Circuit breaker supplying direction ?

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peter_egypt

Member
Location
cairo,Egypt
Hello Guys ,
thank you for this helpful Forum

my question is related to Circuit breakers position ,and its supplying direction

i mean it is marked as always input or supply side to CB from upper terminals and it connecting to load side from lower terminals
according to NEC ,and according to CB performance
CAN we supply the circuit breaker from the lower terminals ?

2- what is the preferable supplying the main CB or the enclosure from upper and other branch breakers be lower it ,i mean cable entrance the enclosure from the top or the bottom of the enclosure ?
 

jumper

Senior Member
Unless a breaker is marked line and load, it can be fed from either terminals. Most typical is line at the top and load at the bottom.

Another example example is a main lug only panel that is back fed from a breaker. Power is fed from into the lug terminals and fed to the bus from the stab connection.

Whether cables and conductors enter an enclosure/cabinet on top or bottom is a matter of choice, design and ease of install.
 

Smart $

Esteemed Member
Location
Ohio
No matter what orientation a breaker is installed, it is preferred the line be connected to the end towards which the handle points when in the closed (ON) position. I say preferred because it is not a hard rule. You will find some bottom-feed panels with MCB at the bottom, the line terminals are at the bottom of the MCB and the handle must be flipped up to close the breaker. Some manufacturers avoid this discrepancy with the preferred status by mounting the MCB sideways.
 

GeorgeB

ElectroHydraulics engineer (retired)
Location
Greenville SC
Occupation
Retired
No matter what orientation a breaker is installed, it is preferred the line be connected to the end towards which the handle points when in the closed (ON) position.

Not disagreeing ... indeed, I agree .... but preferred by WHOM with "authority" to influence?
 

jumper

Senior Member
so according to code All of these cases is allowed ?


View attachment 18583



View attachment 18584

View attachment 18585

Is that third breaker upside down?

If so, it cannot be installed like that.

240.81 Indicating. Circuit breakers shall clearly indicate
whether they are in the open “off” or closed “on” position.
Where circuit breaker handles are operated vertically
rather than rotationally or horizontally, the “up” position of
the handle shall be the “on” position.
 

Smart $

Esteemed Member
Location
Ohio
Is that third breaker upside down?

If so, it cannot be installed like that.

240.81 Indicating. Circuit breakers shall clearly indicate
whether they are in the open “off” or closed “on” position.
Where circuit breaker handles are operated vertically
rather than rotationally or horizontally, the “up” position of
the handle shall be the “on” position.
Good catch.
 

peter_egypt

Member
Location
cairo,Egypt
Is that third breaker upside down?

If so, it cannot be installed like that.

240.81 Indicating. Circuit breakers shall clearly indicate
whether they are in the open “off” or closed “on” position.
Where circuit breaker handles are operated vertically
rather than rotationally or horizontally, the “up” position of
the handle shall be the “on” position.
thank you i was looking for this
 

peter_egypt

Member
Location
cairo,Egypt
thank you so much for replies
so according the code it is a safety rule
but regardless the code
technical , according to circuit breaker mechanism or operation its performance don't affected by connecting supplying cable on upper or lower terminals
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
thank you so much for replies
so according the code it is a safety rule
but regardless the code
technical , according to circuit breaker mechanism or operation its performance don't affected by connecting supplying cable on upper or lower terminals

Yes, but some breakers, such as AFCI or GFCI or some electronic trip units which contain circuitry powered from the circuit they protect, or DC breakers with a preferred current direction, will be marked with Line and Load terminals for a good reason.
And under the NEC, even if there is no theoretical justification for it, connecting the source to a marked Load side is a code violation.
 

peter_egypt

Member
Location
cairo,Egypt
Yes, but some breakers, such as AFCI or GFCI or some electronic trip units which contain circuitry powered from the circuit they protect, or DC breakers with a preferred current direction, will be marked with Line and Load terminals for a good reason.
And under the NEC, even if there is no theoretical justification for it, connecting the source to a marked Load side is a code violation.

thank you Golddigger for the clarification
 
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