Engineering Documentation

Chapter 2 – Network Electrical Systems
Power Trunk Guidelines
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Example
1. Configure the power trunks so that the total VA rating of all devices does not
exceed 100 VA per trunk. (Many configurations are possible. See Figure
Completed Example Layout for the configuration used in this example.)
– Trunk A: (1 × 5.7) + (3 × 13.6) + (1 × 32.75) = (1 x 15 = 88.55 VA)
– Trunk B: (1 × 27.9) + (1 × 20) + (2 × 19.4) = 86.7 VA
– Trunk C: (1 × 27.9) + (1 × 19.4) + (1 × 5.7) = 53.0 VA
2. Calculate the voltage available at the last controller on each run to verify that it is
greater than the minimum required voltage for the device.
Fig. 42: Completed Example Layout.
3. Calculate how much power is drawn through each leg:
Trunk A
Leg 1 = VA (C1) + VA (C2) + VA (C3) + VA (C4) + VA (C5)
= 15 + 13.6 + 13.6 + 13.6 + 32.75
= 88.55 VA
Leg 2 = VA (C1) + VA (C2) + VA (C3) + VA (C4)
= 10 + 13.6 + 13.6 + 13.6
= 55.8 VA
Leg 3 = VA (C4)
= 13.6 VA
Leg 4 = VA (C1) + VA (C2)
= 15 + 13.6
= 28.6 VA
Leg 5 = VA (C1)
= 15 VA