages and speeds, which are always documented on the motor's label or accompanying data sheet.