When was it first required that neutrals and grounds be separated (not bonded) on any panel past the main service panel?
Monday, June 18, 2018
“Is that some new code thing that wasn’t required when this old house was built?” Actually, the code standard for neutrals and grounds to be bonded only at the main service panel—and nowhere else—dates back to the 1923 edition of the National Electrical Code (NEC). So neutrals and grounds on the same bonded bus bar at a subpanel, or neutral and ground bus bars with a bonding connection between them at a subpanel, is definitely not “grandfathered in” as alright.
For the electrical safety reason behind the code requirement, see our blog post Why is it unsafe to bond neutral and ground wiring at subpanels?
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