Garage or subpanel with loads allowed?

Re: Garage or subpanel with loads allowed?

aj164 wrote: »

This would save a lot of work, but it appears to violate 690.4 (B) "Conductors of Different Systems. Photovoltaic
source circuits and photovoltaic output circuits shall not be
contained in the same raceway, cable tray, cable, outlet box, junction box, or similar fitting as feeders or branch circuits of other systems, unless the conductors of the different systems are separated by a partition or are connected together."

aj164 wrote: »

This is yet another area I got tagged on, sharing the same conduit to get the PV output to the breaker panel as circuits going to other loads in the home. The inspector said it mixes source circuits with load circuits; That it creates a hazard because someone could, in theory, cut power to the home, believing that the wires in the conduit would be dead, but then would be in danger because of the potentially-live PV output circuit.

I realize the grid-tie inverter here shuts down when there is no grid connection, but he did not allow that as an exception here. It seems nit picky, but I guess if someone were to upgrade the inverter in the future with a battery-backup system... :roll:

From my reading, you are correct and the inspector is wrong...

The circuits, if isolated (such as a battery based PV system DC side vs the Inverter output and/or with substantially different voltages/currents/uses where the insulation differences, say insulation rated for 12 volts vs insulation rated for 600 volts) cannot be mixed together...

In your case, the wires are all connected together, through breakers. They are not isolated networks. And they all have the same insulation requirements.

In this case, the grid tied inverter cannot power the box/wiring/bus bars unless the utility power is present--the whole reason for the UL rating.

There is no way--that I can see--where they can make a valid argument about separating wiring (for example, generator backed wiring vs Grid Tied Inverter wiring isolation) for something that is not even planned for the future.

If, you were going to build a battery backed UPS type system--that would require a transfer switch and (probably) a sub panel... No way that type of system would be confused with what you are doing.

No matter the failure type (utility mains fail, main home breaker opens, CB on one branch circuit opens, or CB on inverter circuit opens) would there be any sort of "live/energized" circuit in your shared conduit/box area...

And, technically, I would even argue the case that the PV side of a Xantrex Grid Tied system is tied with the Output of the inverter--they have a common ground (and in the US, safety ground and neutral are tied together in the wiring box)--although the Xantrex PV side is sort of "isolated" through a 1 amp ground fault detection fuse. Since the PV side is electically connected (via safety ground/neutral connections in house wiring), and the PV side is using the same rated wiring (600 Volts RMS Max) as the 240 VAC output of the inverter--they are the "same circuit" in the NEC sense... So no isolation barrier or separate wiring box would be required...

And, if you look in a Xantrex GT inverter (at least my Xantrex 3.0 GT model), there is no barrier between the 240 VAC wiring and the 200-600 VDC PV wiring. The wiring all goes in the same box, and depending on where the PV and Output wiring comes in via the knockouts--the wiring will cross each other (which they do in my box).\

I would only argue for the PV DC vs AC output wiring isolation (separate conduit/metal barrier) if there was a UL approved barrier between the PV DC and the Inverter Output (i.e., UL approved transformer with double insulation and/or internal ground screen). But since the NEC PV code (as written by our "friends") requires grounding the PV panels inside the inverter--they have "voided" and isolation between the input and output sides of a GT inverter (normally, I would have to pass a ~1,800 VAC--don't remember the exact voltage requirement--highpot test between the GT input and output to achieve "proper and meaningful isolation".

In the end, there is no valid reason (that I can see at this point) for disapproving co-locating GT inverter output wiring and other normal branch wiring as in your installation. As you say--the UL regulations prevent the inverter from energizing during any power failure. And if the GT where to energize its output with a mains AC and/or local Circuit Breaker failure--then the UL testing/requirements are bogus and the whole idea of NEC approved GT solar should be killed as being too dangerous.

-Bill