Short answer: order a stainless box rated NEMA 4X-type / IP66, take every cable through a gland in the bottom wall, and fit one membrane breather rated IP66. The heat sets the size. A Pi 4, a LoRa concentrator card and the supply dissipate about 8 W, which lifts a 12 x 10 x 6 in stainless box 6.7 C above outside air: 36.7 C inside on a 30 C day, under the 40 C limit with 3.3 C to spare. Wall-mount boxes here are manufacturer-rated NEMA 4X-type / IP66, not UL listed, and NEMA itself does not test or certify enclosures. The size finder spans 6 x 4 x 4 to 60 x 36 x 16 in (H x W x D).
What the site does to the box
An outdoor gateway wall gives the box four loads, and each one points at a spec choice. Rain arrives wind-driven, and the day someone washes the wall you get jet splash, so the rating must cover water under pressure, not only falling rain. Dust and pollen settle into any opening, which matters for a fanless board with no filter to service. The sun loads the lid: cooling guides add 10-15 C to a small sealed steel box in full sun, more than the Pi's 8 W adds inside it. And a -5 to 30 C swing breathes the box every night. On a 98 % relative-humidity night, air drawn past the gasket condenses on the coldest surface at dawn. Most water damage in outdoor electronics starts there, not at the rain.
The rating to order: Type 4X / IP66
Order NEMA Type 4X with IP66 and move on to the fun parts. IP66 means dust-tight (first digit 6) and proof against powerful jets (second digit 6): IEC 60529 tests it with a 12.5 mm nozzle delivering 100 L/min from 2.5 to 3 m for at least 3 min. That is the driven-rain and wall-wash case. IP66 is a jet rating, though, not immersion; submersion starts at IP67 (1 m of water for 30 min), which a wall-mounted gateway does not face.
The steps down cost more than they save. Type 3R sheds falling rain, and its drain is an open hole of 3 to 6 mm under NEC 314.15, one that dust and splashed water also use. Molded plastic cases sold for single-board computers carry IP65, jets from a 6.3 mm nozzle at 12.5 L/min, which suits a covered porch and falls short of a washed wall. In US installations, NEC 110.28 states that IP ratings are not a substitute for enclosure type ratings, so write the type on the spec, not just the code. The NEMA 4X vs IP66 guide works through the conversion table, and the outdoor enclosures guide covers exposure and mounting in more depth.
304 or 316L stainless
Material follows the air around the box, not the electronics inside it. Inland and under an eave, 304 stainless with a #4 brushed finish handles outdoor weather for decades. Take 316L wherever salt reaches the wall: coastal air, a splash zone off a de-iced road, or industrial chlorides. The molybdenum in 316L lifts pitting and crevice resistance, and it earns its keep here, because 304 can pit at room temperature under a chloride deposit, including inside a gasket crevice. Proximity to salt is the trigger, so grade the site before you grade the steel. The stainless size finder filters every wall-mount box by grade and outside size.
Heat check: Pi 4 and LoRa gateway in a 12 x 10 x 6 in box
Fit the parts before you trust the watts. A Pi 4 board measures 3.4 x 2.2 in [86 x 56 mm], the LoRa concentrator stacks on it or sits beside it on the DIN rail, and a 5 V supply or PoE splitter plus a terminal strip complete the panel. The 9 x 4 x 4 in plastic boxes made for outdoor cable joints swallow a bare Pi and nothing else. A 12 x 10 x 6 in (H x W x D) box fits the rail, the splices and the glands with the door shut, and it sits inside the 6 x 4 x 4 to 60 x 36 x 16 in range the size finder covers.
The inputs:
- Outside air: 30 C, the top of a -5 to 30 C temperate site range.
- Inside-air limit: 40 C, the ambient rating most industrial electronics carry; the Pi board itself is documented to 50 C, so 40 C also covers the supply and the radio card.
- Heat load: 8 W. A loaded Pi 4 draws about 6 W at its 5 V input and about 3 W idle, the LoRa card adds about 1 W, and the supply wastes about 1 W.
- Box: 12 x 10 x 6 in stainless, with wall coefficient k = 3.7 W/m²K, the value this site uses for stainless enclosure heat.
In a sealed box the walls carry all the heat, so the temperature rise equals the heat load divided by k times the outside surface area. The thermal-resistance method behind it works for any box shape.
- Surface area: 2(12 x 10) + 2(12 x 6) + 2(10 x 6) = 504 in² = 0.325 m².
- Heat path: 3.7 W/m²K x 0.325 m² = 1.20 W per degree C.
- Rise: 8 W / 1.20 W per C = 6.7 C.
- Inside air: 30 C + 6.7 C = 36.7 C against the 40 C limit, so 3.3 C of margin.
Order the 12 x 10 x 6 in box for a shaded wall. The threshold worth remembering: with 10 C of allowed rise, from 30 C air to the 40 C limit, this box sheds 1.20 W/C x 10 C = 12 W. Above 12 W, buy surface or cooling. The 16 x 12 x 8 in box moves 1.99 W/C and carries the same 8 W at a 4.0 C rise, and sealed-box cooling options take over beyond that. Halve the load, an idle Pi fed from a PoE splitter at 4 W, and the rise halves to 3.3 C; the relation is linear, so every watt removed buys 0.8 C.
Sun moves the answer. A small sealed steel box in full sun runs 10-15 C above shade air, so at +10 C the design day starts at 40 C and the same box lands at 46.7 C. That is past the 40 C panel rule and inside the Pi's documented 50 C, but it is hard on the supply. The committed decision: mount in shade or under an eave, and size in the shade. When the box must sit on a pole or a roof, work the rooftop heat method and step up to the 16 x 12 x 8 in box, which lands near 44 C on the same design day.
Cold nights: -5 C starts and condensation
The cold end solves itself, because the box heats itself. At -5 C outside, the same 8 W holds the interior at -5 + 6.7 = +1.7 C, above freezing all night. The Pi is documented from 0 C ambient, so only the cold start, the first minutes at -5 C before self-heat builds, sits below the floor, and cold-soaked boards start in practice. If the site runs colder than -5 C, add a 10 W thermostat-controlled PTC heater on the panel: 10 W + 8 W = 18 W, and 18 / 1.20 = 15 C of rise, which holds the interior above freezing down to about -15 C outside.
Condensation is the real night problem. As the box cools, the air inside contracts and draws humid air past the gasket; at dawn it condenses on the back panel right above the board. A membrane breather rated IP66 fixes the cycle: the membrane passes air and water vapor, equalizes pressure, and blocks liquid water. Fit one in the lowest wall, where it doubles as a drain, and give the assembly the breather's rating. The breather-versus-drain comparison explains placement, and the breather rating question covers what the 4X marking survives. A drilled weep hole instead of a breather turns a Type 4X box into a 3R-class one and lets washed-in dust settle on the board.
Antenna, power and Ethernet: where the holes go
The antenna decides whether the install stays sealed. Best route: an N-type bulkhead connector in the lid or the upper side wall, antenna outside, no coax penetration at all. The bulkhead needs a 5/8 in [16 mm] hole and seals on its own gasket. Running the coax through an M20 gland also works, with the gland clamped on the cable and a drip loop below; the antenna feedthrough guide works through both routes.
Power and data land in the bottom wall, one gland per cable. A Cat5e run at 6 mm OD takes an M20 gland with a 4-8 mm insert, and the M20 hole size is 20.5 mm in any wall material. Two cables through one gland work only with a duplex insert that seals both, which the two-cables-one-gland guide sets out. Budget 1 in [25 mm] of depth behind the wall for the gland bodies and nuts. Leave a half-turn of slack in every cable below the box, so water running down the jacket drips off instead of into the gland.
Mounting it under the eave
Eave or shaded wall, every time: the sun load stays off and the top seam stays dry. Set the gland wall facing down, bolt the feet to masonry with stainless anchors, and put the door center near 60 in [1.5 m] so the status LEDs sit at eye level. A lockable latch pays for itself on any wall the public can reach. If mains land inside, NEC 110.26(A) wants clear working space where you service the box live: 3 ft [900 mm] of depth at these voltages, with room for a 90-degree door swing. A PoE-fed build keeps mains out of the box and skips that entirely. Kill the feeder and prove it dead before you open a live box. The mounting guide carries the height and clearance tables.
What to put on the order
Send this and the drawing round-trips once:
| Spec | Order | Why |
|---|---|---|
| Rating | NEMA 4X-type / IP66, manufacturer-rated, not UL listed | Driven rain, hose splash, dust |
| Material | 304 inland; 316L where salt reaches the wall | 304 pits under chloride deposits |
| Size | 12 x 10 x 6 in (H x W x D) | 8 W at a 6.7 C rise; rail, splices, glands |
| Cutouts | Bottom wall: one 20.5 mm hole per M20 gland, one 5/8 in [16 mm] hole for the N bulkhead | Entries off the weather side |
| Breather | One IP66 membrane breather drain in the lowest wall | Stops the night breathing cycle |
| Panel | Removable mounting panel with DIN rail | You build the rail outside the box |
On the custom route you set the material, all three dimensions and every cutout on one drawing, built from one piece, delivered in 10 business days counted from your approval of the drawing. If you would rather start from a size the finder already covers, the enclosure selector walks the same choices by environment and inside dimensions.
Enclosures for this job
Catalog sizes that suit the job this article answers, picked from its subject; open one for its full specifications.
| Enclosure | Material | Outside H x W x D / display | Rating |
|---|---|---|---|
| 12 × 10 × 6 in | 316L stainless | 12 x 10 x 6 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
| 16 × 12 × 8 in | 316L stainless | 16 x 12 x 8 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
| 10 × 8 × 6 in | 316L stainless | 10 x 8 x 6 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
| 20 × 16 × 8 in | 316L stainless | 20 x 16 x 8 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
Questions
Will the Raspberry Pi survive -5 C in a sealed enclosure?
Yes, while it runs. Its own 8 W keeps the air in a 12 x 10 x 6 in box about 6.7 C warmer, so the interior sits near +2 C on a -5 C night. Only the cold start, the first minutes before self-heat builds, sits below the board's documented 0 C floor, and cold-soaked boards start in practice. Sites colder than -5 C take a 10 W thermostat heater, which holds the interior above freezing down to about -15 C outside.
Does an antenna cable through the wall break the IP66 rating?
Not when every part carries its own rating. An N-type bulkhead seals on its gasket in a 5/8 in [16 mm] hole, and an M20 gland clamped on the coax seals in a 20.5 mm hole. The assembly takes the rating of its lowest part, so choose a gland or connector rated IP66 or better and the box stays IP66.
How much heat can a 12 x 10 x 6 in box shed before it needs cooling?
About 12 W. The 12 x 10 x 6 in stainless box moves 1.20 W per degree C through its walls, and with 30 C outside air against a 40 C limit you have 10 C of rise to spend: 1.20 x 10 = 12 W. Above that, buy surface, since a 16 x 12 x 8 in box moves 1.99 W per degree C, or move to a sealed-box cooling option.
Plastic or stainless for an outdoor Raspberry Pi?
Thermally they are close: polycarbonate moves heat at k = 3.5 W/m²K against 3.7 for stainless, about a 5 percent difference. Choose stainless for full sun, salt air and tamper resistance, and 316L wherever salt reaches the wall. A molded fiberglass or polycarbonate box suits a sheltered wall where weight matters.
Can I mount the enclosure in full sun?
Prefer shade. In shade the example box holds 36.7 C inside at 30 C air. Full sun adds 10 to 15 C for a small steel box, pushing the same box to about 47 C, past the 40 C design rule though inside the Pi's documented 50 C. If the box must sit in sun, step up to a 16 x 12 x 8 in box, which lands near 44 C.
