Opening the main circuit breaker question.?

Under most circumstances this would stop an electrical surge. If a lightening strike was close enough to arc across the open breaker contacts it could still cause damage. It takes a voltage potential of 5,000 volts to cross an air gap of 0.25 inches. (dry air, less with humidity) There are thousands of amps behind the thousands of volts in a lightening bolt. So if it crosses that breaker contact gap it WILL do damage. If you were to switch off each individual breaker as well as the main breaker it would be an added layer of protection. If you are leaving for a vacation and live in a lightening prone area such as I am in Southwest Florida (in the rainy season), I would also unplug all sensitive electronic equipment.

the perfect distinction between an Isolator and a CB is: An Isolator is usually a handbook gadget, which ought to be operated manually to shrink off a circuit. A circuit Breaker is a secure practices gadget which journeys right away in the progression of a fault in the circuit.

If you throw the main breakers, no power will enter you house. However, while protecting you home from power surges, you will also not have any electricity to run any thing electrical while the breakers are off. It is six of one, half dozen of the other.

depends on how big the surge is. A close lightning strike will come in on the ground if it is not secured well. I have seen bad grounds start fires when lightning hits close.If a direct hit from lightning strikes the feed to the box, it is coming in whether the mains are open or not.

You should probably unplug your grow lights during a storm . The bulbs are expensive !