Conduit Wiring Systems and Electrical Installations in 1924

Originally Posted By: jtedesco
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I have a book written by McGraw Hill in 1924 called: “Conduit Wiring”


Some interesting images here:

http://www.joetedesco.com/gallery/Conduit-Installations-and-Inspections-in-1924


--
Joe Tedesco, NEC Consultant

www.nachi.org/tedescobook.htm

Originally Posted By: jmyers
This post was automatically imported from our archived forum.



Joe T.


Interesting indeed! I was pretty surprised with the picture that showed the bonding wire jumping over the water meter. I always thought of that as a newer concept, although I did not ever think to check when it originated. To tell the truth, I never really gave it much thought at all, just one of those assumed things that I had gotten used to seeing!

Joe Myers


Originally Posted By: jtedesco
This post was automatically imported from our archived forum.



Joe:


That's why is is important to identify the time when the wiring was first installed.

In the USA, for many years there were home grown codes (and some still are) and although they used the NEC as a basis for them, there were some inspectors who had different ideas about the way in which certain installations, and circuits (to include services and feeders) should be run.

Just the other day, I did a visual inspection of the basements and utility rooms (not to include the dwelling units) in 6 apartment buildings built around 60 years ago.

I was able to recognize some of the different methods, or so-called non conforming methods and I took many pictures.

When I was ready to prepare my suggestions I looked at each picture and decided that some were not to be called a hazard today because of the rule that is now in the Code.

For an example, the service conductors were the old rubber covered types (they were underground conduit laterals run to each service "end box") and the various nipples, and conduits entries were without the required insulation at the bushings for 4 AWG or larger.

![](upload://zWKySSDgO6QrfQEnVRXyhaTy4IA.jpeg)

We can't say that this is illegal, because the rule was not in the code when the wiring was installed.

Also, the NEC should not be considered as a retroactive document.

It is only during the last few code cycles that we have been required to install a GFCI when the "grounded" receptacle was replaced in areas that now call for one such as in 210.8.

I can tell you that the older installations were based on the codes written early on like in the 30', 40's or even 50's.

When I was first starting out, I was introduced to installations around the NYC 5 borough areas, and came across some systems that were very interesting, such as the old "A" base meters (many still in existence) and knob and tube still in use today, and sometimes still allowed according to the NEC.

The questions asked here on this board should be with some history on the date of the installation (can we still find the date in the toilet tank?) to avoid discussing the rules of today when the wiring in a 60 year old building is being discussed.

That's good for those who want to become Code Scholars, but the new kids 20 years from now, who will make the typical inspections that a Home Inspector makes, will look back into an older code.

I have a collection of codes from 1953 on, and some that go back to the beginning.

If I was to go out on an inspection, I could in my mind think about what I have mentioned here and perform the inspection.

Sure recommendations to Upgrade are good, but none of my business.

If the electrical installation is SAFE through a visual, and HI required inspection list, that will be adequate.

I like to talk about the old wiring systems, and have quite a few books on that subject.

I found a book with lesson plans and a list for wiring various rooms in K&T.


--
Joe Tedesco, NEC Consultant

www.nachi.org/tedescobook.htm

Originally Posted By: jmyers
This post was automatically imported from our archived forum.



Joe T.


That would be the very reason that I don't use code references, I am not a clock or a calendar. Like you stated, one could argue the installation was compliant when it was installed and therefore would be grandfathered.

When I do inspections, I am pretty hard on the electrical, mostly because it has the potential to do the most amount of damage to the house, or the occupants.

What I do is tell them it is a safety concern and I leave the interpretations up to the AHJ's. It is pretty hard to argue a safety concern versus a code violation. I like the simplicity of citing it as a safety concern, it saves me wasting a lot of my time and someone else's money paying me to look up code references. ![icon_biggrin.gif](upload://iKNGSw3qcRIEmXySa8gItY6Gczg.gif)

Joe Myers


Originally Posted By: jtedesco
This post was automatically imported from our archived forum.



Joe:


I agree, no numbers! The report will be the same indicating a hazard.

The use of plug fuses of the Edison base type is permitted for replacement when there is no evidence of overfusing, or tampering.

In the image below the two 30 amp fuses will be considered unsafe, and MUST be replaced with the Type S adapter, and Type S fuse of the proper size in accordance with the size of the branch circuit conductor.

One hint I like to share, and that is when the correction is made be sure that the Type S adapter was installed properly, I mean so that it cannot be removed unless use of the special "can opener" type of tool is used.

If the steel wire on the outer part of the adapter is cut off, the adapter can be removed, and the larger fuse can be put back. This was a problem for us in the field as inspectors in furniture stores where so many lamps were used creating overloads.

As an electrical inspector, I used a short piece of a broom stick that was tapered to fit into the open adapter that sometimes revealed that the adapter could be easily removed.

However, I guess that the HI cannot remove a fuse though?

PS: No. 14 AWG open knob and tube wiring was permitted to be protected with 20 amp fuses! There was a note in Article 310 that verified that before it was removed a few code cycles ago, maybe in the 1981 edition?

![](upload://vmo5Ns3XS6VtWqrhYk9zuyMsZqU.jpeg)


--
Joe Tedesco, NEC Consultant

www.nachi.org/tedescobook.htm