Nominal Voltage

[mwm1752]

Can any of the following: 12volts -- 24 volts -- under 30 volts -- under 50 volts -- be considered a nominal voltage?

 

[david]

Can any of the following: 12volts -- 24 volts -- under 30 volts -- under 50 volts -- be considered a nominal voltage?

We commonly say a 12 volt system or a 24 volt system

I would say 12 volts or 24 volts would be considered the nominal voltage.

 

[K8MHZ]

'Nominal' just means the name of the system. It can be just about anything.

In a car, the batteries are 12.6 volts, they charge at 14.5 volts and drop to around 11 while cranking the engine. Instead of calling this an 11-14.5 volt system, we name it a 12 volt (nominal) system.

I haven't seen any nominal figure include 'less than' or 'under'. It's always been a single fixed voltage.

 

[GoldDigger]

But a 48V nominal battery system may fit the under 50V limit even though the actual voltage may go over 56V much if the time.

 

[mwm1752]

Part of the reason for this question is related to another post on conductor identification == the NEC requires black & red for circuits under 50 volts and also if you have more than a single nominal voltage in a structure they are to be of different identification colors == does that mean you are not able to use black or red as 120v branch circuit colors if you have circuits under 50 volts in the structure?

 

[GoldDigger]

The systems are not required to be different colors. Other methods of marking are allowed, color is just the simplest. Especially at intermediate points between terminations.

 

[mwm1752]

The systems are not required to be different colors. Other methods of marking are allowed, color is just the simplest. Especially at intermediate points between terminations.

Means of Identification. The means of identification shall be permitted to be by separate color coding, marking tape, tagging, or other approved means.
you are correct, tagging does not generally include color -- 210.5(2) a & b certainly describe stranded tray cable,

 

[Carultch]

Can any of the following: 12volts -- 24 volts -- under 30 volts -- under 50 volts -- be considered a nominal voltage?

Nominal means that it is named based on that number.

For AC, it is usually the root-mean-square voltage that will generate the DC equivalent power, and the center of tolerances for voltage variation. So a 120V nominal AC voltage will spike instantaneously at +170V and -170V, but on average delivers the equivalent power to a linear resistor as if it were a continuous 120V DC source.
For DC, it is usually a rounded voltage, and actual voltage may be a few volts higher or lower.

In the case of a PV system, it is the upper limit on the maximum open circuit voltage that you design to meet. Usually 600V or 1000V, even though a 600Vdc nominal PV system typically operates closer to 400V, and a 1000Vdc nominal PV system usually operates around 800V.