What Are Capacitors & Does Your Furnace Need A New One?

Do you know that component that provides the electrical current to activate and power your car, cellphone, laptop and even your HVAC system? Most, if not all, electrical devices that run through batteries have capacitors to start and keep your devices and equipment running.

Capacitors are very essential components of your home’s heating and cooling system. They function by storing energy to send a jolt and provide the additional torque and electricity to start your unit’s motor or to keep it running.

Types of Capacitors

There commonly two different types of capacitors installed various varying types of systems in the HVAC field.

Start Capacitors

What Are Capacitors & Does Your Furnace Need A New One? 1Condensing or blower fan motors in your HVAC system sometimes need a boost to start running. A start capacitor is what is used to get those motors moving by providing an extra charge to increase torque and quicken startup. Thus, a start capacitor is only in operation when the motor is starting and a relay removes it from the circuit as the motor approaches full running speed.

Start capacitors are usually pre-installed on high-end factory HVAC models but it can also be installed in older and low-end versions if you want to achieve flawless motor startups especially in outdoor air conditioner and heat pump units.

Super Boost Capacitors

A super boost capacitor is a type of start capacitor that has a built-in potential relay designed to give your HVAC unit’s compressor a quick and more efficient electrical boost upon startup under ambient conditions such as low voltage or high head pressures.

Run Capacitors

What Are Capacitors & Does Your Furnace Need A New One? 2

Run Capacitors are the most common type of capacitors. Unlike start capacitors that are detached in the circuit as the motor picks up speed, run capacitors stay while the motor is working. It boosts efficiency and intensifies motor starting torque throughout the motor’s operation.

Run capacitors can be either a single or dual capacitor and can be oval or round-shaped.

Dual Run Capacitors

Dual run capacitors are installed in addition to a start capacitor, and like start capacitors, dual run capacitors are usually installed in outdoor air conditioner and heat pump units. They are designed to assist the compressor and fan motor

Single Run Capacitor

Single run capacitors are generally used in furnaces to support the furnace blower motor. While your furnace is operating, single run capacitors also run continuously to provide consistent operating torque to the blower motor.

Does your HVAC unit need a new capacitor?

What Are Capacitors & Does Your Furnace Need A New One? 3

Like any other part or component of your HVAC system, capacitors are also inclined to wear and tear over time and will, in turn, be weak or totally damaged that will cause problems in starting or keeping your unit running.

In fact, even though capacitors are particularly small and may be unnoticeable, they are a common cause of HVAC system malfunction.

Here are some telltale signs of a capacitor that needs to be replaced.

Swollen Capacitor

What Are Capacitors & Does Your Furnace Need A New One? 4

The most obvious way to tell a faulty capacitor is to check it visually. In some cases, defective capacitors swell. You might notice its end unusually expands and bulges to the point of bursting (in some rare cases).

Unusual Noise

A unit generating louder noise than usual, a fan motor producing humming sounds, or clicking sounds upon unit startup all indicate a worn-out capacitor that needs replacing.

Burning Odor

A faulty capacitor rather than helping motors to run efficiently will cause the motor to overheat instead. This may cause some wires and tiny components to melt, hence the burning odor.

Unit Runs Weakly/ Won’t Start

A weak capacitor will also provide a weak support to run a motor. This will cause your unit to operate weakly or intermittently. A powerless operation must be reason enough to check the capacitor and replace it before it turns totally damaged to cause your unit to not run at all.

Increasing Bills

What Are Capacitors & Does Your Furnace Need A New One? 5

When your unit is hindered to operate at its maximum efficiency due to a weak or bad capacitor as explained above, bills will naturally go up while your comfort continues to spiral down.

In replacing your capacitor, various factors must be considered like the size and shape, as well as the microfarads and the VAC, or voltage amp current. You can have these information by simply checking your capacitor’s ratings in the product label.

At ACEHVACPARTS, we categorized our capacitor inventory by shape, voltage and type to help you find what you’re looking for easily.

Always make sure to purchase a capacitor with THE SAME microfarads as your old one. However, you may get a capacitor with higher VAC but NEVER a lower one. If you are having trouble identifying your capacitor rating and type, contact us with your unit’s model and serial numbers so we can help you find the right capacitor.

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