What You Should Know About Your HVAC Electrical Components

Inside of a HVAC system

Air conditioners are a load-bearing beam in the structure of society. Without air conditioning, we’d never be able to spend long hours inside our homes away from the extreme temperatures outside of them.

However, many people take their air conditioning systems for granted. After all, they’ve been a part of our modern world for many decades now – why would we need to know more?

The truth is that your air conditioner could go out at any moment, no matter its age. While we like to recommend you keep your system as up-to-date on maintenance and repairs as possible, unforeseen circumstances can always rear their ugly heads.

That’s why we recommend that all homeowners learn as much as they can about the electrical components that make up their air conditioning systems. With even the most basic understanding of how these parts work, from the thermostat to the condenser, evaporator coil, fan motor, and compressor, you can save your family from some serious discomfort.

Today, let’s take a look at some of the most essential elements of understanding your HVAC system’s electrical components.

Basic Electrical Components in Your HVAC System

Your air conditioner unit is comprised of many electrical components that work in tandem with each other to provide heating and cooling for your home.

Many of those parts are considered the main electrical components of your system – including the thermostat, furnace, blower fan, electrical wiring, and relays, as well as crankcase heaters, the compressor, condenser, evaporator coils, heat pumps, and much more.


The thermostat in HVAC systems is one part of many components that tell the system when it should be heating or cooling your home. Some air conditioners have multiple thermostats which control the temperature in multiple rooms or spaces of the home. Usually, your thermostat is located as far as possible from areas with concentrated temperature differences in a conditioned space.

The temperature switch, also known as a thermostat sensor, makes sure the temperature in your home is accurate to what you set on the thermostat. Essentially, it tells HVAC systems to kick on if it gets too hot or too cold.


For when it gets chilly, your HVAC furnace is one of your best friends in the world. Your furnace heats the air sent throughout your home, usually using electricity or natural gas.

It’s important to consider the combustion efficiency of any furnace your HVAC system might use. Whether you are utility bill-conscious or worried about the environment, differences in these components have a huge impact on your yearly energy use.


Cool or hot air is forced through your system by a blower. Blowers are driven by electric motors with variable speeds. This allows homeowners to change the speed of their blowers, reducing or increasing efficiency, noise, and energy consumption.


Wiring inside of a system

Electric wiring is responsible for connecting each of the electrical components inside your HVAC system. Since the network of wires inside your system is quite complex, many HVAC technicians use circuit schematics or other visual guides to keep track of it.

Wiring can come in a huge range of layouts and types, which might make certain issues more difficult to detect. The main voltage for your unit enters via a disconnect box. The disconnect box is connected to your air conditioner by wiring commonly referred to as a whip. The main power, or high voltage, flow goes through the main contactor which opens and closes to control the unit.

HVAC systems have high voltage and low voltage electrical circuits. The relays and controls are powered by 24 volts. The 24 volts is developed by a transformer.


Your HVAC system, in many ways, works like a large circuit board. The most important concept to understand about your air conditioner’s functionality is how electricity flows through it. This is done through electrical components known as relays.

Relays, which control voltage, are either switched open or closed – when they’re open, the relay is off. When they’re closed, the relay is on and allows electricity to travel through to each other components.


When an electrical relay receives at least 24 volts of electricity, it closes and turns on, enabling it to deliver power to the next component in the system.


Some HVAC equipment features relays that turn closed when a specific amount of pressure is applied, both for low pressure and high pressure. This turns the relay on and distributes power to the next component.


If your air conditioner gets too hot, the relay will open and cease powering the various electrical components of your system.

Common Electrical Issues in HVAC Electrical Components

Electrical Connection Issues

For the most part, connection issues with the electrical components in your air conditioning unit are rarely a serious problem. You can usually rely on a skilled HVAC tech to identify and rectify the issue within a few minutes. All they need to do is tighten up your connections and check the line voltage to get your air conditioner up and running again.

However, if you do have a connection or line voltage issue, it could indicate larger problems with the electrical circuit or other wiring difficulties. That’s why it’s wise to keep your air conditioning unit well-maintained year-round to avoid switching devices.

Compressor Issues

The compressor – the most expensive electrical component of your entire HVAC system – can create several mechanical failures related to its electrical pull. For instance, if your system requires a certain amount of energy and the compressor pulls less or more than that number, it can overheat.

You may also have an issue with your crankcase heater. The crankcase heater is designed to keep the oil in your compressor at a specific temperature so the refrigerant pressure stays nominal and doesn’t mix with the oil. Crankcase heaters malfunctioning can cause oil to become less effective for lubrication, cause damage to the bearings, and altogether ruin other parts of the system.

Additionally, if the refrigerant pressure goes down or you lose refrigerant from a leak, your compressor will lose efficiency overall.

If any of these issues occur, it can cause a total meltdown over time. In other words, don’t put off repairing compressor issues – contact an HVAC repair specialist as soon as possible.  

Circuit Breaker Issues

Your air conditioning system could very well be pulling too much electricity if you repeatedly find your fuses tripped. Other issues that cause an air conditioner to trip include:

  • Dirty, clogged, debris-filled condenser unit
  • Dirty, clogged air filters
  • Issues with the circuit system itself
  • Shorted fan motor
  • Compressor not starting
  • Grounded compressor
  • Having both heat pumps and air conditioners installed

The best way to figure this out quickly is to have a local HVAC technician check all your electrical components to see if your air conditioner requires a circuit or electrical wiring system made of sturdier stuff.

Other Wiring Issues

Electric wiring may have come a long way in the past century, but it’s still subject to a whole host of problems. Air conditioner units often have frayed, corroded, or disconnected wires that can lead to an array of problems.

The line voltage may be too low, making your air conditioner work harder than it should to bring your home to the desired temperature. When this happens, air conditioners can break down altogether or cost you a tremendous energy bill at the very least.

Some homeowners connect their air conditioning units to what they believe is an indoor surge protector. In truth, these are simple power strips, which can cause electrical fires. Most HVAC techs recommend homeowners install surge protectors into their AC units themselves or use actual surge protector power strips inside.  

Should My Air Conditioning Unit Have a Separate Circuit?

Some homes have dedicated electrical circuit breakers for their home air conditioners. The main reason for this is that a separate breaker installed by an HVAC technician can protect their heating and cooling unit from being tripped and shutting off. Maintaining a dedicated circuit may be necessary for keeping your electrical equipment in the best possible shape – and working at optimal efficiency.

How Home Appliance Amperage Ratings Work

Every appliance in your home – including every electrical device and light bulb, have a specific amperage rating. These ratings will range anywhere from .75 amps to more than 10amps. As long as all of these ratings added together are below the limit of your circuit breaker, you’ll be in good shape.

However, if your total amperage rating exceeds your breaker’s safety limit, you can overtax your electrical wiring and create some serious issues down the road. That’s why it’s critical to know the amperage ratings of your appliances – and if you may need a separate circuit to handle the amperage required by your home HVAC system.

When You MUST Have a Separate Circuit Breaker                     

If your home’s electrical wiring is outdated or if it never had an HVAC unit incorporated into its wiring, you may not have the power to put out the voltage necessary to keep your home at the right temperature. Thus, you may need extra electrical services to install a new, independent circuit to ensure you can provide power to your equipment.

Any HVAC technician will be able to let you know the exact quality of your home’s existing electrical wiring and how it can handle a newly installed HVAC unit or other equipment. Even if you already have a separate control circuit, it’ll still need a thorough checkup to determine if the amperage is up to snuff.

A general rule of thumb when it comes to voltage, power, wiring, relays, etc. is if your new wiring is between 110 and 120 volts at over 7 amps, you’ll likely need a new circuit just to keep your air conditioner powered.  

DIY HVAC Repair Techniques

If you feel like you know enough about the electrical components of your air conditioning system, you can attempt some simple repair techniques to keep it running smoothly. These include:

  • Examining your breaker box.
  • Checking the thermostat. Has it been turned off, or does it need new batteries? Is the temperature setting too low or too high to correctly heat or cool your home?
  • Replacing the filter often. Sometimes, dirty air filters can stop the flow of air in your home.
  • Turning your unit off for a time. If your air conditioner unit has frozen over, or if one specific electrical component of your system has ice on it, it won’t work properly. You can either turn it off altogether or simply run the fan motors for a time to circulate warm air through the unit to melt the ice.
  • Cleaning out your air ducts. Are they so dirty they stop air from flowing through, even with the condenser fan motor blowing at full blast? While you’re at it, check the registers to make sure they haven’t been accidentally closed or blocked by debris.

Reach Out to the Experts

Have you had any issues with the electrical components inside your air conditioner? Do you have questions about voltage, relays, switches, heat pumps, fan motors, crankcase heaters, or other components related to home heating and cooling?

Or maybe you’d like to become an HVAC technician yourself?

Wrapping your head around the core components of how your air conditioner works are the first step. Not only will you get a better idea of how your equipment runs – you’ll also learn about electricity, pressure, temperature, modern manufacturing processes, and much more.

If you need assistance with the electrical components in your HVAC system, don’t shoulder the burden on your own. Reach out to the friendly, knowledgeable team at Blue Water Climate Control today to learn more.

Written by Jeremy James

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