Fluctuating voltages and an offline electrical feed are two reasons why a dimmer isn’t working after a power outage.
Fluctuating voltages often precede unplanned power outages. These unusual voltages cause damage to electronic components inside the dimmer. Contacting the company that manages the local power lines should give more information about the power outage.
A damaged light (LED) is another reason why the dimmer won’t work. This post will explain these two reasons in more detail from the perspective of an electrician.
Dimmer Wiring & Fault Finding
A dimmer is typically wired in series with the light and light switch.
The type of dimmer mechanism used depends on the type of lighting installed.
For example, LED lights use a different type of dimmer to halogen lights. Knowing what type of lights are being dimmed will help establish what type of dimmer you have.
Some dimmers contain variable resistors which affect the brightness of the light (generating heat in the process). Other dimmers affect the AC sine wave producing the same effect.
With this being said, both dimmers will fail when exposed to unusual voltages because the electronics inside dimmers are designed to operate at a constant, steady incoming voltage supply. When this changes problems start to occur.
In the switchboard, the lighting circuit should be protected by circuit breakers (or fuses) designed to prevent a fire in the event of a short circuit or overload. These circuit breakers are typically rated at 10 amps but could be more or less depending on the electrical load used by the lights.
The lighting circuit should also be protected with an RCD. The RCD will protect people from getting a potentially fatal shock from the lighting circuit. It does this by shutting off power to the lighting circuit within a set time and electrical threshold. As RCD’s are a relatively new invention, they may not be present in older switchboards.
With this being said, an RCD or MCB breaker won’t protect appliances or fittings such as dimmer switches from a power surge.
For this surge protectors are required which I will discuss below. Let’s first look at what can go wrong causing the dimmer to not work.
Dimmer Switch Not Working After Power Outage? – Reason #1
Temporary High Voltage Damaging Dimmer
Likelihood: This can be common with unplanned power outages in our experience. Get in contact with the company that manages the local power lines for more information.
Fixable? No, the dimmer will need to be replaced. The condition of the lighting should also be checked. Install a surge protector to protect appliances in the future.
Abrupt voltage changes preceding a power outage are a common reason for appliances not working. This is mainly due to the presence of electronics in most appliances including dimmer switches.
Dimmer switches contain electronic components such as resistors and semiconductors. Both of which are designed to operate at a steady voltage. If the voltage gets too high these electronic parts will go bang. Leaving burnt or melted areas around the dimmer switch.
If the dimmer switch has been damaged due to a voltage surge it is unlikely to be repaired. Instead the dimmer should be replaced and a surge protector installed to protect the dimmer and all other appliances in the home.
Dimmer Switch Not Working After Power Outage? – Reason #2
Damaged LED Light Or LED Driver
Likelihood: High for LED lights. A component inside the LED light or driver is damaged making the light non-dimmable.
Fixable? Checking and replacing the LED light and or driver can resolve the problem.
As mentioned earlier, voltage surges cause damage to electronic components. Both the LED light and LED driver contain electronics.
When the voltage surges, damage can be sustained to those parts resulting in it either not dimming or not working altogether. In this case, checking and replacing these lights and drivers could resolve the problem.
Install Surge Protection
A surge protector is a device designed to redirect high voltages away from appliances and discharge it safely to earth.
This protects appliances such as dimmers from needing to be replaced. Normally, surge protectors are small ‘breaker’ sized devices found in the switchboard.
These surge protectors will protect the entire home from surges. Surge protectors can also be found on devices like multi boards. These multi boards will only protect whatever appliances are plugged into it.
Electricians Perspective
Fluctuating high voltage surges preceding the outage is the most likely reason why the dimmer switch isn’t working in my opinion.
The dimmer, LED light and LED driver may be damaged. Checking and replacing these is the most economical way to resolve the issue. Installing a surge protector will help ensure it doesn’t happen again in the future.
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