PV Wire Requirement

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Anode

Member
Location
Washington, USA
This feels like back to the basics but I was wondering if someone could point me to where PV Wire is a requirement in 2014 NEC for the dc side of our solar systems.

We have already standardized using PV wire across the board for the dc side of our installations, but I am curious to know if this is absolutely necessary by code.

Is using USE-2 not allowed anymore under 2014 NEC? What if conductors were managed properly, not exposed to sunlight, and in metal conduit to the inverters. Is this no longer permissible?

Are we simply looking at 690.31 being a deciding factor on this? Please advise. :?
 
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shortcircuit2

Senior Member
Location
South of Bawstin
Anode said:
This feels like back to the basics but I was wondering if someone could point me to where PV Wire is a requirement in 2014 NEC for the dc side of our solar systems.

We have already standardized using PV wire across the board for the dc side of our installations, but I am curious to know if this is absolutely necessary by code.

Is using USE-2 not allowed anymore under 2014 NEC? What if conductors were managed properly, not exposed to sunlight, and in metal conduit to the inverters. Is this no longer permissible?

Are we simply looking at 690.31 being a deciding factor on this? Please advise. :?
Click to expand...

690.35(D)(3) requires PV wire for ungrounded systems. Transformerless inverters have become common on most installations so most are installing PV wire exclusively. This is also a best practice because if a system was connected as grounded but the inverter was to fail, it is likely that a transformerless inverter would be the replacement.

Note that almost all PV modules come with PV wire whips now. Most PV wire is 1000-2000 volt rated also.
 
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SolarPro

Senior Member
Location
Austin, TX
You really can't install a PV system without having some exposed wiring. (Typically, quite a bit of it.) And you need to use PV wire for the conductors installed in free air.

And ungrounded PV systems are far more common now than they used to be. Form an inventory management point of view, it's probably simplest to standardize on PV wire at this point in time.
 
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Carultch

Senior Member
Location
Massachusetts
Anode said:
This feels like back to the basics but I was wondering if someone could point me to where PV Wire is a requirement in 2014 NEC for the dc side of our solar systems.

We have already standardized using PV wire across the board for the dc side of our installations, but I am curious to know if this is absolutely necessary by code.

Is using USE-2 not allowed anymore under 2014 NEC? What if conductors were managed properly, not exposed to sunlight, and in metal conduit to the inverters. Is this no longer permissible?

Are we simply looking at 690.31 being a deciding factor on this? Please advise. :?
Click to expand...

If your wire is in a conduit travelling from enclosure-to-enclosure, it can be any kind of wire that is permitted in conduit, and is suitable for the voltage. Usually THWN-2 is suitable.

It is impossible to do a PV system without some of the wiring being exposed in open air. This is the wire that specifically has to be listed PV Wire for ungrounded systems. For your grounded systems, it is OK for it to be USE-2.

If you have a 1000V PV system, you have to use 1000V wiring, both inside and outside of conduit, until you get to the inverter. This will usually be 1000V PV wire, since I'm not aware of any ordinary building wire that is 1000V rated.
 
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