Fused neutrals

[mopowr steve]

Is it possible the fused neutral was from an ungrounded DC service they may have had originally?

I guess not with 3 blades

Seems plausible, since Edison’s original electric distribution started out as DC until NikolaTesla’s system of AC was better suited for long distribution

 

[mbrooke]

Seems plausible, since Edison’s original electric distribution started out as DC until NikolaTesla’s system of AC was better suited for long distribution

But still, you see it in systems that were AC when brand new at the time.

Did my pics come through btw?

 

[al hildenbrand]

But still, you see it in systems that were AC when brand new at the time.

Did my pics come through btw?

I've got a series of your posts that I have only glanced at that have images.

I wanted to say, in my reading of the early Code (1890s thru about 1913), I was struck by the language describing generators, and whether, and how, to connect them to Earth. Attention was given to floating generator and motor frames. I believe this was a first attempt at an economic use of materials to deliver power while not exposing people to the electricity. As a concept, one might be beguiled by it, without a working knowledge of the interconnected-ness of the bulk of normally-non-energized-conductive-surfaces, especially through Earth, and how little current it takes to stop a heartbeat.

There is, in fact, a good argument that introducing the EGC into a wood, plaster-and-lathe dwelling, built of almost entirely un-conductive materials that are normally kept dry, introduces an increase in electrical hazard. But that is not directly answering your query.

I believe that in those early days of the build out of the Tesla / Westinghouse AC distribution systems, the perceived safety benefit of protecting the neutral from overheating by limiting the current with an overcurrent protective device, was the goal. Insulation, itself, was still in the midst of development, and many were not reliable in tolerating much warmth.

In my work area, with housing stock predating electricity, I have found all manner of K&T service centers that have a history of fused neutrals. Some, a small number, have even survived to the present with the neutrals still fused.

 

[mbrooke]

I've got a series of your posts that I have only glanced at that have images.

I wanted to say, in my reading if the early Code (1890s thru about 1913), I was struck by the language describing generators, and whether, and how, to connect them to Earth. Attention was given to floating generator and motor frames. I believe this was a first attempt at an economic use of materials to deliver power while not exposing people to the electricity. As a concept, one might be beguiled by it, without a working knowledge of the interconnected-ness of the bulk of normally-non-energized-conductive-surfaces, especially through Earth, and how little current it takes to stop a heartbeat.

True- but at that time I think people truly believed that at voltages below 150 volts to earth the common man safe.

There is, in fact, a good argument that introducing the EGC into a wood, plaster-and-lathe dwelling, built of almost entirely un-conductive materials that are normally kept dry, introduces an increase in electrical hazard. But that is not directly answering your query.

But it hints at the thinking that may have influenced it.

I believe that in those early days of the build out of the Tesla / Westinghouse AC distribution systems, the perceived safety benefit of protecting the neutral from overheating by limiting the current with an overcurrent protective device, was the goal. Insulation, itself, was still in the midst of development, and many were not reliable in tolerating much warmth.

In my work area, with housing stock predating electricity, I have found all manner of K&T service centers that have a history of fused neutrals. Some, a small number, have even survived to the present with the neutrals still fused.

It is these relics which are the most fascinating and I believe hold the secrets to the evolution of grounding, bonding and the modern NEC.

 

[drcampbell]

GU24 is your friend

Did those exist at the same time hot-at-some-times 3-way circuits were being installed?

 

[synchro]

A short discussion about fused neutrals from 1922, under heading "The Solid Neutral":

View attachment Electrical_Record_1922_neutral_fusing_1.pdf

 

[mbrooke]

Did those exist at the same time hot-at-some-times 3-way circuits were being installed?

Nope, but they do now

 

[mbrooke]

A short discussion about fused neutrals from 1922, under heading "The Solid Neutral":

Your PDF is of huge help, I will read it now.

 

[mbrooke]

A short discussion about fused neutrals from 1922, under heading "The Solid Neutral":

Now I'm curious. What "balances of advantage" showed favor for a grounded system?

 

[mbrooke]

This I don't entirely understand. IF 2,300 volts go into the service, I'd think whether or not the incoming service neutral was missing or intact would be the least of concerns making little difference.

 

[al hildenbrand]

1

 

[mbrooke]

Well, I think what you're reading is the results of statistics being used to argue for changing behavior. The underlying science contributes less to any "logic".

I was more impressed with the summary of were the wiring system started:

"After a while, however, the balance of advantage was in favor of a grounded system. . ."

Honestly, I am less impressed due to my understanding of utility power systems. Prior to WWII 22kv sub-transmission and 2.3kv distribution was almost exclusively ungrounded delta. Even short 66kv and 110kv transmission lines from hydro dams were debated as to the advantages of being run ungrounded.

However, what I wonder, is why power systems started off with an emphasis on being completely "sealed off" from earth.

 

[al hildenbrand]

utility power systems. . .
However, what I wonder, is why power systems started off with an emphasis on being completely "sealed off" from earth.

What you are trying to understand, in my opinion, predates "utility power systems." This goes back into DC motors and generators, which were, in their early years, serving very small geographies.

That is, the generator was in the same facility with the motor.

 

[mbrooke]

What you are trying to understand, in my opinion, predates "utility power systems." This goes back into DC motors and generators, which were, in their early years, serving very small geographies.

That is, the generator was in the same facility with the motor.

Perhaps here the idea of sealing everything off from earth originated?

 

[al hildenbrand]

I don't know how much of an "idea" it was.

I think it was more like me in my first days with my Gilbert Fun With Electricity set, back in third grade, and I was learning not to cross the wires between the battery and the bulb.

We're talking about two - three decades before J. J. Thompson discovered (proved) electrons in 1897.

 

[mbrooke]

I don't know how much of an "idea" it was.

I think it was more like me in my first days with my Gilbert Fun With Electricity set, back in third grade, and I was learning not to cross the wires between the battery and the bulb.

We're talking about two - three decades before J. J. Thompson discovered (proved) electrons in 1897.

Makes me wonder what drove people to earth power systems.


This sheds some light however:

https://pdfs.semanticscholar.org/0e06/3ebfba33c84f9619e46573f34f13434700f9.pdf

 

[mbrooke]

I don't know how much of an "idea" it was.

I think it was more like me in my first days with my Gilbert Fun With Electricity set, back in third grade, and I was learning not to cross the wires between the battery and the bulb.

We're talking about two - three decades before J. J. Thompson discovered (proved) electrons in 1897.

Makes me wonder what drove people to earth power systems.


This sheds some light however:

https://pdfs.semanticscholar.org/0e06/3ebfba33c84f9619e46573f34f13434700f9.pdf

 

[PaulMmn]

I noticed that the knife switches are shown in the proper orientation-- with the 'on' being with the handle 'up.' If the switch failed, the handle would fall to the 'off' position.
I suspect this is why most utility switches are 'off' in the down position!

A side note on electrification-- when electric street cars started to be made of steel instead of wood, people were very concerned about electricity and steel and getting electrocuted while on the street car. The solution was to emboss the steel with 'wood grain' paneling, so people would think it was still a nice, safe, wooden street car.

 

[mbrooke]

I noticed that the knife switches are shown in the proper orientation-- with the 'on' being with the handle 'up.' If the switch failed, the handle would fall to the 'off' position.
I suspect this is why most utility switches are 'off' in the down position!

A side note on electrification-- when electric street cars started to be made of steel instead of wood, people were very concerned about electricity and steel and getting electrocuted while on the street car. The solution was to emboss the steel with 'wood grain' paneling, so people would think it was still a nice, safe, wooden street car.

But it sure made them look good. I have a thing for wood grain even though it was an 70s-80s thing. Just as long as the appliances, bathtub and sink aren't avocado

 

[K8MHZ]

I have, in my collection a 120 volt service that not only has the neutral fused, but both the neutral and the hot have 2 fuses in series.

If I wasn't feeling so lazy I would take a pic of it and post it. There is an inspection sticker in it from the 20's