Sure, let's solve this step-by-step to determine the appropriate size of copper branch circuit conductors required for an air conditioning unit with a nameplate rating of 33.5 A, 208 V, 3-phase.
### Step 1: Calculate the Required Current
Given the nameplate rating is 33.5 A, we must account for a safety factor. Generally, this factor for continuous loads is 1.25. Therefore, the required current can be calculated as:
[tex]\[ \text{Required Current} = 33.5 \, \text{A} \times 1.25 \][/tex]
### Step 2: Perform the Multiplication
[tex]\[ 33.5 \times 1.25 = 41.875 \, \text{A} \][/tex]
### Step 3: Determine the Appropriate Conductor Size
Now, we need to choose the proper conductor size based on the calculated required current, which is 41.875 A. Below are the standard sizes for copper conductors and their corresponding ampacities:
- No. 10 AWG: Up to 40 A
- No. 8 AWG: Up to 55 A
- No. 6 AWG: Up to 75 A
- No. 4 AWG: Up to 95 A
Since the required current, 41.875 A, exceeds the ampacity of a No. 10 AWG conductor, we move to the next size.
- No. 8 AWG: Capable of handling up to 55 A, which covers our required current of 41.875 A.
Therefore, the proper size copper branch circuit conductor for this air conditioning unit is No. 8 AWG.
### Final Answer
The correct size copper branch circuit conductor for a 33.5 A, 208 V, 3-phase air conditioning unit is:
- b. No. 8
