Electrical Labeling Cheat Sheet

A one-page quick reference for the garage wire/box labeling convention — meant to be printed and posted in the mechanical room so the rules are at hand while wiring. The full rationale, code citations, and per-box checklist live in Electrical Planning → Wire & Box Labeling Convention; this page is the condensed field copy.

Print copy

A print-ready version is at printable/electrical-labeling-cheat-sheet.html (and the rendered printable/electrical-labeling-cheat-sheet.pdf). Print color, letter-size, and tape it inside the panel door or next to the workbench.

Golden rule

Label every cable as you pull it, before wire-nutting. Retrofitting labels onto installed wiring is the #1 cause of “what is this wire?” mysteries — second only to no labels at all.

Which tool labels what

Tool	Media	Use for
Brother P-touch PT-D210 (purchased 2026-06-05)	TZe-FX231 (½” Flexible ID, black on white)	Wire & cable labels inside boxes. Flexible-ID tape wraps round NM-B and sticks to itself; laminated and water-resistant. Flat labels lift off PVC sheath within a few years.
Brother P-touch PT-D210	Standard laminated TZe-231 (came with bundle)	Flat, durable labels — coverplate/box IDs, faceplates, parts bins. Not for wrapping round cable.
DYMO LabelWriter	30336 Multipurpose / 30252 Address	Flat surfaces only: panel directory, breaker faces, coverplate/box IDs, faceplates, Shelly covers, parts bins. Never on wire jackets.
Black Sharpie	permanent marker	Box ID on framing stud at rough-in (temporary until drywall).
Colored vinyl tape	½” — 9-pack on hand	Conductor color-banding (wrap twice, visible without disturbing the wirenut).

Tape note

The wire-wrap tape is TZe-FX231 (Flexible ID), not TZe-SL self-laminating — the SL line only runs on industrial P-touch printers and won’t fit the PT-D210.

Cable label format (every cable, every box)

Two lines on the sheath, 1–2” from the box entry, readable after wire-nutting:

• Line 1 — Circuit number, matching the panel directory exactly
• Line 2 — Direction + source/destination: IN from upstream / OUT to downstream

CKT 22              CKT 22                 CKT 14/16 MWBC
IN from B-14        OUT to BAY-3 LIGHTS    IN from PANEL

Source/destination = a box ID (B-15), PANEL, or a function (BAY-1 LIGHTS).

Conductor color-banding

Conductor function	Band	Notes
Constant hot (line, Leg A)	none — bare black	The bare black wire is itself the ID
Switched hot (load)	🔴 Red	~1” from device end
Traveler (3-way)	🔵 Blue	Both travelers, both ends
Shared neutral (MWBC)	🟡 Yellow	Both ends + written MWBC on jacket
UPS-protected hot	🟠 Orange	Mirrors orange-outlet UPS convention
Leg B / Phase B (240V, feeder)	🟤 Brown	L2 on 240V circuits & subpanel feeder
White re-identified as hot	⚫ Black on white	Both ends — NEC 200.7(C)
Low-voltage / Class 2 jacket	⚪ Grey	Flags Cat6 / alarm / sensor vs. line voltage
Equipment ground	none (bare/green)	Green tape reserved for retrofit re-ID only
White	not used	Invisible on neutrals, ambiguous on hots

Box numbering — B- means Box, not a circuit

• Format: B-NN — B = Box. Numbered sequentially across the entire garage in install order (B-1, B-2, … B-37), independent of circuit. B-14 is just the 14th box in the garage; there is no “B circuit.”

• B-NN vs CKT NN are two different IDs that get recorded together:

  ID	Means	Answers
  B-14	Box #14 — a physical location	Where is it?
  CKT 22	Breaker in panel slot 22	What feeds it?

  One circuit usually feeds several boxes: CKT 22: B-14 → B-15 → B-16.

• Marked twice: Sharpie on framing stud at rough-in, then DYMO label inside the cover plate after finish

• Recorded in the circuit schedule with location + height: B-14: N wall workbench, 48" AFF, CKT 22

• Already assigned: B-1–B-7 are taken by the opener / cord-reel / pillar circuit (see the ceiling-door install brief). New boxes start at B-8.

Switches, relays & other devices

A switch box, relay box, or disconnect is still just a box — it gets a B-NN like everything else, and its cables use the same CKT / IN-OUT format. What’s different:

• Conductor banding (plain outlet runs need none; switch legs do):
  • 🔵 Traveler (3-way) → blue, both ends · 🔴 Switched hot / load → red · ⚫ White used as hot → black band, both ends (NEC 200.7(C))
• Shelly relay: DYMO label on the device/cover; the switch-input wire gets a P-touch SHELLY SW INPUT label
• Coverplate DYMO names the function so it’s readable without opening the box: B-12 · BAY LIGHTS 3-WAY
• Rule of thumb: the box gets B-NN; the coverplate/device gets the human-readable function; the panel directory ties CKT → boxes → function together.

Worked example — the 3 vehicle-bay light outlets

Three ceiling outlets, one per bay (depth-midpoint), feeding the linked Barrina rows. On their own dedicated 20A lighting circuit, 3-way + Shelly switched. The lights plug in (cord-and-plug), so there’s no “OUT to lights” cable — only the NM-B chain between boxes. Numbers below are illustrative; assign real ones in install order.

Box IDs (Sharpie on joist + DYMO inside coverplate):

B-8 · BAY-1 LIGHTS    B-9 · BAY-2 LIGHTS    B-10 · BAY-3 LIGHTS

Cable labels (P-touch, chained from the switch/relay box B-11):

B-8     CKT 7                CKT 7
        IN from B-11         OUT to B-9 (BAY-2 LIGHTS)

B-9     CKT 7                CKT 7
        IN from B-8          OUT to B-10 (BAY-3 LIGHTS)

B-10    CKT 7
        IN from B-9          (end of run — no OUT)

Panel directory (DYMO): 7 20A CKT 7 Vehicle bay lights (B-8 → B-10) — 3 rows, Shelly 3-way

Special-purpose labels

Scenario	Label content	Where
Dedicated 240V circuit	30A 240V — LIFT / 50A 240V — WELDER	Cable + disconnect/receptacle face
Critical-load (UPS) circuit	UPS — orange outlets only	Cable + faceplate (DYMO)
MWBC	CKT 14/16 MWBC — handle-tied	Cable (P-touch) + breaker face (DYMO)
3-way traveler run	3-WAY: B-22 ↔ B-23	Both cables in the run
Shelly relay SW input	SHELLY SW INPUT	On the small-gauge switch wire
Outdoor / wet location	WET	At box entry
Empty conduit / future pull	LV — empty — 2026 / LV — 1× Cat6	Both ends of the tube

Panel directory (DYMO — one row per breaker)

1    20A    CKT 1    Perimeter outlets — N wall (B-1 → B-7)
3    20A    CKT 3    Perimeter outlets — E wall (B-8 → B-13)
5    30A    CKT 5    2-post lift (240V) — B-30 mech room disconnect

Update the directory the same day any circuit is energized.

MWBC — extra care (NEC 200.4 + 210.4)

A lost shared neutral puts 240V across 120V loads. So:

• Both hots on a handle-tied 2-pole breaker (NEC 210.4(B))
• Shared neutral grouped/wire-tied to its two hots at the panel (NEC 200.4(B))
• Jacket label lists both circuit numbers in red-leg / black-leg panel order: CKT 14/16 MWBC
• Shared neutral gets a 🟡 yellow band at both ends, every box and at the panel

Photo-document before drywall

1. Open every box; fan the cables so all labels read
2. Photograph the framing box ID and all cable labels in one shot
3. File to pictures/YYYY-MM/ with a paired .md noting box ID + circuit(s)
4. Re-photograph each box with cover-plate labels after finish

Related

• Wire & Box Labeling Convention — full convention with code citations
• Critical Circuit UPS Strategy — orange-outlet UPS convention this mirrors
• Decisions Log — “2026-05-18 — Electrical Wire & Box Labeling Convention” decision record