By David Wren
A question that is sometimes asked is, how can I check the operational temperature of a cable when it is working under design conditions?
This is quite straightforward and can be easily viewed in Wiring’s Schedules, which can be selected from the Display ribbon in both Sub Mains and Final Circuit modes.
In this example of a Final Board’s Schedule shown below, for Sub Section 2 of a Split Board, the information relating to the cable temperature can be seen on the right side of the Schedule, in the column ’Temp Factor/Ct/Cable Temp/Max Temp’. Here the last two sets of figures show the Operational Temperature of the cable under its design conditions and the cable’s Design Temperature Rating.
In this example, because the worst-case maximum design temperature must be for the PVC cables (which are rated at 70°C), I have entered a value of 70°C in the 'Operation Temp' box, as a maximum operational temperature for the cables. Any cables having a maximum operational temperature greater than the entered value, their results in the 'Temp Factor/Ct/Cable Temp/Max Temp' column will be shown in Red. As illustrated below.
Reviewing the data for the TP&N Ways 6 & 7, the cable type used here is LSF which is a 90°C rated cable. Under its design conditions it can be seen that the Operational Temperature is only 76.4°C, which is well within the performance specification for this cable type, but is also greater than the maximum temperature rating of the 70°C PVC cables in this final board.
By examining the cable data here in the Schedules, you can easily see that you simply need to increase the size of the LSF cables on Ways 6 & 7 from 2.5m² to 4mm², to reduce their operating temperature to be less than the 70°C rating of the PVC cables.
In this example, the Operational Temperature of these cables has been reduced to 65.8°C, which is within the temperature range of the adjacent 70°C PVC cables.