Modern Living: Part Fifteen

[Chetlaham]

I am just like you, I am beyond words fascinated by vintage electrical. Everywhere from residential to EHV. Especially 5kv class, which I have I have a soft spot for.

I secretly fantasize about wiring a house with vintage type equipment but with a modern twist to the equipment. Two wire service, double fused main and branch circuits, black and red BVVB (see last pic), two slot receptacles, ect.

Kind of like this:

(note, none of the pics are mine, they are from Google)

 

[circlew]

Double fusing (fused neutral)

That has been a violation of the NEC since at least the 1928 edition, due to it being a dangerous system. If the fuse on the grounded neutral side blows, is removed, becomes loose, or fails for any reason, the circuit is still live. Many people were shocked or worse because they thought the circuit's power was shut off, and it wasn't. If they touched anything grounded while touching the still live wire, they received a shock. This is the same reason a switch is not permitted to be installed on the neutral side of a circuit, as was also common a very long time ago, especially in knob & tube wiring. There are very rare exceptions to that rule, but it doesn't involve residential or most commercial wiring.

 

[combo52]

Wow, no wonder so many houses used to burn down

Post number 20, all that dry wood near electrical wiring and wiring devices inside wooden boxes.

All the wiring I do in my own home I do the commercial standards. Everything is in metal I even use metal outlet switch plates no Romax wire.

I’m used to doing it this way from the commercial building spaces and my house was built this way originally so I’ve continued it with all the additions and upgrades we’ve done.

Knob and tube wiring burned down many homes.

John

 

[Chetlaham]

Correct

Fused neutrals mixed with things like Edison screw base sockets become rather dangerous. And indeed, a fused neutral is a code violation.

Though that all becomes a rather moot point when there is no neutral to speak of

With modern design techniques proper isolation, guarding and shielding prevent reverse polarity or having both conductors energized above from becoming a danger. Think type C or type F schuko plugs as an example.

I'm imagining a single phase 2 wire ungrounded system. Two service wires with 230-250 potential between them, double pole breakers or fuses, non conductive wiring devices and double insulated appliances.

Simple system that would make wiring a home rather fun for me.

 

[Chetlaham]

None Conductive Wiring Devices

I'm imagining these outlets in a modern living home. All plastic yoke, plastic box with plastic conduit or BVVB wire. Double insulated appliances of course. There would be no way for anything external to become energized as there would be no exposed metal for the user to contact.

Which takes me to reply #22- wood, plastic or bakelite around electrical equipment does not present a fire hazard. Correctly installed conductors (including knob and tube) and wiring devices will never reach flammable temperatures let alone those which may dry out wood to the point of pyrophoric carbonization. What can happen is a high resistance connection from a bad splice or loose terminal. In that case the heat generated is of such degree the material can not contain it or stop it. A metal box will become hot enough to ignite a stud assuming the plastic wire nut or wiring device does not catch fire first. Metal plates, rigid conduit or a RACO box make no difference.

Lastly I would trust the porcelain insulators around knob and tube any day over the cracking, drying rubber cloth covered cables which followed it or that old BX cable without the bonding strip.

If I had to choose between knob and tube or NM cable installed before the mid 70s I would hands down choose knob and tube. Knob and tube is among the safest wiring method ever installed in residential, the only hazard (and bad rep) comes from knob and tub being disturbed by DIY hack jobs latter on in a home's existence. Same goes for fuse boxes, the only real danger was people screwing larger fuses or placing pennies behind them.

There is nothing wrong with old technology.

 

[combo52]

Chet it’s a good thing you’re not writing standards

You’re basically saying that every commercial building in the United States is dangerous because they use metal around the wiring, you know so little about this even BX cable with the metal sheath around it you can have a lightning strike and the conductors inside can turn red hot and it will not set The wood that it is pulled through on fire.

The other big danger with using plastic sheathing is if there is a fire in the building, even unrelated to the electrical installations, all that plastic insulation burning will end up, killing people in the building that are trying to escape or are trapped inside waiting for rescue.

John

 

[Chetlaham]

Re-read what I wrote- I said "make no difference" In other words if the box/conduit/gutter ect is steel, aluminum, PVC, fiberglass, ect it makes no difference, a high resistance splice is trouble (fire) either way (equally).

BX cable doesn't glow red hot because of lightning strikes. It glows red hot due to not having an aluminum armor bonding strip like modern AC cable and not having an equipment like modern MC cable. The interlocking metal spirals oxidize resulting in turn to turn contact becoming electrically restive greatly increasing the impedance of the armor. As such when a ground fault occurs inside a metal box or a fault in occurs an appliance the increased I2R resistance of the metal armor causes it to heat up while carrying ground fault current. Because this resistance also impedes the flow of electrons, the amount of amps seen by the breaker or fuse may be to low to trip the device quickly, or even trip it at all- the armor will glow red hot indefinitely until it ignites a fire.

It is for this reason that NEC 250.118 (10) essentially forbids the armour by itself (alone) of type MC cable being the sole effective ground fault current path unless listed as such.

https://www.snellheatingandair.com/blog/bx-wiring-life-cycle-and-ways-to-replace/


Even THHN, TW, XLPE, ect wire in metal conduit has PVC/Vinyl/Rubber which can become toxic when burned. Metal vs plastic conduit or jakceting makes little difference. Other means like fire sprinklers, fire stops, dampers, exit signs, horizontal and vertical containment, stairs wells, ect, ect are what save people during a fire.

 

[Chetlaham]

*aluminum armor bonding strip

To clarify I don't mean that old BX cable armour was made out of aluminum- since I know that is what you will say I intended to say. Rather the steel armor of BX cable lacks an aluminum bond wire as found in modern AC cable.

 

[whitewhiskers]

Mister Magoo for GE Light Bulbs

 

[Ultramatic]

Alexander Smith 1941

 

 

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Chemstrand 1957

 

 

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Corningware 1988

 

 

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Crane 1929

 

 

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Duplexalite 1919

 

 

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Gilbert 1922

 

 

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Heywood-Wakefield 1958

 

 

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Inco Nickel 1961

 

 

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International 1958

 

 

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Mitchell 1949

 

 

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Alliance 1950

 

 

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