Testing Capacitor & Ballast Performance

The proper test procedure is as follows:

- Disconnect the Metal Halide, High Pressure Sodium or Pulse Start capacitor from the circuit and discharge it by shorting the terminals or wires together.

- Check the capacitor with an ohmmeter set to the highest resistance scale

- If the meter indicates a very low resistance then gradually increases, the capacitor does not require replacement.

- If the meter indicates a very high initial resistance that does not change, it is open and the Metal Halide, High Pressure Sodium or Pulse Start capacitor should be replaced.

- If the meter indicates a very low resistance that does not increase, the Metal Halide, High Pressure Sodium or Pulse Start capacitor is shorted and should be replaced.

- The ohmmeter method of testing capacitors will only determine open or shorted capacitors. The capacitance value can be tested by many available portable TRUE RMS meters having that capability, though a test using a dedicated capacitance meter is more conclusive. The capacitance value will affect lamp performance of Constant Wattage ballasts in ways that cannot be determined by the ohmmeter method. A capacitor may look good visually, but should be tested for capacitance value or replaced.

- The capacitor in a reactor or high reactance ballast circuits will only affect the ballast power factor and not ballast operation. Capacitor failure in these circuits will cause line supply current changes possibly causing circuit breakers to activate or fixture fuse failures.