3Com 4210G manual Temperature/Humidity, Cleanness, Electromagnetic Susceptibility

Temperature/Humidity

You must maintain a proper temperature and humidity in the equipment room. Long-term high humidity may lead to bad insulation, electricity leakage, mechanical property changes, and metal corrosion. However, if the relative humidity is two low, captive screws may become loose as the result of contraction of insulation washers and static electricity may be produced in a dry environment to jeopardize the circuits on the device. High temperature is the most undesirable condition, because it accelerates aging of insulation materials and can thus significantly lower reliability and service life of your switch.

For the temperature and humidity requirements of different models, refer to Table 1-1.

Cleanness

Dust is a hazard to the operating safety of your device. The dust accumulated on the chassis can be adsorbed by static electricity and result in poor contact of metal connectors or metal contact points. Especially when the indoor relative humidity is low, electrostatic adsorption is more likely to happen. This can not only shorten the service life of your device but also cause communications failures. The following table lists the dust concentration limit.

Table	2-1Dust concentration limit in the equipment room
	Substance	Unit		Concentration limit
Dust		Particles/m³	≤ 3 x 104	(no visible dust on the tabletop
			within three days)

Note: The dust particle size ≥ 5 μm.

Besides dust, there are rigorous limits on the content of harmful substances in the air that can accelerate the corrosion and aging of metals, such as chloride, acid, and sulfide in the equipment room, and the equipment room must be protected against ingression of harmful gases such as SO2, H2S, NH3, and Cl2. For specific requirements, see the following table.

Table 2-2Harmful gas limits in the equipment room

Gas	Maximum concentration (mg/m3)
SO2	0.2
H2S	0.006
NH3	0.05
Cl2	0.01

Electromagnetic Susceptibility

The operation of your switch can be affected by external interferences, such as conducted emission by capacitance coupling, inductance coupling, electromagnetic wave radiation, and common impedance (including the grounding system) coupling, and leads (power cords, signaling cables and output wires). To eliminate the interferences, pay attention to the following:

zAs the AC power system is a TN system, use a single-phase three-wire power socket with Protection Earth (PE) to effectively filter interference from the power grid.

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