690.31g

[dm9289]

I’m having a problem understanding 690.31g.
Example conduit running outside house then goes in attic to roof.

So from inverter can you run PVC to attic entry then switch to EMT at the house penetration with a metal box and bond?


I have heard it said no PVC for DC but I don’t believe that is code.

Helpful explanation would be appreciated.

 

[Carultch]

DC circuits from PV require a metal raceway or cable clad, in some form or another. It has to do with the risk of faults, when an ignorant home-owner drives a fastener through the conduit. Requiring grounded metal housing for the wire will A) hopefully work as a physical barrier to stop the home-owner from continuing to fasten, B) mitigate the damage by grounding the rogue fastener, and C) provide a return path for fault current, which PVC cannot do.

The reason for the double standard on AC vs DC for this, is that DC is of higher risk of arcing, due to the lack of voltage zero crossings that AC has. DC circuits also historically had been "wild PV", which couldn't be shut off without the sun going down. Even though "wild PV" in buildings is no longer allowed, rules written around it, are still in effect.

 

[dm9289]

DC circuits from PV require a metal raceway or cable clad, in some form or another. It has to do with the risk of faults, when an ignorant home-owner drives a fastener through the conduit. Requiring grounded metal housing for the wire will A) hopefully work as a physical barrier to stop the home-owner from continuing to fasten, B) mitigate the damage by grounding the rogue fastener, and C) provide a return path for fault current, which PVC cannot do.

The reason for the double standard on AC vs DC for this, is that DC is of higher risk of arcing, due to the lack of voltage zero crossings that AC has. DC circuits also historically had been "wild PV", which couldn't be shut off without the sun going down. Even though "wild PV" in buildings is no longer allowed, rules written around it, are still in effect.

But if I’m reading the rule correctly outside of house can be PVC

 

[dm9289]

DC circuits from PV require a metal raceway or cable clad, in some form or another. It has to do with the risk of faults, when an ignorant home-owner drives a fastener through the conduit. Requiring grounded metal housing for the wire will A) hopefully work as a physical barrier to stop the home-owner from continuing to fasten, B) mitigate the damage by grounding the rogue fastener, and C) provide a return path for fault current, which PVC cannot do.

The reason for the double standard on AC vs DC for this, is that DC is of higher risk of arcing, due to the lack of voltage zero crossings that AC has. DC circuits also historically had been "wild PV", which couldn't be shut off without the sun going down. Even though "wild PV" in buildings is no longer allowed, rules written around it, are still in effect.

 

[dm9289]

This too me says PVC ok on outside. Please feel free to correct me I’m confused

 

[jaggedben]

PVC is allowed outside the building, but it must be marked for higher temperatures, and I consider it poor practice. I've heard anecdotes of PVC degrading in sunlight. Also it needs more support to keep it from sagging and touching the roof and that raises wire derating issues.

If you wanted to run PVC outside and transition to metal conduit in the attic, that would be allowed.

 

[dm9289]

PVC is allowed outside the building, but it must be marked for higher temperatures, and I consider it poor practice. I've heard anecdotes of PVC degrading in sunlight. Also it needs more support to keep it from sagging and touching the roof and that raises wire derating issues.

If you wanted to run PVC outside and transition to metal conduit in the attic, that would be allowed.

I do not install solar but have a bad habit of looking at work, then trying to learn the code better.

 

[dm9289]

I do not install solar but have a bad habit of looking at work, then trying to learn the code better.

PVC is allowed outside the building, but it must be marked for higher temperatures, and I consider it poor practice. I've heard anecdotes of PVC degrading in sunlight. Also it needs more support to keep it from sagging and touching the roof and that raises wire derating issues.

If you wanted to run PVC outside and transition to metal conduit in the attic, that would be allowed.

Do you know where in code it states must be high temp pvc or specially rated.
Thank you for your knowledge

 

[dm9289]

DC circuits from PV require a metal raceway or cable clad, in some form or another. It has to do with the risk of faults, when an ignorant home-owner drives a fastener through the conduit. Requiring grounded metal housing for the wire will A) hopefully work as a physical barrier to stop the home-owner from continuing to fasten, B) mitigate the damage by grounding the rogue fastener, and C) provide a return path for fault current, which PVC cannot do.

The reason for the double standard on AC vs DC for this, is that DC is of higher risk of arcing, due to the lack of voltage zero crossings that AC has. DC circuits also historically had been "wild PV", which couldn't be shut off without the sun going down. Even though "wild PV" in buildings is no longer allowed, rules written around it, are still in effect.

Thank you for your input on best practices

 

[jaggedben]

Do you know where in code it states must be high temp pvc or specially rated.
Thank you for your knowledge

352.12(D)

 

[pv_n00b]

PVC is allowed outside the building, but it must be marked for higher temperatures, and I consider it poor practice. I've heard anecdotes of PVC degrading in sunlight. Also it needs more support to keep it from sagging and touching the roof and that raises wire derating issues.

If you wanted to run PVC outside and transition to metal conduit in the attic, that would be allowed.

PVC needs to be rated for the location and COU. If it's exposed to sunlight it needs to be labeled sunlight resistant. If you want to use 90deg rated conductors at the full 90deg rating then the wet rating of the PVC needs to be 90 deg too. But I know a lot of people who don't like PVC outside, I'm not a proponent myself. There are some areas where it is the best choice because of a corrosive environment, like Hawaii. But otherwise, EMT is the ticket.

 

[solarken]

Ohio is still on NEC2017, and I thought PA was too. IMO PVC is ok for outside buildings, and transitioning to EMT at penetrations is fine. Metallic raceways are required from the point of penetration to the first readily accessible disconnect means in 2017 690.31G. In 2020, the requirement in 690.31 was changed to 690.31(D) and an exception was added to permit non-metallic raceways to be used indoors with PV hazard control systems, so for systems like SolarEdge I interpret it that you can use either PVC or EMT or any other permitted raceway regardless of location once that code is adopted.

 

[dm9289]

Ohio is still on NEC2017, and I thought PA was too. IMO PVC is ok for outside buildings, and transitioning to EMT at penetrations is fine. Metallic raceways are required from the point of penetration to the first readily accessible disconnect means in 2017 690.31G. In 2020, the requirement in 690.31 was changed to 690.31(D) and an exception was added to permit non-metallic raceways to be used indoors with PV hazard control systems, so for systems like SolarEdge I interpret it that you can use either PVC or EMT or any other permitted raceway regardless of location once that code is adopted.

Thank you and yes PA currently 2017