EET

Now not just anybody can install PV systems

The latest version of the National Electrical Code contains revisions that could greatly impact alternative energy systems. Specifically, Article 690 in the Code, which applies to solar power systems, has industry watchers buzzing because it specifies that only "qualified persons" can install a PV system. In the past, the issue of qualifications was generally left to state and local agencies.

Other parts of the revised code deal with nuances of handling and sizing conductors. For example, when an enclosure contains conductors from more than one PV system, the conductors now must be grouped; in some cases circuit conductors now must be sized to handle 125% of currents calculated in a way Article 690.8(A) dictates.

Overcurrent protection devices get a lot of attention in the new revisions, probably not surprising given the headlines generated by fires in PV installations. The NEC now says some PV installations don't need overcurrent protection. Specifically, it isn't necessary if the short circuit current of the PV source doesn't exceed the ampacity of the conductors or equipment. Fuses get attention as well.

One hazardous situation the Code envisions is the possibility of replacing a fuse that is under load, not a particularly safe practice. So the requirement is now for a means of disconnecting a fuse from all sources of power if it can be energized from both directions.

Another measure possibly inspired by news reports of PV fires is one dictating that PV conductors be spaced away from the underside of any roof. This is meant to keep firefighters from cutting the power cables if they need to vent the roof.

The subject of NEC Article 690 for PV systems got a thorough review in an article published by EC&M Magazine: http://ecmweb.com/code-basics/nec-rules-alternative-energy-systems-part-1

PV related fires are a hot topic (pun intended):

http://eetweb.com/solar/PV_systems_catch_fire_8910/

http://eetweb.com/mag/safe_reliable_alternative/

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