Why Is My Doorbell Transformer So Hot? 4 Reasons

Doorbells use transformers to reduce the voltage, but sometimes they can get a bit too hot. If your doorbell transformer feels hot, it’s important to diagnose the issue and make sure that it doesn’t pose an electrical hazard.

Your doorbell transformer is so hot because the core is worn down, the wires are arcing between the terminals, or the transformer has too big of an electrical current. Doorbell transformers are often warm from inefficient electrical exchanges, but they should never be hot.

If you’re wondering why your doorbell transformer is so much hotter than normal, you’re likely ready to take actionable steps. You’ll soon learn all of the potential causes and what you can do to get your doorbell back in good shape.

What Would Cause a Doorbell Transformer to Burn Up?

It’s not uncommon for a doorbell transformer to feel slightly warm, but a hot transformer is often an indicator of an electrical issue. Your transformer might need to be replaced, or the wires might need to be tightened. Flip the breaker, then check if the wires are tightened in their terminals.

So, what would make your doorbell’s transformer suddenly burn up?

Old, Worn Transformer Problems

If your doorbell transformer is old, it likely doesn’t have a durable core. These transformers have vibrating cores that corrode and rust. Once the core is exposed, the transformer stops working. It gets incredibly hot before reaching this point, though.

Foter explains that you can install a doorbell cover, but you shouldn’t enclose it completely; otherwise, you’ll end up overheating the unit.

Electrical Arcing

Electrical arcing is caused by wires not making complete contact with their terminals. This also happens when two wires are exposed and close to each other. The generated spark caused a ton of heat, which is why doorbell transformers can overheat and buzz.

The Doorbell Transformer Is Overloaded

Doorbell transformers often have labeled wire gauges. When you choose a wire gauge that’s too big, or you add multiple wires with a stronger current than necessary, you’ll risk making the doorbell’s transformer too hot. Always test the doorbell transformer voltage at the terminal to see if it’s around 120V to 220V.

Exposed Copper Wires

Your doorbell wires should be stripped at the ends, but there shouldn’t be exposed copper in between the terminals. The ground wire is the only wire that can be bare (though I suggest getting a green ground wire to prevent potential hazards and to identify it as an earth wire).

Overheating is very common with doorbells and other appliances. For example, your washing machine overheats without water because there’s nothing to cool it down. This can also happen if your appliances have arcing, exposed wires going to and from their corresponding transformers.

Should a Doorbell Transformer Get Hot?

A doorbell transformer shouldn’t get hot, but it can be a little warm. A small amount of heat is generated by inefficient electrical signals. However, this isn’t necessarily a bad thing. The problem is when your doorbell’s transformer feels so hot that it warms the air around it.

If you notice your doorbell is getting louder while it’s hot, then it could be burning. Doorbells don’t use a lot of electricity, but they can definitely cause fires. Normal operation will make a doorbell transformer a little warm. That being said, it shouldn’t be incredibly hot. Never touch the transformer to check its temperature.

Mercury Magnetics recommends using a non-contact thermometer to check any transformer’s temperature. This allows you to monitor how warm it is without risking getting shocked or moving the wires too much.

Most doorbell transformers shouldn’t exceed 90 degrees. Check with the company to know how hot it can safely get.

If you don’t have one, try the Klein Tools Infrared Thermometer. This non-contact thermometer ranges between -4 degrees to 752 degrees. It includes a 9-volt battery, too. Point the thermometer at the doorbell transformer, pull the trigger, and read the temperature on the digital display.

Turn off the transformer if it gets too hot. An ever-increasing temperature can quickly turn into smoke and fire, so it should be handled appropriately.

Does it always seem like your doorbell transformer is way too hot? Read on for simple instructions.

What to Do if Your Doorbell Transformer Is Hot

If your doorbell transformer is hot, try these suggestions:

1. Turn off the doorbell’s connected circuit breaker to stop the electrical current from overheating. The only way a transformer can get hot is if there’s electricity moving through it. Once the power is off, use a voltmeter to make sure it reads 0 volts at all four terminals.
2. Check if each of the wires is tight on their terminals, then look for exposed or stripped copper. Wires loosen all the time. I’ve had to tighten electrical wires simply because the wire wasn’t stripped enough. I usually strip one 3/4″ to 1″ off the end of the wire, then tighten it in its terminal.
3. Move the doorbell transformer to a place with plenty of airflow. A lack of airflow will most likely make the transformer too hot. Mount it on a wall or a stud with at least one foot on all three open sides. If you have a cover, make sure it’s porous enough to let air through.
4. Make sure the transformer is rated to be compatible with the doorbell. Most doorbell transformers can convert 120V or 220V down to 20V to 25V. If the transformer doesn’t suit your doorbell’s electrical requirements, the inefficient energy transfer will cause it to overheat.
5. Replace the transformer if its core is worn or vibrating. There’s no way to repair a doorbell transformer that has a damaged core. Your only option is to get another. I suggest getting one that’s recommended by the company or one that’s rated with the same specifications.

Hot doorbell transformers that are accompanied by burning odors should be turned off and replaced immediately. The same thing happens when your heating pad smells, or when a pump’s motor starts producing unexpected scents.