Nec 90.5(c)

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kacper

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In the recent days I experience an argument with my Building official who claims that wire sizing & NEC can’t enforce OCPD caused by voltage drops. His quote:
"Due to it being a fine print note voltage drops are not enforceable"
My answer to his statement was:
"Boss,
If a contractor to size and run wires based only on allowable ampacities of conductors without considering voltage drops required by table 8 in Chapter 9 or 310.15(B)(2)(a), a fire will inevitably occur. For example: An entire parking lot of lights of a shopping center could be run on #14 or #12 AWG wires, and it would instantly cause a fire.

The calculation assumes uncoated copper or aluminum conductors operating at the temperature selected and is based on the ac/dc resistance or impedance from NEC 2005 Tables 8 and 9 for stranded conductors operating on a DC or AC 60Hz system. The ampacity of each conductor size in the dropdown menu below is based on NEC 2005 Table 310.16 for 60C insulated conductors rated 0 through 2000 volts with not more than three current carrying conductors in raceway, cable or earth with an ambient of 30C (86F).

Voltage drop for ac systems should total no more than 5% under full load conditions. Drops may be significantly larger during surge or motor starting conditions -- sometimes in the 15% to 25% range if other devices on the system can withstand this momentary dip. Voltage drop for DC systems should be designed as low as possible or less than 2%.

Section 90.5 (C) page 6 of the NEC states…”Footnotes to tables, although also in fine print, are NOT explanatory material unless they are identified by the abbreviation FPN. Table footnotes are part of the table and are necessary for proper use of the tables.”

BO's response:
So you are saying that the electrical code requires conformance to the voltage drop FPN?

Please help me out with suggestion or explanation that he will understand.
Thank you
Adam K
 
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kacper said:
Please help me out with suggestion or explanation that he will understand.
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I can offer only one, and you won’t like it. My explanation would be, “You are right, and I am wrong.”
kacper said:
If a contractor to size and run wires based only on allowable ampacities of conductors without considering voltage drops required by table 8 in Chapter 9 or 310.15(B)(2)(a), a fire will inevitably occur. For example: An entire parking lot of lights of a shopping center could be run on #14 or #12 AWG wires, and it would instantly cause a fire.
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It the entire parking lot of lights were run on #14, then I would expect the total load (all light bulbs added together) to have been less than 12 amps. Otherwise, there would be a code violation related to exceeding the ampacity of the conductor. How are you figuring that that load will cause a fire?

Welcome to the forum.
 
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Adam,

Voltage Drop is not enforceable by referencing the NEC. The FPN's provided in the NEC are only guidelines. However, I see you are a Florida inspector. That being the case, you need not the NEC to enforce voltage drop. Chapter 13 of the Florida Building Code provides voltage drop requirements. See Section 13-413 of the 2004 FBC. VD is primarily a energy conservation concern, rather than a safety concern.

On another note, please be careful when mentioning names or identifying persons and places within your posts. While I don't feel you have said anything derogatory towards your BO, he may be a little embarrassed by the way you presented your discussion with him. There are many members on this Forum which live and work in Florida and know each other. As a Building Code Administrator and Secretary of the Florida Gulf Coast Chapter of BOAF, I personally know and am friends with many building officials, inspectors, and plans examiners across the state. Please take this into consideration.


Welcome to the Forum !!!
 
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I?m having problems with your original citation. This is what 90.5 (C) actually says.

Explanatory Material. Explanatory material, such as references to other standards, references to related sections of this Code, or information related to a Code rule, is included in this Code in the form of fine print notes (FPNs). Fine print notes are informational only and are not enforceable as requirements of this Code.

Brackets containing section references to another NFPA document are for informational purposes only and are provided as a guide to indicate the source of the extracted text. These bracketed references immediately follow the extracted text.
FPN: The format and language used in this Code follows guidelines established by NFPA and published in the NEC Style Manual. Copies of this manual can be obtained from NFPA.
​
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You are citing the Page 6 of the NEC Handbook; but in fact, every authentic statement about voltage drop is also an authentic FPN
 
In a more stealth mode, you could see if the equipment at the eol will actually work if the voltage drop is not considered. 110.3(B) per manufacturer's instruction...
 
Rockyd said:
In a more stealth mode, you could see if the equipment at the eol will actually work if the voltage drop is not considered. 110.3(B) per manufacturer's instruction...
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How would 110.3(B) fit in to this discussion?

110.3(B) must be the most overused and abused code section in the entire NEC.
 
Thanks Bryan, new "secret weapon" to put in the bottom of the bag of tricks (90.2), but would have liked to have used it for defense in the past....those times when you look at something, you know it's bad, but they are determined to build a monument to ugliness, that will will be taken down later.
 
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.

I believe that if voltage drop is an issue then you could argue 110.4 because the voltage will not be at the "normal" voltage of the circuit, it will be less.
 
acrwc10 said:
I believe that if voltage drop is an issue then you could argue 110.4 because the voltage will not be at the "normal" voltage of the circuit, it will be less.
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I would argue, in return, that 110.4 is talking about the rating of the equipment, not the value of voltage that the equipment will see at any given point in time.
 
charlie b said:

I would argue, in return, that 110.4 is talking about the rating of the equipment, not the value of voltage that the equipment will see at any given point in time.
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If you don't connect anything to the circuit why would it matter what the voltage is ? The circuit and the equipment need to be compatible, if one is wrong the whole thing is wrong. If you can get equipment that will run properly at the "dropped voltage" would it be a problem ?
 
I was taking issue with the attempt to use 110.4 as the means of enforcing a voltage drop rule.

If I have a power system with a nominal voltage rating of 240 volts, and if I connect a range that has a voltage rating of 250 volts, I will have complied with 110.4. That remains true, even if I use a very long wire, and if the voltage at the range is more than 5% below its rated voltage.

There is a difference here between having a piece of equipment operating efficiently, which the NEC does not care about, and enforcing a Fine Print Note, which the NEC does not allow.
 
I would like to point out that if either 110.3 or 110.4 required the full voltage of the voltage system indicated on the equipments label that would mean we could never use a dimmer or VSD/VFD.
 
iwire said:
I would like to point out that if either 110.3 or 110.4 required the full voltage of the voltage system indicated on the equipments label that would mean we could never use a dimmer or VSD/VFD.
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and if I am allow to add a lot of people wouldn't be able to use anything.

My brother only has 110 volts on one leg at his house that drops even lower durning peak times and no the power company will not address the issue
 
charlie b said:
I was taking issue with the attempt to use 110.4 as the means of enforcing a voltage drop rule.

If I have a power system with a nominal voltage rating of 240 volts, and if I connect a range that has a voltage rating of 250 volts, I will have complied with 110.4. That remains true, even if I use a very long wire, and if the voltage at the range is more than 5% below its rated voltage.

There is a difference here between having a piece of equipment operating efficiently, which the NEC does not care about, and enforcing a Fine Print Note, which the NEC does not allow.
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You are right I was thinking in reverse on this, when I reread the section I realized I am mistaken, the code does say"The voltage rating of electrical equipment shall not be less than the nominal voltage of a circuit to which it is connected."

bphgravity said:
Adam,

Voltage Drop is not enforceable by referencing the NEC. The FPN's provided in the NEC are only guidelines. However, I see you are a Florida inspector. That being the case, you need not the NEC to enforce voltage drop. Chapter 13 of the Florida Building Code provides voltage drop requirements. See Section 13-413 of the 2004 FBC. VD is primarily a energy conservation concern, rather than a safety concern.
QUOTE]

I don't live in FLA but I am interested in what the code says if you don't mind posting that section I would appreciate it. Thanks.
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2004 FBC with 2005, 2006, and 2007 Supplements:

13-413.1 Prescriptive requirements.

13-413.1.ABC-Basic Prescriptive requirements for Methods A, B and C.

13-413.1.ABC.1 Voltage Drop.

13-413.1.ABC.1.1 Feeders. Feeder conductors shall be sized for a maximum voltage drop of 2 percent at design load.

13-413.1.ABC.1.2 Branch circuits. Branch circuit conductors shall be sized for a maximum voltage drop of 3 percent at design load.
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Originally Posted by Rockyd
In a more stealth mode, you could see if the equipment at the eol will actually work if the voltage drop is not considered. 110.3(B) per manufacturer's instruction...

How would 110.3(B) fit in to this discussion?

110.3(B) must be the most overused and abused code section in the entire NEC.
Click to expand...

From the OP-

Voltage drop for ac systems should total no more than 5% under full load conditions. Drops may be significantly larger during surge or motor starting conditions -- sometimes in the 15% to 25% range if other devices on the system can withstand this momentary dip. Voltage drop for DC systems should be designed as low as possible or less than 2%.
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I know it's a stretch, but most gear out there is designed to operate plus or minus 10 percent. If the Voltage drop exceeds this, I would call the manufacturer to see if I can run their machinery on the voltage at the location it is supposed to be hooked up at. Even on Guam the voltage was within bounds....
 
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