I am planning on installing a sub panel in an adjoining room for a wood shop. I am planning on feeding the sub panel with a 100A breaker from my main panel. A friend told me that because the sub panel is in another room "out of sight" of the main panel it is required that another 100A "main"breaker be installed in the sub panel. I realize that the panel must be fed with a 4 wire circuit but was unaware of the need for an "extra" main. Is this correct?