Excessive Heat
The chassis is designed to dissipate heat with force convection cooling (drawing air
from the front and exhausting hot air out the back). Therefore, the rack must provide
sufficient air circulation paths in the front and back areas. The chassis temperature is
usually elevated above ambient temperatures in a rack environment. Maximum ambi-
ent temperatures in and around the rack must not exceed the maximum temperature
specification (see page 17).
When the air temperature is higher than the specified maximum in the rack, use a fan
or air conditioner to lower the temperature.
Electrical Noise
Electrical noise is seldom responsible for damaging components, unless extremely
high energy or high voltage levels are present. However, noise can cause temporary
malfunctions which can result in hazardous machine operation in certain applications.
Noise may be present only at certain times, may appear at widely-spread intervals, or
in some cases may exist continuously.
Noise commonly enters through input, output, and power supply lines and may also be
coupled through the capacitance between these lines and the noise signal carrier lines.
This usually results from the presence of high voltage or long, close-spaced conductors.
When control lines are closely spaced with lines carrying large currents, the coupling of
magnetic fields can also occur. Use shielded cables to help minimize noise. Potential
noise generators include switching components, relays, solenoids, motors, and motor
starters.
Refer to the relevant Federal, State/Provincial, and local electric codes which provide
data such as the size and types of conductors, color codes, and connections necessary
for safe grounding of electrical components. It is recommended that high- and
low-voltage cabling be separated and dressed apart. In particular, AC cables and switch
wiring should not be in the same conduit with all communication cables.
Line Voltage Variation
The power supply section of the unit is built to sustain the specified line fluctuations
(see page 17) and still allow the system to function in its operating margin. As long as
the incoming voltage is adequate, the power supply provides all the logic voltages nec-
essary to support the processor, memory, and I/O.
Unusual AC line variations may cause undesirable system shutdowns. As a first step to
reduce line variations, you can correct any possible feed problems in the distribution
system. If this correction does not solve the problem, use a constant voltage trans-
former. The constant voltage transformer stabilizes the input voltage to the systems by
compensating for voltage changes at the primary in order to maintain a steady voltage
at the secondary. When using a constant voltage transformer, check that the power rat-
ing is sufficient to supply the unit.
25
Installation