Short answer: ENCL tells you how the motor is built and the IP code tells you what was tested, so write both on the order line instead of converting between them. An open drip-proof (ODP) machine turns away drops and solid particles falling at up to 15 degrees from vertical, and builder practice puts it near IP23. A totally enclosed fan-cooled (TEFC) machine separates its internal air from the room and almost always carries IP54 or IP55. NEMA MG 1 defines the names, the IEC 60034 series carries the protection and cooling codes, and your nameplate prints both.
What the ENCL field promises
NEMA MG 1, the standard for motors and generators, defines these as constructions, and the ENCL field names the one you bought. An open machine has a ventilated path between its windings and the room. An open drip-proof machine shapes those openings so drops or particles arriving at up to 15 degrees from vertical cannot interfere with its operation. The louvers do that work, and they assume a horizontal shaft.
A totally enclosed machine allows no free exchange of air between inside and outside, and that statement covers air, not water. TEFC adds a fan on the machine's own shaft — cooling code IC411 in the IEC vocabulary — blowing room air over the frame ribs, so internal air and external air never mix.
| ENCL | How it is built | What you get |
|---|---|---|
| ODP | Open machine, louvers over the ventilation openings | Drops within 15 degrees of vertical stay off the windings; dust, oil mist and horizontal spray get in |
| WPI / WPII | Open machine with long, multi-turn intake passages; WPII is the outdoor grade | Rain, snow and airborne dirt thrown out of the airstream; still breathes outside air; large machines |
| TEFC | No free air exchange; shaft-mounted external fan over the frame | Windings isolated from room air; cooling follows shaft speed |
| TENV | No free air exchange, no fan | Small frames with low losses; the frame surface does all the cooling |
| TEAO (air-over) | Enclosed, cooled by the driven equipment's airstream | Fan decks and conveyors; cooling stops when the airstream stops |
"Totally enclosed" is the name that misleads people, so pin down what you are buying: no dust path to the windings, and water resistance exactly to the coded digit. IPX7 means 1 m of water for 30 min, and a standard TEFC machine stops well short of that.
The IP half of the nameplate
The IP code is two tested digits — the first counts solids, the second counts water — applied to motors under the IEC rotating-machine standards using IEC 60529 test conditions. These are the digits you will meet on a motor datasheet:
| Digit | First digit: solids | Second digit: water |
|---|---|---|
| 2 | blocks objects of 12.5 mm and larger (fingers) | vertical drops with the enclosure tilted up to 15 degrees |
| 3 | blocks 2.5 mm tools | spray at up to 60 degrees from vertical |
| 4 | blocks 1 mm wires | splashing from any direction |
| 5 | dust-protected | jets from a 6.3 mm nozzle at 12.5 L/min |
| 6 | dust-tight | powerful jets from a 12.5 mm nozzle at 100 L/min |
| 7 | — | temporary immersion at 1 m for 30 min |
Two 15-degree numbers appear in this article, and they are different tests. MG 1's 15 degrees is the angle at which drops may fall onto an upright ODP machine. IPX2's 15 degrees is how far the tester tilts the enclosure while dripping on it. The same number, unrelated tests, and neither one covers a hose aimed horizontally.
For the same digits on the boxes that hold your drives and starters, the NEMA 4 vs 4X vs IP66 guide walks the enclosure side of the ladder, and the IP55 vs IP65 comparison for motors works the pair that washdown specifications argue over.
The mapping you can rely on
The two systems convert only as families, not one-to-one, and the families are tight enough to plan with:
| Construction | Digits you will usually see | Why |
|---|---|---|
| ODP | IP23 | First digit 2 keeps fingers out of the windings; second digit 3 turns spray up to 60 degrees from vertical |
| WPI / WPII | rarely IP-coded | The baffle path is the protection, and an open machine cannot claim the tested dust digits |
| TEFC | IP54 or IP55 | First digit 5 is dust-protected; second digit 4 is splash, 5 is jets |
| TENV / TEAO | IP54 to IP56 | Same enclosed family; the difference is how the frame is cooled |
Two rules keep you honest. An open machine breathes room air across its windings, so it cannot carry first digit 5; if a datasheet pairs ODP with IP54, one of the two claims is wrong. NEMA publishes MG 1 but certifies nothing, so the IP digits on the nameplate are the builder's own classification unless a certification mark sits beside them. The value that counts is the one printed next to ENCL, not the family average.
The IP digits also stay silent on cooling. They never tell you whether air crosses the windings or only the frame, which is exactly what ENCL and the IC code carry — the reason a machine can be dust-protected and still overheat on a slow drive.
Cooling check: a 5 hp TEFC held at 900 rpm on a mixer
Inputs: a 5 hp, 4-pole, 60 Hz machine, nameplate 1750 rpm at full load, ENCL TEFC, IP55, IC411 — a typical enclosed general-purpose motor — driving a mixer that holds full torque continuously at 900 rpm on a drive, in a room at 35 C.
Rule: a fan of fixed size moves one swept volume of air per revolution, so airflow scales directly with shaft speed, and the pressure it develops scales with speed squared — the standard fan laws.
Arithmetic: the drive holds the machine at 60 Hz x 900/1800 = 30 Hz. Airflow falls to 900/1750 = 0.51, about 51 percent of what the nameplate cooling assumes. Cooling pressure falls to 0.51 squared = 0.26, about 26 percent. Meanwhile, full torque at reduced speed keeps load current near full-load current. The winding's copper losses — the ones that scale with current squared — stay close to full-load heat while the cooling air halves. The 35 C room leaves you margin against the 40 C ambient an MG 1 rating assumes, so the binding problem is airflow, not ambient.
Result: about half the air at a quarter of the pressure, carrying nearly the full heat. Decision: for sustained full-torque duty below about half of base speed — roughly 30 Hz on a 4-pole machine — order the separately powered blower (forced ventilation) or take the drive-duty derating curve from the datasheet and size the machine up. Above that band, the shaft fan generally holds the winding inside its insulation class. The corner moves machine to machine, and the datasheet curve is the number that counts. An ODP machine suffers the same speed loss through its internal air path, so slow drive duty argues for the enclosed machine with the blower either way.
Choosing by environment
One question picks the construction: does the location put water or dirt into your motor's air path?
| What the location gives you | Order | Digits to write |
|---|---|---|
| Conditioned indoor room | ODP | IP23 |
| Settling dust: flour, cement, sawdust | TEFC | IP54 |
| Rinse hoses, splash, food-plant washdown | TEFC | IP55 |
| Heavy hose, big nozzle | TEFC | IP56 |
| Rain and sun, no hose | TEFC | IP55 |
| Salt mist and brine | TEFC with a corrosion package | IP55 minimum |
| Classified area | The certified variant, by its nameplate marking | per Class, Division or Zone and T-code |
For the washdown rows, the IP64 vs IP65 choice for motors works the finer split, and whether IP55 is enough outdoors covers the rain-only case. In salt air the motor is half the problem — the box holding its starter is the other half, and that is where the 304 or 316L decision lands. The enclosure holding your control gear follows its own ladder, so choose the minimum IP for factory enclosures separately. For pump rooms, TEFC vs ODP selection for industrial centrifugal pumps works the efficiency-versus-protection tradeoff with numbers.
A classified area changes the question. Suitability comes from certification marks naming the class, the division or zone and the temperature class. Using a TEFC motor in a classified area is decided by those marks, with ENCL and IP carrying none of it.
Where the wrong choice shows up first
| What you see on the floor | Most likely cause | The fix |
|---|---|---|
| Winding failures that cluster after washdown | An open or IPX3 machine in a spray zone | TEFC at IP55; IP56 where the nozzle runs 100 L/min |
| Drive trips on winding overtemperature below half speed | Shaft-fan cooling following speed down | Forced-ventilation blower or the datasheet derate, as in the worked example |
| Dust cake in the vent path and a temperature that creeps week over week | An open machine in a dusty room | TEFC at first digit 5; clean the frame ribs with a vacuum rather than an air hose |
| An inspector refuses the motor in a classified area | Certification marks missing from the nameplate | Order the certified variant by its marking |
Lock out and prove the absence of voltage before you open a terminal box or its starter enclosure; every row above is cheaper to read from a nameplate than from burnt windings.
What to write on the order line
Write the whole line and let the vendor quote against it: '5 hp, 1750 rpm, 4-pole, ENCL TEFC, IP55, IC411, horizontal foot-mounted, 40 C ambient, drive duty to 30 Hz with forced ventilation, terminal box drilled for 3/4 in glands.' State the mounting orientation your datasheet permits, because the ODP louver geometry assumes a horizontal shaft.
The control enclosure follows the same logic from the other side. In US installations, NEC 110.28 states that IP ratings do not replace enclosure type ratings, so the box needs its type. Our stainless enclosures are rated NEMA 4X / IP66 by the manufacturer and are not UL listed; if your inspector needs a listed box, the UL 50E listing guide explains what that involves. Custom boxes are delivered in 10 business days anywhere in the world, counted for custom work from your approval of the drawing. Pick the box with the enclosure selector, and if the motor's own terminal box is the mismatch, specifying a replacement motor terminal box covers the bolt pattern and the gland plate.
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 |
| 24 × 20 × 8 in | 304 stainless | 24 x 20 x 8 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
| 30 × 24 × 10 in | 304 stainless | 30 x 24 x 10 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
Questions
Does a higher IP code always mean a better motor?
No. An open machine breathes room air through its windings, so it cannot reach first digit 5 at any price, and a tightly enclosed machine sheds its heat through the frame, which makes it run a size larger for the same power. Buy the digits the location needs: IP23 for a clean dry room, IP54 for dust, IP55 for hose splash, IP56 for a heavy nozzle.
What does IC411 mean on a motor nameplate?
It is the IEC 60034 cooling code for a machine whose frame is cooled by air from a fan on its own shaft, the same arrangement NEMA MG 1 calls TEFC. The ENCL line and the IC line describe one machine in two vocabularies, which is why you write both. When you add a separately powered blower for drive duty, the cooling code changes with it, so copy the new code from the manufacturer's datasheet.
Can I mount an ODP motor with the shaft vertical?
Usually not without losing the drip protection. The louvers turn away drops arriving within 15 degrees of vertical because the shaft is horizontal, so a shaft-up installation points the top openings straight into falling water. Datasheets list the permitted mounting positions for each construction, so read them before you change orientation.
Is a TEFC motor suitable for a Class I Division 2 area?
TEFC alone does not answer that question. Suitability comes from the certification marks on the nameplate, which name the class, the division or zone, and the temperature class from T1 to T6. Builders do certify TEFC machines for Class I Division 2, and that variant is ordered by its marking; ENCL and IP digits never carry it.
Does IP55 make a motor safe in the rain and sun?
IP55 stops jets from a 6.3 mm nozzle at 12.5 L/min, and rain at any angle is a milder attack, so water entry is covered. The code says nothing about UV on the insulation, corrosion of the frame, or condensation when the machine cools at night. Outdoors you add a paint system or a canopy, and in freezing climates a small terminal-box heater.
Where is the formal definition of ODP published?
In NEMA MG 1, the standard for motors and generators, in its family of open-machine definitions. Buy the current edition from NEMA, and note which edition your plant specification cites, because wording and test references have moved between editions. The matching international vocabulary for protection and cooling, the IP and IC codes, sits in the IEC 60034 series.
