add_filter( 'pre_get_posts' , 'custom_search' );
function custom_search( $query ) {

    if ( $query->is_admin )
        return $query;

    if ( $query->is_search ) {
        $category_id = get_cat_ID('type_category_id');
        $query -> set( 'category__not_in' , array( $category_id ) ); // Cat ID
    }
return $query;
}