You can use this module: [menu_block][1].

Print sub-menus or any level menus.

    echo theme('links__system_main_menu', array(
     'links' => menu_navigation_links('main-menu', '1'),
     'attributes' => array(
     'id' => 'main-menu-level-2-id',
     'class' => array('links')
     ),
    ));


  [1]: https://drupal.org/project/menu_block