What is the minimum size THHN branch circuit conductor required for a noncontinuous load of 27 kW in an EMT raceway with two 3-phase, 480-volt branch circuits?

To determine the minimum size THHN branch circuit conductor required for a noncontinuous load of 27 kW in a three-phase system at 480 volts, you can follow these steps:

First, calculate the current (in amps) using the formula for three-phase power:

[

P = \sqrt{3} \times V \times I \times \text{Power Factor}

]

Assuming a power factor of 1 (since it's a noncontinuous load), you can rearrange to solve for current (I):

[

I = \frac{P}{\sqrt{3} \times V}

]

Substituting the values:

[

I = \frac{27,000 \text{ W}}{\sqrt{3} \times 480 \text{ V}}

]

[

I \approx \frac{27,000}{830.3} \approx 32.5 \text{ A}

]

Once you have the current, you must choose a conductor that can handle this load safely. According to the National Electrical Code (NEC), THHN conductors have specific ampacity values that change based on their ambient temperature rating, insulation type, and whether the conductor is in a raceway