Should I Discharge an AC Capacitor before Replacing It?

Start and run capacitors are found in the majority of AC systems and furnaces sold on the market today. Unfortunately, these components are also prone to failure, which means most homeowners will need to deal with repairs at some point.

While repairing an AC capacitor can be a relatively easy fix on some systems, there’s one thing many homeowners forget. That’s whether they should discharge the AC capacitor or not, something we are going to address in case you plan on fixing the system yourself.

Capacitors used in HVAC Systems

There are two types of capacitors used in furnaces and central heating & air systems with start and run capacitors. These small components can have a very similar design, but serve completely different purposes in a unit. The one thing they have in common, however, is their ability to hold a charge.

Capacitors essentially act as a battery by storing a charge to give your system a boost. They can become damaged by a variety of issues from lightning strikes to high temperatures, but can still maintain a charge. Even if you can see the capacitor and it appears to be damaged, it is better to be safe and discharge electricity from the capacitor before removing it.

How to Discharge an AC Capacitor

There are a few steps to discharging an AC capacitor and several ways you can go about it as well. That includes a popular method used to discharge capacitors quickly although you will need to locate and access these components first.

Before proceeding, you need to cut the power to the air handling unit in your home. To do this, you need to locate the breaker panel for your home and shut off the circuit breaker for the AC unit. If you want to be completely safe, you can also use a non-contact circuit tester to ensure the system is off.

Once the power is off, you will need to locate the capacitor. This can vary depending on the type of unit you have but is typically easy to access through a removable panel on the side of the system. When you locate the capacitor inside, the quickest way to discharge it is through using a screwdriver with an insulated handle.

Holding the screwdriver by the insulated handle, place the metal end across the two terminals on top of the capacitor you need to discharge. This causes a “short” which discharges the low-voltage capacitors safely. With the capacitor discharged, you can loosen any brackets holding it in place, disconnect the wires, and remove it from the air handling unit.

Final Thoughts

If you are uncomfortable dealing with electricity, discharging a capacitor is something better left to an HVAC professional. Failure to cut power to your system can result in serious injury while not discharging a capacitor can give you a nasty shock. If you are considering replacing a run or start capacitor yourself, you will definitely want to check out our guide to AC capacitor cost and replacement beforehand.

Written by

Rene has worked 10 years in the HVAC field and now is the Senior Comfort Specialist for PICKHVAC. He holds an HVAC associate degree and EPA & R-410A Certifications.

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