A 3-phase, 4-wire feeder supplies a continuous load of 75 amperes and a noncontinuous load of 75 amperes. What is the total demand for this feeder?

To determine the total demand for the feeder, it is essential to apply the demand calculation method as stipulated in the National Electrical Code. For feeders, especially when dealing with both continuous and noncontinuous loads, the approach includes the following considerations:

1. Continuous loads must be 125% of their rated value, as they are expected to carry a load for three hours or more.

2. Noncontinuous loads are considered at their full value since they do not have the same sustained load conditions.

In this case, the continuous load is 75 amperes. According to the code, we calculate 125% of this continuous load:

• 75 A x 1.25 = 93.75 A.

Next, we also consider the noncontinuous load, which is 75 amperes and included in full:

• Noncontinuous load = 75 A.

Now, to find the total demand for the feeder, we sum these two components:

• Total Demand = Continuous load (after applying the 125% rule) + Noncontinuous load

• Total Demand = 93.75 A + 75 A = 168.75 A.

While the total demand calculated is approximately 169 A, rounding per code compliance typically leads us to the nearest practical