National Electrical Code Tips: Article 690 -- Solar Photovoltaic Systems, Part
Only about 15% to 20% of the work of installing a Solar Photovoltaic (PV)
System is electrical. But that electrical portion can easily result in disaster
if not done correctly. Thus, Article 690 provides requirements for that portion.
- When you size the circuit conductors that run between the inverter output
and the structure disconnect, base that on the output rating of the inverter [690.10(B)].
- Protect those conductors per Article 240, locating the overcurrent
protection at the inverter [690.10(B)].
- Yes, you can use the inverter output of a standalone PV system to supply
120V to single-phase, 120/240V service equipment or distribution panels. But if
you do this, there can't be any 240V outlets or any multiwire branch circuits.
- It is not a code violation to connect a standalone PV system without a
battery bank or backup power system [690.10(D)]. If your power goes out, that's
not going to cause the building to burn down. In fact, cutting the power is one
of the first things the fire department will do. However, such a configuration
is risky in other ways because it could leave you without power. For a family
residence, such an arrangement is just a bad design.
- Don't backfeed circuit breakers that are marked "line" or "load"
- Arc fault circuit interruption appeared a few code cycles ago, and it was
only a matter of time until it would make its way into Article 690. With the
2011 revision, it did [690.10(F)]. At first glance, the requirements seem more
detailed than is necessary. But the power supply you're using is a bit more
complicated. That's why the requirements include an annunciator and other
provisions beyond what you normally have in an arc fault protection scheme.
- The disconnect must be able to disconnect all current-carrying conductors of
the PV system from all other conductors in the structure [690.13]. Notice in
this text that the NEC does not use the word "neutral," but instead says,
"grounded conductor." You will find the relevant definitions in Article 100.
Don't get them confused with each other; they are not automatically synonymous.
- As with a standard electric utility service, you're limited to 6 disconnects
for the PV system [690.14(C)(4)].
- The grouping rule applies, also [690.14(C)(5)].
- Utility-interactive inverters don't have to be readily accessible. You can
even mount them on the roof. But you must meet the requirements of