What is it? #395 : Branch circuit panel
- Thread starterderekleffew
- Start date
JohnHartman
Member
A live front split-phase panelboard? I notice that there are no knife switches with poles connected across the outer two feed lugs, and thus is unlikely to have been used for three phase.
Last edited by a moderator:
CrazyTechie
Well-Known Member
BrianWolfe
Active Member
I used one of these back in the early 60's.
[This response was previously hidden. Revealed 03/22/11.]
From http://www.codecheck.com/cc/wiring_history.htm#fusedneutral :
From http://www.codecheck.com/cc/wiring_history.htm#fusedneutral :
Last edited:
The neutral bus is the middle bar. No idea why it would fused however.
BrianWolfe
Active Member
[This response was previously hidden. Revealed 03/22/11.]
The middle shared bar. And it is easier to quote than try to explain:
Putting fuses in the neutral was done away with in the early 1900s. I believe it is closely related to the expanding uniform practice of bonding the neutral to other conductive systems (water pipe, steel, etc.) and to earth, as the local voltage stabilization problems of AC transmitted over long distance was studied and understood.
The shared, or common, neutral of the standard 240 / 120 Volt single phase AC service, has its origin in DC. This multiwire circuit was, and still is, called an Edison Circuit. Thomas Edison's power distribution scheme required lots of small 240 /120 V generators located no more than a quarter mile from the most distant load. DC transformers were not economic or practical.
Until 1900, it was common for the generators to be supported on beds that were monitored to maintain isolation from earth or other conductive systems. Whether to ground the generator, or not, was a design choice.
The early National Electric Codes were written including rules for ungrounded generator frames.
For an ungrounded generator customer, if a neutral conductor on a branch circuit shorted to ground, and there were other shorts of hots (from the same generator) to ground elsewhere in the system, the greatest current would occur in the neutral, the fuse would clear, and trouble would be indicated, and, presumably, the electrician would be brought in.
The middle shared bar. And it is easier to quote than try to explain:
Putting fuses in the neutral was done away with in the early 1900s. I believe it is closely related to the expanding uniform practice of bonding the neutral to other conductive systems (water pipe, steel, etc.) and to earth, as the local voltage stabilization problems of AC transmitted over long distance was studied and understood.
The shared, or common, neutral of the standard 240 / 120 Volt single phase AC service, has its origin in DC. This multiwire circuit was, and still is, called an Edison Circuit. Thomas Edison's power distribution scheme required lots of small 240 /120 V generators located no more than a quarter mile from the most distant load. DC transformers were not economic or practical.
Until 1900, it was common for the generators to be supported on beds that were monitored to maintain isolation from earth or other conductive systems. Whether to ground the generator, or not, was a design choice.
The early National Electric Codes were written including rules for ungrounded generator frames.
For an ungrounded generator customer, if a neutral conductor on a branch circuit shorted to ground, and there were other shorts of hots (from the same generator) to ground elsewhere in the system, the greatest current would occur in the neutral, the fuse would clear, and trouble would be indicated, and, presumably, the electrician would be brought in.
Last edited by a moderator:
MPowers
Well-Known Member
Earlier I mentioned that I had used one of these before, but not in the intended way.
It was at a small theatre in Myrtle Beach back in 1969. An old 100 seat movie house converted to a community theatre. Everything in the place was DIY by some volunteer. Some how they had managed to get 3 phase power into the building and at some point someone had rewired the device in question to be a 3 phase fuse panel. All the legs shown were hot and the neutral was a separate neutral/ground buss bar next to the "main" The "Main" was a large, 3 pole cartridge fuse, knife switch. Not that unusual a home made device then, especially in areas away from major metro areas.
It was at a small theatre in Myrtle Beach back in 1969. An old 100 seat movie house converted to a community theatre. Everything in the place was DIY by some volunteer. Some how they had managed to get 3 phase power into the building and at some point someone had rewired the device in question to be a 3 phase fuse panel. All the legs shown were hot and the neutral was a separate neutral/ground buss bar next to the "main" The "Main" was a large, 3 pole cartridge fuse, knife switch. Not that unusual a home made device then, especially in areas away from major metro areas.
Similar threads
