The maximum voltage you can have on exposed rails

low-voltagenec

In this question, someone has a desk lamp with power totally exposed on metal parts. You also have installed overhead lighting on open rails doing the same thing.

What does NEC say about the maximum voltage permitted on such installations?

I am interested in fixed installations (not cord-and-plug) which are readily accessible, e.g. Low hanging low-voltage lighting that you could reach out and touch.

I am also interested in the outdoor rules, because my nefarious plan is to use the racks which hold up solar panels to carry the current from the panels, so the racks become massive feeder wire that lets me keep voltage low. Some of the panels will be on the ground.

Is the maximum voltage different for AC versus DC? If AC, does it mean RMS (the normal way AC is measured) or peak (1.4x more)?

Best Answer

690.31(A) nixes your diabolical plan

Unfortunately, unless you could find a racking system specifically listed to connect the contained panels in parallel as you describe, you can't do what you're after, as 690.31(A) requires a Chapter 3 wiring method, or a wiring method explicitly listed for use with PV panels, for all PV system wiring:

690.31 Methods Permitted.

(A) Wiring Systems. All raceway and cable wiring methods included in this Code, other wiring systems and fittings specifically listed for use on PV arrays, and wiring as part of a listed system shall be permitted. Where wiring devices with integral enclosures are used, sufficient length of cable shall be provided to facilitate replacement.

(1) Identification. PV system circuit conductors shall be identified at all accessible points of termination, connection, and splices.

Where PV source and output circuits operating at voltages greater than 30 volts are installed in readily accessible locations, circuit conductors shall be guarded or installed in Type MC cable or in raceway. For ambient temperatures exceeding 30°C (86°F), conductor ampacities shall be corrected in accordance with Table 690.31(A).

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