# Which is correct, A or B **URL:** \ **Category:** Electrical Inspections\ **Created:** [March 19, 2014, 4:55pm UTC](https://forum.nachi.org/t/which-is-correct-a-or-b/85392 "2014-03-19T16:55:56Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![kshepard](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/kshepard/32/59504_2.png) [@kshepard](https://forum.nachi.org/u/kshepard)\ **Post date:** [March 19, 2014, 4:55pm UTC](https://forum.nachi.org/t/which-is-correct-a-or-b/85392/1 "2014-03-19T16:55:56Z")
The numbers in B have been changed to reflect Mexican voltages, so you can ignore the slightly higher voltage. Which image reflects the correct condition? Why? ![136.jpg](https://global.discourse-cdn.com/internachi/original/3X/8/5/85a7f339b9624070b56c3b514582f2653aa4fb78.jpeg) ![136_Multiwire_branch_circuit copy 3.jpg](https://global.discourse-cdn.com/internachi/original/3X/8/3/83ce933b6deecbe4b73669497c5ee2265695378e.jpeg) ---
**Author:** ![rcooke](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/rcooke/32/57038_2.png) [@rcooke](https://forum.nachi.org/u/rcooke)\ **Post date:** [March 19, 2014, 5:04pm UTC](https://forum.nachi.org/t/which-is-correct-a-or-b/85392/2 "2014-03-19T17:04:11Z")
I emailed you the answer Roy ---
**Author:** ![jjimenez](https://avatars.discourse-cdn.com/v4/letter/j/a87d85/32.png) [@jjimenez](https://forum.nachi.org/u/jjimenez)\ **Post date:** [March 19, 2014, 5:18pm UTC](https://forum.nachi.org/t/which-is-correct-a-or-b/85392/3 "2014-03-19T17:18:06Z")
A I am hurting my head trying to answer why ---
**Author:** ![kshepard](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/kshepard/32/59504_2.png) [@kshepard](https://forum.nachi.org/u/kshepard)\ **Post date:** [March 19, 2014, 5:20pm UTC](https://forum.nachi.org/t/which-is-correct-a-or-b/85392/4 "2014-03-19T17:20:46Z")
> [@jjimenez](#): > > A > > L1 and L2 have opposite polarity. What do you mean “opposite polarity”? ---
**Author:** ![jjimenez](https://avatars.discourse-cdn.com/v4/letter/j/a87d85/32.png) [@jjimenez](https://forum.nachi.org/u/jjimenez)\ **Post date:** [March 19, 2014, 5:30pm UTC](https://forum.nachi.org/t/which-is-correct-a-or-b/85392/5 "2014-03-19T17:30:27Z")
> [@kshepard](#): > > What do you mean “opposite polarity”? Sorry I confused myself. It’s definitely A. I think its because those breakers on the bottom are the same Line. ---
**Author:** ![cfoley1](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/cfoley1/32/2081_2.png) [@cfoley1](https://forum.nachi.org/u/cfoley1)\ **Post date:** [March 19, 2014, 5:32pm UTC](https://forum.nachi.org/t/which-is-correct-a-or-b/85392/6 "2014-03-19T17:32:36Z")
A. 240 v. Circuit should read 240 between the two Hot conductors and 120 between hot and ground or neutral ---
**Author:** ![jjimenez](https://avatars.discourse-cdn.com/v4/letter/j/a87d85/32.png) [@jjimenez](https://forum.nachi.org/u/jjimenez)\ **Post date:** [March 19, 2014, 5:34pm UTC](https://forum.nachi.org/t/which-is-correct-a-or-b/85392/7 "2014-03-19T17:34:59Z")
Voltage is the movement between two different potentials. You will get 0 on the bottom situation because its the same line, and thus the same potential. B must be wrong ---
**Author:** ![cfoley1](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/cfoley1/32/2081_2.png) [@cfoley1](https://forum.nachi.org/u/cfoley1)\ **Post date:** [March 19, 2014, 5:36pm UTC](https://forum.nachi.org/t/which-is-correct-a-or-b/85392/8 "2014-03-19T17:36:57Z")
> [@cfoley1](#): > > A. 240 v. Circuit should read 240 between the two Hot conductors and 120 between hot and ground or neutral Forgot the 3rd part of diagram Bottom has zero cause on same phase ---
**Author:** ![cevans](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/cevans/32/244194_2.png) [@cevans](https://forum.nachi.org/u/cevans)\ **Post date:** [March 20, 2014, 12:20am UTC](https://forum.nachi.org/t/which-is-correct-a-or-b/85392/9 "2014-03-20T00:20:20Z")
A Looking at the voltage meter B in both images. What will be the relationship of the amperage carried by the grounded conductor compared to the amperage of the ungrounded conductor pair in: Scenario A? vs. scenario B? ---
**Author:** ![btoye](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/btoye/32/58400_2.png) [@btoye](https://forum.nachi.org/u/btoye)\ **Post date:** [March 20, 2014, 1:48am UTC](https://forum.nachi.org/t/which-is-correct-a-or-b/85392/10 "2014-03-20T01:48:46Z")
I think they are both wrong. A-A should be 240/254V, B-B should be 254V Edit: I’m wrong. Diagram A is correct ---
**Author:** ![mgratton](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/mgratton/32/58251_2.png) [@mgratton](https://forum.nachi.org/u/mgratton)\ **Post date:** [March 20, 2014, 2:40am UTC](https://forum.nachi.org/t/which-is-correct-a-or-b/85392/11 "2014-03-20T02:40:15Z")
A is right. It display 120V from phase 1 & 120V from phase 2. Both phase amount to 240V. ---
**Author:** ![rmayo](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/rmayo/32/59218_2.png) [@rmayo](https://forum.nachi.org/u/rmayo)\ **Post date:** [March 20, 2014, 12:39pm UTC](https://forum.nachi.org/t/which-is-correct-a-or-b/85392/12 "2014-03-20T12:39:04Z")
I think both are wrong. A in the first picture should be 240 volts and B in the second picture should be 254 volts. ---
**Author:** ![jjimenez](https://avatars.discourse-cdn.com/v4/letter/j/a87d85/32.png) [@jjimenez](https://forum.nachi.org/u/jjimenez)\ **Post date:** [March 20, 2014, 12:55pm UTC](https://forum.nachi.org/t/which-is-correct-a-or-b/85392/13 "2014-03-20T12:55:11Z")
> [@rmayo](#): > > I think both are wrong. A in the first picture should be 240 volts and B in the second picture should be 254 volts. A in the first is correct at 0. Those breakers are the same line. Voltage is the movement of electrons between different potentials. Since both breakers are on the same line, there is no difference in potential. ---
**Author:** ![cevans](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/cevans/32/244194_2.png) [@cevans](https://forum.nachi.org/u/cevans)\ **Post date:** [March 20, 2014, 1:04pm UTC](https://forum.nachi.org/t/which-is-correct-a-or-b/85392/14 "2014-03-20T13:04:05Z")
> [@cevans](#): > > A > > Looking at the voltage meter B in both images. What will be the relationship of the amperage carried by the grounded conductor compared to the amperage of the ungrounded conductor pair in: Scenario A? vs. scenario B? Nobody wants to tackle this? It’s important to know. ---
**Author:** ![cbottger](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/cbottger/32/206_2.png) [@cbottger](https://forum.nachi.org/u/cbottger)\ **Post date:** [March 20, 2014, 2:26pm UTC](https://forum.nachi.org/t/which-is-correct-a-or-b/85392/15 "2014-03-20T14:26:14Z")
I am going with B I like to be different!!!😉 ---
**Author:** ![cbottger](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/cbottger/32/206_2.png) [@cbottger](https://forum.nachi.org/u/cbottger)\ **Post date:** [March 20, 2014, 2:30pm UTC](https://forum.nachi.org/t/which-is-correct-a-or-b/85392/16 "2014-03-20T14:30:21Z")
> [@rmayo](#): > > I think both are wrong. A in the first picture should be 240 volts and B in the second picture should be 254 volts. B in the second image should be 0 those two breakers should be on the same leg if they are on opposite legs you would be correct it would read 240 ---
**Author:** ![kwood](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/kwood/32/473_2.png) [@kwood](https://forum.nachi.org/u/kwood)\ **Post date:** [March 20, 2014, 4:50pm UTC](https://forum.nachi.org/t/which-is-correct-a-or-b/85392/17 "2014-03-20T16:50:53Z")
It took 16 posts for this. ---
**Author:** ![cbottger](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/cbottger/32/206_2.png) [@cbottger](https://forum.nachi.org/u/cbottger)\ **Post date:** [March 20, 2014, 5:06pm UTC](https://forum.nachi.org/t/which-is-correct-a-or-b/85392/18 "2014-03-20T17:06:56Z")
> [@kwood](#): > > It took 16 posts for this. Well who is correct A or B:roll: ---
**Author:** ![kshepard](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/kshepard/32/59504_2.png) [@kshepard](https://forum.nachi.org/u/kshepard)\ **Post date:** [March 20, 2014, 5:42pm UTC](https://forum.nachi.org/t/which-is-correct-a-or-b/85392/19 "2014-03-20T17:42:05Z")
A is is correct. In B I tweaked the numbers. Key to understanding this is that there will be 240v potential difference between ungrounded conductors connected to separate supply bus bars. There will be 0 voltage difference between conductors connected to the same bus bar. The two bottom breakers align horizontally and are connected to the same bus bar. ---
**Author:** ![Jim\_Port](https://avatars.discourse-cdn.com/v4/letter/j/bc8723/32.png) [@Jim\_Port](https://forum.nachi.org/u/Jim_Port)\ **Post date:** [March 20, 2014, 6:18pm UTC](https://forum.nachi.org/t/which-is-correct-a-or-b/85392/20 "2014-03-20T18:18:54Z")
> [@cevans](#): > > A > > Looking at the voltage meter B in both images. What will be the relationship of the amperage carried by the grounded conductor compared to the amperage of the ungrounded conductor pair in: Scenario A? vs. scenario B? Both A and B show a properly wired MWBC with a shared neutral. The neutral current will be the difference between A and B. [Next page](https://forum.nachi.org/t/which-is-correct-a-or-b/85392.md?page=2)