Short answer: order the 10 x 8 x 4 in 316L stainless wall-mount enclosure, manufacturer-rated NEMA 4X / IP66; not UL listed. Let an 8-port fanless switch inside draw its power over IEEE 802.3af PoE down one of the five Cat5e runs that already reach the balcony box. The switch adds about 5 W, and a sealed box that size sheds it through 0.196 m² of wall for a 7 K rise. The worst case is 42 °C inside on a 35 °C day. No mains reaches the wall, the conduit takes no new cable, and the basement switch spends 15.4 W of spare PoE budget to run the whole upper floor.
Which enclosure rating does a covered balcony need?
Pick a sealed stainless wall box manufacturer-rated NEMA 4X / IP66: the type covers the splash and wind-driven rain a covered spot still catches, and the -10 to +35 °C ambient range is decided by the switch's rating, not the box's.
NEMA 250 adds the X as an extra 200 hours of salt-spray corrosion testing against an AISI 304 stainless specimen, which is why the suffix belongs on any outdoor metal box. Stainless walls and the common gasket elastomers take the cold without complaint: EPDM stays flexible down to about -50 °C and silicone to about -60 °C, typical O-ring handbook values. The cold-sensitive part is the switch. Fanless industrial units are routinely rated -40 to +75 °C, while consumer switches start at 0 °C and would cold-start outside their rating on a -10 °C morning, so one industrial-grade purchase covers both ends of the year. In US installations, NEC 110.28 says an IP code cannot stand in for an enclosure type rating, so write the Type 4X on the drawing as well. The tests behind each letter are compared in the NEMA 4 vs 4X vs IP66 guide.
How does the switch get power without mains at the wall?
Yes: IEEE 802.3af guarantees 12.95 W at the powered device after cable loss, a fanless 8-port switch draws about 5 W, and one of the existing Cat5e runs carries the uplink data and the switch's whole supply.
Set the basement port to deliver PoE, or feed a midspan injector from a socket in the basement, and mains stays where it belongs. An af port reserves 15.4 W of the basement switch's PoE budget even though the box draws about a third of it. At the box the supply arrives near 48 V DC, so the draw is about 0.10 A (5 ÷ 48 = 0.104 A). The cable barely notices: Cat5e loop resistance is about 18.8 Ω per 100 m (9.4 Ω per conductor), a 20 m run is 3.8 Ω, and the loss works out to 0.104² × 3.8 = 0.04 W. The satellite coax keeps its own route and stays untouched. A box that also holds a battery-backed supply is a different problem; an outdoor enclosure for a PoE switch and UPS covers it. If a future change does put mains out there, bringing mains power into an outdoor enclosure safely is the routine to follow.
How much heat does the switch add inside a sealed box?
A 5 W fanless switch lifts the inside of a 10 x 8 x 4 in box about 7 K over ambient: 42 °C beside the switch on a 35 °C afternoon, inside a 45 °C consumer rating and far inside a 75 °C industrial one.
In a sealed box the walls are the only way heat leaves, and the rise follows ΔT = Q ÷ (U × A) with U = 3.7 W/m²K for stainless walls. Worked for the 10 x 8 x 4 in box at that load:
- Outside size 0.254 x 0.203 x 0.102 m gives A = 2 × (0.254 × 0.203) + 2 × (0.254 × 0.102) + 2 × (0.203 × 0.102) = 0.196 m².
- ΔT = 5 W ÷ (3.7 W/m²K × 0.196 m²) = 5 ÷ 0.73 = 6.9 K, call it 7 K.
- 35 °C ambient + 7 K = 42 °C inside.
Three inputs move that number. A managed switch drawing 10 W doubles the rise to 14 K, about 49 °C at that ambient, still easy for a 75 °C industrial unit. A 5 to 10 W anti-condensation heater takes the total to 15 W and a 21 K rise, which matters only in cold weather: at a 0 °C night the box sits at 21 °C. A switch rated only to 40 °C misses this box by 2 K, and the fix is the 12 x 10 x 6 in size, whose 0.325 m² holds the same load to a 4.2 K rise, about 39 °C on the hot design day. The fuller sizing routine is in sizing a sealed enclosure for a PoE switch heat load.
What size box fits the switch, the plugs and the service loops?
The 10 x 8 x 4 in box measures 9.91 x 7.91 x 3.91 in inside, which takes a typical DIN-rail 8-port industrial switch of about 1.7 x 4.3 x 3.4 in with 2 in [50 mm] clear above and below the rail.
Those 2 in are the number to protect. RJ45 overmolds run about 1 in long, a Cat5e jacket is about 0.25 in [6 mm] OD, and the usual bend rule of 4 × OD asks about 1 in, so a plug plus its loop wants 2 in of room in every direction. The 1.7 x 4.3 x 3.4 in switch is a typical 8-port DIN-rail industrial unit, an example figure to swap for your model's dimensions; the 2 in clearance is the rule that stays. Ports add up fast: the PoE uplink, the four remaining runs and the access point fill 6 of 8 ports with 2 spare. Bolt a short DIN rail to the removable mounting panel, clip the switch on, and let the wall-mount feet carry the weight. If a second switch or an 802.3at pass-through model is on the roadmap, the 12 x 10 x 6 in size, 11.91 x 9.91 x 5.91 in inside, keeps the same clearance with room to grow. The wall-fixing side of the job, anchors and entry positions for a switch box outdoors, is worked in PoE switch enclosure size for outdoor wall mounting.
How do the Cat5e runs enter without losing the IP66 rating?
Take every Cat5e run through the bottom wall in glands the manufacturer rates IP66 or better, and fit one IP66-rated membrane breather high on a side wall, because the lowest-rated part sets the whole assembly's rating.
Drill the bottom face, deburr both edges, and install each gland to the hole size and torque its datasheet gives; the step-by-step is in field-drilled conduit entries that keep a NEMA 4X rating. The breather does the quiet work: temperature cycles breathe the box in and out, and a membrane breather lets that happen while blocking liquid water, which is what drags moisture into a perfectly sealed-looking box. It must carry the same IP66 rating as the box, or it caps the assembly at its own. Do not fit an open drain plug and call the result IP66; on a rain-shielded wall with this much self-heat there is no standing water to drain. When a drain genuinely is the right tool, breather vent vs drain for a sealed enclosure sets out the choice, and junction box breather and drain requirements by volume sizes them.
Which stainless grade should the balcony box be?
Order 316L when the balcony smells of sea air or sits above a salted road, because chloride deposits pit 304 even at room temperature, while 304 serves a dry inland balcony under a roof.
The molybdenum in 316L is what buys pitting and crevice resistance near chlorides. Both grades share a chloride stress-corrosion threshold around 60 °C (140 °F), and this box never gets there: the hottest case in the heat section is 49 °C, and even a heater stuck on through the hot design day stops at 56 °C. What will mark the box year to year is wet-dry condensation cycling, which stains any stainless when salty deposits sit in crevices and gasket grooves; why wet-dry cycling rusts 316L before you blame the grade explains the mechanism. Keep the gasket groove clean at each service visit and the choice stays a one-line decision: 316L for salt, 304 for dry inland air.
Is fiber still the better answer for a full conduit?
Stay on copper until one room needs more than 2.5 Gb/s to itself: IEEE 802.3bz carries 2.5 Gb/s over Cat5e to 100 m, so the five existing runs hold roughly 12.5 Gb/s in aggregate.
The switch multiplies ports, not bandwidth, and no port here needs more than an internet feed and an access point. 10GBASE-T wants Cat6a, so Cat5e tops out at 2.5 Gb/s per run as specified, with 5 Gb/s a Cat6-class upgrade. Fiber's case gets worse in that conduit: a pre-terminated LC duplex patch has a jacket about 3 x 6 mm and connector ends that snag on the ripple crests of flex conduit, and field terminating needs a fusion splicer bought for one job. The move also lightens the conduit: the uplink leaves it carrying one Cat5e instead of the traffic of five, and the spare runs either pull back or stay as future spares. Decision: the switch serves this floor; fiber waits for a run past 100 m or a single room that outgrows 2.5 Gb/s.
What goes on the order?
Order the 10 x 8 x 4 in 316L wall-mount enclosure with its removable panel, add the IP66 membrane breather and the bottom-wall glands to the same order, and it is delivered in 10 business days anywhere in the world.
| Line item | What to order | Number behind it |
|---|---|---|
| Enclosure | 10 x 8 x 4 in (H x W x D) wall-mount, 316L stainless, hinged gasketed door, removable mounting panel, wall-mount feet | 9.91 x 7.91 x 3.91 in inside; 0.196 m² of wall for a 7 K rise at 5 W |
| Rating | manufacturer-rated NEMA 4X / IP66; not UL listed | IEC 60529 tests the second digit 6 with a 12.5 mm nozzle at 100 L/min |
| Breather | IP66-rated membrane breather, upper third of a side wall | keeps the assembly at the box's own rating |
| Cable entry | bottom-wall glands sized to the 6 mm [0.25 in] Cat5e jacket | seal on the jacket, one gland per run |
| Mounting | short DIN rail on the panel | 2 in [50 mm] clear above and below the switch |
| Size step-up | 12 x 10 x 6 in, 316L, if the switch is rated only to 40 °C or the port count grows | 0.325 m² holds the load to a 4.2 K rise, 39 °C on the hot design day |
| Grade alternative | 304 stainless for a dry inland balcony | 316L for sea air or road-salt spray |
The exact boxes behind this article are the 10 x 8 x 4 in 316L wall-mount enclosure, the same size in 304, and the 12 x 10 x 6 in 316L for the headroom case. To shortlist by environment, listing need and usable size first, the enclosure selector does it in one pass, and the full wall-mount range runs from 6 x 4 x 4 in up to 60 x 36 x 16 in. Everything is made to order and delivered in 10 business days anywhere in the world, counted from your approval of the drawing when you add custom cutouts.
Enclosures in this article
| Enclosure | Material | Outside H x W x D / display | Rating |
|---|---|---|---|
| 10 × 8 × 4 in | 316L stainless | 10 x 8 x 4 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
| 10 × 8 × 4 in | 304 stainless | 10 x 8 x 4 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
| 12 × 10 × 6 in | 316L stainless | 12 x 10 x 6 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
Questions
How much spare PoE budget does the basement switch need?
One IEEE 802.3af port reserves 15.4 W of the basement switch's PoE budget even though the balcony box draws about a third of it, because the powered device advertises its class at detection. Keep 15.4 W spare for this uplink, or 30 W if you later fit an 802.3at pass-through model that also feeds the access point; a midspan injector in the basement sidesteps the budget entirely.
Can the upstairs switch also power the access point over PoE?
Only with a PoE pass-through model. IEEE 802.3af guarantees 12.95 W at the powered switch, and an 802.3at access point draws up to 25.5 W, so a switch fed by af cannot feed the radio. Choose a pass-through unit that draws 802.3at on its uplink and outputs 15.4 W af ports, and reserve 30 W in the basement budget for it.
What stops condensation through a damp winter?
The IP66 membrane breather and the switch's own heat cover most damp spells: the membrane equalizes pressure while blocking liquid water. If droplets still collect after a cold soak, add a 5 to 10 W anti-condensation heater. Switch plus heater is 15 W and a 21 K rise, so a 0 °C night sits near 21 °C inside, and even a heater stuck on through a 35 °C day stops at 56 °C, under the 60 °C chloride threshold.
Does the PoE uplink overheat the conduit with the other cables?
No. The uplink carries about 0.10 A at 48 V, and a 20 m Cat5e run has about 3.8 Ω of loop resistance, so the cable dissipates 0.104² × 3.8 = 0.04 W, under one percent of the switch's heat load. Bundle-ampacity guidance starts to matter when a whole bundle carries several amperes, an order of magnitude above this single port.
What changes if the mounting spot gets afternoon sun?
Treat the sun as extra ambient. Clear-sky sun delivers about 1 kW/m² at midday, and a metal box facing it runs above shaded ambient even in polished stainless, so keep the box on the shaded side or under the soffit where the wiring box sits now. The 7 K self-heating rise is unchanged; only the ambient term moves, and the shaded spot holds the worst case at 42 °C.
