Short answer: keep the meter standard and move the weather protection around it. Use a 304 stainless NEMA 4X enclosure with a UV-stabilized polycarbonate window in the door. Size the digit to the standing spot: a 0.7 in [18 mm] digit reads cleanly at 10 ft [3 m], which covers a driver watching a fertilizer truck unload. An exposed plastic-lens meter hazes in direct sun within about a year, and fertilizer dust plus dew leaves a corrosive film on every face it settles on. Behind the window, the meter stays dry and legible; the box is manufacturer-rated NEMA 4X / IP66, not UL listed. This page gives the rating, the material, the digit math and the exact order spec.
What the weather does to a meter left outdoors
Sun gets there first. A polycarbonate meter lens left in the weather crazes and yellows; count on about a year before the digits sit behind fog of their own. The same sun washes out a red LED readout at midday, so a meter that looks fine at dawn disappears at noon.
Fertilizer adds the corrosive part. Potash, urea and DAP dust are hygroscopic: overnight dew turns settled dust into a chloride-bearing film on the roof, the hinges and the gasket line. That film pits 304 stainless even at room temperature.
Condensation is the quiet one. A sealed steel box in full sun runs 15-20 C [27-36 F] above air temperature on a calm day, then gives that heat back after sundown. The air inside crosses its dew point, and the moisture lands on the coldest surface — the back of the window you read through. A tight box in partial shade, facing away from the afternoon sun, keeps all three attacks small. The outdoor enclosure guide carries the site-side basics from there.
The rating that fits a fertilizer yard
Specify the box Type 4X and carry the IP code with it. Type 4 covers rain, sleet and hose-directed water, because someone will eventually point a washdown hose at the conveyor gallery. The X adds the corrosion resistance that fertilizer dust and coastal air demand. IP66 on the same plate means dust-tight, plus the IEC 60529 powerful-jet test: a 12.5 mm nozzle at 100 L/min. For a US installation, NEC 110.28 lists the enclosure types that suit each condition in Table 110.28 and treats a lone IP code as insufficient. Write both marks into the spec; the NEMA 4 vs 4X vs IP66 guide and the IP rating chart show which digit means what.
Ratings on our boxes are manufacturer ratings, not UL listings. If the project spec demands a UL listing, that is a different box with its own evaluation. Settle it before the order, not after delivery.
304, 316L, or the PVC box you had in mind
304 stainless is the default for this box: the standard yard material for outdoor panels that get rinsed now and then. Place the pole with the chloride caveat in view. Potash is potassium chloride, and 304 pits under chloride deposits sitting on faces and in gasket crevices even at room temperature. If the pole stands inside the dust cloud off a live-bottom trailer or walking floor, order 316L. Its molybdenum buys pitting and crevice margin exactly where the dust lands. Both grades share a chloride stress-corrosion threshold at about 60 C (140 F). Keep chlorides off hot surfaces; a shaded meter box stays far below it. The 304 vs 316L stainless guide carries the full trade, and 304 stainless outdoors in coastal air covers the salt-air version.
The PVC or polycarbonate idea is half right. Molded Type 4X polycarbonate boxes are documented for -35 to +130 C ambient and shrug off rain and hose. What plastic wins in rain it loses in sun and abrasion: the UV that fogs a meter lens attacks the box, and fertilizer dust is hard on hinges and sight windows. A non-metallic box also provides no grounding path. NEC 314.3 permits nonmetallic boxes with metal raceways only where the metal parts are bonded together inside the box. That is one more joint to make and keep on a pole by the conveyor. The metal vs plastic outdoors comparison and the grounding notes for plastic boxes in salt spray both bear on the call.
Digit size starts at the standing spot
Work out where the driver stands when the truck unloads, then buy the digit for that distance. The display-industry rule of thumb is 1 in of digit height per 25 ft [7.6 m] of viewing distance. Panel-meter digits run from about 0.35 in [9 mm] bench units to 100 mm [3.9 in] large-format indicators. Sunlight is the second constraint. A red LED readout washes out in direct sun, so face the window away from due south and pick a high-brightness red or amber meter. A lightly tinted window holds the LED's contrast at midday, the way sunglasses hold yours. If the pole sits in full afternoon sun all season, a sun shield trims the box's heat rise and the glare together.
The HMI version of the same problem — window versus open door, glare versus legibility — ends the same way: keep the door closed and read through the glass, as the sunlight-readable HMI outdoors article argues in detail. The cover options for outdoor operator consoles lay out the window and shade hardware for that pose.
Sizing the digit for a 10 ft [3 m] viewing distance
Inputs. Viewing distance 10 ft [3.0 m], taken from where the driver stands at the pit edge while the truck unloads. Digit candidates 0.4 in, 0.7 in and 1.0 in, the common LED panel-meter heights. Rule of thumb: 1 in of digit height reads cleanly at 25 ft [7.6 m] for a bright LED in daylight.
Arithmetic. The 0.7 in digit reaches 0.7 in x 25 ft/in = 17.5 ft [5.3 m]. The 10 ft spot needs 10 ft / 25 ft/in = 0.4 in [10 mm] of digit.
Result. The 0.7 in digit carries 17.5 ft of readable range against a 10 ft requirement — 1.75 times the margin.
Decision. Order the 0.7 in [18 mm] digit and mount the window within 17 ft [5.3 m] of the standing spot. If the pit layout pushes the driver past 15 ft [4.6 m], step up to a 1.0 in [25 mm] digit, which reaches 25 ft [7.6 m]. The rule of thumb assumes clean daylight, and glare eats margin.
Box size, mounting height and the window cutout
One meter, its supply terminals and a CT terminal block fit easily. Count on 3-4 in [75-100 mm] of meter depth plus 2 in [50 mm] for terminals and wire bends. A 16 x 12 x 8 in (H x W x D) wall-mount box covers that with room to spare. The stainless wall-mount range runs from 6 x 4 x 4 in to 60 x 36 x 16 in, and the size finder filters it by outside size. Keep about 30% of the backplate free for the alarm relay or signal isolator that follows. Mount the meter on the removable panel so the display lands behind the window. Center the digits 4.5-5.5 ft [1.4-1.7 m] above grade, square-on to the standing spot; LED contrast falls fast off-axis. The mounting practice for a DC panel meter transfers as-is.
Entries go in the bottom wall: one for the CT secondary pair, one for the meter supply. Seal each with a gland matched to the cable outside diameter and run a drip loop below the entries outside. The cutouts, glands and windows guide sizes the entries. Order the window as part of the build, cut 0.5 in [13 mm] larger than the meter's display opening on every side. A factory window belongs to the manufacturer-rated design, so the plate still reads NEMA 4X / IP66. What a panel keeps after you cut it and mount devices is the honest ledger for that call.
The meter, the CT and the shorting block
The 5 hp, 480 V conveyor motor draws about 6 A at full load. The arithmetic: 5 hp x 746 W/hp = 3,730 W; at a nameplate-class 88% efficiency and 0.86 power factor, I = 3,730 W / (1.73 x 480 V x 0.88 x 0.86) = 5.9 A. A 15:5 A current transformer puts running load at 6 A / 15 A = 40% of scale and leaves the whole top half for the overload. Scale the meter 0-15 A to match the CT, so a fast unload climbs visibly toward full scale.
One wire carries a permanent warning: the CT secondary. Never open it while the primary is energized — the secondary develops a hazardous voltage. Land it on a shorting-type CT terminal block before the meter goes in, and the circuit stays closed and safe.
The box handles the rest: sealed glanded entries, drip loop outside, meter and terminals inside. Every connection stays dry, which is the part an exposed meter lacks.
The decision, site by site
| Site | Box to order | Why |
|---|---|---|
| Outside the dust cloud, hosed down now and then | 304, Type 4X / IP66 | The default yard box; rinse settled dust in the weekly walk |
| Inside the fertilizer dust (potash chloride) | 316L, Type 4X / IP66 | Molybdenum earns its keep where dust settles on the box |
| Coastal salt air or frequent chemical washdown | 316L, Type 4X / IP66 | Same box, wider pitting and crevice margin |
| Inside the MCC room | 304, Type 12 | Dust and dripping liquid only; no hose, no sun |
Whichever line you take, add the alarm. Most digital panel meters carry one or two setpoint relays; a horn set at 110-120% of running current — near 7 A on the 6 A motor — pulls a driver's attention faster than any digit. The meter shows the trend. The horn stops the overload.
What to put on the order
| Line | Spec for this conveyor-meter box |
|---|---|
| Material | 304 stainless, #4 brushed; 316L where fertilizer dust settles on the box |
| Rating | Manufacturer-rated NEMA 4X / IP66; not UL listed |
| Outside size | 16 x 12 x 8 in (H x W x D) |
| Window | UV-stabilized polycarbonate in the door, 0.5 in [13 mm] oversize per side |
| Meter digit | 0.7 in [18 mm] minimum for a 10 ft [3 m] reading distance |
| Cutouts | Two bottom-wall glanded entries, sized to the cable outside diameters |
| Internals | Removable mounting panel; shorting-type CT terminal block |
| Delivery | Delivered in 10 business days from approval of the drawing |
Send the meter bezel and display-opening dimensions with the request and we send back a cutout drawing. The 10 business days run from your approval of that drawing, to anywhere in the world, from a minimum of one box. The custom builder takes material, size and every cutout from the same form.
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 |
|---|---|---|---|
| 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 a standard digital ammeter survive outdoors?
Yes, behind a window. An exposed plastic lens hazes in direct sun in about a year; inside a manufacturer-rated NEMA 4X / IP66 box, the UV-stabilized polycarbonate window takes the sun and the meter stays a cheap standard part. The box carries the rating, so replace the window if it ever clouds, not the meter.
How large a digit do I need at 10 ft?
The rule of thumb gives 1 in of digit height per 25 ft of viewing distance, so a 10 ft spot needs a 0.4 in [10 mm] digit. Order 0.7 in [18 mm] and the readout stays legible out to 17.5 ft [5.3 m]; step to a 1.0 in [25 mm] digit if the driver stands beyond 15 ft [4.6 m].
Is a PVC enclosure good enough for this?
For rain alone, yes: molded Type 4X polycarbonate boxes are documented from -35 to +130 C ambient. Outdoors in fertilizer dust, sun and abrasion work against plastic, and a non-metallic box has no grounding path, so the metal raceway parts must be bonded inside per NEC 314.3. Stainless with a window moves the wear to a replaceable part.
Does a window keep the NEMA 4X rating?
Yes, when the window is part of the manufacturer-rated build; our boxes are rated NEMA 4X / IP66 by the manufacturer, not UL listed, and a factory window belongs to that rated design. A field-cut hole with an aftermarket window hands the rating question back to you, so dimension the window on the order instead.
What current transformer suits a 5 hp, 480 V motor?
About 6 A at full load — 3,730 W at 88% efficiency and 0.86 power factor — so a 15:5 A CT reads running load at 40% of scale with the top half in reserve. Use a shorting-type CT terminal block, and never open the secondary under load: it develops a hazardous voltage.
How fast does a custom window enclosure arrive?
Delivered in 10 business days, counted from your approval of the drawing for custom work, anywhere in the world, from one piece. Send the meter bezel and display-opening dimensions with the request; the cutout drawing comes back for approval and the clock starts.
