Is NEC 610.61 crane and hoist grounding to be applied to an installation from 1997 retro-actively?
I have never know the NEC to require "retro-active" changes to meet current code. But when you do more than simple maintenance to something it is generally a requirement by the AHJ the you bring whatever it is you're working on up to the current code.
I don't believe so. But check with your local AHJ as they may have an amendment or ordinance to such effect.
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