You need to make the following changes in your settings/settings.ini.php file.

Find in settings "cacheEngine" section and set it's content to for memcached

'cacheEngine' => 
    array (
      'cache_global_key' => 'dev_livehelperchat',
      'className' => 'erLhcoreClassLhMemcache'
),

"cache_global_key" should be different across different installs of Live Helper Chat on the same server. For redis set className to 'erLhcoreClassLhRedis'