Which part of this gets overloaded?
It's a 120V supply, regardless of source, with 120V loads?
What am I missing?
If I've got it wrong or drawn it wrongly, perhaps you could reciprocate with a drawing of what I should be looking at?
120V
- Thread starter resistance
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Which part of this gets overloaded?
It's a 120V supply, regardless of source, with 120V loads?
What am I missing?
If I've got it wrong or drawn it wrongly, perhaps you could reciprocate with a drawing of what I should be looking at?
T
T.M.Haja Sahib
Guest
Which part of this gets overloaded?
It's a 120V supply, regardless of source, with 120V loads?
What am I missing?
If I've got it wrong or drawn it wrongly, perhaps you could reciprocate with a drawing of what I should be looking at?
Sorry.My assistants have left a short while ago and so it is difficult for me to upload a diagram.
My suggestion is you please take a mirror image of your diagram,merge the 'B' lines into one and designate it as 'N' (i.e neutral).The 'A' designates phase wire from 120V source. Now you have got a pseudo MWBC.You can easily see the neutral will be overloaded in this circuit.......
- Location
- Massachusetts
So if you change the drawing entirely you can show the neutral as subject to overload.
Fascinating point.
Just another thread taken off track by TM. :roll:
- Location
- Massachusetts
By definition it is not an MWBC if supplied from the same phases, however I do understand what you are trying to say.
If the person installing it is unqualified and does not provide over current protection as required the neutral is subject to overload.
Single phase 120V circuit. Two wires. Thee are no B lines to be merged together.
How can that simple 120V circuit result in one of the two conductors being overloaded.
T
T.M.Haja Sahib
Guest
T
T.M.Haja Sahib
Guest
Greetings.:thumbsup:
Hendrix
Senior Member
- Location
- New England
My inlaws lived in NY on Long Island. Their electrical service was 120vac and was fed out of the basement of a house down the street where the meter was located.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
If the supply is a two lead source technically there is no neutral.
If the supply is a 3 lead 120/240m source and you are only using one lead plus neutral you still have same thing at this panel for all practical purposes of this discussion.
If this panel is supplied by a feeder there is no way to overload anything if proper ovefrcurrent protection is applied to the feeder.
If this panel is supplied by a service (which the OP says "non-service rated panel" so that would be a problem right there) you would need the grounded conductor to have the sum of the ampacity of the two ungrounded conductor ampacities to prevent overloading.
Have done this many times on farms where supplying some outbuilding with 120 volt only and limited loads like two circuits only.
Lets say we only have two 20 amp circuits - the grounded conductor needs to be at least 40 amps, the ungrounded conductors can be only 20 amps if running two of them otherwise 40 amps if running a single conductor.
If you are supplying a 100 amp panel with two 100 amp capacity ungrounded conductors you will need a 200 amp grounded conductor, in most cases you should also seriously consider making this 120/240 if there is any way possible.
Most of the time when this is done it is in places where the load is somewat minimal.
Cow
Senior Member
- Location
- Eastern Oregon
- Occupation
- Electrician
I've seen it done for some water trough heaters in large cattle feedlot. Triplex ran overhead to two circuit cans with individual breakers for each water trough heater. All 120v.
What's the problem?
kwired
Electron manager
- Location
- NE Nebraska
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- EC
- Location
- Tennessee NEC:2017
- Occupation
- Semi-Retired Electrician
As I recall, they were using 2-pole breakers. Hot on 1 pole and neutral on the other. If someone else worked in the panel and didn't know how it was set up they could easily be confused, especially if they tried to connect a 240V load. Also you would have to be careful to land the correct neutral with each hot on the 2-pole breaker. And you can't have white wires on the breakers without re-identifying them. In this case, re-identifying them would be wrong since they are not ungrounded conductors.
Speedskater
Senior Member
- Location
- Cleveland, Ohio
- Occupation
- retired broadcast, audio and industrial R&D engineering
Probably not what you are thinking about but see page 21.
Note that the neutral must handle twich the line current.
http://www.middleatlantic.com/power.htm
http://www.middleatlantic.com/pdf/PowerPaper.pdf
Note that the neutral must handle twich the line current.
http://www.middleatlantic.com/power.htm
http://www.middleatlantic.com/pdf/PowerPaper.pdf
- Location
- Illinois
- Occupation
- retired electrician
Assuming the feeder grounded and ungrounded conductors are the same size and assuming all of the branch circuits are two wire circuits there is no neutral loading issue.
Other than the possible issue of more than one conductor in the line side termination point in the panel I don't see any NEC issues with doing this.
- Location
- Illinois
- Occupation
- retired electrician
What says you can't have white wires on breakers that are switching the grounded conductor? They are still grounded conductors. There is at least one code section that requires the breaker to disconnect both the hot and neutral conductor and the whites are landed on that breaker.
resistance
Senior Member
- Location
- WA
[With the source being 120/240]Does that make sense to you—if a person intentionally runs a 2 wire feed with ground to intentionally serve a non service rated panel @ 120v only??? Goodness, I hope not!! Doesn’t it make since to run a 3 wire feed with ground? This seems to be unprofessional to me. Meaning: something a DIY’er would do! Or a cheap electrical contractor. Why would anyone deliberately bid a job this way!
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rcwilson
Senior Member
- Location
- Redmond, WA
A common application is distribution for a 120 Volt single phase UPS output. Hot, Neutral and Ground, with neutral bonded to ground in the UPS or the Bypass Transformer. (The UPS could be bought with a 120/240V output but it was supplied with a 120V output winding.)
The UPS output goes to a standard distribution panel, 120 V, single phase with a neutral bus, isolated ground bus and EGC bus. The two hot busses are jumpered together so any breaker postion supplies 120V.
The UPS output goes to a standard distribution panel, 120 V, single phase with a neutral bus, isolated ground bus and EGC bus. The two hot busses are jumpered together so any breaker postion supplies 120V.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
If load is limited as in the example both Cow and myself had with the drinking water tank heaters for livestock there is absolutely nothing wrong with it. Two wire feed instead of three (plus EGC of course) In feed yards there may be lot of length to the feed, yet a little voltage drop is rather insignificant so you don't worry about increasing conductor size much for that.
resistance
Senior Member
- Location
- WA
IC.
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texie
Senior Member
- Location
- Fort Collins, Colorado
- Occupation
- Electrician, Contractor, Inspector
Duh....what was I thinking? You're right, guess I didn't think that thru to well.
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