PV Interconnect

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Anthony1965

Joined Feb 13, 2023
1
The PV Array Interconnect cabling connected between the supply side(Utility) of the building Main OCPD and the PV Main OCPD is currently installed within the building envelop(35'). Theses conductors(In Conduit) are terminated via current limiters on the supply side(utility) but are not provided with overload protection.
Are the interconnected conduit /conductors permitted per NEC to be installed within the building without overload protection?
 

Externet

Joined Nov 29, 2005
2,201
Welcome.
A photovoltaic array does connect to the utility grid with a voltage and frequency matching inverter in between as the PV array generates direct current and the utility is alternating current, as well as the building main 'AC loads'
At dawn the inverter awakes from solar exposure and supplies AC to the building demands and any extra is fed back to the utility. The DC current limiting is within the inverter input if a PV array is overdimensioned. The same inverter limits its AC output fed to building or grid or both by being incapable of exceeding its design.
Overload protection in the AC consumption within a building is managed by circuit breaker (1) or fuses. Overload protection to back-feed energy into the utility grid is also managed by another dedicated circuit breaker at the AC outlet of the inverter, located also at the breaker panel (2) or within the inverter. Both (1) and (2) shown in image below within 'Main AC panel'

1676314550573.png

Everything which is not the PV array or 'AC switch' above is or can be installed within the building, and already includes wiring, conduits, equipment, electrical boxes and the overload protections sheltered from weather elements. The 'AC isolation switch' is to be mounted outside the building for emergency crews to safety disconnect, usually next to the energy meter.
At my house, I have about 25' cabling in-conduit from PV on roof to inverter in basement and about 35' wiring from inverter to main panel not in-conduit.

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MisterBill2

Joined Jan 23, 2018
18,167
You can’t get overcurrent from a solar panel.
Certainly a solar panel must have adequately sized conductors to avoid an over current condition during even normal operation.
Thus it is entirely possible to install adequate wiring such that any over current is not possible. NOT ALL INSPECTORS ARE CAPABLE OF UNDERSTANDING THIS. Some are only able to recite a script, which may, or not, be applicable.

An entirely different concern is current during a lightning strike event. Solar arrays are subject to lightning because of being atop structures. Avoiding lightning strike damage is another concern that must be addressed.
 

Ian0

Joined Aug 7, 2020
9,667
Certainly a solar panel must have adequately sized conductors to avoid an over current condition during even normal operation.
Thus it is entirely possible to install adequate wiring such that any over current is not possible. NOT ALL INSPECTORS ARE CAPABLE OF UNDERSTANDING THIS. Some are only able to recite a script, which may, or not, be applicable.

An entirely different concern is current during a lightning strike event. Solar arrays are subject to lightning because of being atop structures. Avoiding lightning strike damage is another concern that must be addressed.
The problem comes from the other end. For a panel with Isc=14A, the sun would have to shine twice has hard to produce the 30A that would be guaranteed to blow a 15A fuse.
The problem occurs if there is a short and something happens at the MPPT end which allows battery voltage to connect to the short.
 

Externet

Joined Nov 29, 2005
2,201
Not lightning. That failure of solar panels can be by fatigue of materials, corrosion, exposure to extraordinary elements (heat?), moisture ingress, tree branch fall, stone throw or specifications just being too chinese. An open circuit from a weak weld, open contact, gap or underrated conductor breaks continuity and arcing takes care of set fire from inside-out.

Fuses are not inside a solar panel, and if implemented, would do nothing against arcing between rows or in series connections. The roof on the image above is of plain sandy asphaltic shingles typical as used in U.S. The amount of luck, was in the other hand, very high quality.

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