Emerson Rosemount 700XA Reference Manual page 41

July 2020
Grounding precautions
Follow these general precautions for grounding electrical and signal lines:
■ For shielded signal conducting cables, shield-drain wires must not be more than two American Wire Gauge (AWG) sizes smaller
than the conductors for the cable. Shielding is grounded at only one end.
■ Metal conduit used for process signal wiring must be grounded at conduit support points (intermittent grounding of conduit
helps prevent induction of magnetic loops between the conduit and cable shielding).
■ A single-point ground must be connected to a copper-clad, 10-ft. long, ¾-in. diameter (3 m long, 19.1 mm diameter) steel rod,
which is buried, full-length, vertically into the soil as close to the equipment as is practical.
Note
The grounding rod is not furnished.
■ Resistance between the copper-clad steel ground rod and the earth ground must not exceed 25 Ohms.
■ On ATEX-certified units, the external ground lug must be connected to the customer's protective ground system via 9 AWG (6
2
mm ) ground wire. After the connection is made, apply a non-acidic grease to the surface of the external ground lug to prevent
corrosion.
■ The equipment-grounding conductors used between the gas chromatograph (GC) and the copper-clad steel ground rod must
be sized according to your local regulations.
Electrical conduit installation precautions
■ Conduit cutoffs must be cut at a 90-degree angle. Cutoffs must be made by a cold cutting tool, hacksaw, or by some other
approved means that does not deform the conduit ends or leave sharp edges.
■ All conduit fitting-threads, including factory-cut threads, must be coated with a metal-bearing conducting grease prior to
assembly.
■ Temporarily cap the ends of all conduit runs immediately after installation to prevent accumulation of water, dirt, or other
contaminants. If necessary, swab out conduits prior to installing the conductors.
■ Install drain fittings at the lowest point in the conduit run; install seals at the point of entry to the gas chromatograph (GC) to
prevent vapor passage and accumulation of moisture.
■ Use liquid-tight conduit fittings for conduits exposed to moisture.
When a conduit is installed in hazardous areas, follow these general precautions for conduit installation:
■ All conduit runs must have a fitting, which contains explosion-proof sealing (potting) located within 3 in. (76.2 mm) from the
conduit entrance to the explosion-proof housing. The seal should have a minimum IP rating of IP54 or equivalent NEMA
rating on the conduit sealing devices.
■ The conduit installation must be vapor tight, with threaded hub fittings, sealed conduit joints and gaskets on covers, or other
approved vapor-tight conduit fittings.
WARNING
Failure to observe precautionary signs may result in serious injury or death to personnel.
Observe all precautionary signs posted on the certified explosion-proof equipment. Consult your company's polices and procedures
and other applicable documents to determine wiring and installation practices that are appropriate for hazardous areas.
Rosemount 700XA
®
/Type
41