Emerson Bristol 2808 Series, Instruction Manual

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Section 3 - Grounding & Isolation Page 3-1 S1400T-2808B
Section 3 - Grounding & Isolation
3.1 POWER & GROUND SYSTEMS
Series 2808-XXB Transmitters are similar in that they both have basically two system
grounds, i.e., Chassis Gnd and Circuit Ground. Chassis Ground is galvanically isolated
from Circuit Ground by 600V (ac/dc).
Series 2808-XXB Transmitters have an input power range of +5 to +42 Vdc. Power supplies
are not provided with Series 2808-XXB Transmitters. Series 2808-XXB Transmitter
electronics are galvanically isolated from the case and should not be affected by cathodic
protection or other EMF on the pipeline. Grounding to the pipeline, i.e., completing a
connection between the 2808’s internal Ground Lug and the mounting media (valve,
manifold, pipeline, etc.) is not recommended even if the media in question is earth
grounded.
When grounding a 2808 Transmitter, always connect directly to a known
good Earth Ground.
NOTE
Never connect the Series 2808-XXB Transmitter’s Power (-) or Signal
(V-) Ground Terminals to Earth Ground. These Grounds must always
be isolated from the case. A 2808-XXB Case Ground connection
should be made to connect the case to a known good Earth Ground.
3.2 IMPORTANCE OF GOOD GROUNDS
Series 2808-XXB Transmitters are utilized in instrument and control systems that must
operate continually and within their stated accuracy over long periods of time with
minimum attention. Since many system sites are unmanned and located in remote areas,
failures resulting from an improperly grounded system can become costly in terms of lost
time and disrupted processes. A properly grounded system will help prevent electrical
shock hazards resulting from contact with live metal surfaces, provide additional protection
of equipment from lightning strikes and power surges, minimize the effects of electrical
noise and power transients, and reduce signal errors caused by ground wiring loops.
Conversely, an improperly grounded system may exhibit a host of problems that appear to
have no relation-ship to grounding. It is essential that the reader (service technician) have
a good under-standing of this subject to prevent needless troubleshooting procedures.
WARNING
This device must be installed in accordance with the National Electrical Code
(NEC) ANSI/NEPA-70. Installation in hazardous locations must also comply
with Article 500 of the code. For information on the usage of Model 2808-XXX
units in Class I, Division 2, Groups A, B, C & D Hazardous and Nonhazardous
locations, see appendix A of manual CI-2808B. For information on the usage of a
Model 2808-I-XXB units in Class I, Division 1, Groups C & D Hazardous
locations, see CI-3530-IStran.
3.3 EARTH GROUND CONNECTIONS
To properly ground a Series 2808-XXB Transmitter, connect the Earth Ground wire
between the green Ground Screw (adjacent to the Terminal Blocks on the inside of the units