*Applies to NEC 408.4(B) (2023 edition; the 2026 change summaries we reviewed show no change). Checked November 2026. Written by Panel Label Company in Clayton, NC. Our founder spent 13 years in commercial construction as a project manager and superintendent.*
Every switchboard, switchgear lineup and panelboard fed by a feeder in a commercial or industrial building needs a permanent label saying where its power comes from. That's NEC 408.4(B). It's one of the easiest labels to get right, and a common punch list item when it's missing or written in marker. We make these as custom engraved electrical panel labels.
The reason is practical. When someone needs to kill power to a panel, they shouldn't have to trace conduit across the building to find the feeder breaker. The source label tells them which piece of equipment to go to and where it sits.
On a commercial job, source labels usually get ordered at the same time as the panel nameplates and directories, near the end of the job. If you build them from the one-line diagram early, they're ready before the inspector or the owner's punch walk.
What 408.4(B) requires
NEC 408.4(B) requires all switchboards, switchgear and panelboards supplied by a feeder, in buildings other than one- and two-family dwellings, to be permanently marked with:
- The identification of the equipment where the power originates, such as the switchboard or panel name.
- The physical location of that equipment, such as the room or area.
- A label that's permanently affixed and durable enough for the environment it's in.
- A method that is not handwritten. A marker on masking tape or the inside of the door doesn't count.
The 2026 change summaries we reviewed show no change to 408.4 itself. Check the edition your state has adopted with our NEC adoption by state tracker, and confirm local amendments with your inspector.
Where it applies, and where it doesn't
- Applies: panelboards, switchboards and switchgear fed by a feeder in commercial, industrial, institutional and multifamily buildings. Think of every downstream panel on a job: lighting panels, receptacle panels, mechanical panels, distribution panels, and panels fed through a transformer.
- Doesn't apply: one- and two-family dwellings. The rule specifically excludes them.
- Service equipment: a main switchboard fed directly by service conductors isn't "supplied by a feeder." Many project specs and inspectors still expect it to be identified, so label it anyway.
- Project specs can ask for more. Commercial specs often include section 26 05 53, which typically calls for engraved nameplates on every panel showing its name, voltage, and source. Duke University's spec is one example. When the spec and the code differ, meet both.
What to put on the label
Keep it to two facts: what feeds this equipment and where that equipment is. Use the same names that appear on the one-line diagram and the panel schedules, so the label, the drawings and the directory all agree.
| Equipment being labeled | Example label text |
|---|---|
| Lighting panel LP-2A | FED FROM: DP-2 / ELEC RM 210 |
| Receptacle panel RP-1B | FED FROM: XFMR T-1B (DP-1, ELEC RM 105) |
| Distribution panel DP-2 | FED FROM: MSB, BKR 4 / MAIN ELEC RM 101 |
| Mechanical panel MP-1 | FED FROM: SWBD-1 / ROOF ELEC ENCL |
| Panel fed by a transformer | FED FROM: XFMR T-3 / MEZZ (T-3 FED FROM DP-3) |
A few habits that keep inspectors and facility staff happy:
- Include the breaker number in the source equipment when space allows. It saves the next electrician a search.
- For transformer-fed panels, name the transformer and where it gets power, so the full path is clear.
- Match the job's color convention. Many specs assign colors by voltage or system, such as black/white for 277/480V, blue/white for 120/208V and red/white for generator-fed or emergency equipment. Check your spec before ordering.
- Put the source label on the panel itself, not only on the directory card. The directory card gets lost; the label stays.
Not handwritten, and built to last
408.4(B) rules out handwriting and requires a label durable enough for its location. In practice there are three common choices:
| Option | Good for | Watch out for |
|---|---|---|
| Engraved 2-ply acrylic (phenolic replacement) | Indoor and outdoor panels, mechanical rooms, specs that call for engraved nameplates | Costs more than a printed sticker |
| Printed industrial vinyl | Indoor panels where the spec allows adhesive labels | Cheap paper or office labels fade and peel |
| Label maker tape | Temporary use during construction | Often not accepted where a spec calls for engraved nameplates |
Engraved acrylic is the safe default. The text is cut into the material, so it can't rub off, and it can be screwed or riveted on where adhesive isn't allowed. Panel Label engraves on UL-recognized Rowmark DurMark two-ply acrylic (UL File E354751), the same kind of material many specs describe as "engraved laminated plastic."
Related rules on the same panel
- 408.4(A), circuit directory: every circuit and circuit change needs a legible, permanent description. It has to be clear and specific, cover spare positions, not depend on who occupies a space ("Bob's office" fails once Bob leaves), and explain any abbreviations. On a switchboard it goes at each breaker; on a panelboard, in a directory on or inside the door or in an approved spot next to it. Build one free with our panel schedule template.
- 408.6, available fault current and SCCR: in the 2023 NEC, switchboards, switchgear and panelboards outside one- and two-family dwellings need the available fault current and the date it was calculated field marked on the enclosure at the point of supply. The newer edition text adds a field-marked short-circuit current rating based on the breakers installed. Check which edition your state enforces. Our fault current labeling guide covers what goes on the label.
- 110.16, arc flash warning: most commercial panels also need an arc flash label. See arc flash labels.
- 110.22, disconnect identification: each disconnect needs to be marked with what it serves. Our NEC 110.22 guide covers it.
- New in 2026, 408.10(F): caution signs and labels on switchboards, switchgear and panelboards go in a readily accessible spot on the front of the enclosure, according to Minnesota's 2026 NEC change summary.
Ordering source of supply labels
Most "fed from" labels fit on a 3" or 4" wide plate with two lines of 1/4" text. Prices are $3.90 per label plus $0.40 per square inch:
| Size | Typical use | Price each |
|---|---|---|
| 3" x 1" | Short source names, one or two lines | $5.10 |
| 4" x 1" | Source plus room, two lines | $5.50 |
| 5" x 1.5" | Source, breaker and room, three lines | $6.90 |
| 6" x 2" | Panel nameplate and source on one plate | $8.70 |
- Design online with live pricing in the label designer, with no minimum order.
- Labeling a whole job? Upload your panel list as an Excel or CSV file and every label gets generated at once.
- Fast and free: most orders ship in 1-2 business days from Clayton, NC, with free shipping over $99. Net 30 terms are available for approved contractors.
Order engraved electrical panel labels
FAQ
Does a residential panel need a source of supply label? Not under 408.4(B). One- and two-family dwellings are excluded. Multifamily buildings are not excluded.
Can I write the source on the panel directory card? No. The marking can't be handwritten, and it has to be permanently affixed. A typed directory card can supplement the label, but it shouldn't replace it.
Does the main switchboard need one? If it's fed directly by service conductors, it isn't "supplied by a feeder," so 408.4(B) doesn't strictly apply. Most specs and inspectors still expect it to be identified, so label it.
What size text should I use? The NEC doesn't set a size for this label. Many specs call for 1/4" letters. Our label readability calculator suggests text size by viewing distance.
Do transformer-fed panels need a source label? Yes. A panel fed through a transformer is still supplied by a feeder. Name the transformer and where it gets its power, so the whole path is clear.