Light switches are some of the simplest electrical components in existence. However, dimmer switches do have a little more complexity to them, and that can sometimes mean that they can cause problems.
But can they cause a breaker to trip?
Or is it more likely to be another part of your lighting circuit that’s triggering the breaker?
A bad dimmer switch can definitely trip a breaker. It could have a loose connection that arcs, which would trip the breaker randomly. If it trips instantly, then the dimmer is likely overloaded. Other dimmer faults won’t trip a breaker but will cause other problems, too.
Let’s explore this a little further and take a look at:
- Whether a bad dimmer will trip a circuit breaker
- The likely cause if a breaker is tripping randomly
- What’s happening if a dimmer causes a breaker to trip instantly
Can A Bad Dimmer Switch Trip The Circuit Breaker?
Dimmer switches tend to have a lifespan of around 15 years, which is a long time but obviously is not infinite.
Eventually, a dimmer switch is going to go bad.
However, they won’t all last 15 years either.
You may have installed an unsuitable dimmer for your home, or if you’ve tried to buy a cheap one that isn’t manufactured to a high standard, it could fail sooner.
But what happens when they fail – will they cause the circuit breaker to trip? If not, how else do you know that the dimmer is bad and needs replacing?
In some cases, the dimmer will trip the breaker; if that’s happening, you’ll need to investigate.
It’ll either cause the breaker to trip randomly or immediately, and the causes for those are different. More on those below.
But there are also times when the dimmer will go bad without tripping the breaker.
The signs you need to look out for are:
- The dimmer not dimming all the way down as it should be, cutting the lights out early
- A loud buzzing sound coming from the dimmer
- Excessive heat coming from the dimmer – it’s not unusual for a dimmer to be warm, but ‘hot’ is a bad sign
- Signs of physical damage to the dimmer, including cracking
- The switch on the dimmer losing its snap, feeling loose
If you notice any of these issues, even if the breaker isn’t tripping, you should consider replacing the dimmer before it causes any further headaches.
What Causes A Breaker To Randomly Trip When Dimmer Is On?
It’s infuriating when you’re sitting in a room, and the lights suddenly cut out for no reason, especially if you flip the breaker back into the on position and everything seems to be working again.
Because now you have a mystery on your hands – why did it trip like that, and how do you stop it from happening again?
It might just be a power surge if it happens once, but if you notice it happening a few times. Still, at random intervals, the likely cause is a loose connection somewhere.
When there’s a loose connection, the current often flows normally, but there is a small gap in the circuit somewhere, or an intermittent one.
When that gap reaches a certain distance, the current jumps – or arcing – to maintain its flow.
And when it does this, it can cause a small surge, which can be dangerous.
However, your circuit breaker should have an AFCI installed – an Arc-Fault Circuit Interrupter.
These are really clever devices that will automatically flip the breaker when they detect an arc.
Originally they were a requirement only on socket circuits.
In 2002 the code was changed to change the word ‘receptacle’ into ‘outlets,’ implying that lights and other hard-wired devices such as ceiling fans also had an ACFI breaker fitted.
So, suppose your AFCI breaker is tripping randomly when you need to investigate for a loose connection. In that case, that’s likely at the switch or at a light fixture.
It may not be a loose wire that you can see, but it could be a loose internal connection inside the dimmer.
If it is a loose internal connection, that’s when you’re potentially likely to feel the heat coming from the dimmer or notice that the switch has lost its snap.
Replace the dimmer, and you should stop the breaker from being tripped.
Breaker Keeps Tripping When Light Switch Is Turned On
Say you’ve installed some brand new lighting, and every single time you try to switch them on via the dimmer, it’s tripping the breaker immediately.
What’s causing that?
The most likely cause is that you’ve overloaded your dimmer switch.
Typical lighting circuits in the US can handle 1,800 Watts of lighting, although you wouldn’t want to push it close to that limit.
The supply voltage is 120v, and a lighting circuit typically has a 15 amp breaker, which you multiply to get the maximum wattage you can load onto the circuit.
But while regular switches aren’t limited on wattage since they’re just a mechanical break in the circuit, a dimmer switch is limited and usually can’t handle anywhere near 1,800 watts.
Common dimmer wattage ratings are 150 watts (designed for a single light), 300 watts, 600 watts, and 1,000 watts, with 600 watts tending to be the most common.
Now that’s still quite high, and if you’re using LED bulbs, you’re not going to get anywhere close to that – you’d have to have around 80-100 bulbs on the circuit.
But still, using older halogen or even incandescent bulbs that could consume up to 100 watts per single bulb?
Then putting a dimmer on a circuit with 6 lights or more might overload it.
If the breaker is tripping immediately, check that your bulbs aren’t overloading the dimmer.
If they are, you damage the dimmer switch every time you try to turn it on.
Even if you replace the bulbs with lower-wattage options, you might already need to replace the dimmer.
And if you can’t change the bulbs, or don’t want to, check your dimmer’s wattage rating and consider replacing it with a higher one.
Overloading not the problem?
Then an instantly-tripping breaker is a sign of a more severe fault and would need the entire circuit to be inspected – probably by a trained professional to identify the cause.
There aren’t too many situations where a bad dimmer will trip a circuit breaker, but it can happen.
Usually, it is a sign that your dimmer has either worn out, or it’s not capable of managing the demand of your bulbs.
Thankfully, replacing dimmer switches is a relatively easy task and not something you’d normally need to hire a pro to help you with – providing you remember to switch off the power before doing anything electrical!
Have you had any issues with dimmer switches failing or found other causes of your lighting circuit breaker tripping?