Lights Flickering & Dimming in the House

Power Sags

• The chief cause for flickering or dimming lights is sagging power. A power sag occurs when the voltage in an electric circuit drops below a pre-determined level. Most electrical devices that use household electrical power are designed to operate normally when the line voltage is between 110 and 125 volts AC. If there is a momentary voltage sag below 110 volts, the light may flicker; if the sag lasts for more than a second, the light may dim noticeably.

Momentary Power Outages

• Flickering may also be caused by a momentary power outage. Many utility companies utilize high-speed switching systems that interrupt power if there is a problem with a power line. If the power cycles on and off quickly, any light bulbs connected to the electrical service will appear to flicker.

What Causes Power Sags and Power Outages

• Momentary power outages may be caused by lightning strikes near a power line, fallen tree branches, small animals contacting the utility’s power equipment, or other such occurrences. Inductive loads, such as air conditioners or electric motors, may cause power sags that last a few seconds, while overloaded electrical circuits can cause power sags that will dim lights for a longer period of time.

How to Prevent Flickering or Dimming Lights

• Since overloaded circuits can cause dimming lights, make sure that the total load on the lighting circuit does not exceed the limits of that circuit. Each circuit is marked at the fuse box or circuit breaker box as to how much electric current that circuit can handle (normally between 15 and 20 amps). If you plan to use an inductive load, such as an air conditioner or an electric motor, wait until the device has been running for a few seconds before switching the light on. If this is not practical or safe to do, allow the air conditioner or motor to run for a few seconds before switching on any additional devices.