Why A Bad Light Bulb Trips A Breaker – In Simple Terms

When out with my partner, she often comments on my unusual fascination with staring up at the ceiling to look at the lighting and see how it has been installed. This can be anywhere from friends’ houses to coffee shops. I appreciate it sounds really sad but try it next time you are out in a store. Look up and take note of all the work that has gone into the lighting.

So much effort is put into the lighting design as the right lighting can make or break an environment. There are so many cool bespoke designer lights out there that instantly transform the feel of the room. However, no matter how great the light fitting is, it is only going to be as good as the light bulb that is installed in it.

In this brief post, we’ll talk about what to look for when choosing a light bulb and discuss if a bad light bulb can trip a breaker.

A new bathroom LED light fitting I installed negating the risk of a bad light bulb tripping a breaker
A new bathroom LED light fitting I installed negating the risk of a bad light bulb tripping a breaker

Can A Bad Light Bulb Trip A Breaker?

A bad light bulb can absolutely trip a breaker. When a bad light bulb blows, it causes a short circuit resulting in a rush of current through the circuit breaker. The circuit breaker sees this current rush (or overload as it is known) and jumps to the rescue by disconnecting and keeping everyone safe.

Circuit breakers are the safety devices in electrical systems. They are unsung heroes in that they sit in the fuse board (consumer unit as it is known) without any fuss constantly monitoring the current passing through them. As soon as the current gets to an unacceptable level, they will trip.

The reason for this monitoring and tripping is super important. If excessive current is allowed to run through a cable without interruption, that cable is not designed to handle such a high current and it would overheat causing a serious fire risk. A bad light bulb blowing causes too much current to flow as there is no resistance in the circuit anymore. Choosing more premium-named brand bulbs like these on amazon can help.

Why Did Bad Light Bulb Trip Entire Fuse Board?

When a bad light bulb trips the main circuit breaker it is usually because that main circuit breaker is an RCD. Without getting into the technical weeds, RCDs are more sensitive to electrical imbalances in the circuit and can operate quicker than the MCB in some cases.

When designing electrical systems we always try to ensure that a fault on one circuit won’t cause the entire consumer unit to trip out – as this is very disruptive. Instead, the wiring regs tell us that something called discrimination should be used (this is why the main fuse to the house doesn’t blow every time a light bulb blows)

In reality, we are talking about such small time frames, (0.4 seconds) that under fault conditions it is possible that the main RCD will trip disconnecting all the circuits in that consumer unit. Whilst breakers tripping can be frustrating, it’s worth remembering that they’re doing their job and protecting the electrical systems and occupiers, even if hunting for the fuse board in the dark is a little frustrating.

How to Choose Light Bulbs That Won’t Blow and Trip the Breaker

Even though the breaker tripping when the light bulb blows is all part of the circuit breaker protecting everyone, it is far from convenient. With that in mind perhaps the best thing homeowners can do to lessen the risk of this happening is to purchase good quality bulbs from reputable suppliers.

Just a quick check on Amazon shows me that there are so many light bulbs for sale at all different price points it can make choosing the right ones tricky. I wrote an article comparing how long different LED lightbulb brands last, linked here.

As an electrician, I always pay a little more (not a lot more, we’re talking about choosing ones in the middle of the range) and I always go for a well-known brand name. Brands like Philips or Osram are well established and we can be pretty confident they are going to be manufactured to a high, safe standard and reduce the risk of blowing.

Final Thoughts

It can be really annoying when a bad light bulb trips a breaker but it’s important that we don’t take our frustrations out on the circuit breaker. That circuit breaker is simply doing its job and jumping to the rescue of the cable and the occupants of the home.

If we want to angle frustration anywhere it should be turned towards the bad light bulb itself. If the bulb has lasted a long time and has come to the end of its lifespan we can symphysis that the filament has weakened and blown. If it is a relatively new bulb then it’s usually worth reaching a little deeper into our pockets and buying a better quality bulb from a recognised brand name for the next attempt.

As always, if you are in any doubt about the safety of the electrical systems in your home please contact a local electrician. Whilst having an electrical safety check carried out may seem daunting, electrical safety is serious business and the consequences for faulty systems can be lethal.

Dave Nicholas

I have worked as a professional electrician for many years and like to use my experience to help others in any little way I can.

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