What's backfeed?


Old 01-05-07, 08:27 AM
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Smile What's backfeed?

What exactly does back feed, or back fed means? Thanx in advance. You all are the greatest
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Old 01-05-07, 08:46 AM
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When talking about a breaker or breaker panel, it means that the power source feeding the panel connects to one of the "regular" breakers instead of through the main breaker or main lugs. Thus, the power is being fed "backwards" into the panel; there are correct ways to backfeed panels in certain circumstances, however it is very dangerous if done incorrectly. For example, backfeeding power into a main panel from a generator without a proper interlock switch can kill linesmen working outside on power lines.

When talking about a circuit, it means that somewhere in the house two circuits have been accidentally interconnected so that one circuit supplies power backwards into the other. In this case neither circuit can be safely de-energized without flipping two breakers. Backfed circuits are never legal because they are dangerous; you may flip one breaker, assume the circuit is dead, and be shocked by the backfeed. Backfed circuits are usually created by ignorant homeowners or handymen who make big electrical mistakes.
Old 01-06-07, 12:08 AM
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Thank you Ben for your quick response. I understood part one concerning backfeed when talking about the main panel, but don't quite understand how one branch curcuit will feed into another? I'll have to sit down with pencil and paper, and try to draw out a situation like this. Would a branch circuit (120 volts) be somehow , alternately fed from L-1 and L-2? Something like that maybe? Am I on the right track? Thanx for your time?
Old 01-06-07, 05:09 AM
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An example of a back fed circuit could be when one phase is lost to a 240V electrical load, and the energized phase will back feed the dead phase when the load is turned on.
Old 01-06-07, 05:10 AM
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If a branch circuit is back feed from L1 and comes back on L2 one of the breakers will trip right away.

What is more dangerous is if the first breaker is backfeed to the same phase. The breakers will not trip right away. Someone could turn off a breaker and think that the circuit is off, when in fact the other breaker is still on.
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