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newSchoolWorks.com › VoTechWorks › Building & Construction › Electrical › Conduit Bending: Rigid, IMC, and EMT Systems for Building Wiring › Lesson 12
BLD-ELEC05-04 · Lesson 12 · 20 clock hours · practice

Conduit System Integration: Full-Run Design, Bend, Install, and Document

Objective. Students independently design, calculate, bend, install, and document a complete conduit system—including at least one 90° stub, one offset, and one saddle—connecting two panel locations on a full-size mock-up wall, producing a conduit schedule and as-built sketch.

Conduit System Integration: Full-Run Design, Bend, Install, and Document

This lesson brings together every skill you have built in this course. You will design a conduit run from scratch, calculate every measurement, bend and install the pipe, verify conductor fill, and leave behind a record that any electrician can follow years later. That final document—the as-built sketch and conduit schedule—is what separates a professional installation from one that just passes rough-in.

Safety First

Before you pick up a bender, review your PPE requirements. Wear safety glasses whenever cutting or reaming—metal chips travel fast. Wear cut-resistant gloves when handling cut conduit ends; freshly cut EMT and IMC edges are razor sharp. When drilling into the mock-up wall, confirm there are no hidden conductors in the path, and use a GFCI-protected outlet for the drill. If at any point a live circuit is nearby, lockout/tagout (LOTO) procedures apply—de-energize, lock, tag, and verify zero energy before working within reach. Never assume a panel is de-energized; use a non-contact voltage tester to confirm. Keep the work area clear of trip hazards, especially pull string and scrap conduit.

Reading the Design Brief

Your design brief gives you a start point (panel A knockout), an end point (panel B knockout), two obstacle heights, and a conductor count. Before touching material, extract these values and sketch a rough centerline path on graph paper. Identify where each bend type is required:

Label each bend location with a letter (A, B, C…) and note the obstacle height for offsets and saddles. This map becomes the backbone of your calculation sheet.

Calculation Sequence

Work through calculations in a fixed order to avoid errors.

1. Gain and developed length. Every 90° bend in EMT introduces a gain—the pipe takes a shorter path through the corner than the sum of two straight legs. Standard gains are published in bender charts; always use the chart for your specific bender and conduit size rather than memorizing a single number. The developed length of a 90° bend is the arc length your bender consumes from the pipe stock.

2. Offset shrink. An offset raises the conduit by the obstacle height. The shrink is the amount by which the two-bend offset shortens the straight-line run. Shrink = obstacle height × a multiplier that depends on the bend angle. Common offset angles and their multipliers:

3. Saddle shrink. A three-bend saddle over an obstacle uses a center bend equal to twice the obstacle height (e.g., 45° outer bends, 90° center) and introduces its own shrink value, also found in bender charts.

4. Cut list. Subtract all gains and shrink values from the straight-line segment lengths to produce the actual cut lengths for each stick. Record every number on your bending log before cutting.

Execution at the Mock-Up Wall

With approved calculations in hand, work through a repeatable sequence:

1. Cut each stick to the calculated length using a pipe cutter; never use a hacksaw if a cutter is available—it leaves a cleaner, rounder end.

2. Ream every cut end inside and out to remove burrs that would damage conductor insulation during the pull.

3. Bend using your marked arrow and reference lines. Make the 90° stub first, check the stub height with a tape, then complete offsets and saddles in order from one end to the other.

4. Dry-fit the entire run before strapping. Confirm the run sits flush to the wall at all strap points and that panel knockouts align.

5. Strap at intervals required by the applicable NEC section for the conduit type. EMT and IMC each have their own maximum support-spacing and within-distance-of-box rules—look them up in the current NEC rather than relying on memory.

6. Pull conductors. Apply listed conduit lubricant; never use petroleum products on thermoplastic insulation. Pull all conductors simultaneously where possible to reduce jamming.

7. Verify fill. Count conductors and look up the allowable conduit fill percentage in NEC Chapter 9. For three or more conductors the limit is 40% of the interior cross-sectional area.

Producing the As-Built Documents

An as-built sketch reflects what was actually installed, not what was originally planned. Draw a plan view (top-down) and an elevation view (side) to scale on graph paper. Dimension every segment, note bend locations with their angles, and mark every strap location. Legibility matters—another electrician must be able to pull conductors or replace a section using only your sketch.

A conduit schedule is a table. Each row represents one conduit run and includes at minimum: trade size, conduit type (EMT, IMC, RMC), total length, number and size of conductors, and support-spacing intervals. Leave a column for remarks (e.g., expansion fittings, conduit bodies).

Stand-Up Presentation

Your five-minute presentation must walk the class through your design logic, your calculations, and one thing you would do differently. Speak to the sketch—point to specific bends and dimensions. Be ready to justify your conductor fill calculation and your support spacing choice. The rubric awards points for accuracy, documentation quality, and clear communication, with 80% required to pass.

Key terms10

Developed lengthThe length of conduit stock consumed by a bend, measured along the arc; must be accounted for when calculating cut lengths to avoid short sticks.
GainThe amount a 90° bend shortens the total run compared to two straight legs meeting at a right angle; always use the bender manufacturer's chart for the specific bender and conduit size.
ShrinkThe reduction in the straight-line distance of a run caused by an offset or saddle bend; calculated as obstacle height multiplied by the multiplier for the chosen bend angle.
Conduit fillThe ratio of the total cross-sectional area of all conductors to the interior cross-sectional area of the conduit; NEC Chapter 9 limits this to 40% for three or more conductors.
As-built sketchA dimensioned drawing made after installation that records exactly what was installed, including bend locations, strap points, and segment lengths, for future reference and maintenance.
Conduit scheduleA tabular document listing each conduit run by trade size, type, length, conductor count and size, and support intervals; part of the permanent project record.
Offset multiplierA fixed number corresponding to a chosen offset bend angle used to calculate shrink; for example, a 30° offset multiplier is 2.0, meaning shrink equals twice the obstacle height.
Lockout/Tagout (LOTO)An OSHA-required procedure to de-energize equipment, apply a personal lock and tag, and verify zero energy before performing any work on or near electrical systems.
ReamingThe process of removing burrs from the inside and outside of a freshly cut conduit end to protect conductor insulation from damage during the wire pull.
Trade sizeThe nominal designation of a conduit by diameter (e.g., ½", ¾", 1"), which is used to look up fill tables and support-spacing requirements in the NEC.

Worked examples4

1. A ¾" EMT run must rise 8" as a 45° offset to clear a beam. Calculate the shrink and the distance between the two offset bends (spread) if the center-to-center spacing is determined by the 45° multiplier approach. The 45° shrink multiplier is 1.4.
  1. Identify the obstacle height: 8 inches.
  2. Select the shrink multiplier for a 45° offset: 1.4.
  3. Calculate shrink: 8 × 1.4 = 11.2 inches. Wait—that is the spread (distance between bend marks), not the shrink. Clarify: for a 45° offset the shrink = obstacle height × 0.4 (the portion beyond the height itself), and the spread = obstacle height × 1.414 (hypotenuse of a 45° right triangle). Use the standard trade formula: shrink = obstacle height × (multiplier − 1) only applies to certain references. Use the accepted trade values: shrink for 45° offset = obstacle height × 0.4.
  4. Shrink = 8 × 0.4 = 3.2 inches. This 3.2" must be subtracted from the straight-line run length when calculating the cut length of the stick containing the offset.
  5. Spread (distance between the two bend marks on the conduit) = obstacle height × 1.414 = 8 × 1.414 ≈ 11.3 inches. Mark the first bend arrow, measure 11.3" toward the second bend location, and mark there.
Answer: Shrink = 3.2 inches; spread between bend marks ≈ 11.3 inches. Subtract 3.2" from the straight-line segment length when building the cut list.
2. A 30° offset must clear a 6-inch obstacle. Calculate the shrink and the spread between the two bend marks.
  1. Obstacle height = 6 inches.
  2. For a 30° offset: shrink multiplier = 2.0 (this is the spread multiplier); the shrink fraction is 0.5 × obstacle height using the accepted trade shortcut, or more precisely shrink = obstacle height × (1/sin 30° − 1/tan 30°). Use the trade shortcut accepted in NCCER materials: shrink = obstacle height × 0.5.
  3. Shrink = 6 × 0.5 = 3.0 inches.
  4. Spread = obstacle height × spread multiplier for 30° = 6 × 2.0 = 12.0 inches.
  5. Mark the first bend arrow on the conduit, then measure 12.0" and mark the second bend location.
Answer: Shrink = 3.0 inches; spread = 12.0 inches. The straight-line run length is reduced by 3.0" on the cut list.
3. A three-bend saddle in ½" EMT must clear a 4-inch pipe crossing. The center bend is set at 45° and the two outer bends are each 22.5°. The saddle shrink for a 4-inch obstacle using a center 45° three-bend saddle is approximately 3/16" per inch of obstacle height (a commonly published value is 3/16" × obstacle height in inches). Calculate the saddle shrink.
  1. Identify obstacle height: 4 inches.
  2. Use the published shrink value for a three-bend 45° center saddle: 3/16" per inch of obstacle height.
  3. Convert 3/16" to a decimal: 3 ÷ 16 = 0.1875 inches per inch of height.
  4. Shrink = 4 × 0.1875 = 0.75 inches (¾").
  5. Subtract ¾" from the straight-line distance of the run segment that contains the saddle when building the cut list.
Answer: Saddle shrink = ¾ inch (0.75"). Reduce the cut length of that stick by ¾".
4. A ¾" EMT conduit run has a straight horizontal segment of 48 inches followed by a 90° stub-up. The bender chart for this bender shows a gain of 5 inches for a 90° bend in ¾" EMT. The stub height (finished measurement from the floor to the center of the box knockout) must be 12 inches. What length do you mark on the conduit as the stub, and what is the cut length of the stick?
  1. The stub mark on the conduit is the distance from the end of the pipe to the bender's arrow mark. For a 90° bend, stub mark = desired stub height − gain = 12 − 5 = 7 inches. Place the arrow mark 7 inches from the end of the conduit.
  2. The total cut length of the stick = horizontal segment + stub mark distance = 48 + 7 = 55 inches.
  3. Cut the stick to 55 inches, mark 7 inches from one end as the bend arrow location, bend at that mark, and the finished stub will measure 12 inches.
Answer: Arrow mark = 7 inches from the end; cut length = 55 inches.

The math in this lesson2

Learners compute offset shrink and spread, saddle shrink, and stub-up marks with gain for a full conduit run.
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Brush up in the math halls at newSchoolWorks.com:
In class: Each student receives a design brief specifying start point, end point, two obstacle heights, and conductor count; they independently calculate all developed lengths, shrink, and cut lists before touching any material, submitting calculations for instructor review. · Students execute the full installation on the mock-up wall: cut, bend, ream, strap, and terminate all conduit sections, then pull conductors and verify fill; instructor observes and may not assist except for safety issues. · After installation, students produce a neat as-built sketch (plan view and elevation) and a completed conduit schedule listing trade size, type, number of conductors, and support locations; present the completed package to the class in a 5-minute stand-up explanation.
Materials: Full-size mock-up wall with panel knockout locations, hand benders, EMT and IMC stock, pipe cutters, reamers, straps, drill, conductors, pull string, lubricant, tape measure, combination square, graph paper, ruler, NEC codebook, bending log
Check: All bends within ±¼″ of design dimensions; conduit schedule accurate and complete; as-built sketch legible and dimensionally consistent with installed run; 5-minute stand-up explanation addresses all instructor questions; instructor uses a 10-point rubric with 80% required to pass.

Practice check8

Answer each question, then check it. Nothing is recorded; this is your own practice.

NCCER Electrical – Conduit Bending
1. When a 45° offset is used to clear a 10-inch obstacle, what is the shrink that must be subtracted from the straight-line run length?
NCCER Electrical – NEC Code Application
2. Which NEC resource do you consult to verify that the conductors you are pulling comply with conduit fill requirements?
OSHA 10 – Electrical Safety / Hazard Control
3. A worker is about to drill through a mock-up wall that may contain an energized branch circuit. What is the correct first action before drilling?
NCCER Electrical – Conduit Installation
4. After cutting a stick of EMT to length with a pipe cutter, the next step before bending or connecting should be:
NCCER Electrical – NEC Code Application
5. For a three-conductor pull in ¾" EMT, the maximum allowable conduit fill percentage is:
NCCER Electrical – Documentation
6. An as-built sketch differs from a design drawing primarily because it:
OSHA 10 / NCCER Electrical – Safe Work Practices
7. During a conductor pull, which lubricant is NOT acceptable for use with thermoplastic-insulated (THHN) wire?
NCCER Electrical – Documentation / State Journeyman Knowledge
8. A conduit schedule entry for a run should include at minimum:
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