6
Ground Location
(smaller holes for self-tapping machine screw)
Junction Box
Label
Backside
The ground holes
are on the backside of
the module frame.
Figure 3.1
Module Ground Position
Ground Location
(larger holes for bolt and nut)
The array frame shall be grounded in
accordance with NEC Article 250
(USA) or the CEC in Canada.
Bonding shall be by a positive means,
such as clamping, riveting, bolted or
screwed connectors, or welding,
soldering or brazing. If the bonding
means depends upon screw threads
two or more screws or two full
threads of a single screw must
engage the metal
Great care should be exercised to
ensure that corrosion caused by the
grounding means be avoided.
Corrosion can increase the resistance
of the grounding connection on the
module, or can even cause the
grounding connection to fail entirely.
Corrosion can be caused by the
effects of weather, humidity, dirt
and so on. It can also be caused
when two dissimilar metals are in
contact (galvanic reaction).
The
module
frame
material
is
aluminum/magnesium alloy.
All fasteners (nuts, bolts, washers,
screws, etc.) must be stainless steel
unless otherwise specified.
Length
of
self-tapping
machine
screw or bolt should not be more
than 0.78’’ (20 mm) in order to
avoid contacting the back-sheet of
the module.
Acceptable
grounding
wire
is
following.
Ilsco Corp. GBL-4DBT 10-14AWG-
Solid,
4-6,
8,
10-14AWG-Strand
Burndy L L C CL501TN 14AWG-Solid,
14-4AWG-Strand
Tyco Electronics Corp. 1954381-
1/1954381-2 10-12AWG Solid
Each ledge on the module frame has
two smaller holes for self-tapping
machine
screws
(0.165’‘diameter
(4.2 mm)) and two larger holes for
bolts (0.205’‘diameter (5.2 mm)).
These ground holes are marked with
a “G” adjacent to their location on
the frame rail (see Figure 3.1).
Ground wires must be connected to
the module’s metal frame at one of
these locations.
Lay-in lugs or grounding clips can be
used
to
ground
Panasonic
PV
modules.
Both
methods
are
explained below, please choose one.
Grounding Locations (or grounding
holes)
Using a self-tapping machine screw (see
Figures 3.2 and 3.4)
If using this method, use one of the
smaller holes with diameter of
0.165’‘ (4.2 mm)
The self-tapping machine screw size
must be No.10 (0.190’‘diameter
(4.83mm)).
This method requires a minimum
number
of
threads-per-inch
to
achieve
an
adequate
electrical
connection. For a single screw, the
thread pitch must be at least 32
threads per inch (TPI). A single screw
less than 32 TPI does not provide
sufficient thread contact. Note: Self-
tapping machine screws are also
called thread cutting screws.
Recommended
torque
value
in
tightening
self-tapping
machine
screw is 2.3 N.m (20in-lb).
Using bolt and nut (see Figures 3.3 and
3.5)
If using this method, use one of the
larger
holes
with
diameter
of
0.205’‘ (5.2 mm)
The bolt and nut size should be
No.8
(0.164’‘diameter
(4.16
mm)), or No.10 (0.190’‘diameter
(4.83
mm))
or
M5
(0.197’‘diameter (5.0 mm)).
Star washers must be used to
make
contact
through
the
anodization of the module frame.
In this case, the screw threads are
not providing the electrical ground
contact.
Recommended
torque
value
in
tightening bolt and nut is 2.3 N.m
(20in-lb).
Grounding Methods
Where
common
grounding
hardware (nuts, bolts, star washers,
spilt-ring lock washers, flat washers
and the like) is used to attach a
listed
grounding/bonding
device,
the attachment must be made in
conformance with the grounding
device manufacturer's instructions.
Common hardware items such as
nuts,
bolts,
star
washers,
lock
washers and the like have not been
evaluated for electrical conductivity
or for use as grounding devices and
should be used only for maintaining
mechanical connections and holding
electrical grounding devices in the
proper
position
for
electrical
conductivity. Such devices, where
supplied with the module and
evaluated through the requirements
in UL 1703, may be used for
grounding
connections
in
accordance with the instructions
provided with the module.
