Short answer: yes, you can field-drill a NEMA 4X stainless enclosure and keep the rating. Every opening then needs a fitting the manufacturer rates for the same type: a gasketed Myers-type conduit hub on each conduit entry and a low-profile drain fitting at the lowest point of the floor. A bare drilled hole, a weep slot or a bead of sealant ends the rating at that opening. The weakest opening sets the rating for the whole assembly. Our enclosures are rated NEMA 4X / IP66 by the manufacturer; not UL listed. Better still, order the holes with the box: the cutout designer checks spacing and exports the layout with the quote, and a custom enclosure arrives within 10 business days of your drawing approval.
Where the rating survives a drill hole
The rating belongs to the finished assembly, holes and fittings included. NEMA 250 and UL 50E define Type 4 as protection against hose-directed water from any direction and against external icing. The X in 4X adds a corrosion test: 200 hours of salt spray against an AISI 304 stainless specimen, per Table 5-1D of NEMA 250. IEC 60529 pairs the type with IP66, which is dust-tight plus protection against powerful jets. When you cut a hole, the body keeps its rating and the opening takes the rating of whatever seals it. A hub offered for Type 4X wet locations on rigid conduit and IMC holds the seal; a dry hole holds nothing. The fundamentals sit in the NEMA 4X vs IP66 guide and in the cutouts and glands guide.
What you need
- One gasketed conduit hub (Myers type) per conduit entry, sized to the conduit trade size and rated by its maker for Type 4X outdoor use on rigid conduit and IMC. The 1 in trade size passes rigid conduit with a 1.315 in [33.4 mm] outside diameter.
- One low-profile drain fitting rated Type 4X / IP66 by its maker, for the lowest point of the floor.
- A hole saw with pilot bit, cutting oil and a deburring tool. Stainless work-hardens, so keep the saw cutting.
- The hole diameter from the hub datasheet. Stamped knockouts of the same trade size follow UL 50, Table 71-1A, which sets knockout diameters and fitting dimensions.
- The layout drawing, with every hole positioned. On a custom box you set the size and every cutout; send the openings through the cutout designer, and the custom stainless page shows what to send with the quote.
Drilling and fitting each entry
- Mark each hole from the hub datasheet, from the flange and threaded body rather than from the conduit outside diameter. The gasket seals on the hub flange.
- Keep at least 25 mm [1 in] of flat sheet around every hole. Keep it clear of bends, weld seams and the door gasket path, so the seat and the locknut land on flat metal.
- Center-punch, drill a pilot hole, then cut with a hole saw at steady medium speed with cutting oil. If the saw rubs without biting, the stainless work-hardens under it.
- Deburr both faces and clear the chips out of the box before anything goes back in.
- Fit the hub from the outside, gasket against clean, dry metal, and run the locknut up inside until the gasket shows the same squeeze all round. The seal works by that gasket alone; the Myers hub with PVC conduit article shows the joint in section.
- Make the conduit joint up into the hub. Give each conduit on a vertical outdoor run a slight fall away from the box. Water traveling inside the raceway then drips clear of the wall, and the conduit hub vs sealing locknut comparison sets out the fitting choice for outdoor entries.
- Fit the low-profile drain fitting at the lowest point of the floor, with its drain seated at floor level, and check it carries a Type 4X / IP66 rating from its maker. The bottom conduit entry article covers the layout when the entry itself sits in that floor.
- Log every opening on the drawing, hubs and drain alike, so the rating you state for the assembly matches the openings that exist.
What a raised drain seat holds
Worked example, on a 500 x 400 mm floor, a common footprint for a mid-size wall-mount box. Take 10 mm as the seat height, a common height for the boss under a threaded plug and an input you replace with the seat height your own fitting shows. Water has to fill the floor to 10 mm before the drain sees any of it: 0.5 m x 0.4 m x 0.010 m = 0.002 m³, about 2 L [2.1 qt] standing across the whole floor. A low-profile fitting with the drain at floor level starts passing water at 0 mm.
That arithmetic also sets the position: fit the drain where water gathers, at the true low point of the floor or the end wall of a run. A field-drilled opening is a different route entirely. NEC 314.15 permits drainage openings of 1/8 to 1/4 in [3-6 mm] in boxes and conduit bodies listed for damp or wet locations, which is Type 3R practice; on a Type 4X enclosure the same hole ends the rating where it is cut. The NEMA 3R vs NEMA 4 guide walks through that split.
Why a tight seal still breathes
A sealed outdoor run inhales. Conductors warm the air inside, the air expands and pushes out at the weakest joint, then rain cools the wall and the contracting air pulls water back in. The numbers are not small. A 30 C [54 F] swing on a 300 K day drops the trapped-air pressure by 30/300 = 10 percent, about 10 kPa, close to the suction of a 1 m [3.3 ft] water column. Water arrives through the conduit entries and collects at the low point, which is why the rated hub and the rated drain do the work. If condensation is the bigger load, a breather drain rated Type 4X trades a controlled opening for a dry box; the breather vent article sets out when that keeps the rating.
Checks before you close the door
Isolate the panel and verify absence of voltage before any wet test on equipment that has been energized.
- Hose each new entry and the drain zone for 3 minutes at the IP66 condition: 12.5 mm nozzle, 100 L/min, from 2.5 to 3 m. The interior should stay dry.
- Pour 0.5 L of water into the lowest corner with the drain fitting open. It should pass at once and leave no more than a film on the floor.
- Check every gasket for an even squeeze line around the full circumference, with no gap where the sheet runs into a bend.
- Mark the as-built hole positions on the drawing and keep it with the panel records.
Mistakes that end the rating
| Mistake | What it costs | The fix |
|---|---|---|
| A bare hole plugged with sealant | The opening carries no rating and the assembly drops with it | Fit a rated hub, or close the hole with a rated blanking plug; the wrongly drilled hole article shows both |
| A weep hole in a Type 4X box | The rating ends at that cut | A low-profile drain fitting rated Type 4X / IP66 at the low point |
| A drain plug rated only for Type 3R | The weakest part sets the assembly rating | Swap for a fitting the maker rates Type 4X / IP66 |
| A hole over a bend or weld seam | The gasket bridges the radius and lifts at the first hose-down | Keep 25 mm of flat sheet around the hole, or order it factory-cut |
| Indoor set-screw connectors outdoors | They are not wet-location fittings and weep in rain | A wet-location hub on rigid conduit, or a rated liquid-tight fitting |
The whole spec fits on one line: a rated gasketed hub on every conduit entry, a rated low-profile drain at the true low point, flat metal around every hole, and a drawing that matches the finished box.
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 |
|---|---|---|---|
| 12 × 10 × 6 in | 304 stainless | 12 x 10 x 6 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
| 16 × 14 × 8 in | 304 stainless | 16 x 14 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 |
| 12 × 10 × 6 in | 316L stainless | 12 x 10 x 6 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
Questions
Can you drill a conduit entry in a NEMA 4X enclosure and keep the rating?
Yes, when the opening gets a fitting the manufacturer rates for the same type: a gasketed Myers-type hub on a conduit entry or a Type 4X / IP66 low-profile drain at the floor. A bare hole, a weep slot or a sealant bead leaves that opening unrated, and the assembly rating drops to its weakest opening. On a custom box the holes can arrive factory-cut, delivered in 10 business days from drawing approval.
Do weep holes in the bottom keep a NEMA 4X enclosure rated?
They end the rating where they are cut. A field-drilled drainage opening of 1/8 to 1/4 in [3-6 mm] is the route NEC 314.15 gives boxes and conduit bodies listed for damp or wet locations, which is Type 3R practice. The drain that keeps a 4X box rated is a low-profile fitting rated Type 4X / IP66, seated at floor level at the lowest point.
What size hole does a 1 in conduit hub need in a stainless wall?
Cut the diameter the hub datasheet states for that trade size; stamped knockouts follow UL 50, Table 71-1A, which sets knockout diameters and fitting dimensions. For scale, one-inch rigid conduit measures 1.315 in [33.4 mm] outside diameter, and the hole must clear the threaded body and gasket seat, so mark from the datasheet rather than from the conduit.
Is a bead of sealant enough to make a drilled hole watertight?
A sealant bead carries no rating and lifts with temperature and washdown. At the IP66 hose condition, 100 L/min from 2.5 to 3 m, an unrated opening shows itself in one 3 minute pass. The lasting fix for a wrongly placed hole is a fitting or blanking plug the manufacturer rates for the enclosure type, sealed by its own gasket.
