Why Do Lights Dim When a Motorized Appliance Is Turned On?

Have you ever noticed that the lights in your home dim slightly when you start a motorized appliance, such as a washing machine? This phenomenon, often attributed to a sudden increase in electrical demand, is a common occurrence in homes with older or less optimized electrical systems. In this article, we will explore the reasons behind this issue and provide practical solutions to address it.

The Science Behind Dimming Lights

When a motor starts, it draws a significantly higher current than it does while running normally. This burst of current is known as inrush current. This high demand can cause a temporary reduction in the voltage available in the electrical circuit, leading to dimming of lights.

A Closer Look at the Electrical System

1. Inrush Current

When a motor starts, it draws a substantial amount of current immediately, which is much higher than the steady-state current required for normal operation. This surge can cause a dip in the available voltage in the circuit, especially if the system is not designed to handle such peaks.

2. Shared Circuits

Many household appliances, including washing machines, are connected to shared electrical circuits. When the washing machine's motor starts, it draws more current from the circuit, which can reduce the voltage available for other devices, such as light bulbs. This leads to a noticeable dimming of the lights.

3. Voltage Drop

The wiring in a home has inherent resistance. When a motor starts, the increased load causes a voltage drop along the wiring. This drop in voltage can affect any devices sharing the same circuit, including lights. This is particularly noticeable in older homes with outdated electrical systems.

4. Circuit Breaker Rating

The circuit breaker is responsible for limiting the amount of current that flows through the circuit. If the circuit breaker is rated too low for the combined load of the washing machine and other devices, it may not handle the sudden surge well, leading to dimming lights.

5. Older Electrical Systems

Older homes often have outdated electrical systems, which may not be capable of handling the modern demands of household appliances. This can result in more noticeable dimming when high-demand appliances are used.

Addressing the Issue

Fortunately, there are several solutions to prevent or mitigate the issue of lights dimming when a motorized appliance is turned on:

Dedicated Circuits: Running high-demand appliances, such as washing machines, on dedicated circuits can help prevent lights from dimming. This ensures that the motor has its own dedicated power supply, reducing the impact on other devices.

Upgrading Wiring: Ensuring that the wiring in your home is adequate for the load can significantly reduce dimming. Upgrading to thicker or more efficient wiring can help manage the flow of electrical current more effectively.

Using LED Lights: Switching to LED bulbs can also help reduce the visibility of dimming. LED lights generally have less noticeable fluctuations in brightness compared to traditional incandescent bulbs.

Addressing Additional Electrical Concerns

For those dealing with older electrical systems, it is important to be aware of potential risks and the need for upgrades. Here are some additional considerations:

1. Breaker Efficiency

Many homes are wired with 100-120amp breakers, which were more common before the widespread adoption of 240amp breakers. If your home still uses a 100-120amp breaker, consider upgrading to a 240amp breaker to handle the increased load.

2. Wiring Safety

Old copper wiring is prone to fire risks. If you suspect that your home has old copper wiring, it is crucial to have it professionally inspected and replaced to ensure safety.

3. Proper Wiring Practices

Professional electricians recommend pig tailing the wires when making electrical connections. Check with local regulations to ensure that this practice is still allowed in your area, as some regions may have updated codes.

Conclusion

In conclusion, the dimming of lights when a motorized appliance is turned on is a common issue related to inrush current, shared circuits, voltage drops, and circuit breaker ratings. By implementing solutions such as using dedicated circuits, upgrading wiring, and switching to LED bulbs, you can significantly reduce or eliminate this problem. If the issue is severe or frequent, consider consulting a professional electrician to assess and upgrade your home's electrical system.