Engineering Documentation

Table Of Contents
Chapter 2 Network Electrical Systems
Power Trunk Guidelines
70
| 231
125-3002
1 × 20.0
VA
=
20.0
VA
3 ×
19.4
VA
=
58.2
VA
228.25
VA
2. Determine the minimum number of power trunks you will need:
- Minimum number of trunks = 228.25 VA ÷ 100 VA = 2.28
-
Since this number is greater than 2, it will be necessary to use a minimum of
three power trunks.
NOTE:
This does not imply that transformers totaling 300 VA will be required.
Step 3 - Determine the Wiring Runs and Calculate the
Voltage Available at the Last Controllers of Each Trunk
Type
A wiring run is the distance from the transformer to the end controller in a series. It can
be composed of one or more legs. A leg is the distance from the transformer to the
first controller, or the distance from one controller to the next controller.
Figure Wiring Run shows the following:
L1, L2, and L3 are all legs of a wiring run to C3.
L1, L4, and L6 are all legs in a wiring run to C6.
L1, L2, and L5 are all legs in a wiring run to C5.
Fig. 41: Wiring Run.
1. Configure the power trunks so that the total VA rating of all controllers does not
exceed 100 VA per trunk.
2. Calculate the voltage available at the last controller on each run. Verify that it is
greater than the minimum required voltage for the controller.