The sub panel in my shed(about 75ft run from main panel)is very outdated and gfci breakers aren't available for it so I want to update the panel as gfci are required for pool equipment. The panel has 220v and currently has 2 tandem 15amp breakers powering 4 outlets and 3 lights and one double pole 20amp breaker powering the pool pump. Their used to be a pool heater but since has been removed. The supply from the main panel for this sub panel is on a 50 amp double pole breaker. Their is not a bare copper grounding wire ran to the sub panel either and I would like to add one
My questions: Will a 60 amp subpanel be sufficient? If so will the 50 amp double pole breaker in the main panel need to be changed? Would it be nearly impossible to run a bare 10ga ground wire through the existing pvc conduit that is run underground?