How to Discharge a Grow Light Capacitor

HID (high-intensity discharge) fixtures are typically used for grow lights. These fixtures contain a high-voltage transformer and a large capacitor. The capacitor acts like a storage battery and aids the light bulb's illumination. Most HID capacitors will use an on-board resistor to automatically discharge the unit when not connected to electricity. By following a basic procedure, you can safely discharge any large capacitor that does not have an on-board discharging resistor.

Things You'll Need

• 2 pairs of alligator-clip connectors
• Ceramic resistor minimally rated for 10 watts at 20 ohms

Instructions

1. Remove all electrical power from the HID light.

2. Connect one end of the alligator-clip connectors to the capacitor. One connector each to the two power connections on the capacitor.

3. Lay the ceramic resistor on an insulated surface. Spread the wire connectors outward so they do not touch each other.

4. Attach one alligator clip to one of the resistor wires. Connect the second clip to the other resistor wire creating the discharge circuit.

5. Allow this connection to remain for two to three minutes. It is normal for the resistor to get warm while draining the capacitor.

6. Disconnect the alligator clips from the resistor. Connect both ends of the clips together to short out the capacitor. A small spark may occur when completing the circuit. This shorting of the capacitor will keep it discharged while working on the light fixture. Remove the clips before energizing the circuit with electricity.

Tips & Warnings

• Capacitors can absorb static electricity. This will create a storage charge in the capacitor even though it is not connected directly into an electrical circuit.

• Never use a metal object such as screwdriver to short across the connections of a large capacitor. The result can be explosive.

References

• Audio Systems