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I'm just curious - when the NEC talks about the magic 50v threshold for things like grounded vs floating systems, etc., do they mean 50v RMS, or 50v real-world-attainable? Eg., would a 48v battery bank fall under that 50v limit even though it could be almost 60v during the bulk charging phase, since it's a 48v nominal system? Or "48v" solar panels in series that have a VOC much higher than 48v?
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The 50v limit is what OSHA and the NEC lists as an acceptable voltage that "should not" be able to pass through the resistance of a normal body. That does not mean it can't if the conditions are in place to lower the bodies resistance and allow the flow of current to go through critical organs to ground.
Some of the "old timer" electricians use to touch live 120volt terminals to determine if they were energized or not. IMO they got lucky and did not complete a circuit through their body to ground which could have killed them.
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Ok cool, thanks! So I should read it as a literal voltage, not a nominal one. That's what I had assumed, but you know what happens when you assume...
(I'm planning a small 24v nominal setup, and my VOC shouldn't hit above 50v in the winter, but wanted to ask to satisfy my curiosity.)Comment
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Just remember that even 9volts will cause a tingle. If you don't understand go ask someone that has "tested" a 9volt battery by placing the terminals on their tongue.
The same "tingle" could happen if your hand was wet and you touched the positive end of a 12volt car battery terminal and a metal watch band on the same hand came in contact with the cars frame. You will see a spark and feel a shock through that arm even at 12volts.Comment
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Article 100 has a definition for "Voltage (of a circuit)", "Voltage, Nominal", and "Voltage to Ground". Nominal value is as you suggest the assigned value for purpose of conveniently designating its voltage class - not what it always operates at. So look for those terms in the text - for example NEC 690.71(B)(1) discusses 50V nominal in the latest edition.Comment
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Awesome, thanks for the additional info!Comment
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