Nonmetallic conduit is not legal for use inside the
building envelope—it does not meet Code. [NEC 690.31(E).]
It also is not recommended for high-performance systems
with lower maintenance in hot climates.
Outdoor individual conductors must be equipped with
90 degree Celsius insulation. Those conductors include:
RHW- 2
THW-2
THWN-2
XHHW-2
Others properly rated for use
Conductors with wet ratings are the only conductors to be placed outside or
underground. The conduit housing the conductors can be thick-walled or
thin-walled.
Use metallic raceways to route PV conductors through attic spaces. Running
conductors through attics is common. Article 690.14 sets guidelines for discon-
nect locations. There are also specific requirements for running conduit and con-
ductors below the roof surface.
With regard to work beneath roofs, NEC Article 690.31(e)1 states that wiring
methods shall not be installed within 25 cm (10 in.) of the roof decking or
sheathing except when the wiring is running directly below a roof surface covered
by PV modules and associated equipment. You should run all circuits perpendic-
ular to the roof penetration point to support a minimum of 25 cm (10 in.) below
the roof decking.
Module Connectors
There are several requirements for module connectors, including:
Resistance to the environment
Coping with short-circuit currents
Designs with latching mechanisms to guard terminals that assure a proper
securing of the two-terminal connections
Array Grounding Continuity
Make certain that all module grounding is continuous. According to NEC Article
690.4(C), the removal of a module shall not interrupt connectivity of grounded
conductors. PV installers can use detachable modules for easy accessibility. PV
modules that are not welded to the mounting frames provide easy access to junc-
tion boxes.
TECH TIPS
Exposed individual insulated conductors
may be used only for module
interconnection wiring.
CHAPTER 8
Connecting the Sun to the Home and the Utility 189
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