Michigan Electrical Contractor Exam Preparation

Below is a small sample of our exam prep questions:

1. What would be the calculated minimum trade size for a rigid metal conduit (RMC) that contains only two (2) 250 kcmil THHN conductors?
◦ Step_1: Use Chapter 9, Table 5 which lists the area as 0.397 sq-in.
◦ Step_2: Calculate the total area of the conductors: 0.397 x 2 = 0.794 sq-in
◦ Step_3: Use Table 4: “Article 344 – Rigid Metal Conduit (RMC)” Wires 31% column, find an area equal to or larger than 0.794 sq-in, which is 1.056 sq-in, slide to the left to size a trade size 2 inches.

2. What is the maximum size instantaneous trip breaker allowed for a 10-hp, three phase, 230-volt, squirrel cage, full load current motor?
◦ Step 1: Table 430.250 lists the FLC at 28 A
◦ Step 2: Table 430.52 for the multiplier of 800%. Therefore, 28 Amps x 8 = 224 A
◦ Step 3: Per 430.52(C)(1) use Table 240.6(A) 200 A.

3. Using the optional method, what size service is required in a dwelling that has a floor area of 1,000 square feet, a 10 kW range, a 5 kW water heater, a 1 kW dishwasher, a 5 kW clothes dryer, and a 3 ton (30 amp) heat pump with 10 kW of backup heat?
◦ Step 1: Add the following; (3,000 General Lighting, 3,000 Small Appliance, 1,500 Laundry, 10,000 Range, 5,000 Water Heater, 1,000 Dish Washer, 5,000 Clothes Dryer) = 28,500 VA General Load.
◦ Step 2: Then derate; 28,500 – 10,000 = 18,500 x 40% = 7,400 VA. Then the larger of the Heating or AC loads; 30 amp x 240-volts = 7,200 VA + 10,000 VA for backup heat = 17,200 VA.
◦ Step 3: Then derate, 17,200 VA x 40% = 6,880 VA.
◦ Step 4: Then add these loads all up; 10,000 VA + 7,400 VA + 6,880 VA = 24,280 VA / 240-volts = 101.17 amperes.
◦ Step 5: Therefore, the minimum service rating would be 125 A

Why Wait? Call Jessica Martinez 980 417 0160 Click to call now!, or click ADD TO CART