Have you ever come home, switched on your electric heater, and instead of the unit starting to heat up, it instead trips the circuit breaker and goes off? If so, you’re not alone.

The electric furnace consumes massive amounts of electricity to the extent that overloads aren’t uncommon. The circuit breaker will trip without hesitation in case of overload, shutting down the furnace in the process.

So, you might be asking why this doesn’t happen all the time. Why does the furnace work just fine most of the time? Why doesn’t the breaker trip every time you start the appliance? That’s where the heat sequencer comes in handy.

Read on to understand more about the sequencer, how it works, what it does, and what can go wrong with your heat sequencer. We also discuss how to test, fix, and bypass the sequencer.

What’s Furnace Sequencer?

The heat sequencer is a mall circuit designed to help stabilize circuits and quickly turn switches ON and OFF. Generally, the sequencer stages different parts of the heating system to prevent overloading or tripping of the circuit breaker. Other appliances that use sequencers include engines and mechanical devices, where the sequencer prevents overheating and overloading.

It shouldn’t be too difficult to identify the sequencer. Although they come in different sizes, most HVAC sequencers comprise two different segments attached using a smaller middle piece. You’ll know you’ve found it if you find such a device constructed from rigid metal. Sequencers are also typically heavy.

How Does the Furnace Sequencer Work?

The primary function of a furnace sequencer is to ensure that the appliance has enough power to run. This helps prevent incidents like the example above where the circuit breaker trips when you turn on the furnace. The sequencer allows the furnace to use only a portion of the available power in portions rather than all at once.

As a result, only the necessary parts of the heater are on at any given time, meaning that the furnace users only a fraction of the power at its disposal. This helps keep circuits from blowing, motors from overheating, and the various components wearing too fast. Remember that the heating elements in an electrical furnace are coils that warm up when electrical current passes through them.

The sequencer’s role is to route power to the first heating element only and only move to the next conduit once the first one has reached a specified temperature. This goes on sequentially until all the conduits are turned on for the heating cycle.

Why is it Important to Have a Sequencer in a Heating System?

There are many benefits to using furnace sequencers on your electric furnace. We’ll only list the most critical advantages.

• Save power: The main benefit of heat sequencers is saving power on different appliances. The sequencer only allows power to flow to critical components of the furnace at any given point, thus overall low running power.
• Fewer or no circuit breaks: By only powering critical parts of the furnace during startup and throughout furnace operation, the sequencer prevents overloads. So, you don’t have to worry about the furnace going off when starting.  
• Prevents overheating: The sequencer spaces power so that all the different parts of the furnace don’t have to run at any given time. This significantly reduces the risk of parts overheating and consequential shutdown.
• Slows down wear and tear: Finally, the furnace sequencer can significantly increase the appliance’s lifespan. Although it’s difficult to say by how long, reduced heating, fewer circuit breaks, and fewer restarts often mean a much longer appliance life.

Where is the Furnace Sequencer Located?

The furnace is located in the top compartment, connected to several pairs of wires. Each of these wire pairs attaches to a different heating element/conduit inside the furnace.

How Do I Know if my Furnace Sequencer is Bad?

It’s pretty easy to tell that you may have a bad furnace sequencer, though you may need additional tests to prove that the sequencer is indeed broken. The following are the most common signs of a bad sequencer.

The breaker trips when you start the furnace.

As we mentioned initially, the clearest sign that you may have a bad heat sequencer is a tripped circuit breaker. You’re almost sure that the sequencer is faulty if the breaker trips right when you start the furnace. Why does this happen? Because a broken sequence means the entire heating will attempt to draw power from the main supply.

For instance, if your electric furnace has six conduits or heating elements, all six will attempt to draw power from the supply when you switch on the heater. Unfortunately, your home’s supply cannot supply six heating elements at a go. It’s too much load. Therefore, the circuit breaker will trip to protect the appliance and your electrical wiring.

The blower fan comes on with no heat.

You may also have a damaged sequencer if you turn on the furnace and the blower fan come on, but the unit produces very little or no heat. This usually means that the heating elements are not working. But, why?

It depends. Maybe the sequencer is partly damaged. Maybe one part is working, but others aren’t. This happens a lot. Fortunately, you can fix the problem with simple repairs.

The opposite is also possible, i.e., the heating elements may turn on but not the blower. In both cases, you’ll not get meaningful heat in your rooms. This can happen if wires to the sequencer are loose or if the connectors are corroded. Fortunately, this is another issue you can easily fix with repairs.

The furnace kicks on, but with very little heating.

Finally, you may also encounter circumstances where the furnace runs and produces heat, but the heat is just too little. Unless the heating elements are defective, you may have a sequencer problem. This usually happens when only the first heating element comes on, but the others don’t.

For example, maybe your electric furnace has ten heating elements, but only the first two come on. You’d be left in the cold. A common reason here is a dying sequencer that can no longer generate signals appropriately to keep the furnace running normally. Maybe it generates a signal for the first few heating elements then loses track.

What Causes a Heat Sequencer to Fail?

Heat sequencers can fail for many reasons. However, the three most common reasons a furnace sequencer can fail are as follows.

• Frequent use throughout the season: Heat sequencers essentially use a coil and bimetallic switch, which serves as a “thermostat.” Unfortunately, using the electric furnace throughout the season can cause stretching and flexing of the bimetallic switch, resulting in inaccuracy.
• The bimetallic switch is stuck: The switch can become stuck in an open or closed state, causing it to fail wholly or partially. Causes of a stuck sequencer bimetallic switch include electric short-circuiting and dirt buildup.
• Disuse: Finally, your heat sequencer can also fail following extended periods of disuse, such as continuing to use the electric furnace during the summer.

How to Test my HVAC Heat Sequencer

If you’ve observed one of the signs above, you can test your heat sequencer to confirm whether it’s indeed damaged. Fortunately, it’s not too difficult to test a heat sequencer. All you need is a multimeter. Proceed as follows once you have a multimeter.

1. Shut down the furnace at the main breaker.
2. Use an electric test to make sure that it’s indeed off.
3. Open the furnace and locate the heat sequencer.
4. Disconnect the wires from the sequencer.
5. Take out your multimeter and connect the leads to the heat sequencer. You need to connect the probes to the locations where you just removed the wires.
6. Check the reading on the meter.

You should get a voltage reading of around 24V. The sequencer is damaged and needs replacing if the voltage reading is zero or too low.

How to Bypass the Heat Sequencer

If you’re wondering, yes, you can bypass the furnace’s heat sequencer. This is never a good idea, considering the importance of the sequencer. For one, bypassing the sequencer means your furnace will attempt to engage all the heating elements in your furnace at a go, likely causing the overload and consequently tripping the circuit breaker.

However, it’s OK to bypass it temporarily, perhaps for a few minutes, to confirm that it’s broken. The sequencer is bad if the furnace works when you bypass the sequencer.

The good news is that bypassing the heat sequencer is also a straightforward process. As you may recall, we mentioned at the beginning that the sequencer has pairs of wires running into it that connect to different heating elements in the furnace.

So, with the furnace off (make sure to double-check this), all you need to do is remove one pair of wires and connect the wires directly. If heating resumes once you bypass the heat sequencer, then the sequencer might be dead or dying. Or maybe it’s broken.

Summary 

Now you know how heat sequencers work, the importance of the heat sequencer, and most importantly, how to troubleshoot and bypass a faulty sequencer. Make sure to consult a professional if you need sequencer repairs or replacement.