Do Dimmer Switches Get Hot?

test Do dimmer switches get hot? It’s a common question that a lot of people have been wondering about, especially after reports of overloaded dimmer switches causing fires. We will explore why they feel warm, when they are too hot and also discuss what to do if you think your dimmer switch might be overloaded.

Do Dimmer Switches Get Hot? 

Yes, dimmer switches can get hot, they have a lot of electronic components inside them that generate heat when they are in use.

However, if your switch is uncomfortable to touch there could be an issue to resolve, and can even be dangerous. If in any doubt do turn off the electricity to that lighting circuit and call an electrician.

Provided you feel it is safe to investigate further, let’s look into why dimmer switches get hot with some tips on possible options to help reduce the heat.

Why Do Dimmer Switches Get Hot?

Dimmer switches get hot because of the management of electricity that passes through them on its way to your lighting.

The reason why dimmer switches get hot depends on a variety of potential reasons:

1. The technology being used in the dimmer. LED ready versions will feel cooler than traditional ones.
2. The age of the dimmer switch. Older technology dimmers designed for tungsten filment lamps will feel warmer as they create a resistance which creates heat.
3. The type of lighting that is being dimmed. High wattage circuits are usually not LED but older lamping technologies that require a dimmer to handle higher wattages.
4. Overloading. Too much is being asked of the design of the switch and it cannot handle the amount of electricity passing through it.
5. Faulty wiring. A faulty loose wire can cause a fire hazard as parts of the switch are being made live when they are not designed to be.
6. Heat sink unconnected. Some have small metal parts inside that are used to take the heat from the dimmer and help dissipate it. If they are not installed correctly when being fitted then they cannot take the heat away quick enough and it will run hotter than expected.
7. Power Surges. Electrical power surges spike electrical components with too much power and stresses them resulting in running too hot.
8. The LED lighting load has not been derated. It’s an odd feature of LED lighting but some dimmers required the LED load to run at 30% capacity or they cannot start or run properly. Check with the manufacturer.
9. The lighting circuit is not being turned off properly. If the lighting circuit is not being completely turned off but to your eyes it looks off, this is where the switch is working at its hardest by creating an almost 100% dim and creating maximum heat. Ensure that it turns off, so when using a rotary knob dimmer rotate until a click is heard or you cannot go any further.

How Hot Should a Dimmer Switch Feel?

Generally, a dimmer switch should operate at around 140°F (60°C). However, some switches can be designed to tolerate up to 195°F (90°C).

Is a Hot Dimmer Switch Dangerous?

A hot dimmer switch is not necessarily dangerous but some of the reasons why they run with heat will reveal if a potential hazard is forming.

1. Power surges can break electrical components and LED lighting falls within this category, but are not usually dangerous unless significant.
2. Faulty wiring is very dangerous, consult your electrician if suspected.
3. Overloading is potentially dangerous if left undealt with as it can cause a fire.

Overloaded Dimmer Switch

An overloaded dimmer is the most likely reason you are worried, and this happens when too much electricity is passing through the switch. This can be for a number of reasons, but most commonly it is because the wrong type of light bulb is being used with the dimmer switch. 

How to Tell if Your Dimmer Is Overloaded

A few signs of electrical overloading a lighting circuit are:

1. Touch. The dimmer should feel warm, not uncomfortably hot to touch
2. Flickering lights. Another way to tell if your dimmer switch is overloaded is by looking at the light bulbs that are being used with the switch. If the light bulbs are flickering or not working
3. Age of light bulbs. Another way to tell if your dimmer switch is overloaded is by looking at the light bulbs that are being used with it. If older style tungsten or halogen bulbs are added to a recently installed lighting circuit designed for use with LED, the additional loading of the inefficient light sources is taking the switch past its capacity to work properly.
4. Calculate if the lighting load is too high. Add up how many lighting sources are being served by the switch and calculate the total wattage being used. Does it fall within the parameters of the dimmer?
5. The maximum loading of the switch is exceeded. Most older style standard dimmer switches are rated for 400 or 600 watts for incandescent bulbs or 150 watts to 250 watts for CFLs and LEDs. It is important to make sure that your switch is equipped to handle the wattage on your circuit. Take the cover plate off and read the wattage on the inside.
6. Has a 2. 3 or 4 Gang Dimmer Switch been Derated? When two or more switches are installed next to each other in the same electrical box, the rating of each switch is reduced. This is because there will be less space between them for air to circulate and help cool the switch.

How to Stop a Dimmer From Being Overloaded

If you have too many bulbs on a single switch, you have a few options:

• Replace some of the bulbs with lower wattage bulbs of the same type
• Upgrade to LED bulbs which will run significantly lower.
• See if you need as much lighting on the circuit and keep some turned off.

Ask an Electrician

Some potential fixes will require qualified help:

• Put some of the bulbs on different switches so the load is divided up.
• Install a higher capacity dimmer switch.
• Ensure that the lighter load of LED will still work with the chosen dimmer switch.

Will a Dimmer Switch Fail?

If the total wattage of the bulbs and lighting fixtures exceeds your dimmer switch’s wattage rating, you run the risk of burnout. This means that if too many bulbs are connected to the switch, it will have been working too hard, run too hot, and eventually caused it to break. When a dimmer switch stops working because of overloading it will do so without warning.

If this occurs, the dimmer is beyond repair. When you buy a new switch, make sure it is a higher wattage than your total bulb wattage.

If you use a lower wattage dimmer switch with too high a wattage of bulbs and light fixtures, you risk burning out the dimmer switch and the bulbs as well. 

When a bulb is overloaded with too much current, it damages the filament inside the light bulb or overruns the semiconductor LED causing them to fail early too.

Conclusion

If your dimmer switch is hot, turn it off, and don’t use it again until you have checked it. If your dimmer switch is overloaded, disconnect any appliances or light bulbs that are drawing too much power. You may need to replace the fuse or circuit breaker with a higher-rated one. If this doesn’t work, call a qualified electrician.

If you have any doubts about your ability to safely investigate or repair your dimmer switch, please don’t hesitate to contact a qualified electrician for assistance. Hot dimmer switches can be dangerous and cause fires, so it’s always better to be safe than sorry.

For more tips we look at What is Dimming. Methods for dimming LED Lights

Thanks for reading and stay safe!

Andrew Orange, the owner of Orange Lighting qualified and worked as an interior designer in 1993 before specialising in lighting working on high profile projects based in London. Since starting Orange Lighting Ltd in 2003 he has been sharing his knowledge and unique teaching style mostly to his designer clients, offering practical real life advice born from running a busy consultancy and lighting supply business. Launching in 2020, his blog has evolved into Quick & Easy Lighting, curating some 25 years design experience into making the lighting choice and design process achievable and easy to understand for all.