NEMA 2 vs NEMA 3R for an indoor transformer near a sink

Short answer: a NEMA 2 enclosure is the right rating for a 112.5 kVA dry-type transformer 3 ft [0.9 m] from an indoor sink, as long as the unit sits above the splash line and nothing sprays at it. NEMA 250 writes Type 2 for exactly that water — dripping and light splashing indoors. Type 3R earns its keep with rain, sleet and ice tests that never run inside. The step that matches a pre-rinse spray or hose is Type 4/4X, not 3R. Here are the tests behind each rating, the splash numbers to hold, the heat math that keeps the transformer in its own ventilated enclosure, and the lines to put on your order.

What is the difference between NEMA 2 and NEMA 3R?

Type 2 is an indoor drip-proof rating: NEMA 250 tests it against falling dirt, dripping and light splashing water — 30 minutes of continuous drips at 20 drops per minute or more from each drip source. Type 3R is the outdoor rating, tested against rain, sleet, snow and external icing.

Side by side:

The left column is your sink and the right column is your parking lot. Water that lands 3 ft [0.9 m] away indoors arrives as drips off a pipe or splash off a counter, and that is the whole list — a kitchen has no rain, no sleet and no ice. NEC Table 110.28 pairs each enclosure type with the conditions it suits, so a spec that names a Type is a line anyone can hold you to, and a listed box carries its type number on the label. The drip test and what it passes are detailed in NEMA Type 2 enclosure rating: indoor drip protection; the NEMA enclosure types guide maps every type, and NEC Table 110.28: where the code lists NEMA enclosure types shows that pairing.

Is NEMA 2 enough for a transformer 3 ft from a sink?

Yes — indoors, above the splash line and clear of any spray, Type 2 is the rating written for sink water, and the 3 ft [0.9 m] gap holds: a rule of thumb in food-service layout gives a hand sink a splash reach near 2 ft [0.6 m].

That leaves about a foot of margin at 3 ft, and the margin depends on height more than distance. Splash arcs from a hand sink live below the rim of a standard 36 in [915 mm] counter, so a floor-standing transformer outside that arc stays dry even in a busy kitchen. Hold the rating with three checks:

• Flick water toward the wall from the sink: anything wetted is the splash zone, and your enclosure sits outside it.
• Look up: a valve, a sweating cold line or a roof leak above the enclosure is a drip source — the exact hazard the 30-minute drip test covers.
• Walk the room for pressurized water: hose reels, pre-rinse guns, floor sinks that get flushed. Any of those within reach ends the Type 2 conversation, and the next section takes over.

What moves the margin: a busier sink pushes splash farther, and any hose multiplies it. Those cases get a bigger gap or a bigger rating.

When does a NEMA 3R transformer enclosure earn its place?

Pick 3R when the space behaves like outdoors: an unheated dock room, a wall under an open overhead door, or any spot where driven rain, sleet or ice can reach the enclosure — then its rain, sleet and external-icing tests protect something real.

Indoors those tests idle. They wake up in cases like these:

• Winter weather blows through an overhead door or a missing panel on an outside wall.
• The wall the transformer shares faces the loading dock, so sleet lands on the vents.
• The unit will move outdoors later; the 3R version ordered today makes that move a bolt-on job.

Dry-type practice makes that easy: the same ventilated tank ships as an indoor Type 2 unit or, with a weathershield over the vents, as an outdoor Type 3R unit — one kit of difference, not a redesign. For what the rain, sleet, icing and corrosion tests behind the 3R mark actually run, NEMA 3R rain, ice and corrosion standards page walks through each one. The rust side of the outdoor decision is covered in NEMA 3R vs NEMA 4X outdoors: rain rating and rust life and the outdoor enclosures guide; if the wall moves outside for good, move an indoor panel outdoors without losing the rating is the checklist.

What if the sink area gets hosed down?

Washdown is where both ratings run out: NEMA 2 stops at light splashing and NEMA 3R stops at rain, so a pre-rinse spray or hose demands Type 4 or 4X — the boxes jet-tested at the IP66 level of 100 L/min through a 12.5 mm nozzle.

The IPX6 jet test behind that number fires the 12.5 mm [1/2 in] jet from 2.5 to 3 m [8-10 ft] away for at least 3 min, which is wetter and harder than any sink. The split between the jet levels is laid out in IP65 vs IP66 water jet tests: what actually differs, and the rain-tested vs jet-tested split in NEMA 3R vs NEMA 4: rain or hose?. Keep one rule in mind with any rated assembly: a vent, drain or connector with a lower rating drags the whole box down to its own, so every hole in a washdown box stays gasketed and rated.

Decision by environment:

A 112.5 kVA transformer cannot wear a sealed 4X skin — the next section shows why — so inside a washdown cone you give it distance, a stainless drip shield above, or a purpose-built washdown housing with the heat load checked.

Why does a 112.5 kVA transformer keep its own enclosure?

Heat keeps the transformer out of any sealed box: dry-type losses run about 1-3 % of rating, so a 112.5 kVA unit releases 1.1-3.4 kW [3,800-11,500 Btu/h], while a sealed 16 x 12 x 8 in stainless box sheds roughly 20 W per 10 K of rise.

Worked example, with illustrative assumptions: 2 % loss (the middle of the 1-3 % range) and a 10 K wall rise. Swap in the nameplate loss and your target rise before sizing anything.

1. Heat in: 112.5 kVA × 2 % = 2.25 kW = 2,250 W, or 2,250 × 3.412 = 7,677 Btu/h [about 7,700 Btu/h].
2. Box skin: 2 × (16 × 12) + 2 × (16 × 8) + 2 × (12 × 8) = 832 in² ≈ 0.54 m² of wall on a 16 x 12 x 8 in box.
3. Wall loss: k = 3.7 W/m²K for stainless (the value in the enclosure sizing guide) with ΔT = 10 K: 3.7 × 0.54 × 10 ≈ 20 W.
4. Verdict: 20 W out against 2,250 W in — the sealed box runs more than 100× short, so the transformer stays in the ventilated enclosure it was built with, where room air passes through the windings and out the top.

Ventilation is the transformer's cooling system, which is why NEMA 250 gives ventilated Type 2 boxes a drip-proof design rather than a gasket. One kitchen effect to plan for: humid air that enters a ventilated box at service condenses on the windings after a cool-down — the pattern and fixes in controls above a steam kettle: stop the condensation apply as written.

The sealed stainless box still belongs in this room, just for the smaller gear: a 16 x 12 x 8 in 304 stainless wall-mount enclosure carries the contactors, a 24 V DC supply and the transformer's temperature monitor, and the same skin comes in 316L for brine-heavy rooms.

How should you mount a transformer beside a sink?

Raise it and keep the code working space clear: set the enclosure on a 4 in [100 mm] concrete pad so floor water and mop splash stay below the vents, and keep the sink, carts and shelving out of the depth NEC 110.26(A) demands in front of 480 V gear.

That working space is the check most installs miss. NEC 110.26(A) wants clear depth in front of equipment you may service while it is energized — at least 3 ft [0.9 m] for 0-150 V to ground in Condition 1, more at 480 V — at least 30 in [760 mm] wide or the equipment width, and room for doors to swing 90°. Measure it on your floor before the transformer lands: a sink or cart route inside that depth is the real conflict, and the fix is moving the transformer, not changing its rating. If the feeding panel shares the wall, its highest breaker handle tops out at 2.0 m [6 ft 7 in] above the floor under NEC 240.24(A). The enclosure mounting guide walks the height and working-space math.

What goes on the order for a transformer near a sink?

Order the transformer as an indoor ventilated unit with a Type 2 enclosure, add a weathershield only if the space sees rain, and spec the control box as gasketed 304 stainless — or 316L once sanitizers and brine enter the room.

• Transformer: 112.5 kVA, 480 V 3PH 4W dry-type, ventilated enclosure, Type 2; switch to the Type 3R version the day rain or sleet can reach it. Note the nameplate loss (1-3 % of rating) so the room's air change can be sized.
• Control box: the 16 x 12 x 8 in 304 wall-mount enclosure or its 316L twin — gasketed, rated NEMA 4X / IP66 by the manufacturer and not UL listed, with every cutout machined before it ships.
• Cutouts: specify gland and conduit holes at order time; the cutouts, glands and windows guide shows why a field-drilled hole is the part that costs the rating.
• Material: 304 for most back-of-house rooms; 316L where brine, salt or aggressive sanitizers live — 304 or 316L at a glance. The wall-mount shop section holds both grades in every size.
• Delivery: made to order and delivered in 10 business days anywhere in the world, counted from your order or, for custom cutouts, from your approval of the drawing.
• Before the terminal work: lock out and verify absence of voltage on the 480 V side.

The decision in one line: NEMA 2 for this room, NEMA 3R the day rain or sleet arrives, Type 4/4X stainless the day a hose can reach either box — and the transformer itself always in its ventilated skin, never in a sealed one.

Enclosures in this article

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