Electrical Components and Controls Flashcards
7 cards from real Air Conditioning Repair practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Electrical Components and Controls flashcards as text
A homeowner reports the outdoor unit runs continuously even after the thermostat setpoint is satisfied. Which component is the most likely culprit?
Answer: Welded or stuck-closed contactor contacts
Welded contactor contacts keep the compressor and condenser fan energized regardless of the thermostat signal.
What does the term 'MFD' (or µF) represent on a capacitor label?
Answer: Microfarads, a unit of electrical capacitance
MFD stands for microfarads, the unit measuring a capacitor's ability to store an electrical charge.
A technician is checking motor winding insulation integrity. Which test instrument is used, and what minimum reading is acceptable?
Answer: Megohmmeter; minimum 1 megohm
A megohmmeter applies high DC voltage to measure insulation resistance; readings below 1 megohm indicate degraded insulation that could lead to winding failure.
In a 240V single-phase circuit, what is the voltage measured between either hot leg and the neutral conductor?
Answer: 120V
A standard residential 240V circuit is center-tapped, providing 120V from each hot leg to the neutral and 240V between the two hot legs.
What is the purpose of a ground fault circuit interrupter (GFCI) outlet required near HVAC equipment in some installations?
Answer: To trip when current imbalance between hot and neutral exceeds ~5 mA, preventing shock
A GFCI detects small current imbalances caused by current flowing through an unintended path (like a person) and opens the circuit within milliseconds.
A condenser fan motor runs but the compressor does not start and hums loudly. Capacitance testing shows the HERM section of the dual-run capacitor is reading 12 MFD instead of 40 MFD. What is the correct action?
Answer: Replace the dual-run capacitor with one matching the original MFD and voltage ratings
A degraded capacitor must be replaced with one of matching MFD and equal or higher voltage rating; adding capacitors in parallel is not an approved field repair.
Which tool is best suited for measuring the actual running amperage of a compressor without breaking the circuit?
Answer: Clamp-on ammeter
A clamp-on ammeter measures current by sensing the magnetic field around a conductor, allowing non-invasive current measurement on live circuits.