A dirty electrical outlet is one that connects to a noisy electrical supply. When other frequencies are added -- noise -- the supply is said to be dirty. Electromagnetic noise can originate from external sources such as power lines or from sources inside the home. A clean power outlet is one with little to no noise.
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The Domestic Electricity Supply
In the United States, the standard domestic mains electricity supply is 120 V; for some outlets, such as those used by dryers, the electricity supply can be increased to 240 V. The alternating current has a waveform with a particular frequency -- typically 60 hertz. Theoretically, the supply is a pure sine wave; in practice, there is almost always at least some noise.
Sources of Noise
External sources of noise include power lines and electrical substations, which have strong electromagnetic fields around them. This can interfere with your power supply, causing noise. Motors starting and stopping can create noise in the form of voltage spikes. Inside the home, sources of noise include dimmer circuits for lights, fluorescent lighting including low-energy bulbs that consist of coiled fluorescent tubes, computer power supplies and televisions.
Consequences of Dirty Electricity
Dirty electricity, or DE, can have a negative effect on the life and performance of components and appliances. It can cause equipment to function poorly -- for example, a sound system connected to a dirty electrical outlet may pick up the noise in the electricity, and this can affect sound reproduction. Television picture quality also can be affected by noise on the electrical supply. Certain electrical components can be damaged if they have to handle DE instead of a clean supply.
Dealing with Dirty Electrical Outlets
You can address DE by removing as many noise sources as possible from an electrical circuit. Electrically noisy appliances can be connected to one circuit, while noise-sensitive equipment is connected to clean outlets on a separate circuit. Another solution is to use a power conditioner, also known as a mains filter. This device connects to a dirty outlet and electrically cleans the power it receives, outputting it as clean electricity. Power conditioners are often built into socket strips, giving you several clean outlets. A power conditioner protects your equipment from the effects of DE and prevents damage from sudden spikes in the power supply.