Last Updated: July 2026 • Reviewed for NEC 2023 Compliance
Conduit installation is a craft that combines mechanical skill with code knowledge. Whether you are running EMT in a commercial building, RMC for a service entrance, or PVC underground, the National Electrical Code (NEC) dictates fill limits, support spacing, bending radii, and approved applications. This field guide covers the conduit types, bending techniques, NEC fill calculations, support requirements, and step-by-step installation procedures with worked examples.
Conduit Types and When to Use Each
EMT (Electrical Metallic Tubling) — NEC Article 358
EMT is thin-wall steel tubing, the most common conduit in commercial interiors. It is lightweight, easy to bend with a hand bender, and relatively inexpensive. EMT is permitted in exposed and concealed locations, concrete, and dry locations. It is not permitted where subject to severe physical damage, in cinder concrete, or in wet locations unless all supports are corrosion-resistant and the fittings are listed for wet locations (NEC 358.10 and 358.12).
RMC (Rigid Metal Conduit) — NEC Article 344
RMC is heavy-wall galvanized steel pipe with threaded connections. It provides maximum physical protection and is used for service entrances, industrial environments, and areas subject to damage. RMC can be used in all atmospheric conditions and is approved for direct burial without additional protection. It requires a heavy-duty bender or threaded fittings for direction changes.
Rigid PVC Conduit — NEC Article 352
Rigid PVC (Schedule 40 or 80) is nonmetallic conduit used primarily underground and in wet or corrosive environments. PVC is lightweight, non-conductive, and resistant to moisture and chemicals. It is not permitted in locations subject to physical damage unless Schedule 80 is used. PVC requires expansion joints for long runs because it expands and contracts significantly with temperature changes (NEC 352.44).
| Type | NEC Article | Best Use | Bending Method |
|---|---|---|---|
| EMT | 358 | Commercial interiors, exposed work | Hand bender |
| RMC | 344 | Service entrances, industrial, direct burial | Hydraulic bender or threaded fittings |
| Rigid PVC | 352 | Underground, wet/corrosive locations | Heat bender or factory elbows |
Bending Techniques
Hand Bending EMT
EMT is bent using a hand bender, which has a shoe (the curved channel that forms the bend), a foot pedal, and a handle. The four most common bends are:
- Stub-up (90°): A single 90-degree bend to change direction vertically or horizontally. Measure from the end of the conduit to the desired height, subtract the take-up (found on the bender, typically 5 inches for 1/2" EMT, 6 inches for 3/4"), and mark the conduit at that point. Place the mark at the arrow on the bender, foot on the pedal, and pull the handle to 90°.
- Back-to-back: Two 90-degree bends to create a U-shape. Measure the distance between the bends, place the first mark at the star on the bender, bend 90°, flip the conduit, and align the second mark at the arrow.
- Offset: Two bends in the same direction to shift the conduit path around an obstacle. Use the offset multiplier based on the bend angle: 30° bends use a multiplier of 2.0, 45° uses 1.4, and 60° uses 1.15. Mark the conduit at the desired offset distance multiplied by the factor, then bend at the marked angle.
- Saddle: A three-bend or four-bend configuration to cross over a pipe or obstruction. A 3-point saddle uses a center bend (typically 45°) and two side bends (22.5°) in the opposite direction.
Bending Fundamentals
The minimum bend radius for conduit is defined in NEC Chapter 9, Table 2. For EMT, the radius must not be less than that shown in Table 358.24. A kinked or flattened bend is a code violation and must be re-bent. Always check the bender's markings for the correct take-up and multiplier values.
NEC Fill Calculations (Chapter 9, Table 1)
The NEC limits how much of a conduit's cross-sectional area can be filled with conductors. The fill percentages from Chapter 9, Table 1 are:
| Number of Conductors | Fill Percentage |
|---|---|
| 1 | 53% |
| 2 | 31% |
| 3 or more | 40% |
To calculate fill, use the conductor cross-sectional areas from NEC Chapter 9, Table 5 (for individual conductor types) or Table 5A (for compact conductors). Compare the total conductor area against the conduit internal area from Chapter 9, Table 4. Equipment grounding conductors, if present, are counted in the fill calculation per NEC 250.122 and Chapter 9, Note 2.
Fill Calculation Example
Scenario: 3/4-inch EMT with four 12 AWG THHN copper conductors.
Step 1: Find conductor area: 12 AWG THHN = 0.0133 in² per Chapter 9, Table 5.
Step 2: Total conductor area: 4 × 0.0133 = 0.0532 in²
Step 3: 3/4" EMT internal area (Chapter 9, Table 4) = 0.213 in²
Step 4: Fill percentage: 0.0532 ÷ 0.213 = 24.9%
Result: 24.9% is under the 40% limit for 3+ conductors. Approved.
Support Spacing Requirements
Conduit must be securely fastened at specific intervals. The support spacing requirements differ by conduit type:
| Conduit Type | NEC Section | Fastened Within | Max Spacing |
|---|---|---|---|
| EMT | 358.30 | 3 ft of termination | 10 ft |
| RMC | 344.30 | 3 ft of termination | 10 ft |
| Rigid PVC | 352.30 | 3 ft of termination | Per Table 352.30 (varies by size: 3 ft for 1/2"-1", 5 ft for 1-1/4"-2") |
EMT and RMC have a straightforward 10-foot maximum spacing. For RMC, NEC 344.30(A) also allows fastening within 3 feet of each termination (box, fitting, etc.). For PVC, the spacing varies by trade size and is specified in NEC Table 352.30. Straight runs of EMT and RMC that are threaded into boxes or fittings may be unfastened for up to 10 feet if the run is in a finished surface (NEC 358.30(B) Exception and 344.30(A) Exception).
Step-by-Step Installation with Worked Examples
Example 1: EMT Stub-Up in a Commercial Wall
Run 3/4" EMT from a junction box up 8 feet and through a stub-up into the ceiling space.
1. Measure 8 feet from the box. Subtract 6 inches take-up for 3/4" EMT. Mark at 7'-6".
2. Place mark at the arrow on the hand bender. Pull to 90°.
3. Cut the conduit to length after the bend. Deburr the cut end.
4. Install a connector and coupler at each end. Secure with a setscrew or compression fitting.
5. Fasten within 3 feet of the box and at 10-foot intervals. Since this run is 8 feet, one strap at 3 feet from the box suffices.
Example 2: PVC Underground Run to a Detached Garage
Run 1" Schedule 40 PVC underground, 24" deep (per NEC Table 300.5 for direct-buried nonmetallic raceway), 50 feet to a subpanel.
1. Dig trench to 24" depth. Lay PVC with solvent-welded joints (primer and cement per manufacturer instructions).
2. Install factory 90-degree elbows at each end to rise into the buildings.
3. Install an expansion joint if the run exceeds 25 feet to accommodate thermal expansion (NEC 352.44).
4. Pull a ground wire (equipment grounding conductor sized per NEC 250.122) since PVC is non-conductive.
5. Backfill with material free of rocks. Mark the conduit path for future reference.
Example 3: RMC Service Entrance
Run 2" RMC from the meter base to the service panel through an exterior wall.
1. Use threaded RMC with a hub at the meter base and a connector at the panel.
2. Thread each end with a 3/4" NPT thread per inch. Apply anti-oxidant compound to the threads.
3. Install a grounding bushing on the panel end to bond the metal conduit to the grounding system (NEC 250.92).
4. Fasten within 3 feet of each termination and at 10-foot intervals.
5. Seal the conduit at the wall penetration to prevent moisture ingress.
Example 4: EMT Offset Around a Pipe
Run 1/2" EMT that needs to shift 2 inches to pass a 1" water pipe.
1. Use 30° bends with a multiplier of 2.0. Distance between marks: 2" × 2.0 = 4".
2. Mark the conduit 4 inches apart. Bend the first mark to 30° on the bender.
3. Flip the conduit, align the second mark at the arrow, and bend to 30° in the same direction.
4. The conduit now offsets 2 inches, clearing the pipe. Verify the bend is smooth and the conduit is not kinked.
Shop Conduit, Fittings, and Bending Tools at PES Supply
Browse our full selection of EMT, RMC, PVC, fittings, connectors, and hand benders. Call (502) 790-0600 for quantity pricing and project support.
Frequently Asked Questions
How many conductors can I put in a conduit?
The limit depends on the conduit size and conductor gauge. Use NEC Chapter 9, Table 1 fill percentages (53% for one conductor, 31% for two, 40% for three or more) and compare the total conductor area from Table 5 against the conduit internal area from Table 4. Always account for equipment grounding conductors.
What is the maximum spacing between conduit supports?
For EMT (NEC 358.30) and RMC (NEC 344.30), the maximum spacing is 10 feet, with fastening required within 3 feet of each termination. For Rigid PVC, the spacing varies by trade size and is specified in NEC Table 352.30.
Can EMT be used outdoors?
EMT can be used in wet locations if all supports, fittings, and boxes are corrosion-resistant and listed for wet locations (NEC 358.10(B)). However, EMT is not permitted where subject to severe physical damage. For exposed outdoor runs subject to damage, RMC is the better choice.
Do I need a separate ground wire in PVC conduit?
Yes. PVC is non-conductive, so it cannot serve as an equipment grounding conductor. You must install a separate equipment grounding conductor sized per NEC 250.122 inside the PVC raceway.
What is the minimum burial depth for PVC conduit?
For direct-buried rigid PVC conduit carrying circuits up to 30V, the minimum depth is 24 inches per NEC Table 300.5. For 0-30V residential branch circuits with GFCI protection, the depth can be reduced to 6 inches. For circuits over 30V, consult Table 300.5 for the specific depth based on the circuit voltage and location.
Disclaimer: This guide is for educational and informational purposes. Always verify installations with a licensed electrician and confirm compliance with the applicable NEC edition and local amendments. PES Supply is located in Louisville, KY. Call (502) 790-0600 or (888) 876-0007 for assistance.
