Question about lightning and circuit breakers


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Old 05-29-15, 06:44 PM
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Question about lightning and circuit breakers

This falls under the category of "something I've always wanted to ask but thought it might be a stupid question.."

I, like many people, try to be vigilant about unplugging major appliances if a thunderstorm is coming in order to protect them from lightning strikes, surges, etc. However, would I get the same effect by simply shutting off the main breaker, thereby killing all power to the house until after the storm passes? In other words, does shutting off a breaker have enough of a disconnect to safeguard any power from a lightning strike from getting through?
 
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Old 05-29-15, 07:15 PM
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I'm not an electrician. But if a direct hit takes place the chances are good the strike will jump the main switch disconnect. But it needs to be a direct hit. Normally no harm will be done to the wiring from an indirect strike if the breakers are closed. But appliance and electronic damage will most likely occur. Precautions can be taken to help minimize damage but the experts here can give a better idea.
 
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Old 05-29-15, 07:32 PM
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It's better than doing nothing but not as effective as completely disconnecting the appliance. Opening the main breaker will provide some isolation against smaller surges and transients, but a large surge will just arc across the open contacts in the breaker. Also, the breaker only disconnects the hot legs of the circuit, not the neutral, and a surge on the neutral can cause damage as well. The neutral is tied to ground in your breaker box, but a close lighting strike (or a direct strike) can still cause high voltage transients on the neutral.

A decent option is to add a whole house transient protector to your main panel. This provides decent protection that works whether you are home to unplug stuff or not. It won't save you if you get a direct strike to your power line, but fortunately that is rare compared to nearby but not direct strikes.
 
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Old 05-30-15, 12:16 AM
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Excellent points- thank you for the responses!
 
 

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