Grounding; Figure 5 - Earthing - Elpro Technologies 915U-2 User Manual

915U-2 Wireless I/O
30005 Local Supply voltage (8-40V scaling)
30006 Local Battery voltage (8-40V scaling)
30007 Local 24V loop voltage (8-40V scaling) – Internally generated +24V
supply used for analog loop supply. Maximum Current limit is 100mA
30008 115S Supply Voltage (8-40V scaling)
38005 – 38008 Floating Point Registers, also indicate the Supply voltage, Battery
Voltage, +24V Supply and 115S Supply voltages but in a voltage
scale.
There are no dedicated discrete low voltage alarm indicators however each supply
voltage does have a High and a low Set point Status which can be used for this type of
alarm.
See section 0 "Analog Inputs" for details on how to configure these alarms.

2.2.4 Grounding

To provide maximum surge and lightning protection each module should be effectively
earthed / grounded via a "GND" terminal on the module – this is to ensure that the
surge protection circuits inside the module are effective. The module should be
connected to the same common ground or earth point as the enclosure "earth" and the
antenna mast "earth".
The 915U-2 has a dedicated Earth connection screw on the bottom end plate next to
the Supply terminals. All EARTH wiring should be minimum 2mm² - 14 AWG
If using the 915U-2 with serial Expansion I/O modules then all expansion modules must
have a separate earth connection from the front terminal back to the common earth or
ground point. See Figure 5 - Earthing below
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Figure 5 - Earthing

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User Manual