Rice Lake Truck Scales - Manual (Page 22)

18 Survivor
®
SR Siderail Truck Scale Assembly Instrucitons
A separate grounding system conductor must extend uninterrupted from the main service panel ground to the scale
to protect load cells and scale wiring from lightning and other transient damage. This ground wire conductor must
be an unsheathed #10 copper wire or larger. Run the bare ground wire conductor intact from the AC power ground
rod to the scale in a separate trench. Bring the wire up from the trench near the junction box and attach it to the
ground lug of the junction box. Then use a short length of #10 wire to ground the scale frame by running a ground
wire from the junction box ground lug to a mounting bolt for the junction box on the scale frame.
8.3 Junction Boxes
Each junction box is large enough to hold the summing board, optional transient protection devices, packaged
desiccant, and extra load cell cable coiled inside the enclosure.
In a single-platform scale, the single junction box location is determined by the length of the load cell cables and
the four pre-drilled mounting holes in the siderail beams. In a multi-axle scale with independent sections, each
section requires its own junction box to sum the load cell signals from that section.
A summing card mounted within the
junction box is used to make all cable
terminal connections. All terminal pins
are clearly marked as to function.
A ground lug on the bottom of the j-box
is used to connect the buried ground
cable from the AC power ground rod.
A DC transient protection board can be
conveniently located within the junction
box to help protect load cells from
power surges. If that option is used, run
a short #10 grou nd wire from the
board’s ground connection to the inner
ground lug of the junction box.
An industrial corrosion inhibitor and
d e s i c c a n t s u c h a s o u r I n d u s t r i a l
Corrosion Inhibitor (PN 16037) should be added to the junction box enclosure before final closure. This 2.5"
desiccant “ball” protects an enclosure up to 5 ft
3
from internal corrosion for approximately one year.
8.4 Transient Protection Insurance
A two-year lightning protection package comes standard on all SR scales. The individual components of this
comprehensive package are designed to protect AC and DC portions of the system, as well as any serial
communication lines. The lightning protection package includes:
• DC transient protection board(s) mounted within the junction box(es). This DC transient protector handles
up to eight load cells and also protects serial communication lines. Scales with more than eight load cells
will require a DC transient protection board in each junction box.
• Self-contained DC transient protection unit in homerun cable at indicator.
• #10 bare ground conductor cable buried in earth from scale frame to DC transient board in junction box to
DC transient board at indicator and finally to the AC power ground lug.
• 120 VAC uninterruptable power supply/surge protector in AC line before indicator.
Figure 8-2. J-box grounding.
10 ga. bare ground wire to
DC protection ground
before indicator
Ground Lug
Located in
J-box Pocket