Weatherproof Box Symbol
Definition: The Weatherproof Box symbol represents an outdoor-rated electrical enclosure used in wiring diagrams to denote a junction box, outlet box, or device box fitted with a cover that protects its contents from moisture, dust, and physical impact in compliance with NEMA 3R/IEC IP54 or higher ingress-protection ratings.
Also known as: outdoor junction box, in-use cover box, WP box, exterior electrical box, rain-tight box, NEMA 3R box.
What the Weatherproof Box symbol means
The Weatherproof Box symbol identifies an enclosure installed in outdoor or damp locations where standard open-face boxes would expose conductors and devices to rain, condensation, or debris. In a wiring diagram the symbol marks the physical location of a protected box on an exterior wall, deck, post, or equipment pad.
The symbol communicates that all wiring entering and exiting the enclosure must be routed through weatherproof fittings, conduit hubs, or liquid-tight connectors, and that any devices housed inside—outlets, switches, or junction points—must be rated for wet or damp locations per NEC Article 406 and IEC 61439.
How to identify the Weatherproof Box symbol
The glyph is drawn as a square or rectangular outline with a small 'WP' label or a drop/rain indicator, sometimes shown with a hinged cover line across the top. The four sides have connection terminals labeled Top, Right, Bottom, and Left indicating conduit or cable entry/exit points. The enclosed rectangle distinguishes it from an open or indoor box.
Function in a circuit
A weatherproof box provides a sealed, mechanically protected enclosure for electrical connections in outdoor or wet environments. It prevents moisture ingress that could cause short circuits, corrosion, or shock hazards, and it provides a secure mounting point for devices such as GFCI outlets, switches, or cable splices. The cover—either a bubble/while-in-use type or a flip-lid—maintains the IP/NEMA rating even with cords plugged in.
Standards: IEC vs ANSI
| IEC 60617 | IEC 60670-1 covers general requirements for enclosures for accessories for household and similar fixed electrical installations; weatherproof boxes comply with IP54 (dust-protected, splash-proof) or IP65 (dust-tight, jet-proof) per IEC 60529 ingress-protection classification. |
|---|---|
| ANSI/IEEE 315 | NEMA 250 and UL 514C classify weatherproof boxes in the United States; NEMA 3R (rain-tight, outdoor) and NEMA 4 (watertight) are the most common ratings. NEC Article 314 governs box installation requirements and NEC Article 406.9 governs outdoor outlet covers. |
| Key difference | IEC uses IP-code ratings (IEC 60529) to specify the degree of protection; NEMA uses category numbers (3R, 4, 4X) that map approximately but not exactly to IEC IP codes—NEMA 3R is roughly equivalent to IP54, and NEMA 4 to IP65. |
Terminals / pins
| Pin | Name |
|---|---|
| top | Top |
| right | Right |
| bottom | Bottom |
| left | Left |
Typical values
Enclosure material: PVC, galvanised steel, or aluminium; NEMA 3R / IP54 minimum for outdoor damp locations; NEMA 4 / IP65 for direct water exposure; box volume sized per NEC 314.16 conductor-fill calculations (typical 18–52 cubic inches for residential).
Where the Weatherproof Box symbol is used
- Exterior wall-mounted GFCI outlets on patios, decks, and pool areas requiring NEC-mandated weatherproof covers
- Outdoor lighting circuit junction points where branch cables are spliced and routed to landscape or security fixtures
- Service entrance conduit bodies and meter-base feed points exposed to rain and UV
- Industrial equipment pads where motor feeders transition from underground conduit to surface wiring
- Irrigation system controller wiring junctions in lawn and garden installations
- Carport and garage apron EV-charger circuit termination boxes
Example
In a residential backyard wiring diagram, the weatherproof-box symbol appears at a deck post where a GFCI outlet is fed from a 20 A outdoor branch circuit; conduit enters through the bottom knockout, the GFCI device mounts inside, and a bubble while-in-use cover attaches to the face, maintaining NEMA 3R protection when a cord is plugged in.
Key facts
- The Weatherproof Box symbol has four entry/exit terminals (Top, Right, Bottom, Left) representing conduit or cable knockouts on each side of the enclosure.
- Minimum ingress-protection rating for outdoor damp locations is NEMA 3R (rain-tight) or IEC IP54; direct water exposure requires NEMA 4 or IEC IP65.
- NEC Article 406.9 requires a weatherproof in-use cover for 15 A and 20 A receptacles installed in outdoor locations, even when a cord is inserted.
- Box volume must be calculated per NEC 314.16 to ensure adequate space for all conductors, devices, and fittings—insufficient fill is a common code violation.
- All conduit entries into a weatherproof box must use weatherproof hubs, LB conduit bodies, or liquid-tight fittings to maintain the enclosure's IP/NEMA rating.
- In NEMA 3R-rated boxes, weep holes at the bottom allow condensation to drain without allowing rain entry—these holes must remain unobstructed.
- Weatherproof boxes used in corrosive environments (coastal, pool decks) should be Schedule 80 PVC or 316 stainless steel to resist chloride corrosion.
Frequently asked questions
What does the weatherproof box symbol mean in a wiring diagram?
The weatherproof box symbol indicates an outdoor-rated or wet-location electrical enclosure at that point in the circuit. It tells the installer that all wiring connections must be made inside a NEMA 3R/IP54 (or higher) rated box and that weatherproof entry fittings and in-use covers are required.
What is the difference between a weatherproof box and a standard junction box?
A standard junction box is rated for dry indoor locations only. A weatherproof box has a gasketed, sealed cover and rated conduit hubs to prevent moisture ingress, meeting NEMA 3R, NEMA 4, or IEC IP54/IP65 requirements for damp or wet outdoor environments.
What does NEMA 3R mean for a weatherproof box?
NEMA 3R (rain-tight) means the enclosure is constructed to prevent rain from entering and provides limited resistance to ice formation, but is not fully watertight. It is the minimum rating acceptable for most outdoor residential and commercial installations per NEC Article 406.9.
What is the IEC equivalent of NEMA 3R for an outdoor box?
NEMA 3R is approximately equivalent to IEC IP54 (protected against splashing water from any direction). NEMA 4 is approximately equivalent to IP65 (protected against water jets). The IEC IP rating system is defined in IEC 60529 and is used outside North America.
How many terminals does a weatherproof box symbol have?
The weatherproof box symbol has four terminals—Top, Right, Bottom, and Left—representing the knockout or conduit-entry locations on the four sides of the enclosure. The actual box may have additional knockouts depending on its size and manufacturer.
Does a weatherproof box need a special cover when an outlet is in use outdoors?
Yes. NEC Article 406.9(B) requires a weatherproof 'in-use' or 'bubble' cover for 15 A and 20 A receptacles in outdoor locations so the enclosure maintains its rating even when a cord is plugged into the outlet.
What standard governs weatherproof electrical boxes in the United States?
NEMA 250 defines the enclosure types, UL 514C covers metallic outlet boxes and fittings, and NEC Article 314 sets installation rules for electrical boxes. For outdoor receptacle covers specifically, NEC Article 406.9 applies.
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