How to Discharge a Grow Light Capacitor

HID (high intensity discharge) fixtures are typically utilized 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.

Difficulty: Moderate

Instructions

Things You'll Need:

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

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 alligator lead 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

• Grow Light Basics
• Audio Systems