Electrical Grounding for Metal Buildings

      Good grounding (and fire insurance) are prudent measures for a metal sawmill building. March 31, 2008

From Professor Gene Wengert, Sawing and Drying Forum technical advisor:
There is a sad story posted on another forum about lightning destroying a wood business in a metal building. The business did not have fire insurance. We do not know details about the particular building that burned. But here are some general questions and comments about metal buildings and insurance.

It is important to have every vertical metal support beam grounded (required in the building code) with a metal building. Further, in a dry environment, it might be necessary to water the grounding stakes to assure good contact with the surrounding soil; dry soil is an insulator. Likewise, the electrical system needs to have a good, active ground.

Regarding insurance, I am curious how many sawmill and drying operations have some sort of fire insurance. I know in one business that I worked for, the insurance company checked the grounding (and other items) as part of their insurance package (to protect their investment by reducing the risk).

The company that had this $500,000 fire did not have fire insurance because it was too expensive. I wonder if fire insurance on an investment is part of the cost of doing business. The cost of insurance would increase the cost of the lumber slightly and/or reduce profits. Using a high deductible will lower the cost somewhat.

I know some stationary lumber mills also carry flood insurance. I suspect almost everyone has liability insurance; even my small consulting company has $1 million liability. I suspect that rolling stock also is insured in most cases.

So, what type of insurance do you have? Fire, flood, liability, theft, bonding of employees that handle money, injury, life? Deductibles? I recently worked with a mill that had a 30% loss. They had fire insurance that was equal to 80% of the value of the mill. They found out that only 80% of the 30% loss was covered (after the deductible).

From contributor C:
I am a small operation with no more than 20 to 30 thousand bdft on hand and run my operation in the backyard. My homeowner's policy covers my sawmill and equipment but I'm not sure about the lumber. I will be calling today to find out if I need to add/change policies.

From contributor A:
What does grounding the building have to do with lightning? If your building is not grounded, it is more insulated than if it were grounded and would offer a better path for the lighting. The grounding of a metal building is for keeping it at the same potential as ground in case of electrical problems or failures.

From Professor Gene Wengert, forum technical advisor::
A grounded building will apparently form a Faraday shield and that will keep the lightning on the outside, rather than letting it go on the inside. Perhaps lightning rods would also be a good idea? Rods actually attract lightning and then the cables deliver it to the ground.

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