Table 11: Ground Resistivity Recommendations - Allied Telesis AT-IE300-12GP Installation Manual

Chapter 2: Beginning the Installation
58
restrictions on site requirements, and to follow all guidelines and
safety warnings.
The switch and DC power source should be installed close to each

other so that the DC power cables are kept as short as possible to
minimize voltage loss.
When installing the switch in an indoor or outdoor metal enclosure,

select an enclosure that is large enough for both the switch and DC
power supply so that the DC power cables are kept short.
The switch and power supply should be properly connected to a

protective earth ground.
The switch and power supply should be individually grounded to

the grounding conductor. Do not daisy-chain the ground wires.
When installing the switch in an indoor or outdoor metal enclosure,

be sure to properly ground the enclosure to a protective earth
ground following local electrical codes and the instructions in the
manufacturer's installation guide.
Powered devices connected to the LAN ports on the switch should

be grounded to the same grounding conductor at the service
entrance as the switch.
LAN ports should have additional lightning protections as specified

in 803.3at Section 33.4.1.1.2, Environment B Requirements, when
connected to powered devices that are not grounded to the same
grounding conductor at the service entrance as the switch.
Electromagnetic interference might occur between switches and

other devices when multiple switches are powered by a single DC
power supply. This can be addressed by installing clamp-on ferrite
beads on the DC power cables, between the DC power supply and
switches.
Recommendations for ground resistivity are given in Table 11.

Table 11. Ground Resistivity Recommendations
Level
Best Practice
Acceptable
Marginal
Non-compliant
Recommendation
<5 ohms
5 to 15 ohms
15 to 25 ohms
>25 ohms