Theoretically, room lights should never be on the same circuits as any large appliances.
Why? Because if the appliance, be it a refrigerator, a large TV or a hot electric fry pan, blows a fuse, you don't want to be thrown in the dark.
When these are on the same circuits, on the same fuse or circuit breaker, turning on a large appliance will easily cause a little temporary drop in the voltage, hence a flicker of the lights. If the light dims and stays dimmer, then you definitely have a problem of being on the limit of how much electricity the circuit can take. If the lights dim when they are not even on the same circuit, that is a sign that you are close to your maximum use of the electricity available from your entire distribution panel. This can happen when 60 amp or 100 amp services are now supplying power to computers, TVs, Sound Systems, Microwaves and other things all at the same time.
Our electrical lifestyles have grown and often our house electrical systems have not grown with them. In some regions of Canada, especially where electrical heating is common, 200 even 400 amp service is now common.
One other thing can cause the problem of flickering. When a motor, any motor, starts up it requires about twice as much electricity to get started than it does to keep turning. So when the refrigerator, freezer, washing machine or furnace fan kicks in, there is a large electrical surge. If they are on the same line as the lights, that will easily make them flicker once. If the house power is low, they will dim a lot and then come back to a little less than when the motor is off.
Bottom line? Too much flickering and you should have an electrician check the balance of your circuits, or the overall power of your distribution panel.
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