8/2/2019 Motors Nema Guidelines

1/1

MOTORSNEMA Guidelines

Any motor used in a fan product, suchas bathroom exhaust fans, wall-insert

fans, ceiling-insert fans, attic-exhaustfans, whole-house fans, and ductfans, etc., which are built into orwithin the building structure andwhich are likely to operate unattendedor in situations in which the operatormay not detect a locked rotor (stalledmotor) condition, must have either amanual reset thermal protector or athermal cuto (one-shot) device.Range hoods, circulating fans,pedestal fans, and ceiling-suspendedfans are not included. Agriculturalfans are included if they are built into

the building structure and are likely tooperate unattended or in situations inwhich the person operating the fanmay not detect a locked rotor (stalledmotor) condition; they must haveeither a manual reset thermal protec-tor or a thermal cuto (one-shot)device.

UL 507 Standard

Motors that start automatically (e.g.thermostat controlled) after tripping andare located out of operator sight mustbe protected against dangerous over-heating due to failure-to-start oroverloading. This protection may be aseparate overcurrent device (e.g. motorstarter) complying with Article 430 ofthe National Electrical Code (NEC), athermally protected motor (internalmotor protection), or an impedanceprotected motor.

Motors with automatic reset thermalprotection MUST NOT be used whereautomatic or otherwise unexpectedstarting of the motor could be

hazardous. Applications where auto-matic restarting could be hazardousinclude compressors, conveyors, powertools, farm equipment, and some fansand blowers. Where such a hazardexists, always use a manual reset, ther-mally-protected motor.

Thermal Protection

Information

If you operate a 25 HP premium eciency motor atfull load for 24 hours a day (8760 hours per year) andyour cost per kilowatt hour is 9 cents, you can save$532.00 annually. This comparison is based on apremium eciency motor with a 94.1 eciency ratingvs. a high eciency motor with a 91.0 eciencyrating.

Increased eciency leads to lower operating tempera-tures, resulting in longer life.

Cool Operation: The life of an insulation systemdoubles for each 10C reduction in operating temper-ature.

Longer Bearing Life: The lower the temperature, thelonger the bearing grease will last.

Annual Savings = 0.746 x HP x L x C x N (100E1 - 100E2)

HP = Motor HorsepowerL = Percent Load Divided by 100

C = Energy Cost, Dollars per Kilowatt Hour

N = Running Time, Hours per Year

E1 = Eciency (%) of Standard EciencyMotor

E2 = Eciency (%) of Premium EciencyMotor

Premium Eciency vs.

Standard Eciency

NEMA 48M, 48N AND 56N FLANGE MOUNT

DIMENSIONSCLOSE-COUPLED PUMP SHAFT DIMENSIONS

NEMA Guidelines

OIL BURNER MOTORS

48N48M 56N

AJ 634" 714"

BD 614 max. 7 max.

AK 512 638

CE 734 max. 814 max.

Frame Dimensions (Inches)Designations U EL EM EN EQ ET AH AJ AK BD BF

143JM/145JM 7/8 1532 1 3/8-16 x 3/4 5/8 278 414 578 412 658 3/8-16

143JP/145JP 7/8 1532 1 3/8-16 x 3/4 1916 51516 7516 578 412 658 3/8-16

182JM/184JM 7/8 114 1 3/8-16 x 3/4 5/8 278 414 578 412 658 3/8-16

182JP/184JP 7/8 114 1 3/8-16 x 3/4 1916 51516 7516 578 412 658 3/8-16213JM/215JM 7/8 114 1 3/8-16 x 3/4 5/8 278 414 714 812 9 1/2-13

213JP/215JP 114 134 138 1/2-13 x 1 238 578 818 714 812 9 1/2-13

254JM/256JM 114 134 138 1/2-13 x 1 5/8 3 514 714 812 914 1/2-13

254JP/256JP 114 134 138 1/2-13 x 1 238 578 818 714 812 9 1/2-13

284JM/286JM 114 134 138 1/2-13 x 1 5/8 3 514 11 1212 1378 5/8-11

284JP/286JP 114 134 138 1/2-13 x 1 238 578 818 11 1212 1378 5/8-11

NEMA LETTER DESIGNATIONS FOLLOWING FRAME NUMBER

C Face mount; see previous page.

H Designated 56H motors have twosets of 2F mounting holes3" and 5".

J Face mount for jet pumps; seeprevious page for dimensions.

K Has hub for sump pump mounting;see column at left for dimensions.

M, N Flange mount for oil burner; seecolumn at left for dimensions.

T, U Integral HP motor dimensionstandards set by NEMA in 1964and 1953.

Y Nonstandard mounting; seemanufacturer's drawing for mountingdimensions.

Z Nonstandard shaft (N-W+U

dimensions); see manufacturer'sdrawing for shaft dimensions.

NEMA 48K AND 56K HUB DIMENSIONS FOR

SUMP PUMP MOTORS