Pearson OpScan iNSIGHT 70 Installation Manual page 22

Scanner Installation
Installing the Scanner
Dedicated Ground
A dedicated isolated/insulated ground for the OpScan iNSIGHT 70 system must
be provided. If possible, route a dedicated ground conductor between the main
power panel and the OpScan iNSIGHT 70 system branch circuit (with the
dedicated feeder). If a dedicated ground conductor is not feasible, then another
code-approved method must be used. (The isolated ground conductor is noted in
the National Electrical Code, Section 250-74, Exception 4.) Use of an isolated
ground rod or grounding to a water pipe is not acceptable.
An isolated/insulated ground conductor, equal to or larger in size than the
heaviest gauge AC feeder conductor in the circuit, should be bonded to the
ground bus in the building main power panel. Route it with the circuit conductors
in the wiring conduit. Pass this ground through any intermediate panel boards
without connection to the panel board grounding terminal bars. The National
Electric Code, cited above, allows for the installation at the intermediate panel
board of an isolated ground bus, constructed from a terminal block kit, for the
interconnection of the isolated ground conductor.
This isolated/insulated ground conductor runs as a single, uninterrupted circuit
between the building main power panel and the OpScan iNSIGHT 70 system
branch power panel. It forms the interconnection point for the third-wire grounds
of all OpScan iNSIGHT 70 system components. Connect all OpScan iNSIGHT 70
system component third-wire grounds to this ground; do not connect any
equipment other than OpScan iNSIGHT 70 system components to this ground
conductor. This condition is met if all system components are plugged into the
switched convenience outlet in the base of the scanner.
At some sites, local regulations require that all installed equipment be connected to
Note:
a system common ground. In this case, connect all OpScan iNSIGHT 70 system
components to the common ground at only one point. Connect third-wire grounds of
system components into a common bus connected to the common ground at a single point.
Make sure the equipment third-wire ground (green wire) does not become
Note:
connected to the conduit at the outlet box or connector. To avoid an inadvertent connection,
use a NEMA 5-20R type isolated-ground receptacle such as a Hubble IG-5362.
Grounding in Multi-Story Buildings
When installing the OpScan iNSIGHT 70 system in a multi-story building,
provide a low noise ground by connecting the isolated ground of the system to
the structural steel of the building. Install the isolated ground system as described
above. In addition, bond one end of a heavy gauge wire or copper braid to the
isolated ground bus in the branch circuit panel serving the OpScan iNSIGHT 70
system. Weld the other end of this wire or braid to the nearest vertical steel
structural member. Do not substitute a water pipe or an isolated ground rod for
the vertical steel member.
Ground-To-Neutral Specifications
With circuit power turned off, the resistance between the circuit neutral
conductor and the isolated ground conductor must be less than 2.1 ohms.
2-6
Installation Guide for the OpScan iNSIGHT 70 Scanner