J box history

Any idea of how far back the requirement to keep splices and j boxes accessible?

Is there a way to trace a conductor from a panel to its termination when its behind a wall?


Knob and Tube splices didn’t need junction boxes, so those splices were just taped and tucked away, AFAIK.
Junction boxes must never be covered or made inaccesible, especially important as the splices age, roofs get leaky, corrosion etc., so …
the Code requirement at the time of wiring is i think irrelavent in this case, I would write up any junction box which was inaccesible. :mrgreen:

I’ve got a copy of the 1896 NEC, and the requrement that junction boxes be accessible is in that edition.


The 1896 NEC??? Wow! Do you have that in soft copy?? That would be real interesting reading!!!


To positively trace and locate a cable within any building is very possible. The proper equipment for this can be expensive. Locating the AC cabling while live requires equipment capable of not only inducing a signal on the cable but also being able to trace harmonics of that signal. Higher order harmonics of the signal frequency induced on the cable are less likely to bleedover onto surrounding cables.

Here is a discussion from 3M regarding cable locating techniques. Although the majority of this document is geared toward utility locating the basic concepts apply to almost all cable locating activities. This same equipment can be used inside any structure as well. There are low end cable locator’s on the market that will function well if the cables are not live and a signal can be directly applied instead of using induction methods.



A true electrician geek, Marc. :smiley:

I ran into another electrician who was so happy so show me 40-50 year old NEC books(the size of a reader’s digest). Figured 1800’s one’s were a single page with three rules: 1. Don’t kill anybody. 2. Don’t start fires 3. Don’t start fires on anyone you killed.


WOW! that goes back further then me or my Brothers Great find .
Thanks MARC.
You continually surprise me and I sure do appreciate your info.

Same here. And I enjoy your humor. :smiley:

Thanks all; problems solved. J