How to Safely Discharge a Capacitor

Capacitors come in many sizes and can be found in a wide variety of electrical devices. Their sole purpose is to store energy for a temporary period of time, but if they are removed from the power source, they can actually hold on to that charge for an indefinite amount of time. A charged capacitor can be extremely dangerous to handle. Mishandling of one can cause an accidental electrocution or potential power surges that can damage expensive equipment.

If you have a project or job that requires you to remove or replace an existing low-voltage (120 volts and below) capacitor, you need to safely discharge it before attempting to move it. Here's how to do it safely.

Things You'll Need

• Eye protection
• Gloves
• Screwdriver with insulated handle
• Incandescent light bulb

Instructions

1. Unplug or disconnect the power to whichever piece of equipment you are working on.

2. Put on your eye protection and gloves.

3. Locate the capacitor and disconnect it from its power source. This is usually accomplished by pulling off the rubber cap on the top of the capacitor.

4. Take the screwdriver and use its tip to bridge the gap between the two lead terminals. This will cause a spark, which can sometimes be larger than expected.

5. To make sure that the capacitor is fully discharged, perform Step 4 again. Or, you can take an incandescent light bulb and touch part of its screw base to one of the terminals. If it lights up, there is still a charge on the capacitor.

Tips & Warnings

• DO NOT TOUCH THE TERMINALS ON TOP OF THE CAPACITOR.

• These instructions are for discharging a low-voltage capacitor of no more than 120 volts.