What Is a Sequencer In HVAC? (Operations Explained)

HVAC sequencers are an essential part of any HVAC system, especially for heating. They are specially designed small circuits that help turn switches off and on and stabilize circuits in a typical electrical setting.

Several mechanical devices depend on a sequencer; HVAC systems are no exception. And they are crucial to keeping the various mechanical devices from exploding or overheating.

Daikin Thermostat

What Exactly Is an HVAC Sequencer?

An HVAC heat sequencer prevents voltage from entering your electric furnace and simultaneously turns the heating elements on.

Heating elements are electrical coils that warm up when electricity passes through them.

When voltage enters your HVAC sequencer, it will divert power to the very first heating element. However, it will not allow it to move forward to the next until it has attained a specific temperature.

Meanwhile, if you’re tinkering about looking for it, your HVAC sequencer can be identified by the unique shape and size it has.

Moreover, based on the final product size, the size of the sequencer can vary as well.

Typically, an HVAC sequencer has two diverse segments, and they are assembled via a small middle piece.

And finally, it is built using rigid metal and is quite heavy, and can be used in various equipment including:

  • Furnaces
  • Motors
  • Electric pumps

How Does An HVAC Sequencer Work?

Before we understand the functionality of an HVAC sequencer, we must first understand the role a heating element plays in an electric furnace.

Typically, the heat emitted by your HVAC unit is generated through heating elements. These elements warm the air moving through your furnace and into your home’s ventilation system.

Moreover, this heating element is an electrical coil, and once the current starts to pass through the coil, it becomes hot.

This is known as electrical resistance heating, a principle you may also observe in a toaster.

Meanwhile, your central electric furnace may have a minimum of two heating elements, and based on the size of your furnace, the number can be higher as well.

And if they are all switched on at the same time, your circuit breaker will trip before you even have the time to blink.

That is why a sequencer is a necessary part of any HVAC system. It regulates the way the heating element works, so only one of them is turned on at a time in a ‘sequence.’

The sequence is achieved by creating a circuit series that closes one at a time, thus allowing the electrical power to travel much farther down the system towards every heating element in turn.

There is a series of heat-sensitive circuits that expand upon heating, and once they contact each other, they close. The sequencer then shuts off heating elements as the heating cycle ends.

Related Article – How AC Units Work

HVAC Sequencers Common Features

Every HVAC sequencer has a diverse set of features; however, some common features are shared by almost all types of HVAC sequencers; these include:

Lined Up HVAC AC Outdoor Unit
Ability To Delay A Few Seconds In Sequences

One of the common features in every HVAC sequencer is that it can delay operations for a few seconds between each sequence.

This delay keeps your HVAC unit from overheating, and it also removes the chances of your circuit breaker tripping.

Various Mounting Positions

Another feature observed by many HVAC sequencers is that they have several different mounting positions.

You can mount it in any position that suits your unit; however, the newer models have built-in sequencers, so you do not have to go through the hassle.

But if you have an older HVAC system, you do not have to worry since a sequencer can be mounted in different positions.

Ability To Resist Shocks and Vibrations

We all want our electrical appliances to be shock and vibration-resistant. So, of course, most of the HVAC sequencers have this feature since they will work closely with your electrical furnace.

However, if the sequencer is not vibration resistant, it might do more harm than good, so check if your HVAC sequencer has these capabilities before buying one.

24-volt Input Control

Another feature that ensures less tripping of your circuit breaker is most HVAC sequencers have 24-volt input control.

Many manufacturers use a 24 volt DC to increase the reliability of a control device. In addition, since your sequencer controls the sequence of heating, the limiting circuits help it work efficiently.

Why Do HVAC Systems Need A Sequencer?

There are various reasons why an HVAC sequencer is required, the key one being that it can save power on various electrical devices.

It also helps the equipment run on lower power, thus helping you save money on energy bills.

Furthermore, they protect your HVAC system by preventing equipment loss due to malfunctioning circuit breakers and power shortages.

In addition, your HVAC sequencers space out power, so delicate parts and the engines do not overheat, further conserving money and time.

How To Test The HVAC Sequencer?

Your HVAC sequencer can be found between the furnace thermostat and the heating elements.

The outer housing of the sequencer is a heat-resistant plastic square through which a small heating coil is passed.

And above the heating coil, there are two or more stacked heat-reactive circuits.

So, what to do if you have set up your HVAC sequencer; it is now time to test it:

  1. Plug leads in your electric test meter
  2. Turn the furnace off (do this by shutting off the appliance and turning the breaker)
  3. Touch the probes on the leads end to areas where you removed wires on your heat sequencer
  4. Check the reading on your electric test meter

People Also Ask (FAQ)

How Do I Know If My Heat Sequencer Is Bad?

If your heat sequencer has deteriorated, your heating elements might not turn on, and the furnace will not heat your house. Another indicator is that sequencers might lose control, and they all come on at once, causing the circuit breaker to trip.

How Much Does It Cost To Replace The Heat Sequencer?

Typically, your heat sequencer will not need to be replaced that often. A standard heat sequencer can run for around 12 to 15 years and more with proper maintenance. However, sequencer replacement for an electrical furnace usually costs about $300-350 if the need arises.

Does A Gas Furnace Have A Heat Sequencer?

No, it does not. Even though both the gas and electric furnace operate on a similar principle, one key difference between them is the presence of a sequencer to control electricity and save energy.

How Do You Wire A Sequencer?

Even though you can wire a sequencer for your electric furnace by yourself, since an HVAC system controls the atmosphere of your home, it is better not to risk it and get professional help. Still, here is an HVAC sequencer wiring video to help you understand step by step.


Sequencers have become a critical component to have for your HVAC system. They enhance your electric furnace operations and help you save on your yearly bills.

Other than that, they have so many uses that make them one of the best investments for your HVAC system.

We hope this guide was able to help you understand all there is to know about an HVAC sequencer.

Josh Mitchell

Josh Mitchell

My name is Josh and I am obsessed with DIY and improving my family home. HVAC topics can be tricky for homeowners so I decided to share my knowledge on the subject. When I am not working on DIY projects, you can find me at the beach or my local coffee shop.