Calculation

[Ingenieur]

I don't have them, and I don't have the standard. That table was a graphic on the page linked.

Perhaps those are references to Notes A and B to earlier graphic??? See linked page.

thanks

 

[mivey]

could you post the notes and Range A and B definitions?

Here ya go:

NOTES-
( a) Three-phase three-wire systems are systems in which only the three-phase conductors are carried
out from the source for connection of loads. The source may be derived from any type of three phase
transformer connection, grounded or ungrounded. Three-phase four-wire systems are
systems in which a grounded neutral conductor is also carried out from the source for connection of
loads. Four-wire systems in table 1 are designated by the phase-to-phase voltage, followed by the
letter Y (except for the 240/120-volt delta system), a slant line, and the phase-to-neutral voltage.
Single-phase services and loads may be supplied from either single-phase or three-phase systems.
The principal transformer connections that are used to supply single-phase and three-phase systems
are illustrated in Annex A.
(b) The voltage ranges in this table are illustrated in Annex B.

5 Explanation of voltage ranges
For any specific nominal system voltage, the voltages actually existing at various points at various times
on any power system, or on any group of systems, or in the industry as a whole, usually will be distributed
within the maximum and minimum voltages shown in table 1 . The design and operation of power
systems and the design of equipment to be supplied from such systems should be coordinated with
respect to these voltages so that the equipment will perform satisfactorily in conformance with product
standards throughout the range of actual utilization voltages that will be encountered on the system. To
further this objective, this standard establishes, for each nominal system voltage, two ranges for service
voltage and utilization voltage variations, designated as Range A and Range B, the limits of which are
given in table 1. These limits shall apply to sustained voltage levels and not to momentary voltage
excursions that may result from such causes as switching operations, motor starting currents, and the
like .

5.1 Application of voltage ranges

5.1.1 Range A-service voltage
Electric supply systems shall be so designed and operated that most service voltages will be within the
limits specified for Range A. The occurrence of service voltages outside of these limits should be
infrequent.

5.1.2 Range A-utilization voltage
User systems shall be so designed and operated that with service voltages within Range A limits, most
utilization voltages will be within the limits specified for this range.
Utilization equipment shall be designed and rated to give fully satisfactory performance throughout this
range.

5.1.3 Range B-service and utilization voltages
Range B includes voltages above and below Range A limits that necessarily result from practical design
and operating conditions on supply or user systems, or both. Although such conditions are a part of
practical operations, they shall be limited in extent, frequency, and duration. When they occur, corrective
measures shall be undertaken within a reasonable time to improve voltages to meet Range A
requirements.

Insofar as practicable, utilization equipment shall be designed to give acceptable performance in the
extremes of the range of utilization voltages, although not necessarily as good performance as in Range
A.

5.1.4 Outside Range B-service and utilization voltages
It should be recognized that because of conditions beyond the control of the supplier or user, or both,
there will be infrequent and limited periods when sustained voltages outside Range B limits will occur.
Utilization equipment may not operate satisfactorily under these conditions, and protective devices may
operate to protect the equipment.

When voltages occur outside the limits of Range B, prompt corrective action shall be taken. The urgency
for such action will depend upon many factors, such as the location and nature of the load or circuits
involved, and the magnitude and duration of the deviation beyond Range B limits.

 

[Sahib]

In my opinion that section only permits the designer to specify the voltage, where non-standard voltage systems are being used.

You are also correct. But the intent of the code is that the designer use at least minimum size of the conductor for branch/feeder circuits. In this respect, use of ANSI utilisation voltage by a designer results in a wire size larger than minimum size prescribed by the code and so allowed by the code.

 

[Smart $]

You are also correct. But the intent of the code is that the designer use at least minimum size of the conductor for branch/feeder circuits. In this respect, use of ANSI utilisation voltage by a designer results in a wire size larger than minimum size prescribed by the code and so allowed by the code.

At best (from your point of view), I'll agree you can use 115V where the nominal voltage is in fact 115V.

:slaphead:

 

[Sahib]

Smart$: That is my way of interpretation of the code (as in post#23)