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Originally posted by stoic-one:

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This is good for the high current stuff but all the integrated circuits would need a step down to 5 volts (or whatever they needed) and the only practical way to do that was with a power resistor, which means more current, more heat, added weight, etc.

Not knowing how long ago this was, but there are a lot of ways (transistor/IC) to "step down" DC which doesn't consume a lot of power. Now going up in DC voltage is another animal, usually involving modulation to AC...

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Originally posted by Lefty Sig:
When I was involved in DC component design in cars - 42 volts was the highest allowable voltage to prevent cardiac arrest under a situation where current is flowing from one hand to the other across the chest. Meaning 42 volts cannot push enough current through your heart to stop it. There was some interest in moving to the higher voltage to reduce the size and weight of all 12 volt wires. This is good for the high current stuff but all the integrated circuits would need a step down to 5 volts (or whatever they needed) and the only practical way to do that was with a power resistor, which means more current, more heat, added weight, etc. Eventually they gave up on it and stuck with 12 volts.

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Originally posted by maladat:

I rewired my 22 foot bay boat a few years ago and to meet the standard one of the wire runs that was only about 12 feet long had to be 4 gauge wire.

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Originally posted by PASig:

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Originally posted by maladat:

I rewired my 22 foot bay boat a few years ago and to meet the standard one of the wire runs that was only about 12 feet long had to be 4 gauge wire.

That doesn’t surprise me at all with direct current. I recall reading about in NYC a few years ago when they were excavating a new subway line they uncovered some old Edison DC power lines. They had to run like a half a mile from the generating plant to the building it supplied lighting power to circa the 1880’s or 1890’s and they were literally something like 3 inches in diameter. That’s precisely why he lost that war with Westinghouse and we ended up with alternating current.

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Originally posted by maladat:
I rewired my 22 foot bay boat a few years ago and to meet the standard one of the wire runs that was only about 12 feet long had to be 4 gauge wire.

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Originally posted by Lefty Sig:

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Originally posted by maladat:

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Originally posted by Rey HRH:

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Originally posted by Lefty Sig:
Yep. The US chose 110/120V to limit electrocution risk, although it is still high enough to kill.

The idea of less electricution doesn't pass. I forget the actual number that was drummed into me going through shipyard electronics training but it's the current that kills you, not the volts and the number is very low.

Also, statistics say more people are killed by 110 v because people get complacent.

Sure, it only takes a tiny amount of current across your heart to kill you.

However, your skin has a pretty high resistance. Remember V = I * R (volts = current * resistance). Unless you stick wires through your skin into your wet, salty, very conductive insides, it takes a lot of voltage to push enough current through your skin to kill you.

Thanks for interjecting. I get tired of the "it's not the volts it's the amps!" comments. That is akin to saying "it's not the pressure of the fire house that knocks you down, it's the water flow!". Yeah it's the current that kills you but you need the voltage to get enough current to flow, just like you need the pressure to get the water flow in the fire hose.

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Originally posted by maladat:

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Originally posted by PASig:

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Originally posted by maladat:

I rewired my 22 foot bay boat a few years ago and to meet the standard one of the wire runs that was only about 12 feet long had to be 4 gauge wire.

That doesn’t surprise me at all with direct current. I recall reading about in NYC a few years ago when they were excavating a new subway line they uncovered some old Edison DC power lines. They had to run like a half a mile from the generating plant to the building it supplied lighting power to circa the 1880’s or 1890’s and they were literally something like 3 inches in diameter. That’s precisely why he lost that war with Westinghouse and we ended up with alternating current.

A 12V AC system would be subject to the same voltage drops and require the same thickness of wire.

AC, purely by virtue of being AC, doesn't have any significant transmission benefits over DC. Actually, at a given voltage and current, DC is better. With AC, skin effect increases the effective resistance of the conductor, and there is also more energy lost to corona discharge than with DC.

The reason AC wins for power grid use is that it is easy to bump the voltage up or down, so you can easily run 300,000 V for long range transmission, 100,000 V for short range transmission, 15,000 V for local distribution, 1,000 V in neighborhoods, etc, and easily (read: inexpensively) split off lower voltage branches anywhere you want. Numbers are made up but are about the right order of magnitude.

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Originally posted by PASig:
Fascinating to read that NYC didn't shut down all their original DC electrical systems until like 1976 or so and some even much later into the 2000's!

It turns out most Broadway theater lighting ran on DC and many NYC elevators did too.

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The case of the shocked Pope

By Bernard A. Drew Sep 19, 2009


GREAT BARRINGTON

It was Sunday, Oct. 13, 1895. The evening began quietly enough at the Franklin L. Pope residence on South Main Street, Great Barrington.

Leonard, 15, was reading in the south parlor. He reached to turn on the electric lamp and received a tingle. He told his dad. Franklin Pope left the parlor to investigate and, according to an account in Western Electrician for Oct. 26, 1895, "the next that was known of him was the heavy fall and the crash of glass caused by the breaking of a lamp chimney." Daughter Hannah, 19, went to the basement to check on her father. When she went to the northeast corner, "she saw her father's head on the floor as she approached, and heard the gurgling sound caused by the relaxation of the muscles in cases of this kind."

The family summoned Dr. Alfred Large, who attempted artificial respiration, without success.

Pope had descended the cellar stairs with a kerosene lamp in hand. He went to check on two power transformers near a window. It was raining hard and the window was ajar. A breeze perhaps blew out the lamp. There was moisture on the floor. Pope, it was speculated, reached to shut the window when his hand brushed against a live wire on one transformer. The shock sent him smashing to the floor.


Franklin Leonard Pope had been born in town in 1840. His first job, at age 17, was as telegraph operator in the Great Barrington office. From there he rocketed to success. To mention just a few achievements: he mapped a prospective route across British Columbia and the Yukon for Collins Overland Telegraph in 1864, edited The Telegrapher in 1867 and 1868 and partnered with Thomas A. Edison to develop a one-wire telegraphic printer in 1869. He was chief legal advisor to George Westinghouse in the 1880s.

He semi-retired to Great Barrington in 1890. As consulting engineer to the Great Barrington Electric Light Co., Pope was instrumental in contracting with Stanley Electric of Pittsfield to supply electricity to Monument Mills in Housatonic in 1893, from a station at Alger Furnace. Surplus power was sent to Great Barrington for private customers.

To monitor the system, Pope had transformers placed in his basement. (Usually they would have been outside on utility poles.)

This was a critical period in the ongoing struggle between the interests of direct-current electricity and alternating-current. Edison's d-c backers waged a vigorous campaign and called a-c unsafe. This episode could play into their hands. Thus the American Institute of Electrical Engineers wanted to determine a precise cause of Pope's death.

Joining Dr. Large to perform an autopsy was Dr. Whitmell P. Small -- yes, Drs. Large and Small -- who told the press "death was caused by the full force of the electric current passing through Mr. Pope's body and that death was instantaneous."

Death records at Great Barrington's Town Hall indicate Franklin L. Pope, "electrician," died "accidentally by Electricity." Mrs. Pope did not believe her husband died from the electrical charge. She had the a-c system at Wainwright Hall repaired and returned to service.

A trio of top-notch electrical engineers served as an informal coroner's jury.

William Stanley of Pittsfield, Professor Edward Weston of Newark, N.J., and George A. Hamilton of Western Union Telegraph in New York City examined the transformers, which had been made in 1890. They did not reveal the manufacturer. (They were not Stanley transformers, for which production did not begin until 1892.)

If you find modern-day television dramas such as CSI or Bones or NCIS engrossing for their forensics detail, consider the thoroughness that went into this examination. Stanley, Weston and Hamilton took measurements, made diagrams and collected testimony.

They also looked at evidence on Pope's hands. "It is certain, therefore, that Mr. Pope did not intentionally touch any part of the apparatus and that fact that the marks on the hands are all on parts which are never used for the purposes of adjusting feeling or investigating anything is positive proof that the fatal contact of the hand with the electrical apparatus was accidentally made," they said.

They looked at Pope's shoes. "These spots on the soles of his shoes and the marks on his right hand serve to conclusively prove that the circuit was completed through his feet and right hand and taken alone they would established the fact that some parts of the primary or 2000 volt circuit was connected with the earth or grounded."

A jolt of 2,000 volts, the scientists knew, would not automatically kill someone.

Consider the experience of James E. Cutler, an employee in the transformer department at Stanley Electric Manufacturing. Just a year before, in 1894, he had grasped a live wire and taken a 4,800-volt jolt. It knocked him flat. He stopped breathing. Quick-thinking co-workers restored him to consciousness and his only after-effect was a burned palm.

The Oct. 24 Berkshire Courier summed it up: "Mr. Pope's Death Due to Accident and Not to Carelessness."


Robert Tepper and his wife (and innkeeper) Marja Tepper Grader maintain Wainwright Inn today. Tepper graciously gave me a tour of the "scene of the crime." We descended the same stairs as Pope in 1895. The day of my visit, green yule decorations hung in front of the three-pane window through which electricity entered the house in 1895.

Knob-and-tube remnants of early house wiring cling to the floor joists in front of the window. There is little evidence of the transformers that were mounted on the chimney base.

Was I expecting chalk marks on the floor and blood splatters? Of course not. But I felt wired in to a fascinating episode of electrical history.

Bernard A. Drew is a regular Eagle contributor.

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Originally posted by sigcrazy7:
Similar to the Pope story.

-James Fixx, author of the 1977 best-selling book The Complete Book of Running, died at 52 while out jogging.

-Ken Hendricks, billionaire founder of ABC Roofing, died at age 66 when he fell off a ladder.

-Captain Edward Smith went down with the Titanic on his final voyage.

Moral of the story: If you ever make it big in an industry, stay away from it after your retirement. The Universe is amused by irony.

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Originally posted by sigcrazy7:
What is that panel doing? It looks like the 100A breaker on the right is the main disconnect, and it interrupts both the line and neutral. From there, it looks like a brown and blue come from the main breaker to each 63A breaker, which looks like GFCI breakers. It looks like each of those power a bank of six possible breakers, so a ground fault in any of those six would interrupt the 63A breaker. Essentially it looks like two sub panels inside of one panel.

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Originally posted by sigcrazy7:
What is that panel doing? It looks like the 100A breaker on the right is the main disconnect, and it interrupts both the line and neutral. From there, it looks like a brown and blue come from the main breaker to each 63A breaker, which looks like GFCI breakers. It looks like each of those power a bank of six possible breakers, so a ground fault in any of those six would interrupt the 63A breaker. Essentially it looks like two sub panels inside of one panel.

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Originally posted by snidera:

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Originally posted by sigcrazy7:
What is that panel doing? It looks like the 100A breaker on the right is the main disconnect, and it interrupts both the line and neutral. From there, it looks like a brown and blue come from the main breaker to each 63A breaker, which looks like GFCI breakers. It looks like each of those power a bank of six possible breakers, so a ground fault in any of those six would interrupt the 63A breaker. Essentially it looks like two sub panels inside of one panel.

I suspect you are right about the 100A, but it feeds the bus/rail that's peeking out between the "banks" Rather than the 63A being sub-panels, I suspect they are large-draw devices (hot water, dryer, stove, etc)