MI grounding and bonding practice questions

What the exam actually tests here

Grounding and bonding questions rarely ask you to recite a definition. They hand you a service or a feeder and ask for a conductor size, then wait to see if you pick the right table, read the right row, and catch the exception. The math is light. The judgment is the test.

• Sizing the grounding electrode conductor from the service conductors, using Table 250.66.
• Sizing the equipment grounding conductor from the overcurrent device, using Table 250.122.
• Knowing when an exception caps the size, like the 6 AWG copper limit on a run to a ground rod.
• Telling grounding apart from bonding, and main bonding jumper apart from system bonding jumper.

Worked example: sizing the grounding electrode conductor

Take a service fed with 3/0 AWG copper service-entrance conductors. The question asks for the minimum size of the copper grounding electrode conductor. Work it the way you would in the book, on the clock.

1. Go to Table 250.66 and find the row for the service conductor size. 3/0 copper falls in the “2/0 or 3/0 copper” row.
2. Read across that row. It calls for a 4 AWG copper grounding electrode conductor. That is your answer for a conductor serving the full electrode system.
3. Check the exception before you commit. Under 250.66(A), a grounding electrode conductor that runs only to a ground rod never has to be larger than 6 AWG copper, no matter what the table says.

The trap in this question is the exception. A candidate who stops at the table answers 4 AWG every time and gets burned on the version that runs to a rod. A candidate who skips the table and assumes the exception answers 6 AWG and gets burned on the version that serves the full system. You have to read both, in order, every time.

Why this topic costs points

Grounding and bonding bleeds points for two reasons, and neither is about being weak on theory.

• The right table, the right row. Article 250 holds more than one sizing table. Table 250.66 sizes the grounding electrode conductor from the service conductors. Table 250.122 sizes the equipment grounding conductor from the overcurrent device. Reach for the wrong one and the answer is wrong before you start reading.
• The exceptions hide the answer. The headline number in the table is often not the final number. The 6 AWG copper cap on a run to a ground rod is the classic example. On an open-book exam you are expected to find that exception, so the questions are written to punish anyone who does not.
• The clock. 80 questions in 150 minutes is under two minutes each. If you are flipping Article 250 from scratch on every grounding question, the time is gone by the back half of the exam.

How to drill grounding and bonding for the Michigan exam

Because Michigan is open book, the win is not memorizing Table 250.66. It is tabbing Article 250 in your own 2023 NEC and drilling until you land on the right table and row in seconds, exception check included. That is a lookup skill you build by reps under a timer, not by reading the code straight through.

Where to start

We are honest about what we have. We are not going to claim a specific number of grounding and bonding questions in the Michigan bank, because we have not published per-topic counts and you should not trust prep that invents them. What we do is route you correctly. The free 15-minute diagnostic tells you whether grounding and bonding is actually one of your weak NEC chapters, then sends you into focused practice on the topics costing you the most. No point grinding grounding if your real leak is motors.