Honeywell touchpoint Pro Operating Instructions Manual page 49

MAN0923_Issue 3_04/15
• Instrument Earth is preferred to connect the cable screen
• Risk is that screen is connected at both ends = earth loops
P
Incoming
Client
Earth
• Instrument Earth is preferred to connect the cable screen
• Care must be taken to isolate the screen at the junction box, e.g. terminate it in a spare terminal
• The metal sensor / junction box must be connected to Protective Earth
• Risk is that screen is connected at both ends = earth loops
Three Core Cable with Screen and Armour with Screen Earthed at Controller
P
Incoming
Client
Earth
Figure 4.4 Screened cable with armour (wire or braid) with plastic junction box and plastic sensor
• The armour must be connected to Protective Earth at the sensor, and the screen should be connected to
the enclosure's common earth (ground) rail.
• Care must be exercised to prevent contact between cable armour and cable screen, and between
cable armour and the enclosure in order to prevent ground loops occurring.
4. Electrical Installation
Three Core Cable with Screen Earthed at Contoller
Figure 4.3 Screened cable, metal junction box and/or sensor
and Armour Earthed in Field
49
Touchpoint Pro
Operating Instructions
Junction
Box
Sensor
Armour
Screen
Junction
Box
Sensor