I want to specify encoding that is used by Lyx when it generates LaTeX source for preview or export. That is not a big problem Document->Settings->Language->Encoding->Other->Select encoding from combo box will do just that. But it will also add command \usepackage[selectedEncoding]{inputenc} to preamble of generated document.
How do I prevent that? I want all my LaTeX documents to be generated in UTF-8 but I do not want that inputenc declaration in preamble.

inputencdeclaration is it a problem? – Paul Gaborit Dec 26 '12 at 2:01inputenctherefore there is option clash possible. See tex.stackexchange.com/questions/88177/… – drasto Dec 26 '12 at 14:42