WordPress: Redirect Main Site to Subsite in Multisite Where user is NOT logged in

Try this

function wpse66115_redirect_to_sub_site() { 
  if ( is_main_site() ) {
      if ( is_user_logged_in() ) {
      } else {
        exit( wp_redirect( 'http://old.heiledeg.no', 301 ) );
      }
  }
}
add_action( 'parse_request', 'wpse66115_redirect_to_sub_site' );