Electrical
Electrical tests safe, code-compliant power and control wiring: supply voltage, overcurrent protection, conductor ampacity, disconnects, grounding, thermostat circuits, and component checks. The exam emphasizes nameplate ratings and manufacturer instructions over rules of thumb.
Power wiring
Read the unit nameplate. Minimum circuit ampacity (MCA) sets the minimum conductor ampacity; maximum overcurrent protection (MOP) sets the largest breaker or fuse. Conductors must be sized for MCA and terminal temperature rating, and the breaker must not exceed MOP. Provide a disconnect within sight and a compliant ground. Torque terminations.
Control and components
Thermostat and control wiring is Class 2, typically 24 V; keep it separate from line voltage and use the manufacturer's terminal designations. Check capacitors with a meter rated for microfarads and compare to the nameplate; inspect for bulging. Verify blower and compressor amp draw against nameplate.
Worked example
A condenser nameplate reads 208/230 V, MCA 24.5 A, MOP 40 A. A 10 AWG copper conductor with 75°C terminals has 35 A ampacity, which exceeds MCA, and a 40 A breaker equals MOP, so the circuit is acceptable. A 12 AWG conductor with a 40 A breaker fails because the wire does not carry MCA and is not protected at its ampacity.
Traps
- Sizing the breaker by wire size alone.
- Oversizing the breaker above MOP.
- Omitting the ground or disconnect.
- Reading a capacitor without discharging it.