I've encountered many strange and puzzling wiring and installation methods over the many years I've been inspecting homes. This is a partial list of some of these. While some of these may never be seen by the average person, I feel this series of articles on electrical history in homes would not be complete without including these here. These are not arranged by date or level of danger, they are just presented for home buyers and inspectors to "Be on the Lookout" for. I will be adding to this post every now and then - so check back!
Single conductor metal armored wire:
I have been researching this for a while, and have found out little. A home in West Roxbury, Massachusetts had alot of this wiring - installed throughout the home and possibly original. The wire is a HOT internal wire with no ground or neutral wire present. The wire had the external metal covering connected to the neutral bus and the internal Hot wire was connected to the circuit breakers. THE DANGER in this wire type - is that the external case CARRIES CURRENT and is exposed! Touching this wire (or pipes/metal objects etc. coming in contact with it) poses a serious risk of shock. As far as I can tell this was never an approved type of home wiring - please email me spreiinc@gmail.com if you know anything about it or have seen it before.
The picture below shows 3 of these wires in a single wire connector - removed from the electrical panel. (Excuse the ant frass on the wires)
Below 2 of these wires have their Hot wires spliced in a ceiling box (The box appears to be 1940s or earlier - as does the wire) Note the back of the box - see the clamped single conductor wire (The light/outlet installed in these boxes had their neutrals tied to the metal box casings. I received several shocks while inspecting the wire by simply touching the casing and boxes.) I would note that these old boxes appeared to be made SPECIFICALLY for this wire type - You can see that the wire holes in the box (above the clamp) are sized so that only this wire could be used in it.
Undersized Ground Wires
From the wiring I've seen over the years, there have been a few types of Romex wire with Undersized Ground Wires installed in them. Ground wires in modern romex are typically the same size as the conductors in the wire (so that in case of a short circuit - the ground can handle the full current of the wire). Wires with undersized ground wires in them cannot withstand a full current short circuit - and pose a potential fire risk in worst case situations.
The picture below shows an Undersized Ground wire The 14 Awg (15 amp) wire has what appeared to be 18 Awg (10 Amp) Ground wire.
Aluminum Grounded Copper Wire ("Rag")
The first generation of WWI "Rag" wire had an unusual variant - a version of it with Aluminum Grounding wires. I have encountered this wire only 7 times over all the years I've been inspecting - it is quite hard to find. The aluminum was rarely properly terminated and it would be another 40 years after this wire's time before we discovered the unique connection requirements for safe installation of solid conductor aluminum wires. This wire is not inherently "dangerous" but the potential for poor or corroded ground connections gets it on this list.
I am currently trying to find my samples of this wire - I have them stored with all my antique wire, fuse and panel collection - it may take some time before a picture appears here
BX Style Cable with Paraffin Soaked Paper Sealed Coils:
Another rare variant on the BX style wire. This wire was created to be more water resistant. Paraffin soaked paper was rolled into the metal coil outer wire covering and helped "seal" the coil winding seam. This wire is identified easily under close observation - it has a visible brownish Paper exposed at the entire edge of a coil. Instead of an all metal look of BX, this wire looks like it has a narrow spiral of paper built into the metal covering.
Again, I am searching for my one picture I have of this wire... With 87 Picture Backup CDs and DVDs and numerous old Hard Drives and countless slides... I will find these pictures someday... I hope!
PLEASE NOTE - IMAGES ARE BOTH SENT TO US IN EMAIL AND GATHERED FROM THE WEB FOR EDUCATIONAL PURPOSES - IF YOUR IMAGE APPEARS HERE AND YOU WANT IT REMOVED - EMAIL US AT spreiinc@gmail.com AND LET US KNOW.