Reading an old code book from the 80s and the voltage drop rules were way different

I was cleaning out my dad's garage and found his old NEC code book from 1984. Flipping through it, I saw the voltage drop section and it was just a suggestion, not a rule. It said something like 'for good practice, keep it under 3% for branch circuits.' I checked my 2023 book and now it's a real rule in some places, like for feeders in certain spots. The old book had a whole chart for copper wire that assumed way higher resistance than we use now. It made me think about all those old houses we work on where the lights dim when the fridge kicks on. My dad said back then they just ran 14-gauge for everything and called it a day. Has anyone else run into problems because of this old way of thinking on a rewire job?

2 comments

2 Comments

riverg7516d ago

My uncle's 1979 split-level had a 100 foot run to the garage with 14-gauge. The garage door opener would barely work in winter. I used to just blame old motors, but after seeing a post like this and reading what blakeharris said about checking long runs, I finally measured it. There was a 7 volt drop at the opener terminal. Upgrading that circuit to 12-gauge on the rewire fixed it completely. It really shows how those old suggestions became real problems over time.

blakeharris16d ago

Yeah, those old "good practice" notes are why we find so many borderline circuits now. I always check voltage drop on long runs during a rewire, especially for fridges or AC units.