MAX300-RTG: Installation Manual Hardware Installation
40
External Communications
External Communications Options
OPC Server (Object Linking and Embedding [OLE] for Process Control)
Modbus Master
Modbus Slave
DCS (Distributed Control System)
4-20 mA
Relay
External Communications Disconnect Box
This external communications disconnect box option is used in Category 2 (Zone
1) and Div 1 applications, in cases where fiber optics communications is not
practical. The box contains user wiring connections, and is equipped with devices
that disconnect user wires from the purged enclosure in the event of pressurization
failure. Refer to Figure 19.
The type of flameproof box will differ, depending on communications options
and gas group. The box depicted in figure 19 is suitable for IIB + Hydrogen
(Group B). Consult Extrel CMS for Gas group IIC (Group A) applications.
With this option, Extrel CMS may supply appropriate glands, conduit
connections, and flexible conduit to connect the pressurized enclosure to
the flameproof box. The gland at the pressurized enclosure end is rated at
least IP4X and is able to maintain pressure within the enclosure. The gland
at the flameproof box end is appropriate for the hazardous location.
With this option, Extrel CMS supplies approved conduit plugs for unused
conduit holes in the flameproof box. These plugs may be replaced with user
supplied glands as necessary to handle communications wiring. It is the
user’s responsibility to ensure the glands are approved for use in the
hazardous location where the box is installed. Note that all conduit holes
must have either an approved gland or approved plug installed.
Nothing is to be installed within 50 mm of the joints of the flameproof
enclosure, to avoid having any devices in the flame path.
Refer to Figures 1 through 6 for enclosure conduit fitting locations.
With this option, in Zone 1/Div 1 units, all wiring shall meet applicable
standards, and each wire entering the enclosure must either be intrinsically
safe, or automatically disconnected when loss of pressurization in the
enclosure occurs.
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