General Information
1-10 Rev 2/01
1.5.5 Grounding Installation Requirements
Ground wiring requirements for are governed by the National Electrical Code (NEC).
Proper grounding of the EF-Series Unit helps to reduce the effects of electrical noise on the unit’s
operation and protects against lightning. Lightning protection is designed into the unit, especially for
the built-in field wiring inputs and outputs. You may want to consider installing a telephone surge
protector for the dial-up modem communications card.
All earth grounds must have an earth to ground rod or grid impedance of 25 ohms or less as measured
with a ground system tester. The grounding conductor should have a resistance of 1 ohm or less between
the EF-Series Unit case ground lug and the earth ground rod or grid.
The grounding installation method for the unit depends on whether the pipeline has cathodic protection.
On pipelines with cathodic protection, the EF-Series Unit must be electrically isolated from the pipeline.
Electrical isolation can be accomplished by using insulating flanges upstream and downstream on the
meter run. In this case, the EF-Series Unit could be flange mounted or saddle-clamp mounted directly on
the meter run and grounded with a ground rod or grid system.
On pipelines without cathodic protection, the pipeline itself may provide an adequate earth ground and the
EF-Series Unit could mount directly on the meter run. Test with a ground system tester to make sure the
pipeline to earth impedance is less than 25 ohms. If an adequate ground is provided by the pipeline, do
not install a separate ground rod or grid system. All grounding should terminate at a single point.
If the pipeline to earth impedance is greater than 25 ohms, the installation should be electrically isolated
and a ground rod or grid grounding system installed.
The recommended cable for I/O signal wiring is an insulated, shielded, twisted pair. The twisted pair
and the shielding minimize signal errors caused by EMI (electromagnetic interference), RFI (radio
frequency interference), and transients. A ground bar is provided for terminating shield wires and
other connections that require earth ground. A lug on the outside of the enclosure is provided to
ground the enclosure. Note that the ground bar should be directly wired to the ground lug, rather than
depending on the enclosure to make the connection between the ground bar and ground lug. Refer to
Section 2 for further details.
CAUTION
Do not connect the earth ground to any wiring terminal on the Main Electronics Board.
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