What would happen if...
- Thread starter lunalilo
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chris kennedy
Senior Member
- Location
- Miami Fla.
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- 60 yr old tool twisting electrician
You would have a violation of 310.4.
- Location
- Lockport, IL
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- Semi-Retired Electrical Engineer
Nothing. Is that straight enough an answer for you?
What would happen if you took two wires, tied them together at one end, walked 25 feet to get to the other end, then tied the two wires together there as well? The answer is the same "nothing."
Where did this question come from?
DISCLAIMER:
Please do not try this experiment at home. When I gave the "nothing" answer, I based that answer on the intent to touch the two wires to each other, without touching either wire with your hand.
What would happen if you took two wires, tied them together at one end, walked 25 feet to get to the other end, then tied the two wires together there as well? The answer is the same "nothing."
Where did this question come from?
DISCLAIMER:
Please do not try this experiment at home. When I gave the "nothing" answer, I based that answer on the intent to touch the two wires to each other, without touching either wire with your hand.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
You probably had no other wires or loads involved in mind, too.
You would have a violation of 310.4.
that's funny.:grin:
ok, so if it were broken down...
1)what would happen on a panel currently in use in the household?
2)what would happen if this were done as if it were the only breakers in the main panel?
Same thing, nothing. If there is no load on the far end of the wires and they are on the same leg, and not touching ground or you, the answer stays the same.
Zip, Nada, Zero, nothing, niente, nyet.
Two (or more) wires fed from the same panel at the same potential act as one wire with no load.
Now if those two wires were on the same leg but fed from your panel and your neighbor's there would possibly be some current flow depending on the loads in each panel, resistance of the service drops, and so on.
Electricity will take ALL available paths to flow, dividing up the amount of flow (amperage) in accordance with Ohm's law.
Zip, Nada, Zero, nothing, niente, nyet.
Two (or more) wires fed from the same panel at the same potential act as one wire with no load.
Now if those two wires were on the same leg but fed from your panel and your neighbor's there would possibly be some current flow depending on the loads in each panel, resistance of the service drops, and so on.
Electricity will take ALL available paths to flow, dividing up the amount of flow (amperage) in accordance with Ohm's law.
growler
Senior Member
- Location
- Atlanta,GA
Couldn't he just wire nut the two conductors togather and then turn the breaker on? Working this thing live may be a safety violation. He could measure the effect with an ammeter
Better yet why not just have him study theory and learn why nothing will happen and that this whole experiment is a waste of time. :roll:
kwired
Electron manager
- Location
- NE Nebraska
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- EC
little different perspective
little different perspective
If after they tied together you continue on with a single conductor to a load then you will be capable of overloading the conductor without tripping the breaker(s).
This does happen and not necessarily with twin or tandem breakers, any two poles of same phase if you accidently tie them togehter someplace you essentially have the same thing and you may never know you have done it because nothing will happen to indicate there is a problem.
If you accidently tie different phases together you know right away you have a problem when you turn on the second breaker.
little different perspective
If after they tied together you continue on with a single conductor to a load then you will be capable of overloading the conductor without tripping the breaker(s).
This does happen and not necessarily with twin or tandem breakers, any two poles of same phase if you accidently tie them togehter someplace you essentially have the same thing and you may never know you have done it because nothing will happen to indicate there is a problem.
If you accidently tie different phases together you know right away you have a problem when you turn on the second breaker.
- Location
- Illinois
- Occupation
- retired electrician
When you make this connection you have created a parallel path for current flow. Current always flows on all available paths and divides in inverse proportion to the impedance of the paths.
There will be a very small amount of current that flows when you connect the two wires together, assuming that there is load on the panel bus. This current will be driven by the voltage drop between the two connection points on the bus. This should be a very small drop and the current flow would also be very small.
Note that it is likely that the voltage drop and current flow in this example will be too low to be measured by the types of meters that electricians normally use.
There will be a very small amount of current that flows when you connect the two wires together, assuming that there is load on the panel bus. This current will be driven by the voltage drop between the two connection points on the bus. This should be a very small drop and the current flow would also be very small.
Note that it is likely that the voltage drop and current flow in this example will be too low to be measured by the types of meters that electricians normally use.
growler
Senior Member
- Location
- Atlanta,GA
So you are thinking that this connection will act much like a "shunt resistor". The distance in bus between connection one and two would have some resistance.
The problem with that theory is that this type of breaker (1" twin = tandem) only makes a connection at one place along the bus. So even if we get expensive test equipment there is no current flow.
I do see what you are saying and if he were to connect at two different places along the bus there would be a slight voltage drop and thus some current flow. But for all "practical purposes" it's still nothing.
One time 'something might happen' is if you're using the old Challenger tandem breakers that made it possible to energize the two wires from opposite (or different) phases. They came with the bus-bar attachments in either 'left-' or 'right-handed', so adjacent breakers could have 240 (or 208) volts between them.
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
100518-1018 EST
lunalilo:
Take your two 25 ft wires, forget the breaker, make them into a closed circle of 15.9 ft in diameter, connect an ammeter in series, apply an AC magnetic field within the circle, and you will have current flow.
Next flatten the circle into two closely spaced wires, and maintain the same flux density for the magnetic field, then the current will become very small.
After this twist the two wires together forming a twisted pair and the current becomes even less.
.
lunalilo:
Take your two 25 ft wires, forget the breaker, make them into a closed circle of 15.9 ft in diameter, connect an ammeter in series, apply an AC magnetic field within the circle, and you will have current flow.
Next flatten the circle into two closely spaced wires, and maintain the same flux density for the magnetic field, then the current will become very small.
After this twist the two wires together forming a twisted pair and the current becomes even less.
.
One time 'something might happen' is if you're using the old Challenger tandem breakers that made it possible to energize the two wires from opposite (or different) phases. They came with the bus-bar attachments in either 'left-' or 'right-handed', so adjacent breakers could have 240 (or 208) volts between them.
The OP did say "BR" type breakers. So it would not have the stab on other then one buss at a time.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
I have a handful of GE half-sized breakers that have the stab clip like that one. They aren't made for bridging the space between bus stabs the way others are, like quads and half-sized FP 2p breakers, to obtain 240v.
macmikeman
Senior Member
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- Planet macmikeman
Since you have a freeway named after you, :grin: you should be getting the very best of information... You are a famous guy where I live.
HA! so your the famous "other guy" who lives in Hawaii! Don't forget the school that I'm named after too! JK!
Bjenks
Senior Member
- Location
- East Coast of FL
Another byproduct of this is that if you ran 2 neutrals with the two conductors and ran them 300 ft (tying them together at the end also) and then connected a whole bunch of light fixtures along that 300 ft length all at the same load you would get approximately the same voltage drop at each fixture. This is called the loop method and is used to keep incandescent light at the same light level for long lengths of runs.
Steve Beranek
Member
- Location
- St. Louis, Missouri
I like this,... the question I have is when will the breaker trip based on current?
Will it trip above 20 or above 40 ? (Well of course it'd be more like 35 & 70, if we get the breakers that I see alot of the time.)
Will it trip above 20 or above 40 ? (Well of course it'd be more like 35 & 70, if we get the breakers that I see alot of the time.)
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Actually, the way to do that is to feed one conductor at the near end of the string, and feed the other conductor at the far end of the string. In total, three wires are needed for each string, one of which has no fixtures tied to it; it just feeds the far end.
Holiday highting that has a receptacle on the end opposite the plug, as well as rope lighting that can be extended, is wired like that, too; the latter in sections along the rope so it can be cut between sections, as long as you don't cut within one.
Series lighting is another way to supply a long single run with only two conductors, as long as you can find appropriate bulbs and the right supply voltage. Added: Isn't it amazing how a thread strays off topic?
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