Short answer: you cannot re-rate an indoor panel by boxing it. An outdoor rating was tested on a complete assembly — tub, drip shield, cover and hubs together — so the rating does not travel with the guts. For a load center, order a complete Type 3R outdoor panel in the same breaker series and move the breakers across; the swap commonly runs 2-3 hours. For a controls panel that is not service equipment, the answer flips. An indoor panel can live inside a manufacturer-rated NEMA 4X outer enclosure with rated glands, as long as the heat budget holds — about 33 W in a 24 x 20 x 10 in stainless box at 30 C ambient.
Where the Type 3R rating actually lives
NEMA 250 defines Type 3R for outdoor use: falling rain and sleet, and the enclosure keeps working after ice forms on the outside. The standard's water test runs on the enclosure as assembled. In a residential load center, that assembly is the tub, a drip-shield roof formed into the tub stamping, the gasketed cover, the insulators and the hub openings in the top wall, sized to UL 50's Table 71-1A. Remove any one part and the test result has nothing to attach to.
That roof is not a bolt-on accessory. It is pitched sheet metal over the door opening, so water running down the front wall drips clear of the seam. An indoor tub has flat walls and an indoor cover gasket. That is why a shell built around your indoor panel changes the look and nothing else.
The NEC treats it the same way. Equipment used as service equipment must be listed and marked as suitable for that use, and the code's Table 110.28 is where a location picks its enclosure type. In US installations, NEC 110.28 says an IP code cannot stand in for that type number. A factory outdoor panel arrives with the marking, the type and the tested assembly in one order. The full ladder of types, 3R through 6P, sits in the NEMA enclosure types guide.
What Type 3R is tested for, and what it is not
Falling rain from above, sleet and external icing sit inside the Type 3R story. A hose jet, washdown spray or ground splash is Type 4 territory, and the Type 3R panel has no hose test behind it. That split decides placement. A pole or yard wall with open sky above is 3R work; anything a pressure washer can reach needs Type 4 or 4X. The NEMA 3R vs NEMA 4 guide sets the two water tests side by side.
Corrosion is a separate axis. NEMA 250's Table 5-1D gives Type 4X enclosures another 200 hours of salt spray beside an AISI 304 specimen, and plain Type 3R carries no corrosion test of that kind. For salt air the standard adds Type 3RX: the same rain protection with the same salt-spray test. On a salt-air site, that letter is the difference between a tub that lasts and one that rusts through.
| Type | Water it is tested for | Corrosion test in NEMA 250 |
|---|---|---|
| 3R | falling rain, sleet, external icing | none |
| 4 | rain plus splashing and hose-down water | none |
| 3RX | same water as Type 3R | 200 h salt spray (Table 5-1D) |
| 4X | same water as Type 4 | 200 h salt spray (Table 5-1D) |
Three ways to put a panel outdoors, and where each lands
The request usually arrives as one of three builds. Here is the verdict on each.
- A hood or outer box around the indoor panel. For a load center this fails twice over: the panel keeps its indoor listing while sitting at an outdoor location, and service equipment has to be the listed, marked assembly. Do not box a service panel; order the outdoor unit.
- A closed structure around it. A weather-tight pump house or shed makes the spot a dry location, and the indoor rating holds inside it. Keep NEC 110.26(A) clearance in the room: 3 ft [900 mm] deep for 0-150 V to ground, which covers a 120/240 V load center, 30 in wide or the equipment width, and space for the door to open 90 degrees. Hang it so the highest breaker handle sits at or below 6 ft 7 in [2.0 m] under NEC 240.24(A) — the enclosure mounting guide carries the height and clearance numbers.
- The breaker swap. A complete outdoor panel from the same breaker series takes the guts across in an afternoon. The panel's short-circuit rating is documented for its own breaker set, which is why staying in the series matters. Kill the supply and confirm absence of voltage before any lug comes loose.
The controls case: an indoor panel in a NEMA 4X outer box
Controls gear plays by different rules. A PLC panel carries no service marking to lose, and an outer enclosure is a normal way to take it outside: the outer box holds the water rating and the inner panel stays as built. Our stainless boxes are rated NEMA 4X / IP66 by the manufacturer; not UL listed. When a project wants a UL listed enclosure, the UL 50E vs NEMA 250 listing guide explains what a listing covers, and what an inspector looks for on an unlisted enclosure.
Every opening you cut decides the rating, not the box. Fit a Type 4X-rated cable gland in each drilled wall, chosen to the cable, and a rated plug in each opening you leave unused. A louver or fan-filter set with a lower ingress number pulls the whole assembly down to its own number. The cutouts, glands and HMI windows guide shows the drill-and-fit sequence and what a fitted component does to the type.
Bond the outer box into the fault path. NEC 250.96(A) calls for metal parts serving as equipment grounding conductors to be bonded so they can carry fault current, and NEC 250.12 wants paint cleared from those contact surfaces unless the fitting is built to cut through it. A ground rod at the pole is an auxiliary electrode under NEC 250.54: hang it off the equipment grounding conductor, which stays the real fault path. The grounding and bonding guide carries the full picture.
Mount and seal to the weather. Glands point down or sideways, each conductor forms a drip loop before it enters, and the box stands off the post so splash cannot sit against the wall. The mounting guide and the outdoor enclosures guide carry the loop and standoff detail.
The heat budget, worked out
A sealed outer box cools through its walls and nothing else. Stainless sheet moves roughly 3.7 W per square metre of wall per kelvin of rise, so wall area sets the budget. The worked example uses assumed wattages; swap your own into the same formula.
Take an inner panel dissipating 60 W: a 24 V supply losing 30 W, a compact PLC at 20 W and a 7 in HMI at 10 W. Drop it into a 24 x 20 x 10 in stainless outer box. Total wall area works out to 1.19 m²; mounted on a post, the back gives up little heat, so count 0.9 m² effective. The rise is ΔT = 60 W ÷ (3.7 W/m²K × 0.9 m²) = 60 ÷ 3.33 = 18 K. At 30 C ambient the inside air sits at 48 C; at 35 C summer heat it reaches 53 C. Most PLCs and drives are rated for 40 C ambient unless a datasheet allows more, so the boxed panel spends summer over its limit.
The budget runs the same arithmetic backwards. Holding 40 C inside at 30 C ambient spends 10 K of rise: 3.33 W/K × 10 K = 33 W. Each kelvin of extra margin buys 3.3 W. Step up to a 36 x 28 x 14 in box and the effective wall area reaches about 1.8 m². The same 60 W then costs 60 ÷ (3.7 × 1.8) = 9 K, which lands at 39 C inside at 30 C ambient — inside its rating. At 35 C ambient the budgets halve, to 16 W in the small box and 33 W in the big one. Past those numbers the fix is a Type 4X-rated air conditioner, because a fan-filter set would end the water rating.
Shade the box where you can. Cooling guides commonly put a dark painted wall 10 K or more above shaded air at midday, while bare stainless stays close to shaded air. Under 33 W, box it and order the gland cutouts. From 33 to 67 W at a temperate site, order the bigger box. Above that, or anywhere the summer sits at 35 C with a real load, add rated cooling. A terminal and junction panel with almost no dissipation runs cool in any of them — boxing is safest exactly where the heat is least.
What to order, by case
| Case at the site | What to order | The number that decides |
|---|---|---|
| Load center or service disconnect moving out | Complete Type 3R panel, same breaker series; a typical outdoor residential unit is 24 spaces / 34 circuits with a 100 A main | Swap runs 2-3 hours; handle at or below 6 ft 7 in [2.0 m] (NEC 240.24(A)) |
| Coastal or salt-air site | Type 3RX panel, or a stainless 4X outer box where hoses appear | 200 h salt spray behind the X (Table 5-1D) |
| Controls panel up to 33 W, temperate | Manufacturer-rated NEMA 4X / IP66 stainless outer box, 24 x 20 x 10 in, cutouts for rated glands | 3.33 W/K × 10 K = 33 W at 30 C ambient |
| Controls panel 33-67 W | Bigger 36 x 28 x 14 in outer box | 60 W → 9 K rise → 39 C inside at 30 C |
| Hot summers or above 67 W | Type 4X-rated air conditioner on the outer box | Holds 40 C inside at 35 C ambient |
| Closed pump house or shed | Keep the indoor panel; keep the room weather-tight | 3 ft [900 mm] clearance (NEC 110.26(A)) |
For a custom outer box, send the inner panel's outline dimensions, its heat load in watts, and the cable schedule with outside diameters. We cut every opening to the drawing and deliver in 10 business days, counted from your order or, for custom work, from your approval of the drawing. The enclosure selector narrows the choices by environment and size, or carries the same numbers straight into a custom quote.
Catalog dimensions to compare
Compare these catalog dimensions with your component layout. Open each enclosure for its rating, material and usable space, then check those specifications against your application.
| Enclosure | Material | Outside H x W x D / display | Rating |
|---|---|---|---|
| 24 × 20 × 10 in | 304 stainless | 24 x 20 x 10 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
| 16 × 12 × 8 in | 304 stainless | 16 x 12 x 8 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
| 20 × 16 × 8 in | 304 stainless | 20 x 16 x 8 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
| 24 × 20 × 8 in | 304 stainless | 24 x 20 x 8 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
Questions
Can I buy just the outdoor tub or cover and keep my indoor panel's guts?
Makers sell outdoor load centers as one listed assembly: tub with drip shield, gasketed cover and insulators. A bare outdoor tub is rarely sold separately, and even if you find one, your indoor panel inside it carries no outdoor rating, because the tested assembly was never yours. Buy the outdoor unit whole and transplant the breakers; the swap commonly runs an electrician 2-3 hours.
Does a ground rod at the pole replace the ground wire?
It does not, and the code says so directly. A rod at the pole is an auxiliary electrode under NEC 250.54: you may tie it to the equipment grounding conductor, but the EGC stays the fault path back to the source. Size the EGC from the overcurrent device ahead of it with NEC Table 250.122 — 8 AWG copper for a 100 A main — and bond the panel and any metal raceway under NEC 250.96(A) so the path is metal end to end.
Is a load center inside a closed shed still outdoors?
A closed, weather-tight room keeps the panel in a dry location, and its indoor rating holds there — that is the legitimate version of building a little house. Keep NEC 110.26(A) clearance inside the room: 3 ft [900 mm] deep for 0-150 V to ground, 30 in wide or the equipment width, with the door free to open 90 degrees. Ventilate or heat the room against condensation. An open hood over a pole-mounted panel counts as outdoors, and rain still reaches the door and every entry.
How much heat can a boxed controls panel carry?
Stainless walls move about 3.3 W per kelvin for a 24 x 20 x 10 in outer box with 0.9 m² of effective wall area. At 30 C ambient that is a 33 W load for 40 C inside; at 35 C it halves to about 16 W. A 36 x 28 x 14 in box lifts the budget to about 67 W at 30 C and 33 W at 35 C. Above the budget, order a Type 4X-rated air conditioner.
Which glands keep the outer box rated?
One rated gland in every drilled opening, chosen by cable OD: an M20 gland typically clamps 6-12 mm [0.24-0.47 in] cable and an M25 about 13-18 mm [0.51-0.71 in], as most gland datasheets print the ranges. A gland with a lower ingress number pulls the whole assembly down to its own rating, and sealant over a plain hole holds no rating at all. Unused openings take rated plugs, and each cable gets a drip loop before its gland.
