Rockwell Automation 1747-L5xx SLC 500 Modular Hardware Style User Manual - Manual (Page 262)

Publication 1747-UM011G-EN-P - June 2008
262 Calculating Heat Dissipation for the SLC 500 Control System
Calculated Watts vs. Total Watts
You calculate maximum heat dissipation by using one of these
methods.
• Calculated watts method
• Total watts method
Use calculated watts if you know exactly how many outputs and
inputs on each card are active at any given time. This method will
give you a lower, more accurate heat dissipation calculation than the
total watts method. With this method, use the formula below for
calculating the heat dissipation of each module. Then use these values
in step 1 of the Example Worksheet for Calculating Heat Dissipation
on page 268.
(points energized x watts per point) + minimum watts = heat
dissipation of module
Use total watts if you are not sure how many points on a module are
energized at any time. Total watts is the watts per point (with all
points energized) plus the minimum watts. Total watts generated by
each module are provided in the table on page 263.
Once you have determined which method you will use to calculate
the heat dissipation of your modules, see the Example Worksheet for
Calculating Heat Dissipation on page 268. This worksheet shows you how to
calculate the heat dissipation for the example SLC control system on page 267.