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Lars(wi) ![]() Orange Level Access ![]() ![]() Joined: 14 Sep 2009 Location: Permian Basin Points: 7774 |
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As a ‘rule of thumb’ in residential wiring, how many circuits is the limit that tie into a common neutral?
We’re all familiar with 14-2, 14-3, and 12-2, 12-3, romex wire, but is there 14-4,14-5, and 12-4,12-5 wiring? |
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I tried to follow the science, but it was not there. I then followed the money, and that’s where I found the science.
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jaybmiller ![]() Orange Level Access ![]() Joined: 12 Sep 2009 Location: Greensville,Ont Points: 24401 |
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yes, to the numbers ,but NOT used in houses. I use 14-6 'cabtire' to wire up trailers,10-4 on my welders. I 'think' you can have 12 receptacles on ONE 14-2 NMD house wire circuit. Rules vary according to local electrical code. As a general rule ,do NOT put lights on same circuit as 'loads' ,like a table saw. BAD things can happen when the breaker blows, saw still spinning and the room is dark..........
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3 D-14s,A-C forklift, B-112
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plummerscarin ![]() Orange Level Access ![]() Joined: 22 Jun 2015 Location: ia Points: 3783 |
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In our jurisdiction, common neutral is prohibited in residential wiring. Rarely seen in commercial lighting systems and neutral conductor is larger than the feed.
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Lars(wi) ![]() Orange Level Access ![]() ![]() Joined: 14 Sep 2009 Location: Permian Basin Points: 7774 |
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That means your not allowed to use 14-3, 12-3, 10-3, etc.? |
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I tried to follow the science, but it was not there. I then followed the money, and that’s where I found the science.
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DaveKamp ![]() Orange Level Access ![]() ![]() Joined: 12 Apr 2010 Location: LeClaire, Ia Points: 5973 |
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The problem with running a common neutral for several circuits, is that the neutral will carry the sum of all circuits' loads. IF all those circuits are on the same LEG, then that neutral current could be significantly higher than the individual loads, which is what they DON'T want to have happen. Historically, it was acceptable practice to share a neutral between legs of a split-phase (like 120/240) or a polyphase (208/125Y or 480/277Y) because the neutral leg would be carrying the sum of two phases at two different points of the sine wave, and the result is that return current of ONE of the phases, is actually turning into the supply of the adjacent, so the DIFFERENCE of the loads' phase currents makes the neutral leg's current load LESS than the sum of all legs. The reason why some jurisdictions don't allow this anymore, is because they don't believe that electricians are actually smart enough to know how split- and poly-phase electrical services work. God forbid they decide to prohibit corner-fed delta, split-phase from a T-connected delta... (yes, that's sarcasm) There are times when a 12-4 or 10-4 wire is used... a range plug for a kitchen stove, for instance, is frequently a 10-4 wire- 2 hots and a neutral, with ground. The heating elements for the cooktop have a high and low setting, the light, timer, and electronics run on 120, and oftentimes, the heating element inside the stove sometimes runs a high and low. They accomplish this on the elements by running them on just one leg to neutral, rather than full series of one hot to the other hot. For industrial environments, it is considered 'bad practice' to use a neutral on ANY machine... feed it three phase, or single phase, and make the machine connectable to whatever input voltage is most suitable... and if there's any control voltages, etc., required that are NOT the same line voltage, include a control voltage transformer to provide isolated power to the controls. THis has added benefit of eliminating a possible source of electrocution should a short occur inside the machine. But as Jay noted- 12-6, etc are commonly found in a high-flexibility tough outer jacket, with stranded wires, also very flexible, for trailer main connection wiring. It is also found in travelling cable for elevator cabs, pendant cable for overhead cranes, and electric controls for heavy machinery- like... the control panel for a scissor lift, bucket truck, or armrest-mounted joystick on a mini-excavator. It is also sometimes used by professional soundmen to carry medium power levels from amplifier arrays on the stage sides, up to 'flying arrays' of speakers suspended from overhead trusses. Having 6 conductors of #12 wire means three bays of speakers running 2000w a bay... in one nice package.
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Ten Amendments, Ten Commandments, and one Golden Rule solve most every problem. Citrus hand-cleaner with Pumice does the rest.
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steve(ill) ![]() Orange Level Access ![]() ![]() Joined: 11 Sep 2009 Location: illinois Points: 85973 |
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A 12-3 wire (red-black-white).... ( with bare ground)... is NOT to be used as two separate circuits.. You would have two hot wires from different breakers in the same light or plug box.. That is NOT a good idea........... 12-3 is specifically for light circuits where you need another feed wire to make the switches work... NOT two HOT wires.
and NO, you can not use one neutral ( or ground wire) for two different HOT wire feeds.
Edited by steve(ill) - 17 Jul 2023 at 9:12pm |
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steve(ill) ![]() Orange Level Access ![]() ![]() Joined: 11 Sep 2009 Location: illinois Points: 85973 |
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if you had a 12-3 with ground... and run 20 amps on the black- white .... and 20 amps on the red - white ...( two 120v circuits) ..... the WHITE WIRE could have 40 amps ...... cant do that.
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Lars(wi) ![]() Orange Level Access ![]() ![]() Joined: 14 Sep 2009 Location: Permian Basin Points: 7774 |
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Thanks Steve, for the clarification.
As I am no electrical engineer by any stretch, as per your explanation, a neutral can carry the same amps as the ‘hot’, where does the current flowing in the neutral go once it reaches the breaker panel? As every breaker panel I have looked at has two ‘hot’ wires coming from the transformer on the pole outside. If I’m not mistaken, the neutral bar in the panel meets with the ground, which goes outside to the ‘grounding rod’. Am I missing something? |
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I tried to follow the science, but it was not there. I then followed the money, and that’s where I found the science.
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jaybmiller ![]() Orange Level Access ![]() Joined: 12 Sep 2009 Location: Greensville,Ont Points: 24401 |
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re: A 12-3 wire (red-black-white).... ( with bare ground)... is NOT to be used as two separate circuits. NOT true, at least north of the 49th, every kitchen is required to have 3 'splits'(20A nowadays). They are a duplex receptacle with the brass hot 'connector' removed, red goes to one receptacle, blk to the other. They are fed from a 'double' breaker. allows you to have a toaster AND a kettle connected to the 'duplex receptacle'. If either overloads BOTH kettle and toaster lose power.. What you can't have is them fed from SINGLE breakers. If you did and one tripped, the other receptacle would be LIVE and lethal. |
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3 D-14s,A-C forklift, B-112
Kubota BX23S lil' TOOT( The Other Orange Tractor) Never burn your bridges, unless you can walk on water |
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Lars(wi) ![]() Orange Level Access ![]() ![]() Joined: 14 Sep 2009 Location: Permian Basin Points: 7774 |
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‘Double’ breaker, you mean the ones that have two ‘switches’ in a row in a single breaker slot?
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I tried to follow the science, but it was not there. I then followed the money, and that’s where I found the science.
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Lars(wi) ![]() Orange Level Access ![]() ![]() Joined: 14 Sep 2009 Location: Permian Basin Points: 7774 |
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Jay, I have understand the other outlet of the duplex would be ‘live’ but why would it be ‘lethal’?
We had a couple of those ‘double breakers’ in our previous house, not sure what they fed, as the whole time we were there, they never tripped(15amp). |
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I tried to follow the science, but it was not there. I then followed the money, and that’s where I found the science.
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steve(ill) ![]() Orange Level Access ![]() ![]() Joined: 11 Sep 2009 Location: illinois Points: 85973 |
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In the US when you use RED- BLACK- WHITE.. you "normally" are connecting to a 240 v plug... like the stove or arc welder, etc..... "MOST" of the power usage is from BLACK to RED ( 240v) .. you may have a timer / light bulb / clock that is connected to the BLACK- WHITE and runs at 120v.......
That is the theory in your breaker box also Lars.... "MOST" of the power ( amps) are going between the RED - BLACK ( or your two HOT WIRES INTO THE BOX) that is 240v.... that runs the Air cond, stove, hot water heater, furnace, etc.... The WHITE wire is ( or neutral from the power pole) for the 120v circuits and normally only used for 50 amps ( in a 100 amp box), or 100 amps ( in a 200 amp box)..... it is basically not used ( much) on the 240v circuits.
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Like them all, but love the "B"s.
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steve(ill) ![]() Orange Level Access ![]() ![]() Joined: 11 Sep 2009 Location: illinois Points: 85973 |
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red goes to one receptacle, blk to the other. They are fed from a 'double' breaker. allows you to have a toaster AND a kettle connected to the 'duplex receptacle'
well something dont add up there... If the RED has 20 amps and the BLACK has 20 amps... then the WHITE would have 40 amps.. If its the same size wire it is OVERLOADED....... assuming this is 120v circuits.
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Like them all, but love the "B"s.
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Tbone95 ![]() Orange Level Access ![]() ![]() Joined: 31 Aug 2012 Location: Michigan Points: 12011 |
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Lars, as for where the current goes when it gets back to the panel…it goes back and forth around the loop changing direction 60 times a second. It doesn’t flow down a drain to the ground, that ground is to make for an easier path to ground than yourself if something goes wrong.
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steve(ill) ![]() Orange Level Access ![]() ![]() Joined: 11 Sep 2009 Location: illinois Points: 85973 |
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I looked up "SPLIT PLUG" as jay mentioned in his post. Personally i have not seen a 12-3 wire used to feed two ( split) plug.....You are really running a 240 v wire to TWO 120v sockets.. If you think about it, the power flow FROM the red to white, while it is flowing TO the black from the white... then the SIN WAVE CHANGES and the flow is TO the red (from white) and FROM the black (to the white).. In this way the Neutral (white) will not see excessive current flow... so that should work as long as the two BREAKERS are side by side on different INPUT LEGS of the breaker box.
Edited by steve(ill) - 19 Jul 2023 at 8:56am |
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Like them all, but love the "B"s.
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jaybmiller ![]() Orange Level Access ![]() Joined: 12 Sep 2009 Location: Greensville,Ont Points: 24401 |
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no, you're running two , 120 feeds from a ganged (2 pole) breaker. At no time does either receptacle get 240 . red and wht to 1/2, blk/wht to the other 1/2.
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3 D-14s,A-C forklift, B-112
Kubota BX23S lil' TOOT( The Other Orange Tractor) Never burn your bridges, unless you can walk on water |
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steve(ill) ![]() Orange Level Access ![]() ![]() Joined: 11 Sep 2009 Location: illinois Points: 85973 |
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there is 240 volt "in the plug box" from the black to the red wire... but your right, they are SEPARATE inside the gang box to two INDIVIDUAL PLUGS , so you just have 120v to red to white and 120v black to white..... shows that in the movie.... no way to plug into the red and black with ONE PLUG... but a VOLT METER will show 240v inside that box.
The BREAKERS can not be a SPLIT using two on the SAME LEG inside the breaker box.. You must have the BLACK and RED on DIFFERENT legs inside the breaker box.
Edited by steve(ill) - 19 Jul 2023 at 8:57am |
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Like them all, but love the "B"s.
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Tbone95 ![]() Orange Level Access ![]() ![]() Joined: 31 Aug 2012 Location: Michigan Points: 12011 |
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So if you use both halves of the outlet at the same time, which seems to be the point, the current from both would be carried by the white. How’s that allowed? |
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steve(ill) ![]() Orange Level Access ![]() ![]() Joined: 11 Sep 2009 Location: illinois Points: 85973 |
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think of a sin wave... RED is +120 v.... Black is -120 v .... white is "neutral" in the center.. ZERO on the graph.......you have to picture it as a 240 v SYSTEM.. even tho you are going to divide it into 2 - 120v circuits.
Three phase power does the same thing... Since they are OUT OF PHASE, when you add them up, the neutral ( white) see very little current flow.
The catch is you have to be on BOTH LEGS input to the breaker box, so you have a SIN WAVE. (240 v).. You cant have the Black and Red on two breakers on the SAME LEG INPUT..(120v each, 0 v difference ) if you did, the white wire would pull DOUBLE what the Red or Black is pulling. Edited by steve(ill) - 19 Jul 2023 at 12:47pm |
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Like them all, but love the "B"s.
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Lars(wi) ![]() Orange Level Access ![]() ![]() Joined: 14 Sep 2009 Location: Permian Basin Points: 7774 |
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Is there just as much current flowing thru a neutral, when an appliance, motor, light, etc., is in use as when the appliance is off? |
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I tried to follow the science, but it was not there. I then followed the money, and that’s where I found the science.
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steve(ill) ![]() Orange Level Access ![]() ![]() Joined: 11 Sep 2009 Location: illinois Points: 85973 |
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normally when OFF, the switch is open , so there is an open circuit... NO FLOW.
On a SPLIT plug system, you actually have MORE FLOW thru the WHITE when using one half of the plug.. If you use BOTH halves at the same time, the flow to the WHITE from the RED should cancel out the flow to the WHITE from the BLACK. above movie (YouTube) explains that about the 3 minute mark.
Edited by steve(ill) - 19 Jul 2023 at 1:33pm |
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Like them all, but love the "B"s.
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Coke-in-MN ![]() Orange Level Access ![]() Joined: 12 Sep 2009 Location: Afton MN Points: 41870 |
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366.20 Conductors Connected in Parallel.![]() Click to Enlarge In the 2017 NEC, parallel conductors inside an auxiliary gutter must be grouped together to prevent current imbalance in the paralleled conductors due to inductive reactance. Code Change Summary: A new code section provides requirements for parallel conductors in an auxiliary gutter. Parallel conductor installations are covered in NEC® 310.10(H) and are permitted for each phase, polarity, neutral, or grounded conductor in sizes 1/0 AWG and larger. Joining conductors in parallel is like having two or more smaller conductors connected at each end to make one larger conductor. This is often done to make wire pulling easier. In order to install conductors in parallel, the paralleled conductors in each phase, polarity, neutral, grounded circuit conductor, equipment grounding conductor, or equipment bonding jumper must comply with all of the following: (1) Be the same length. (2) Consist of the same conductor material. (3) Be the same size in circular mil area. (4) Have the same insulation type. (5) Be terminated in the same manner. The above rules ensure that each set of parallel conductors carries the same ampacity. Where run in separate cables or raceways, the cables or raceways must have the same number of conductors and must have the same “electrical characteristics”. The phrase “electrical characteristics” refers to the properties of the raceway such as raceway material. Using the same raceway type (nonmetallic or ferrous metal) for each parallel set of conductors ensures that electrical current is not transferred to the raceway through induction. In the 2017 NEC®, additional code language was added to address proper grouping of parallel conductors inside an auxiliary gutter. Before the code change, the requirements for grouping of the parallel conductors was limited to within each raceway or cable but no mention was made about what goes on inside the gutter box. Section 300.20(A) states the following: Where conductors carrying alternating current are installed in ferrous metal enclosures or ferrous metal raceways, they shall be arranged so as to avoid heating the surrounding ferrous metal by induction. To accomplish this, all phase conductors and, where used, the grounded conductor and all equipment grounding conductors shall be grouped together. Most auxiliary gutters are made of ferrous metal therefore it only makes sense to keep parallel conductors grouped properly behind the gutter box cover. A similar code change occurred in Article 376 for metal wireways. Below is a preview of Article 366. See the actual NEC® text at NFPA.ORG for the complete code section. Once there, click on their link to free access to the 2017 NEC® edition of NFPA 70. 2017 Code Language: |
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Faith isn't a jump in the dark. It is a walk in the light. Faith is not guessing; it is knowing something.
"Challenges are what make life interesting; overcoming them is what makes life meaningful." |
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Coke-in-MN ![]() Orange Level Access ![]() Joined: 12 Sep 2009 Location: Afton MN Points: 41870 |
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While the National Electric Code (NEC) still allows the practice of common or shared neutrals to occur, several other codes (including Federal Law) regulate this unfortunate practice. The shared or common neutral practice is highly debated among the experts, and is has been primarily left in the NEC as an accepted old-school practice. However, there is no disagreement among the experts, including advocates of the practice, that common or shared neutrals are NOT an ideal wiring technique. The advocates simply argue that while never ideal, sharing neutral conductors between phases can be done safely in certain circumstances.
In order to prevent an overcurrent situation, when common neutrals are used, the loads must be on different phases. If the same phase is used, the current on the neutral wire will be equal to load-1 plus load-2, possibly doubling the current and creating an unsafe over current situation. Remember, there is no circuit protection for the neutral wire. When overloaded, it can only heat until it burns open. The verification of “phase alignment” is critical in order to prevent overloads.
In order to avoid the danger of having breakers later re-arranged onto the same leg (which would create a potential overcurrent hazard), shared neutral circuits should be connected to multi-gang breakers rather than to separate single gang breakers. When an Edison circuit is discovered, it is recommended that electricians perform one of the following modifications:
Your company’s standard lockout/tagout procedures should be modified to include a requirement to verify zero energy on the neutral line. Additional dangers to electricians are posed by circuits with common neutrals that are controlled by switches, such as thermostats, that may close unexpectedly. Therefore, it is important to consider the potential presence of Edison circuits. Electricians working on sites with Edison Circuits should be trained, warning signs posted, and should consider the possibility that every circuit may be Edison circuits, and take the necessary safety precautions. |
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Faith isn't a jump in the dark. It is a walk in the light. Faith is not guessing; it is knowing something.
"Challenges are what make life interesting; overcoming them is what makes life meaningful." |
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Lars(wi) ![]() Orange Level Access ![]() ![]() Joined: 14 Sep 2009 Location: Permian Basin Points: 7774 |
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Isn’t this a ‘3 phase’ panel? 120 volt 120 volt ‘wild’ wire Neutral Edited by Lars(wi) - 19 Jul 2023 at 4:27pm |
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I tried to follow the science, but it was not there. I then followed the money, and that’s where I found the science.
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jaybmiller ![]() Orange Level Access ![]() Joined: 12 Sep 2009 Location: Greensville,Ont Points: 24401 |
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re: The shared or common neutral practice is highly debated among the experts, ....meanwhile power from the pole has a common neutral...
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3 D-14s,A-C forklift, B-112
Kubota BX23S lil' TOOT( The Other Orange Tractor) Never burn your bridges, unless you can walk on water |
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Tbone95 ![]() Orange Level Access ![]() ![]() Joined: 31 Aug 2012 Location: Michigan Points: 12011 |
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Yep. I didn’t think of that. |
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DaveKamp ![]() Orange Level Access ![]() ![]() Joined: 12 Apr 2010 Location: LeClaire, Ia Points: 5973 |
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It IS a three-phase panel, but Black/Red/Blue + White in USA is a traditional standard for 208/125Y service (aka 208v 4-wire). In 208/125Y, There is no 'wild' phase. There's three hots at 120 degree intervals, and one neutral in the center. From corner to corner, it measures 208. From centerpoint to any corner is 125v. The term 'high leg' or 'wild' phase is used to identify a corner-grounded delta service... which you might find in some older industrial or commercial buildings, but most places, where corner-grounded delta service is found, usually gets changed out rather quickly. Not to say it's not still found in places, but most electrical utilities want to get them pulled, as they can become a source of very complex and often dangerous problems when stuff fails.
Edited by DaveKamp - 19 Jul 2023 at 9:28pm |
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Ten Amendments, Ten Commandments, and one Golden Rule solve most every problem. Citrus hand-cleaner with Pumice does the rest.
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Coke-in-MN ![]() Orange Level Access ![]() Joined: 12 Sep 2009 Location: Afton MN Points: 41870 |
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The fact one would have a exact load on both legs is the one thing but the idea each is fed from a different leg of transformer means they would balance and the neutral would carry 0 .
I have a 200 A single phase panel but it is 400 A of available power as each leg is 200 A Now granted I did the wiring on my house in 1970 and things have changed . 3 - #2-0 wires used to top of mast , and there the power company spliced onto them with what looks like #6 wires from transformer . Other house has a 60 A circuit / 2 #6 wires to mast and a reduced neutral of about #10 wire , but a ground rod driven below the sequence box and wire from neutral attached . That house was built around 1952 |
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Faith isn't a jump in the dark. It is a walk in the light. Faith is not guessing; it is knowing something.
"Challenges are what make life interesting; overcoming them is what makes life meaningful." |
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steve(ill) ![]() Orange Level Access ![]() ![]() Joined: 11 Sep 2009 Location: illinois Points: 85973 |
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Power Company does NOT have to follow the Electric Code... and MOST of their wires are OUTSIDE in the Atmosphere and Air COOLED.... Yea, the get warm or HOT, but no chance of fire... nothing up there to burn.
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Like them all, but love the "B"s.
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jaybmiller ![]() Orange Level Access ![]() Joined: 12 Sep 2009 Location: Greensville,Ont Points: 24401 |
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found this... shows and tells how they're done. it saves a lot of wire,quicker to install ,so cheaper. here in Canada the new code rules require 20Amp 'T' style receptacles in the kitchen,with/without GFCI is close/not so close to the sink. typical of the guv, turn something simple, into a complicated MESS (lookup arcfault breakers....)
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3 D-14s,A-C forklift, B-112
Kubota BX23S lil' TOOT( The Other Orange Tractor) Never burn your bridges, unless you can walk on water |
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