Short answer: the pumps do not set your panelboard rating — the water does. Three panelboards sharing a room with two jockey pumps are usually fine in plain NEMA 1 boxes, because a healthy pump throws nothing at the wall. Dripping water or circulating dust calls for NEMA 12. A washdown hose, a weeping seal aimed at the mounting wall, or a room that condenses every night calls for Type 4X stainless. NEMA 3R answers an outdoor question about rain, sleet and ice, so it is the wrong instinct indoors. The layout is not negotiable: NEC 110.26(A) sets 3 ft (900 mm) of clear working space in front, and NEC 240.24(A) holds the highest breaker handle at or below 6 ft 7 in (2.0 m) above the floor.
What a pump room does to a panelboard
Jockey pumps top up fire-system pressure between starts, and a well-drained pump room sends nothing toward your panelboards on its own. The room itself decides the type. Walk it while a pump runs, while the floor gets washed, and after the lights go out, and count the paths that reach the wall where the boxes hang:
- Drip from above. Overhead pipework, valve glands and pump seal weep drop water straight onto a wall-mounted door.
- Hose-down. One washdown hose in the room makes every surface inside its sweep a splash zone.
- Condensation. A humid room cooling overnight wets the inside of a sealed box faster than it wets the outside.
- Dust and lint. Sweeping, motor brushes and paper dust circulate and settle into anything without a gasket.
Zero paths ends the survey at NEMA 1. Each path that actually reaches the wall pushes the choice one step up: drip alone to Type 12, hose or nightly condensation to Type 4X. The next table turns your count into an order line.
Which NEMA type answers each room
NEMA 250 defines every type by what the enclosure keeps out, so the count from your walk-through maps straight onto the table:
| NEMA 250 type | Built for | Pick it when |
|---|---|---|
| Type 1 | indoor, against falling dirt and incidental contact | the room is dry, piped tight, never hosed |
| Type 2 | Type 1, plus dripping and light splashing of liquids | drips from overhead valves, clean air |
| Type 12 | Type 1, plus circulating dust, lint and fibers, and dripping or light splashing of noncorrosive liquids | seal weep or dusty air, still no hose |
| Type 3R | falling rain, sleet and external ice, indoors or out | an outdoor wall or open shelter, never a hose |
| Type 4 / 4X | watertight: the hose test drives 65 GPM [246 L/min] at the closed box; 4X adds corrosion resistance | hose-down, a splash zone, or condensation you cannot stop |
Type 3R is the instinct most pump-room specs follow, and it is worth correcting: it keeps rain and ice off an outdoor box and, by design, leaves out windblown dust and any hose protection. Indoors it answers a question your room is not asking. The 3R versus Type 4 comparison shows exactly what the step up buys.
Between a drip-only room and a drip-plus-dust room, Type 12 is the practical pick: its gasketed door covers both, and catalog coverage runs wider than Type 2. The Type 2 indoor drip rating explains what Type 2 alone buys you.
In the US, NEC 110.28 states that IP ratings are not a substitute for enclosure type ratings, and its Table 110.28 lists which type fits which condition — so give the inspector the type and carry the IP code alongside it. The NEMA enclosure types guide holds the full mapping. Type 4X on our wall-mount boxes is rated NEMA 4X / IP66 by the manufacturer; not UL listed — a UL listed enclosure has been evaluated by UL to UL 50E, which a project specification occasionally demands.
When stainless pays, and which grade
Painted Type 12 gear serves a dry room or one with clean water drips; the paint system fails first once washdown chemistry or chlorides arrive. Pick the metal by what lands on it:
- 304 stainless for fresh-water washdown, mild detergent, humidity and condensation.
- 316L stainless where chlorides reach the door: salted floor wash, sanitizers, brackish or coastal air.
Hot water deserves its own check. Chloride stress-corrosion cracking starts near 60 C (140 F) for 304 and 316L alike — the molybdenum in 316L raises pitting and crevice resistance, not that threshold — so a hot washdown onto a warm box is the one case to design around: time the wash for a cool box, or let it dry before chlorides sit on hot metal. What washdown water temperature means for an enclosure works through those numbers.
Even 316L rusts when chlorine chemistry dries into crevices and gasket lines. The 316L washdown article covers the rinse habits that keep a washdown plant's boxes bright.
Laying out three 24 x 20 x 8 in panelboards in the pump room
Inputs. The room described here holds three panelboards and two jockey pumps, indoors. Each panelboard mounts in a 24 x 20 x 8 in (H x W x D) wall-mount box, the outside size from our catalog, with its breaker and gland cutouts on the drawing. The clearances come from NEC 110.26(A): at least 3 ft (900 mm) of clear depth for gear at 150 V or less to ground in Condition 1. It also wants at least 30 in of width or the full equipment width, headroom of 6.5 ft or the equipment height, and doors that open 90 degrees. A 120/208 V panelboard sits at 120 V to ground, so the 3 ft line applies. NEC 240.24(A) holds the highest handle at or below 2.0 m (6 ft 7 in). For the heat check, stainless walls shed about 3.7 W per square metre per kelvin of rise (k = 3.7 W/m²K), the figure our thermal guides use.
Rule. The row's width sets the working-space width. The top of the row sets the handle height. The wall area sets how many watts the box carries for a given temperature rise.
Arithmetic. Row width: 3 × 20 in = 60 in of boxes, so NEC 110.26(A) wants 60 in of clear width in front, wider than its 30 in floor. Height: hang the row with tops at 6 ft 6 in (78 in). Every handle then sits below the 79 in ceiling, and the 24 in boxes reach down to 78 − 24 = 54 in (4 ft 6 in), clear of mop water and floor splash. Heat: outer area A = 2 × (0.61 m × 0.51 m) + 2 × (0.61 m × 0.20 m) + 2 × (0.51 m × 0.20 m) = 1.07 m² [1,660 in²]. With ΔT = Q / (k × A): 20 W gives ΔT = 20 / (3.7 × 1.07) = 5.1 K, and 40 W gives 10.1 K.
Result and decision. In a 35 C (95 F) pump room, 20 W of continuous load keeps the interior near 40 C (104 F), the ambient at which molded-case breakers and most panel electronics carry their ratings. Hold the load near or under 20 W in a 35 C room; a 30 C room doubles the allowance to 40 W. Above that, step up a box size or split the gear across two boxes instead of cutting a fan-filter grille into the wall — the grille's rating becomes the box's rating. If the room itself sits well above 35 C, moving the panel out of a hot room beats fighting the math. The same clearances for other layouts are worked through in the mounting-height guide and the enclosure sizing guide.
Keeping the rating after you cut and seal
A catalog panelboard arrives in its own type-rated cabinet. The moment you rebuild the gear inside custom boxes, the box carries the type, and every hole you cut either keeps it or spends it. Close each conduit and gland opening with a device the maker documents for Type 4X, gasket seated on smooth metal, and the assembly stays 4X; one unrated knockout drags the whole box down to that part's rating. What rating survives your cutouts walks the full checklist, and it is why the cutouts belong on the order drawing rather than on the drill bit.
Condensation is the other quiet spend. A gasketed box in a humid room breathes through every temperature swing, and the moisture lands on your backplate, terminals and breaker faces. If the room swings overnight, fit an anti-condensation heater from the start; why a sealed rating cannot stop condensation explains the cycle and the fixes. Never fit an open drain or louvre to fight it — the drain becomes the new rating.
Mount the row out of the hose's sweep arc with the door seams facing dry wall, and the sealing job stays a gasket job instead of a caulk job.
What to put on the order
Decide by the room, then send one drawing line per panelboard:
| Your room | What to order |
|---|---|
| Dry, tight piping, never hosed | NEMA 1 or painted Type 12 gear; a 304 stainless 4X box also covers it with margin |
| Seal weep, drips or circulating dust | Type 12 |
| Washdown hose or splash reaches the wall | Type 4X in 304 |
| The same, with chlorides, sanitizer or coastal air | Type 4X in 316L |
| Outdoor wall or open shelter | Type 3R minimum; Type 4X when salt or hose can follow |
| Order line | Pick | Basis |
|---|---|---|
| Rating | Type 4X / IP66, manufacturer-rated; not UL listed | covers every wet indoor case on one part number |
| Material | 304; 316L where chlorides or sanitizers reach the door | the corrosion table above |
| Size | 24 x 20 x 8 in outside per panelboard, a size up past 20 W of continuous load at 35 C | the worked layout above |
| Cutouts | breaker, gland and meter cutouts on the drawing | we cut before delivery, so the gasket lands untouched |
| Mounting | tops at 6 ft 6 in (78 in), 3 ft (900 mm) clear in front | NEC 240.24(A) and NEC 110.26(A) |
| Delivery | 10 business days, counted from your approval of the drawing | the custom-order promise |
The wall-mount line runs from 6 x 4 x 4 in to 60 x 36 x 16 in outside in both grades, and the enclosure selector narrows the choice when three boxes is still a guess. Send the panel schedule with the drawing and the boxes arrive ready for the breakers, not for a second trip to the drill press.
Enclosures in this article
| Enclosure | Material | Outside H x W x D / display | Rating |
|---|---|---|---|
| 24 × 20 × 8 in | 304 stainless | 24 x 20 x 8 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
| 24 × 20 × 8 in | 316L stainless | 24 x 20 x 8 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
Questions
Does a panelboard next to a jockey pump need NEMA 3R?
No. NEMA 250 reserves 3R for falling rain, sleet and external ice, which is an outdoor question; an indoor pump room asks about drips, hoses and dust instead. Pick Type 12 when water drips or dust circulates, and Type 4X when a washdown hose or splash can reach the door. The pumps on the same floor change nothing by themselves.
Is an IP66 rating enough on its own in a US pump room?
No. NEC 110.28 states that IP ratings are not a substitute for enclosure type ratings, so an IP66-only line on the drawing can bounce at inspection. Specify the NEMA type the room needs and carry the IP code alongside it; our boxes are rated NEMA 4X / IP66 by the manufacturer, not UL listed, which covers both vocabularies in one part.
Painted Type 12 or stainless: how do I decide?
Type 12 is rated against dripping noncorrosive liquids, so painted steel serves a dry room or one with clean water drips. Chlorides change the call: salted floor wash, sanitizer or coastal humidity pits 304 even at room temperature under chloride deposits, which points to 316L, whose molybdenum raises pitting and crevice resistance.
How do I stop condensation inside a Type 4X panelboard?
Break the dew-point cycle rather than the gasket. Common panel practice fits a 30 W anti-condensation heater under a thermostat that holds the interior about 5 K above ambient, keeping the walls above the room's dew point overnight. The box stays sealed, the rating stays intact, and the heater draws about as much as a lamp.
What happens to the rating after I cut the box for breakers and glands?
The weakest device in the wall sets it. One knockout closed with a hub or gland documented for Type 4X, gasket seated on smooth metal, keeps the box at 4X; a single unrated hole drags the whole assembly down to that part's rating. Cutting on the drawing before the box ships keeps the gasket untouched.
