Honeywell STT850 SMARTLINE, User Manual

Page: 23 / 94

Revision 3 STT850
Temperature Transmitter User’s Manual
Page 13
3.1.8 Grounding and Lightning Protection
Connect a wire from the Earth Ground Clamp or to the Internal Ground Connection (see Figure 7 ) to
Earth Ground to make the protection effective. Use a size 8 AWG or (8.37mm
2
) bare or green
covered wire for this connection.
For ungrounded Thermocouple, mV, RTD or ohm inputs connect the input wiring shield(s) to the
Internal Ground Connection shown in
Figure 7 .
For grounded Thermocouple inputs, connect the Internal Ground Connection shown in
Figure 7 to the
same earth ground as used by the thermocouple.
As noted above, the Loop Power wiring shield should only be connected to earth ground at the power
supply end.
3.1.9 Supply Voltage Limiting Requirements
If your Transmitter complies with the ATEX 4 directive for self-declared approval per 94/9EC, the
power supply has to include a voltage-limiting device. Voltage must be limited such that it does not
exceed 42 V DC. Consult the process design system documentation for specifics.
3.1.10 Process Sealing
The STT850 SmartLine Temperature Transmitter is CSA-certified as a Dual Seal device in
accordance with ANSI/ISA–12.27.01–2003, “Requirements for Process Sealing Between Electrical
Systems and Flammable, or Combustible Process Fluids.”
3.1.11 Explosion-Proof Conduit Seal
When installed as explosion proof in a Division 1 Hazardous Location, keep covers
tight while the Transmitter is energized. Disconnect power to the Transmitter in the non-
hazardous area prior to removing end caps for service.
When installed as non-incendive equipment in a Division 2 hazardous location, disconnect
power to the Transmitter in the non-hazardous area, or determine that the location is non-
hazardous before disconnecting or connecting the Transmitter wires.
Transmitters installed as explosion proof in Class I, Division 1, Group A Hazardous (classified)
locations in accordance with ANSI/NFPA 70, the US National Electrical Code, with 1/2 inch conduit
do not require an explosion-proof seal for installation. If 3/4 inch conduit is used, a LISTED
explosion proof seal to be installed in the conduit, within 18 inches (457.2 mm) of the transmitter.