My heat pump has a drier installed from the factory do I need to add another drier to the liquid line

Has the system been opened up to the atmosphere?

No

THen you shouldn't have to replace it... or use a second one. THere are there to absorb any minute amount of moisture that remains after installation that is not removed in the system vacuuming process prior to charging the system. They are a one shot deal... and need replaced every time the system is opened ot the atmosphere.