Choose a Top-Mounting or Bottom-Mounting System On pitched roofs, mount rails either parallel or perpendicular
to the rafters Assembly sequence is a common determining
factor. Select top-mounting clamps if you prefer to install
modules last – after you’ve attached rails to installed footings.
This sequence is especially convenient with modules that have
Multi-Connect cables. Select bottom mounting clips if you
plan to attach modules to rails prior to final installation. This
sequence is well suited for modules that must be pre-wired.
Bottom-mounting clips use space more efficiently because
they do not require the 1" space between modules needed by
top clamps.
The use of top-mounting clamps is generally easier when
flush-mounting to a roof. Always use top-mounting clamps when flush mounting to standoffs. If using bottom-mounting
clamps with L-feet, follow the installation manual carefully to
make sure footing slots are accessible during final installation.
In roof mounts, when using top-mounting clamps, no extra roof bracing is needed since rails or mounting feet can be adjusted
to match rafter spacing. With bottom-mounting clamps, spacing
between the rails depends on spacing between the mounting
holes of your particular PV module, and it is unlikely that they
will match rafter spacing if rails are mounted parallels to rafters.
In that case, place a stringer over the roof or mounting blocks
beneath it. Never attach footings to the sheathing alone – such
an arrangement will not meet code and will leave the installation
and roof vulnerable to severe damage from wind.
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