How to Run EMT for a New Circuit in a Tenant Space
Why this matters
A light-commercial add is where a residential crew finds out how much the raceway itself is doing. In EMT the conduit is the protection, the support, often the equipment grounding path, and the reason a pull goes smoothly or ends with a stuck fish tape and stripped insulation at the fourth bend. The inspection failures are not exotic: a fifth quarter-bend between pull points, straps 14 ft apart over a ceiling grid, a set-screw connector that was never tightened and leaves the box ungrounded, five conductors where the derating nobody did would have pushed the conductor size. Plan the run on paper first and almost all of it disappears.
Safety first: the panel is in an occupied building
Plan the shutdown with the landlord and the tenant. A tenant-space panel feeds people who are working. Schedule the outage, then open the panel's main or feeder, lock and tag it under 29 CFR 1926.417 for construction work (1910.333(b)(2) where the work is not construction), and prove the bus and every conductor you will touch dead with a CAT III or better meter tested on a known live source before and after, per NFPA 70E Article 120 (120.5 in the 2021 edition, renumbered in 2024). Read the panel's arc-flash label before the cover comes off.
Do not land conductors in an energized panel to avoid the shutdown. Under NFPA 70E (current edition), energized work needs a justification that inconvenience does not meet, and an energized work permit. If the owner refuses an outage, the job waits.
Cutting and reaming. Wear eye protection when cutting EMT and reaming it; a hacksaw or band saw leaves a burr, and a cut-off wheel throws hot metal. Every cut end is reamed before it gets a fitting (NEC 358.28, as adopted) because a burr strips insulation during the pull.
Ladders over a ceiling grid are set on the floor with the grid tiles removed above you, used under 29 CFR 1926.1053, and never leaned against the grid or its hanger wires.
Licensing and the permit follow your state and the AHJ; tenant-improvement electrical work generally needs both.
Plan the run on paper: the layout sheet
The job: a tenant converts a storage room into a work room and wants two new 20 A, 120 V receptacle circuits along one new wall, fed from panel LP-2, a 208Y/120 V three-phase panel in the electrical closet 40 ft away. One run of 1/2 in EMT carries both circuits from the panel to the first box; short runs connect box 1 to boxes 2, 3 and 4 inside the new metal-stud wall.
RUN 1: PANEL LP-2 -> BOX 1, 1/2 in EMT
length: 2 ft up + 38 ft across + 6 ft down = 46 ft
bends: 90 at the top of the panel riser 90 deg
90 from the ceiling run down 90 deg
offset into box 1, 2 x 30 deg 60 deg
total 90 + 90 + 60 = 240 deg
limit 360 deg between pull points: PASS
straps: first 1.5 ft above panel, last 1 ft above
box 1, so 46 - 1.5 - 1 = 43.5 ft between
code, 10 ft max: 43.5 / 10 = 4.35
-> 5 spans, 6 straps
shop, 8 ft max: 43.5 / 8 = 5.4
-> 6 spans, 7 straps
fill: black + red + 2 white + green = 5 x 12 THHN
1/2 in EMT takes 9 x 12 THHN: PASS
CCC: 4 current-carrying -> 80 percent
30 A x 0.8 = 24 A, at least 20 A: PASS
Bends: no more than 360 degrees between pull points. NEC 358.26 caps the bends in one run between pull points (a box, a conduit body) at the equivalent of four quarter bends. Offsets count at their full angle: a 30 degree offset is two 30 degree bends, 60 degrees. If the count runs over, add a pull box or a conduit body and count again from there. The bending itself is its own card; see related: How to Bend a 90 and an Offset in Half-Inch EMT.
Support: within 3 ft of each termination and every 10 ft. NEC 358.30(A) requires EMT securely fastened within 3 ft of each box, cabinet, conduit body or other termination, and at intervals not exceeding 10 ft. Horizontal runs through framing members at intervals of 10 ft or less count as supported, if fastened within 3 ft of terminations (358.30(B)). Support comes from the building structure, never from the ceiling grid or the grid's hanger wires (NEC 300.11).
Fill and derating. Fill comes from Chapter 9 and Annex C; the 9-conductor figure above is the 12 AWG THHN entry for 1/2 in EMT. See related: Conduit Fill + Sizing Quick Reference. The two neutrals are current-carrying because each serves its own circuit, so the conduit carries four current-carrying conductors and NEC 310.15(C)(1) applies 80 percent to the 90 C ampacity (30 A for 12 AWG THHN). The adjusted 24 A still clears the 20 A breaker, and the circuit stays at 20 A anyway under 240.4(D) and the 75 C termination limit. The green EGC is not counted.
The installation, in order
1. Set the boxes first. Mount 4 in square boxes, 2-1/8 in deep, with two-device rings in the new wall at the height on the drawings, secured to the studs (the depth comes from the fill count below). Boxes are the pull points and the strap targets; set them before you measure a single stick.
2. Run the riser from the panel. Use a steel set-screw connector in a top knockout, with an insulated throat or a plastic bushing so the conductors do not drag on the edge. Strap within 1.5 ft above the panel, under the 3 ft limit.
3. Run the ceiling leg. Make the 90 at the top of the riser, run along the structure above the ceiling, and strap at no more than 8 ft (the shop spacing), to framing or to beam clamps on the structure. Couple sticks with set-screw couplings, each screw tightened until it bites; a loose screw is a dead ground path you will find at the test.
4. Drop into the wall and offset into box 1. Make the 90 down, pass through the top track, and put a 30 degree offset at the box so the conduit enters its knockout straight. Strap within 1 ft above the box.
5. Choose fittings for the location. Set-screw fittings are fine in a dry interior. Compression (raintight) fittings go where the run is in a wet location, since NEC 358.42, in substance, wants fittings suited to a wet location there, or where the specification calls for them, which many do for damp areas too. Concrete-tight fittings go in a pour.
6. Pull. Fish from box 1 back to the panel, attach all five conductors together with the ends staggered and taped so the head is no fatter than it has to be, lubricate, and pull in one steady draw. Black on phase A for circuit 1, red on phase B for circuit 2, the two neutrals identified by circuit under NEC 200.4(B) (one white, one white with a colored stripe, or tagged), green for the EGC. Leave at least 6 in of free conductor in every box (NEC 300.14).
7. Terminate. Land the EGC on the box's ground screw and pigtail it to the receptacle; bond the box (NEC 250.148). Torque every termination to its marked value with a calibrated tool (NEC 110.14(D)). Land the breakers last, in the de-energized panel, after finish tests 1 and 2 below.
Boxes 2 to 4: the box depth and the circuit load
Each box on the new wall carries one receptacle from each circuit on a two-device ring, so both circuits pass through boxes 1, 2 and 3 and end in box 4. The short runs between boxes stay level at box height and pass through the stud punch-outs, so they need no bends; fastened within 3 ft of each box, a run through studs at 24 in is supported under 358.30(B).
Box fill for a through box. Four insulated conductors come in and four go out: 8 allowances. Two receptacles at two allowances each: 4. All the EGCs together: 1. That is 8 + 4 + 1 = 13 allowances, at 2.25 cu in each for 12 AWG, 13 x 2.25 = 29.25 cu in. A 4 in square box 1-1/2 in deep holds 21.0 cu in, which fails; the 2-1/8 in deep box holds 30.3 cu in, and 30.3 is more than 29.25, pass, before counting any volume marked on the ring. Box 4, at the end, has 4 + 4 + 1 = 9 allowances, 20.25 cu in, but takes the same box so the wall is uniform. See related: Box Fill Worked Counts for Common Boxes.
Load. Each circuit serves four receptacles. NEC 220.14(I) counts 180 VA per single or duplex receptacle on one yoke in a non-dwelling occupancy: 4 x 180 = 720 VA, and 720 VA / 120 V = 6 A of calculated load on a 20 A circuit. That figure is for the panel schedule, not a cap on what the tenant plugs in; a coffee brewer or a printer that runs for hours is a continuous load counted at 125 percent. See related: Continuous Load and the 125 Percent Rule.
Finish test: the raceway is a continuous ground path
Before re-energizing, with the conductors not yet landed on the breakers:
- Raceway continuity. If the design relies on the EMT as the EGC (NEC 250.118), it has to be proven, not assumed. Disconnect the green conductor at box 1 temporarily and measure, with a low-resistance ohmmeter, from the box to the panel's equipment ground bar. A 46 ft run of tight fittings reads a small fraction of an ohm; the shop treats anything over 0.5 ohm as a loose fitting to find before moving on. Reconnect the green conductor and measure again.
- Insulation resistance of each conductor to ground and to each other, at the voltage the instrument maker and the job's acceptance basis call for. See related: How to Insulation Test a Feeder or Branch Circuit.
- Re-energize with the panel cover on, standing to the side of the panel face as the feeder is restored, then close each breaker. Meter each receptacle: hot to neutral about 120 V, hot to ground about 120 V, neutral to ground near zero.
- Record the bend count, strap count, fill, test readings and circuit numbers, and update the panel directory.
What would change the plan. A sixth quarter-bend's worth of turns needs a pull point, not a stronger pull. A third circuit in the same run brings six current-carrying conductors and the same 80 percent factor (4 to 6 conductors), so 12 AWG still works; a seventh moves you to 70 percent. A wet location, such as a run on an exterior wall exposed to weather, changes the fittings, not the strap spacing. A building whose specification requires a wire EGC in every raceway still gets this continuity test, because the box bonding still depends on the fittings.
References
- NFPA 70, National Electrical Code, 2023 edition (2020 where the section moved), as adopted by your jurisdiction: 110.14(D), 200.4, 250.118, 250.148, 300.11, 300.14, 310.15(C)(1), 358.26, 358.28, 358.30, 358.42, Chapter 9 and Annex C
- NFPA 70E, Standard for Electrical Safety in the Workplace, current edition, Article 120 and energized work provisions; 29 CFR 1926.417 and 1926.1053
- See related: Conduit Fill + Sizing Quick Reference; How to Bend a 90 and an Offset in Half-Inch EMT; How to Insulation Test a Feeder or Branch Circuit