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Most of the places I've lived in have had the following issue. My computer is running on the same physical breaker as a refrigerator and the overhead lights in a room. The refrigerator kicks on, causing at best the lights to flicker and at worst the breaker to trip.

Why does this happen?

Better, if I were designing a house from the ground up, how could I account for this potential problem in the electrical layout of the house and prevent it from happening altogether?

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When was the house built? Older homes simply didn't have good circuit design, since electricity was not as important as it is today. Most of these old systems get added on to, but never completely updated. So you end up with a Frankenstein circuit, with bits and bobs added on throughout the years. – Tester101 Jun 1 '13 at 1:02

The problem is that when the fridge turns on and draws a lot of power, causing the voltage on that circuit to dip. Anything else on the same circuit (lights, etc) may be affected by the voltage drop. In addition, as you say, the high initial electrical draw from the fridge combined with anything else that's running may cause your breaker to trip.

The solution is to put major appliances on dedicated circuits and then have separate circuits for outlets (making sure not to overload those either). The fridge should be on its own circuit for exactly this reason.

Any new building or old one that is up-to-code should not have this problem.

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Unfortunately, "up-to-code" is something that I've never experienced in a place of residence. 16-on-center? Try 12 then 16 then 18.5, then 5. I've seen some pretty strangely built places, I guess. – Naftuli Tzvi Kay May 31 '13 at 21:41
I guess I have another question then: is there any reason why not to make a separate breaker for every outlet/light fixture in the house? As a software developer, an idea of "separation of concerns" comes to mind immediately: separate things out so that if a fault is experienced, it doesn't affect everything else. – Naftuli Tzvi Kay May 31 '13 at 21:42
@TKKocheran In terms of every fixture, it's a matter of cost -- breakers, panel size, amount of wire, labour to install all that wire, and physical space for that many wires to run to the panel. However, there's a practical way to do it: it's not that costly or difficult to always have lighting and receptacles on separate circuits, and you can still have the lights for multiple rooms on a single breaker (to save cost). A nice upside is while you're working on receptacles or lights in a room, you can still have the lights on or plug in a portable light respectively. – gregmac May 31 '13 at 21:50
A nice compromise of cost vs. many circuits is to use subpanels. A subpanel is just a single big circuit (cheap to install, less voltage drop) which supplies many smaller separate circuits (less breaker tripping). And later, if you need another circuit, you don't have to run it very far. – Jay Bazuzi Jun 2 '13 at 20:00
From my fringe point of view, putting a subpanel in a kitchen is a great idea. Modern houses have at least 6 circuits there, so merging them all in to 1 subpanel makes a lot of sense. – Jay Bazuzi Jun 2 '13 at 20:01

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