You guys have covered the issue of a lightning strike affecting the power to the devices - but you must also consider a more vulnerable issue - the network connection. I have seen lightening strikes wipe out entire networks through the ethernet cables initiating through the internet connection. A voltage spike to the network connection to a miner will fry the controller. The best way to protect from this is to use a fiber link somewhere between the Internet connection and the miner farm. Electric surges cannot pass through fiber.