My Lights Flicker When My Air Conditioner Comes On

Home and Office Electrical Systems

• Home and office electrical systems are wired to a main electrical service. This electrical service is made up of several parallel circuits that are wired to one main fuse or circuit-breaker box. Each circuit that the fuse or circuit-breaker box feeds is protected by its own fuse or circuit breaker. If multiple circuits are drawing power from the electrical service, the total amount of power running through the main electrical service will be equal to the sum of the amounts of power running through each circuit.

Inductive Electrical Loads

• Electric motors are considered inductive electrical loads. When voltage is applied to an electric motor, the motor generates something called a "back EMF" (EMF stands for electromotive force). A back EMF is a force that opposes change in electric current through the motor. To overcome the effects of back EMF, an electric motor requires more power at startup than it does while running. This temporary power requirement may cause a power sag at motor startup and a short power surge when the motor stops.

Power Surges

• A power surge is a short-term high-voltage condition in an electric circuit. A power surge occurs when excess electrical power is dumped into an electric power supply. Power surges occur when there is a sudden electric load reduction (such as turning off the air conditioner). Other things -- such as lightning strikes or utility switching -- can cause power surges.

Power Sags

• A power sag is a short-term low-voltage condition in an electric circuit. Power sags occur when high-power electric loads (such as air conditioners) are started up, or when multiple devices on the same circuit are turned on at once.