What Causes A Transformer To Blow In A Furnace? – Simple Guide 2022

What Causes A Transformer To Blow In A Furnace? – Simple Guide 2022

Want to know what causes a transformer to blow in a furnace? If so, don’t worry, we have got you covered. Read this guide thoroughly so you don’t miss anything out!

What causes a transformer to blow in a furnace? You may not know but the answer is pretty simple. It’s a really sad fact of life that a lot of people don’t understand the basics of electricity and how it works. 

So in this article, we’re going to try and explain what causes a transformer to blow in a furnace. We’ll also show you how you can prevent it from happening.

Going over some of the terms, functions, and parts of the transformer will give you a better idea of how the transformer is intended in a furnace.

The following information will help you with your goals, such as installing or replacing the furnace transformer, if you are looking to work on a transformer, or just educating yourself on the subject. 

It will give you a more in-depth look at how the furnace works. Even though there are some differences, this will apply to both residential and commercial furnaces.

What Is A Furnace Transformer?

What Causes A Transformer To Blow In A Furnace?

The main function of the furnace transformer is to provide power to the furnace itself. The high voltage capacity can be lowered to a lower output. This is required for arc furnace operations. You will be able to see that some furnaces need a certain amount of power.

The basic control of the furnace, such as timers, ignitions, circuitry, and temperature controls, is what this is meant for.

The transformer will reduce your home’s voltages to the correct amount for use in your furnace since the standard voltage output for any house is 120 volts. Electric and gas furnaces can have differing voltages, which can include electric and gas.

Regulating The Proper Voltage

There are two different types of volts that you will find when you buy a new furnace. The size of the furnace should be considered, as well as where it is being installed in a residential or commercial structure. Larger furnaces are usually required to fit the square footage in a commercial building.

A standard furnace will do the trick if a residential building has a smaller living space. The transformer used for electric, gas, and oil furnaces will have a 120 or 240 volts rating. 

Some options may use as little as 24 volts. It is possible to locate the volts capacity information within the furnace’s features. If you can’t find a sticker with the information, then you can use a voltage test meter to find out.

When A Furnace’s Transformer Blows, What Causes It?

The main reasons for a transformer to blow in a furnace are loose wiring, the accumulation of dust, and worn-out components.

Accumulation Of Dirt And Debris: 

The various parts of the furnace are likely to collect dust if you have not paid attention to the maintenance. The motor of the blower begins to burn out after the dust reaches it. The transformer blows up as a result of the high limit failing.

Loosening Of Wires:

Internal wires can loosen up because of the functioning of the transformer. The risk of a short circuit is caused by this in turn. Ensuring that the wires are tight and in good condition from time to time is important to avoid accidents.

Worn Out Parts:

If you hear strange noises coming out of your furnace, it might be a sign that some parts are worn out. The transformer of the furnace is used to convert the electrical signals to the correct voltages. The transformer may blow up if it fails to do so.

If Your Furnace Transformer Is Faulty, Here’s How to Check

There might be a problem with your furnace transformer if you are facing issues with your electrical system. It is possible to check the functioning of a transformer with a digital multimeter. It is possible to do here.

Step 1:

The power supply to the circuit has to be turned off first. The panels and covers need to be removed as well. Next, use a digital multimeter to take accurate readings of voltage. Attaching the leads of the digital multimeter to the input lines is required. It’s important to make sure that the transformer isn’t shorted


The transformer needs to be checked to allow the current to flow through the circuit. This can be indicative of a problem in the circuit that is providing the primary power or the transformer itself if the check is lower than expected.

Step 3: 

To measure the transformer secondary, you will have to do. The use of the DC scale of the digital multimeter is needed if there is a possibility of filtering. You can stick to the AC mode if you don’t want to. If the transformer’s expected voltage is not found on the secondary, it may be a sign that the transformer is faulty.

Symptoms Of A Faulty Furnace Transformer

What Causes A Transformer To Blow In A Furnace?

It can be difficult to identify issues with the transformer. If you know what you’re doing, you may be able to detect the signals that are indicative of a faulty transformer.

Some Of The Main Symptoms Are: 

A Drastic Increase In Vibration And Humming Sound:

A humming sound can be heard from the Transformers. The expansion and contraction of the iron core are what make this happen. It is possible that a faulty transformer is to blame for the rapid increase in noise and vibrations.

It is not always necessary to cause the vibration due to an error in the transformer. An error in the installation of the Capacitor may be the reason for it. It’s always a good idea to call a professional technician and ask him to resolve the issue.

Transformer Tripping Frequently:

If the transformer in your furnace is malfunctioning, the circuit breaker will trip frequently. A major breakdown is prevented by this trip preventing voltage surge.

Non-Functional HVAC:

Even if there is an adequate power supply, your heating, ventilating, and air-conditioning unit will not function properly if your furnace uses a bad transformer. The fact that your furnace transformer needs to be attended to is suggestive of all of these symptoms.

What Are The Steps For Testing An Oil Furnace Transformer?

An oil burner is a device that is connected to a furnace transformer. The oil burner can be used to generate heat from any type of heating oil. Below are the steps that you need to follow if you wish to test an oil furnace transformer: 

The source of power will have to be disconnected first. Turn off the breaker if you don’t want to plug it in. Remove the inspection panels, locate the transformer, and move it to a position where it can be easily moved.

The high voltage terminals can be touched easily if the interiors are positioned in a way that makes it easy to touch them. If you want to avoid oil coming out of the transformer, you need to connect the power source to the motor. Turn on the oil burner when it’s connected to the source of power.

Take a well-insulated screwdriver and place it to the transformer’s output terminals in such a way that the screwdriver doesn’t touch one terminal but the other. An arc should form when the gap is not closed. The transformer is malfunctioning if the arcs are shorter than three-quarters of an inch or if there are no arcs at all.

What To Do When A Furnace Transformer Is Humming

During functioning, all appliances make a certain amount of humming noise. It becomes concerning when the noise surpasses the normal level. Several factors could cause a humming noise in a furnace transformer.

Sometimes a humming noise can be caused by the blower motor not having sufficient lubrication. A lot of humming noise can be caused by loose wiring, equipment, loosened ductwork, and failed capacitors, among others.

To get rid of his buzzing noise, it is important to hire a professional technician. To fix the issue, one needs to follow the given steps.

If all the parts of the device are fastened properly, it can reduce the amount of noise. The furnace transformer should be mounted on a dense surface to not amplify the noise. It can be mounted on thin plywood sheets to amplify the noise. It’s possible to reduce the noise by using cushion padding that can absorb the noise and act as insulation.

What’s Wrong With Your Furnace Transformer

Sometimes, the transformer of a furnace isn’t designed to provide the amount of current that is expected to. The transformer tends to get overheated in this situation. The generation of heat occurs when the flow of current leads to it. 

The wires tend to get heated up when the amount of current flowing through the coil increases. The repeated heating and cooling of the wires can cause them to become brittle and fail in the long run.

Before you consider a complete overhaul, there are a few things that you need to consider:

You have to make sure the transformer is not being overburdened by the current flowing through it. It should be in line with acceptable limits.

You need to take a look at the oil levels. If your transformer gets heated up quickly, it may be because of insufficient levels of oil. If your transformer has faulty connections, you should check it out. Try to resolve the connection issue if you find it.

Is There A Reason The HVAC Transformer Keeps Blowing?

The term heating, ventilating, and air-conditioning is referred to as “HVAC“. The thermostat is the primary device of the heating, ventilating, and air conditioning (HVAC) units. These thermostats help regulate the temperature. Like all brands,

I have experienced transformers that blow. A surge in power, loose cables, or a bad contractor can be some of the reasons why this can happen. The transformer on the unit tends to blow off when it fails to handle the strain.

It is possible to take care of this kind of malfunctioning. You can ask a technician to replace the faulty component. You can get rid of melted parts and the device will start working again. Maintenance of electrical components needs to be done timely.

Massive havoc can be caused in the future by even the smallest of knowledge gaps. If you want to prevent nuisances in the future, try to schedule a maintenance session after a specific interval.

FAQs- What Causes A Transformer To Blow In A Furnace?

Why Does My Furnace Keep Blowing Transformers?

A faulty contractor can put the entire system under stress and cause the transformer to blow once the tension becomes too much. If there are loose cables or wires inside your transformer, they can cause a short circuit.

What Would Cause A Transformer To Go Bad?

Transformer failure is usually caused by line surge, which is a very common cause of electrical failure. Surges, voltage spikes, and line faults are some of the most common causes of electrical failure.

Can A Thermostat Blow A Transformer?

In most cases, the thermostat wires have shorted out, and the problem is the thermostat wires. The transformer in the air conditioning system can burn up due to other components inside the system. If the wires are in good shape, you shouldn’t get a reading between them.

Can A Bad Transformer Cause A Fire?

Sparks that may cause the transformer to catch fire and explode can be caused by an exothermic reaction due to a faulty wire or overload.


Many factors can cause a transformer to blow in a furnace. The furnace is likely to be overloaded, so the heating and cooling system may need to be tuned up. If the transformer was not properly installed, it could also be damaged. 

The most common reason for a furnace’s transformer to blow is its internal resistance being too high. This means that there isn’t enough current flowing through the transformer to operate the heating and cooling system at full capacity.

In some cases, even if the transformer is intact, it could still fail because of an overload or other mechanical failure. we hope that this article gave you all the information that you needed.  

Also Read:
Why You’re Not Getting 240 Volts (How To Fix It)
Why Your Oven Keeps Beeping And How To Stop It 2022

Reggie Burton is a technology expert with over nine years of experience in the field. He has worked extensively with both large and small businesses to help them optimize their tech infrastructure and improve their overall efficiency. Reggie is known for his calm demeanor and his ability to quickly assess a situation and find a solution. He is an invaluable member of any team, and his clients are some of the most satisfied in the business.

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