A roadside pad that feeds a 480V to 120V control transformer needs a lockable, corrosion-resistant enclosure rated NEMA 4X / IP66 by the manufacturer; not UL listed. Pre-assembled pad-mounted power units exist, but if you already have the transformer, a plain stainless enclosure with your own busing, breakers and glands usually costs less and gives you exactly the cutouts you want. This is how to pick the rating, material, size and mounting, and what to put on the order.
What this site actually has
We do not build hazardous-location enclosures, and we do not offer a meter base or a utility-style pedestal with integrated distribution. What we build is stainless steel enclosures, made to your dimensions and cutouts from one piece, with a hinged gasketed door, a removable mounting panel and a lockable latch. Ordered empty, or with cutouts you define. That covers the transformer-and-controls job well: you mount the transformer on the back panel, land your breakers on DIN rail, and seal the entries with glands.
For the fundamentals of enclosure types and how the ratings compare, see the outdoor enclosures guide and the IP rating chart.
The environment at a street intersection
A box at the corner of two busy roads sees more than weather.
- Rain and hose water. Landscape crews wash down the area. Water can hit the box from a nozzle, not just fall on it. That rules out an open or louvered design and pushes you past Type 3R toward 4X.
- Road splash and salt. Winter de-icing salt arrives as spray every year. Near the coast, add salt air. Both attack carbon steel and cheap coatings.
- Vandalism. The box must lock, the handle must not invite a pry bar, and it must be anchored so it cannot be walked away with.
- Sun. A dark box on an unshaded pad cooks. Solar gain on a sealed steel box can add 20 to 30 C above ambient on a still summer afternoon; lighter finishes and shade help.
- Dust and dirt. Traffic grime is constant; a gasketed door keeps it off the terminations.
The rating it needs
A manufacturer-rated NEMA 4X / IP66 enclosure (not UL listed) is the right target. Type 4X covers hose-directed water, dust, and corrosion resistance; IP66 covers dust-tight and powerful water jets. Many utility pedestals carry only Type 3R, which covers rain and ice but not hose water or dust, and 3R cabinets are usually vented. At a public roadside spot with a landscape crew nearby, 4X is the safer call.
In US installations, NEC 110.28 states that IP ratings are not a substitute for enclosure type ratings, so a spec that calls for a NEMA type needs the NEMA type, and dual-marked enclosures satisfy both. The NEMA enclosure types guide covers what each type means and what the inspector will look for.
If your authority having jurisdiction requires a listed enclosure for this service, say so up front: ours are rated by the manufacturer and not UL listed. The UL 50E and NEMA 250 listing guide explains what listing means and when it is demanded.
The material
For de-icing salt and road spray, 316L stainless is the right choice. It resists chlorides far better than 304, which itself stains and pits after a few winters of salt exposure. Painted steel is a false economy at a roadside pad: one chip near a fastener starts rust streaks down the door. The trade-offs between grades are laid out in 304 vs 316L stainless and the broader stainless steel enclosure guide.
If the box is well back from the road and salt is rare, 304 stainless in a #4 brushed finish is a reasonable lower-cost option. At an intersection, take the 316L.
Size: transformer heat comes first
A control transformer is the main heat source and the main space consumer. Work through three numbers:
- Transformer footprint. A 0.5 to 2 kVA transformer typically needs a mounting footprint of roughly 6 x 6 in to 8 x 10 in, plus clearance around it. Keep at least the transformer manufacturer's stated clearances, and keep it low on the panel so its heat rises away from breakers.
- Heat load. Count roughly 3 to 5 percent of the kVA rating as continuous loss: a 1 kVA unit sheds about 30 to 50 W. Add breaker and conductor losses for a total.
- Surface area to reject it. A sealed stainless box loses heat through its walls. As a rough planning figure, a 20 x 20 x 8 in box at 35 C ambient rejects on the order of 40 to 60 W for a modest 15 to 20 C internal rise; if your total is above that, go bigger, not louvered.
Then check clearances. Large conductors need bending space at their terminals; NEC 312.6 sets it for cabinets and cutout boxes. Working space matters too: under NEC 110.26(A), equipment likely to be serviced while energized needs clear space in front and room for the door to open at least 90 degrees. At a pad, that means nothing planted in front of the door.
For sizing method and duct-fill rules, see the enclosure sizing guide. If a drive or other heat source joins the transformer later, read the cooling comparison in enclosure cooling: fan vs air conditioner vs heat exchanger.
Locking and mounting at a public site
The lock is not optional. Specify:
- A quarter-turn latch with a padlockable handle, or a stainless hasp that takes a padlock. Confirm the latch is stainless, not zinc-plated steel, which seizes after a salt winter.
- Flush or protected hardware. Anything that sticks out 2 in from the door is a lever. Recessed or reinforced handles resist casual attack.
- Stud anchors through the back panel into the pad, set so no fastener is reachable with the door closed. If the enclosure stands off the pad, use a welded or bolted steel frame designed for the wind load on a 2 ft wide door.
- Height. Convenient for service, high enough to discourage reach-over. The highest breaker handle should stay under 6 ft 7 in (2.0 m) above grade, which NEC 240.24(A) requires for overcurrent devices.
Hinge, latch and lock options are compared in detail in the hinge and latch options comparison.
Wiring entries and cutouts
Plan every hole before the box is built, because a field-cut hole in a stainless wall is where ratings die. Decide now:
- 480V supply entry. A gland or hub sized for the feeder, or a threaded hub into a factory-cut hole.
- 120V load exit. A gland for the cable to the landscape controller, sized with slack for future circuits if the controller is nearby.
- Grounding and bonding. A lug for the equipment grounding conductor on the enclosure itself; the earth is not an effective ground-fault current path under NEC 250.4(A)(5), so a ground rod at the pad supplements but never replaces it. The grounding and bonding guide covers bonding the door and panel.
- Drain management. A sealed 4X box has no drain; keep entries low on the walls so any cable damage leaks where you can see it.
How to specify cutouts, gland sizes and window openings is in the cutouts, glands and HMI windows guide. If you would rather bolt a subpanel of your own, say so and order the box empty with just the entry holes.
What to put on the order
| Spec item | What to specify for this job |
|---|---|
| Material | 316L stainless, #4 finish |
| Rating | NEMA 4X / IP66 (manufacturer rating; not UL listed) |
| Size | Typically 20 x 20 x 8 in or 24 x 20 x 8 in (H x W x D), set by transformer and heat load |
| Door | Hinged, gasketed, lockable latch, padlockable |
| Mounting | Back panel for transformer and DIN rail; pad or standoff frame anchors |
| Cutouts | 480V entry, 120V exit, ground lug; sizes from your cable schedule |
| Options | Removable back panel, Mini PC provision if you add a controller later |
Catalog starting points: the 20 x 20 x 8 in 316L wall-mount, the 24 x 20 x 8 in 316L wall-mount, and the deeper 20 x 20 x 10 in 316L wall-mount. Any of them is delivered in 10 business days, counted from your order. For a size the catalog does not list, or a pad-mount frame with exact cutouts, the custom enclosure builder takes your dimensions from one piece, delivered in 10 business days from your approval of the drawing.
For the drawing you send with a quote, follow the custom enclosure drawing callout and the how to specify a custom enclosure guide, then send it through the contact page.
If this pad later grows into a pump or signal controller with a display, plan the door now: the HMI enclosures guide and the lockable HMI cover on a NEMA 4X door article show how a touchscreen gets added without losing the rating.
Enclosures in this article
| Enclosure | Material | Outside H x W x D / display | Rating |
|---|---|---|---|
| 20 × 20 × 8 in | 316L stainless | 20 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 |
| 20 × 20 × 10 in | 316L stainless | 20 x 20 x 10 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
Questions
Is NEMA 3R enough for a roadside transformer enclosure?
NEMA 3R (rated by the manufacturer) covers rain, sleet and ice, and many pad-mounted utility pedestals carry it. It does not protect against hose-directed water or dust, so it suits a fenced pad but not a public roadside spot. A NEMA 4X enclosure adds hose-down protection and corrosion resistance, which matters where a landscape crew may wash near the box. 4X is the safer call at an unprotected intersection.
How do I keep the enclosure cool with a transformer inside?
Start by adding up the transformer losses: roughly 3 to 5 percent of its kVA rating as continuous heat, so a 1 kVA unit sheds about 30 to 50 W. A painted or stainless steel box rejects heat through its surface; a sealed 20 x 20 x 8 in box typically handles tens of watts before the internal rise gets uncomfortable. If the load is bigger, go larger, or add a sealed cooling solution rather than louvers.
Can you build a true pedestal enclosure?
Our catalog is wall-mount boxes, but a large one mounts to a slab or a steel standoff frame on a concrete pad just as well, and the custom route lets you set any height, width and depth. What matters for a roadside pad is a solid anchor, a body that sheds water, and a door that locks. Send the transformer outline and the pad layout with your quote request and we will confirm the mounting.
What lock should I specify at a public intersection?
Specify a quarter-turn latch that takes a padlock, or a hasp-and-padlock arrangement, and make sure the handle does not protrude enough to be sheared off. Stainless latches resist corrosion and tampering better than plated steel. Pair the lock with the anchor bolts: stud anchors set through the back into the pad, so nothing is accessible from outside.
