Rockwell Automation 1758-RTU202 DataSite Hardware User Manual - Manual (Page 16)

Publication 1758-UM001D-EN-P - June 2011
16 Installing the Controller
Input States on Power Down
The power supply hold-up time as described above is generally longer than the
turn-on and turn-off times of the inputs. Because of this, the input state
change from On to Off that occurs when power is removed may be recorded
by the processor before the power supply shuts down the system.
Understanding this concept is important. The user program should be written
to take this effect into account.
Other Types of Line Conditions
Occasionally the power source to the system can be temporarily interrupted. It
is also possible that the voltage level may drop substantially below the normal
line voltage range for a period of time. Both of these conditions are considered
to be a loss of power for the system.
Preventing Excessive Heat
For most applications, normal convective cooling keeps the controller within
the specified operating range. Ensure that the specified temperature range is
maintained. Proper spacing of components within an enclosure is usually
sufficient for heat dissipation.
In some applications, a substantial amount of heat is produced by other
equipment inside or outside the enclosure. In this case, place blower fans
inside the enclosure to assist in air circulation and to reduce ‘hot spots’ near
the controller.
Additional cooling provisions might be necessary when high ambient
temperatures are encountered.
TIP
Do not bring in unfiltered outside air. Place the controller in an
enclosure to protect it from a corrosive atmosphere. Harmful
contaminants or dirt could cause improper operation or damage
to components.