Nominal VOltage -- step 2.5 110.4 and T110.4

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fmtjfw

Senior Member
Section/Paragraph: 110.4 Voltages.[NEW]Table

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110.4 Voltages.
Throughout this Code, the voltage considered shall be that at which the circuit operates.
The voltage rating of electrical equipment shall not be less than the nominal voltage of a circuit to which it is connected. All voltages specified in this Code are nominal voltages unless explicitly prefixed with actual. Three systems of voltages are used as described in Table 110.4 Voltages. Voltages listed in a single row are meant to be used in describing the same circuit.

Table 110.4 Voltages (60 Hz)

System or Nominal

Device
Rating

Motors

Country

???



Chile*

110



Belize*, British Virgin Islands*, Columbia*, Guam*, US Virgin Islands*, Venezuela*

110/220


Belize*
120 125 115 American Samoa*, Bahamas#, Canada#, Costa Rica*, Ecuador*, Panama*, Puerto Rico*, USA*
120/240 125/250 115/230 American Samoa*, Canada#, USA*
120/240 3-phase125/250115/230American Samoa*, USA*
120/208 Y 125 115 American Samoa*, Bahamas#, Bermuda, Canada#, Puerto Rico*, USA*
120/208 Y(V) 2-Phase 125 115 American Samoa*, USA*
127 Mexico*
190/380 Y 200 Belize*, British Virgin Islands*, Guam*, US Virgin Islands*
208 3-Phase 200 Ecuador*
220 Peru*, Philippines*,
220 3-Phase Mexico*, Peru*
220/380 Y Philippines*
240 250 230 USA*
240 3-Phase 250 230 Canada#, Costa Rico*, Panama*, USA*
240 3-Phase Delta 250 230 American Samoa*, USA*
277/480 Y 250 230 American Samoa*, Canada#, USA*
347 250 230 Canada#, USA*
347/600 Y 250 230 Canada#, USA*
480 3-Phase 460 Canada#, Mexico*, USA*
600 575 Canada#, USA*
2400/4160 2300 USA*
4000 USA*
4600 USA*
6600 USA*

* uses the NEC
# uses the Canadian Electrical Code


Substantiation

General

NEC 2014 contains 317 sentences containing nominal. It contains 2744 sentences containing volts, voltage, or V. It is clear that the use of (or absence) nominal modifying voltage references follows no particular pattern. Having nominal appear and not appear with voltage references when nominal is the intention adds confusion and is in conflict with NEC_StyleManual_2011.pdf:

"3.3.5 Parallel Construction. Parallel construction means stating similar requirements in similar ways for greater consistency. This helps makes the NEC clear for users. Lack of consistency often creates confusion, causing users to ask: Does this difference in wording represent a different requirement? Or is it simply two different ways of trying to say the same thing?"

I suspect that nearly all, if not all, voltages are nominal voltages. It would be simpler to indicate that all voltages are nominal unless denoted actual and remove nominal from the text.

Specific

This submission emphasizes that nominal applies unless actual is specified, and adds a Table 110.4 Voltages. to correlate the voltages (nominal, device rating, and motor) that are equivalent. The table need some or all of the blank spaces filled in by someone to whom the expensive standards are available. The Country column may be deleted and "odd" voltages removed.

Several voltage systems are used in this Code are based on the ANSI-C84 standard, the NEMA device rating voltages, and motor ratings. It is appropriate to indicate that 115V, 120V and 125V and other pairings denote the same "nominal" circuit voltage.


Coordination



Inserted Deleted
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
It appears to me that the table introduces no requirements into the code at all, and thus at best should be relegated to the status of a FPN.

I do not see how this proposed change serves any useful purpose.
 

fmtjfw

Senior Member
It appears to me that the table introduces no requirements into the code at all, and thus at best should be relegated to the status of a FPN.

I do not see how this proposed change serves any useful purpose.

It indicates how to interpret voltages found in the code:
1) Any voltage specified just as a voltage means a nominal voltage -- 250V is actually a range of voltages surrounding 250
2) 250, 240, 230 mean the same nominal voltage
3) Any voltage written as actual voltage such as "not greater than 132 actual volts" means a measurable voltage less than or equal 132.

Prior to these changes it is not clear that a 230 volt motor is appropriate for a 240 volt circuit and requires a 250 volt plug.
 
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