Ocean HVAC Lab

Remove the disconnect handle to shut off power to the unit.
All work should be performed with the power completely turned off.

Set the multimeter to AC voltage and measure between L1 and L2 at the contactor.

This is the line side coming directly from the disconnect, so it is the most reliable way to confirm that power is truly off.

The reading must be 0V before proceeding.

Key Point
Always check L1–L2, not just T1–T2, to confirm power is fully disconnected.

A capacitor stores electrical energy even after the power is turned off.

If you touch the terminals without discharging it, the stored charge can release suddenly and cause an electrical shock.

Use an insulated screwdriver to short between the terminals and safely discharge any remaining energy.

Key Point
Residual charge = stored energy inside the capacitor, not static electricity.

Multiple components are connected to the capacitor through the C (Common) terminal.

If you measure it while everything is still connected, the reading may be affected by the rest of the circuit.

By removing the C wire, you isolate the capacitor and can measure its actual value accurately.

Key Point
Removing just the C wire is enough to isolate the capacitor for testing.

Additional Notes

Voltage Rating (VAC)

The capacitor label includes a voltage rating such as 370V or 440V.

• Same or higher voltage rating → OK
• Lower voltage rating → NOT acceptable

Why?

If the voltage rating is too low, the capacitor may fail, overheat, or even rupture under normal operating conditions.

Example

• Replace 370V with 440V → OK
• Replace 440V with 370V → Not safe

Capacitance Value (µF)

Example: 30/15 µF ±3%

• 30 µF → Compressor (HERM)
• 15 µF → Fan motor

Tolerance Range Example

• 30 µF ±3% → 29.1 – 30.9 µF
• 15 µF ±3% → 14.55 – 15.45 µF

Can You Use a Different µF Value?

The correct practice is to match the exact µF rating

• A small variation (±5–10%) may still work temporarily
• However, using incorrect values can cause:
  • Motor inefficiency
  • Overheating
  • Reduced lifespan
• Always use the same µF rating whenever possible