Michigan Electrical Master Exam Preparation

Below is a small sample of our exam prep questions:

1. Calculate the maximum standard rating of a motor branch circuit, short circuit, or ground fault protective device given the following conditions:
230 volts single-phase, 2 HP, AC polyphase motor, Inverse Time Breaker?
◦ Step_1: Table 430.248 lists the FLC at 12 amperes.
◦ Step_2: Table 430.52 lists the multiplier at 250% (2.50).
→ Calculate; 12 amperes x 2.50 = 30.0 amperes.
◦ Step_3: Table 240.6(A) lists a standard rating fuse as 30 A.

2. Calculate the required minimum ampacity of the conductor size for fire pump power circuits, given: 88 A fire pump motor, 10.6 A pressure maintenance pump, 10 A accessory fire equipment?
◦ Step_1: Per 695.6(B)(1), 125% of the pump motor, and maintenance pumps. Therefore; 88.0 amps + 10.6 amps = 98.6 amps. Then multiply 98.6 amps x 125% = 123.25 amps.
◦ Step_2: 100% of the associated fire pump accessory equipment. Therefore; 10.0 amps x 100% = 10.0 amps.
◦ Step_3: Add all the loads; 123.25 + 10.00 = 133.25 amps

3. What is the minimum size ungrounded aluminum Type THW conductors required for a service for the following four service disconnects with 100A OCP? Disconnects 1-4 rated at: 92.5 A, 83 A, 83 A, 45 A?
◦ Step_1: Per 230.80, 230.79 Calculate the total service load by adding the individual loads; 92.5 + 83 + 83 + 45 = 303.5 amps.
◦ Step_2: Using Table 310.15(B)(16) slide down the 75 deg C, Aluminum column to 310 amps, then slide to the right to size the service conductors at 500 kcmil.

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