How To Discharge AC Capacitor [And Should You?]

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AC compressor and fan motor use large capacitors that store charges. You may be wondering if there is a need to discharge an AC capacitor and how the task can be carried out. Fortunately, we have consulted experts in this field, and here is what they have to say.

You should discharge electricity from your capacitor before replacing it, even if it looks damaged.  Here are step-by-step procedures for discharging an AC capacitor: 

  • Turn off power to your air handling unit.
  • Locate the capacitor.
  • Discharge the capacitor using a screwdriver.

You can efficiently discharge a capacitor without the help of a professional. All you have to do is follow the procedures carefully. Keep reading to get detailed information on how to discharge an AC capacitor.

A white air conditioner, How To Discharge AC Capacitor [And Should You?]

Should You Discharge AC Capacitor?

The ability of capacitors to hold charges for an extended period makes them different from other storage devices. It can be hazardous if their circuit does not have a "bleeder" resistor, which discharges the electric charge when the gadget is turned off.

An electric charge can travel through your body if you come in contact with the terminals of a charged capacitor. Sometimes this can happen over a short distance, like if your fingers are close to the terminals and the charge arcs over. 

Man holding a huge capacitor

Contacts may lead to mild tingling, shock, or burns, depending on how much energy is stored in the capacitor. They should be discharged before any electronic operations are carried out. It is possible to get killed by large capacitors usually found in devices like HVAC equipment, even if the device has been unplugged.

The death scenario occurs when the electric current travels through your body and stops your heart.

How To Discharge AC Capacitor

Start and run capacitors can be found in many air conditioning systems currently available in the market today. Unfortunately, these components are also prone to breakdown, so most homeowners will eventually have to deal with repairs. 

When it comes to certain systems, repairing an AC capacitor can be relatively simple. But can be difficult for some homeowners. Discharging an AC capacitor involves a few steps. Also, there are various ways to carry out this task. 

Below are step-by-step procedures for discharging capacitors:

Step 1: Turn Off Power To Your Air Handling Unit

Before starting the process, your circuit breaker should be turned off from the main electrical panel to avoid electrocution. Using a circuit tester that does not require physical contact, you can check if the power to your air conditioner has been completely turned off.

Step 2: Locate The Capacitor

After turning off your unit's power, check the air conditioner to find the capacitor. To avoid electric shock, do not touch the exposed connectors and cables.

Refer to the owner's air conditioner manual for information regarding the exact place the capacitor is found within the main assembly. The location of internal components like capacitors may vary depending on the manufacturer.

Step 3: Discharge The Capacitor Using A Screwdriver

After locating the capacitor, position the metal end of the screwdriver so that it touches both protruding terminals. The capacitor's internal electrical energy is released when the two terminals are connected using the metal screwdriver, which creates a short in the capacitor's circuit. You can repeat this process if there is more than one capacitor in the AC housing area. 

Technician removing the capacitor of the air conditioner

What Tool Is Used To Discharge A Capacitor?

An insulated screwdriver can be used to discharge a capacitor safely. However, it is a good idea to construct a capacitor discharge tool and utilize it for electronics with larger capacitors.

Simple resistors with two wires tied to each end make up a capacitor discharge tool in its most basic form. It is used to make a path in a capacitor so that the charge can safely drain out. 

LEDs on some capacitor-discharge tools show the current charge of the capacitor to which they are connected. Excluding that, they are all the same. 

How Long Does An AC Capacitor Take To Discharge?

Five time constants are the time it takes a capacitor to discharge. Sixty-three percent of the voltage of a fully charged capacitor can be released in one period. After five time constants, a capacitor discharges to a point where it loses nearly all of its voltage.

If you want to calculate the time constant of a capacitor, you can use the formula τ=RC. The value yields the time a capacitor needs to discharge to 63 percent of the voltage that makes it charged.

Is It Safe To Discharge an AC Capacitor?

When a proper capacitor-discharge instrument is utilized, there is a lower chance that the capacitor will be damaged. The type of capacitor and its capacitance play a role in how safe the capacitor discharges.

Extra caution is required when discharging capacitors with a capacity of more than one farad because a short circuit in the capacitor could damage it and lead to an explosion and electric shock.

When this happens, there is a chance that all the electrical components and other parts of the AC circuit will get damaged.

This may result in electrocution and fire outbreak. The amount of damage increases based on the capacitor's capacitance and voltage. Therefore, before removing the capacitor from the circuit, you should always make sure that it has been discharged. 

Technician changing the capacitor of the air conditioner

Can AC Capacitors Discharge On Their Own?

AC capacitors can discharge on their own. When a capacitor is charged and then unplugged, it will retain its charge. A capacitor has some characteristics that can be bad. Leakage resistors are present in capacitors. 

Therefore, capacitors will discharge on their own over time, and most will discharge after a few days as long as they are not being charged by an external power source or an internal battery.

However, you should always assume that capacitors are charged unless you have verified that they have been discharged.

How Do You Tell If A Capacitor Is Charging or Discharging?

An air conditioner surrounded with grass

When a capacitor is connected to a circuit that uses direct current [DC], the capacitor has the potential to charge or discharge. A charging state occurs when there is an increase in the difference between two conducting plates. During this state, both plates receive a charge that is equal and opposite to one another. 

A flow of electric charge in only one direction is referred to as direct current. When the voltage coming from the power supply and the voltage at the capacitor terminals are the same, the capacitor has been fully charged. 

This process is known as capacitor charging, and the charging phase is complete when the current in the electrical circuit stops flowing. 

The capacitor enters the discharging phase as soon as the power supply is disconnected from it. During the discharging process, the voltage between the two plates will gradually decrease until it reaches 0 volts. 

Can A Capacitor Shock?

Hvac technician checking the capacitor of the air conditioner

A charged capacitor can shock. When you need to operate on the air conditioner's internal components, you should discharge the two primary capacitors, which are referred to as the run and start capacitors.

If you do not discharge them, there is a high chance that you will get electrocuted. At the primary electrical panel, turn off the air conditioner's circuit breaker.

Electrocution caused by high voltage-charged capacitors can lead to death. Even after being unplugged from the power source, the high voltage wires can still have a high amount of charge in them. So, you should be careful when working on a capacitor.

AC capacitors work almost like the capacitors in power lines. That is why workers who maintain power lines (or subterranean cables) are required to discharge the wires using a grounded pole before contacting them to avoid electrocution.

Final Takeaway

A white air conditioner

Discharging an AC capacitor is an easy-to-do task. All you need to do is turn off the power to your unit, find the capacitor, and discharge it using a screwdriver. Your screwdriver should have an insulated handle. If you find it challenging to perform this task, you can consult a professional. 

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