8.4 Probe Installation in Underground
Storage Tanks
1. Install a manhole of at least 18 inches (45.7 cm) diameter
around an unused fitting in the top of the tank. This
manhole must be large enough to accommodate a
weatherproof junction box.
NOTE: If this fitting is not in the center of the tank, additional
measurements are required for probe compensation.
2. When installing the probe, allow enough cable from the
probe to reach a weatherproof junction box.
3. Leave minimum 12 inches of extra, coiled wiring (probe
wire and field wire) inside the weatherproof junction box.
The box must be large enough to accommodate ½-inch
(12.7 mm) conduit, coiled field wiring and epoxy pack, as
shown in field wiring diagram.
CAUTION: Seal-offs are required at any time I.S. wiring enters
conduit.
4. Install the ½-inch NPT bushing (supplied with each probe)
in the weatherproof junction box.
Figure 8-4 Probe Junction Box Wiring Connections
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