Maryland conduit fill practice questions

The worked example

Here is a conduit fill question worked the way you want to work it on test day, with the table you open at each step. The math is the part most people get wrong, so slow down on the first one and let the steps become automatic.

Setup

You have four 12 AWG THHN conductors going into one conduit, and you need the maximum fill percentage that the code allows for that count.

Step 1, count the conductors

Four conductors. Chapter 9, Table 1 splits the rule by how many conductors are in the raceway, so the count is the first thing you establish, before you touch any number.

Step 2, read the row in Chapter 9, Table 1

Table 1 gives three rows. One conductor may occupy 53 percent of the conduit internal area. Exactly two conductors may occupy 31 percent. Over two conductors may occupy 40 percent.

• 1 conductor: 53 percent of the internal area.
• 2 conductors: 31 percent of the internal area.
• Over 2 conductors: 40 percent of the internal area.

Step 3, pick the right row

Four conductors is more than two, so it falls in the over two conductors row. The maximum fill is 40 percent of the conduit internal cross sectional area.

That is the percentage step. A full sizing problem then takes the conductor area from Chapter 9, Table 5 and the conduit area from Chapter 9, Table 4 to confirm the wire fits the trade size. But the decision that trips people up is this first one, choosing the right row in Table 1 for the conductor count in front of them.

Why conduit fill costs points

Conduit fill looks easy because it is open book, and that is exactly why it bleeds points. The number is right there in Chapter 9, so people skip drilling it, then lose time on test day hunting across three tables under the clock.

• The row trap: the 53, 31, and 40 percent rows are easy to swap under pressure. A guy reads the two conductor row for a three conductor pull and the whole answer is wrong from the first line.
• Three tables, one answer: a full fill problem walks Table 1 for the percentage, Table 5 for conductor area, and Table 4 for conduit area. Not knowing which one to open first is what eats the clock.
• The clock: 70 questions in 3 hours 30 minutes for journeyperson, and the master exam packs 30 calculations into 90 questions in 4 hours. Every slow lookup is a question you do not get back.

With 70% to pass and only about 27 percent clearing the exam, the calculation families are where the bar gets decided. Conduit fill is one you can make automatic with reps.

Practice conduit fill the right way

The best way to drill this topic is not a giant trivia pile. It is finding which article families are actually costing you points, then running the flip path on those until the lookup is automatic. We are not going to claim a magic question count for conduit fill, because we have not published verified per topic counts and we are not going to invent one. What we will do is point you at the right work.

Start with the free Maryland diagnostic. It shows your projected score and the article families dragging it down, so you know whether conduit fill is even your weak spot before you spend a night on it. From there the full platform drills your weak areas with original questions on the 2020 NEC.

Ready to see where you stand? Take the free Maryland diagnostic.

Conduit fill questions guys ask