Pull Box Symbol
Definition: The Pull Box symbol represents an enclosed metal or non-metallic junction enclosure installed in a conduit system to facilitate wire pulling, splicing, and routing of conductors between conduit runs, depicted in electrical wiring diagrams as a square or rectangular box with diagonal cross-hatching and the label 'PB', with conduit entry/exit points on all four sides, per NEC (NFPA 70) and ANSI Y32.2/IEEE 315 conventions.
Also known as: pull box, junction box, wire pull box, conduit pull box, PB, cable access box.
What the Pull Box symbol means
The Pull Box symbol in an electrical wiring or site plan indicates a code-mandated access enclosure at a strategic point in a conduit run that allows electricians to pull conductors through long conduit runs without exceeding maximum bend or length allowances, and to splice or redirect circuits as needed.
Pull boxes are required by NEC Article 314 whenever the total angle of conduit bends between pull points exceeds 360°, or when a conduit run exceeds certain lengths (in practice, typically 100 ft or after four 90° bends). The symbol communicates to installers and inspectors that an accessible, code-compliant junction point exists at that location, and to designers that conductors can be transitioned, spliced, or branched at the box.
How to identify the Pull Box symbol
The pull box symbol is drawn as a square or rectangle (typically 8–12 mm on the drawing) with a thin diagonal line from upper-left to lower-right and a second line from upper-right to lower-left, forming an X inside the box. The text 'PB' or 'PULL BOX' is written inside or adjacent to the symbol. Conduit entry and exit lines attach to the top, right, bottom, and left edges of the square, indicating the number and direction of conduit runs entering and leaving the box. This X-inside-square symbol distinguishes a pull box from a general junction box (which uses the same square but without the X, or with a dot at centre).
Function in a circuit
A pull box serves three primary functions in a conduit system: it provides an access point for pulling conductors through conduit without exceeding National Electrical Code fill and pulling-tension limits; it allows conductors to be spliced, tapped, or redirected to different conduit runs; and it provides a removable cover for future access for maintenance, troubleshooting, or circuit modifications. Pull boxes must be permanently accessible (not buried or concealed behind finished walls) per NEC 314.29, and their internal dimensions must be sized per NEC 314.28 to allow adequate conductor bending radius and fill.
Standards: IEC vs ANSI
| IEC 60617 | IEC 60617 does not specifically define a pull box symbol; the general enclosure or junction box symbol from IEC 60617-02 (conductors and connecting devices) is adapted with labelling. IEC 61439 covers the construction requirements for enclosures. |
|---|---|
| ANSI/IEEE 315 | ANSI Y32.2 / IEEE 315-1975 defines the general junction or pull box symbol as a square with diagonal lines or cross-hatching. NEC NFPA 70 Article 314 governs the installation requirements (sizing, accessibility, fill calculations) for pull boxes in North American wiring practice. |
| Key difference | ANSI/IEEE 315 provides the pull box schematic symbol (square with diagonal lines); IEC 60617 does not have an exact equivalent dedicated symbol. North American drawings follow IEEE 315 / NEC conventions almost exclusively for conduit system pull boxes. |
Terminals / pins
| Pin | Name |
|---|---|
| top | Top |
| right | Right |
| bottom | Bottom |
| left | Left |
Typical values
Standard sizes: 4-inch square, 4-11/16 inch square, 6×6, 8×8, 12×12 inches (sheet metal), up to 24×24 inches for large feeder pulls. Maximum conductor fill per NEC 314.28. Cover screws: stainless steel or galvanised. Material: galvanised steel, stainless steel, or NEMA 4X fibreglass for wet/corrosive locations.
Where the Pull Box symbol is used
- Industrial conduit runs exceeding 100 feet between panels or equipment termination points
- Commercial building branch circuit and feeder conduit systems where four or more 90° bends accumulate
- Underground conduit systems in parking structures and site lighting to provide pull points every 200 ft
- Data centre cable management at conduit routing transitions between cable trays and equipment rooms
- Outdoor switchgear and transformer feeders requiring weather-resistant (NEMA 3R or 4) pull access
- Hazardous (classified) locations requiring explosion-proof (NEMA 7 or ATEX) junction boxes at conduit pull points
Example
In a commercial lighting installation drawing, the pull box symbol appears at a corridor ceiling junction where three EMT conduit runs converge — one from the main electrical room (200 ft run), one feeding Zones A and B lighting circuits, and one feeding the emergency circuit. The PB symbol indicates where installers will pull the 12 AWG THWN conductors and make the required splices inside a 6×6×4 inch galvanised steel pull box.
Key facts
- The Pull Box symbol is a square with diagonal cross lines (X pattern) inside and 'PB' label, with conduit lines entering at Top, Right, Bottom, and Left edges, per ANSI Y32.2 / IEEE 315-1975.
- NEC Article 314.28 requires pull boxes in conduit systems where conductors 4 AWG and larger are present; box sizing is calculated as eight times the trade size of the largest conduit for straight pulls and six times for angle pulls.
- Pull boxes must be permanently accessible per NEC 314.29 — they cannot be concealed behind drywall, above sealed ceilings, or under slabs without an access panel.
- The pull box has four conduit entry/exit ports: Top, Right, Bottom, and Left, allowing conductors to enter from any direction in the conduit system.
- Enclosure ratings for pull boxes follow NEMA standards: NEMA 1 (indoor), NEMA 3R (outdoor weatherproof), NEMA 4 (watertight), NEMA 4X (corrosion-resistant), and NEMA 7 (explosion-proof for Class I hazardous locations).
- Pull boxes differ from junction boxes primarily in their larger size and purpose — pull boxes are sized to accommodate conductor bending radius during pulling, while junction boxes focus on splicing and terminal connections.
- In North American electrical drawings, pull boxes are designated PB followed by a number (e.g. PB-1, PB-2) and are typically shown on floor plan, electrical site plan, and conduit routing drawings.
Frequently asked questions
What does the pull box symbol look like in an electrical drawing?
The pull box symbol is a square with two diagonal lines forming an X inside it, labelled 'PB' or 'PULL BOX', with conduit lines connecting to its sides. The X inside the square distinguishes it from a simple junction or outlet box symbol.
What does the pull box symbol mean in a wiring diagram?
The pull box symbol indicates an accessible enclosure in the conduit system where electricians can pull conductors through long or complex conduit runs, make conductor splices, and redirect circuits to different conduit paths. It marks a mandatory code-required access point in the conduit installation.
What standard governs pull box installation?
NEC (NFPA 70) Article 314 governs pull box installation requirements in North America, including sizing (Article 314.28), accessibility (Article 314.29), and fill calculations. The schematic symbol follows ANSI Y32.2 / IEEE 315-1975 electrical drawing conventions.
When is a pull box required?
A pull box is required by NEC 314.28 when a conduit contains conductors 4 AWG or larger and the conduit run has more than two 90° bends, or for straight pulls when conductors must be pulled through sections too long to manage without access. In practice, pull boxes are typically installed every 100–150 feet or after every four 90° bends.
What are the pins or connections on a pull box symbol?
The pull box symbol shows four conduit connection points: Top, Right, Bottom, and Left. Each represents a conduit run entering or exiting the box. In a real installation, the box may use one, two, three, or all four entry points depending on the conduit routing.
What is the difference between a pull box and a junction box?
A pull box is primarily sized to accommodate conductor pulling and bending radius requirements during wire installation — it is usually larger than a junction box. A junction box is primarily used for making conductor splices and connections. In practice, both functions can occur in the same enclosure, and NEC Article 314 covers both under the same sizing and accessibility rules.
What designator is used for a pull box in electrical drawings?
Pull boxes in electrical drawings are designated PB followed by a sequential number, such as PB-1 or PB-3, to uniquely identify each pull box in the conduit routing schedule and drawing notes. This designator appears both in the symbol on the plan and in the panel schedule or conduit schedule.
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