Voltage Drop

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I have an issue with what is the allowable Voltage drop for a branch circuit. Is it 3% or 5 %. FPN No. 4 in article 210.19 states both.
 

raider1

Senior Member
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Location
Logan, Utah
The FPN says that a 3% drop from the final branch circuit overcurrent device to the farthest outlet is recommended, and a 5% voltage drop for a combined feeder and branch circuit to the farthest outlet.

So for just the branch circuit it is 3%.

Chris
 

480sparky

Senior Member
Location
Iowegia
I think it basically states no more then 3% vd on a given branch circuit, and if it's fed from a panel that is supplied by a feeder, the total (feeder and branch) should be no more than 5% vd (from the start of the feeder to the end of the branch).
 
I have an issue with what is the allowable Voltage drop for a branch circuit. Is it 3% or 5 %. FPN No. 4 in article 210.19 states both.

To assure proper and efficient operation of electrical equipment it is recommended that the distribution(2%) - Delivery to distribution point - and branch circuit(3%) - distribution point to use - voltage drops do not exceed 5%. That limit with the combined limitation on Utilities delivery permissive window + and -, should result in the practical limitations of +/-10% maximum voltage extremities.
 
Since this thread is too short, let me add another question.

What if there is no "feeder"?
What if your branch circuit comes from the main disconnect?

What if there are seven level of subdistribution panels?

When you keep the objective in mind all these questions are secondary. Do whatever is necessary to accomplish the objective, eg. deliver acceptable voltage to the user end under all conditions.
 

raider1

Senior Member
Staff member
Location
Logan, Utah
Since this thread is too short, let me add another question.

What if there is no "feeder"?
What if your branch circuit comes from the main disconnect?

Remember that a FPN is not enforceable as code and is only meant for informational purposes.

Therefore I would say that I would recommend that the branch circuit in you question would function best if you kept the voltage drop to less than 3%.;):)

Chris
 

charlie b

Moderator
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Location
Lockport, IL
Occupation
Retired Electrical Engineer
The fundamental message is that stuff works goodest ;) :D if its gots 95% of its rated voltage. Nothing else matters.
 

Volta

Senior Member
Location
Columbus, Ohio
. . . What if there is no "feeder"?
What if your branch circuit comes from the main disconnect?

If it literally did that, then there would be no feeder, like a service drop to a small billboard circuit, for instance. Very rare.

Any other time, there will be a feeder. If there is a panelboard with a main breaker as the service disconnect, and the panel feeds branch-circuit breakers, the panel busbars are the feeder conductors.
 
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