Electric Motors NEMA Motor Frame Sizes

The National Electrical Manufacturers Association has established standards for designating mechanical dimensions and specifications of motors. The motors most commonly used in the HVACR industry are referred to as fractional horsepower motors, between 1/20 and 5 HP, and universally use NEMA42, 48 or 56 frame designations (motors on frames larger than 56 are referred to as integral horsepower). The frame number refers to "D" dimension, expressed in sixteenth of an inch. The "D" dimension is the measurement from the base of the motor to the shaft centerline. Thus, a 42 frame motor has a "D" dimension of 42/16th in., or 2-5/8"; 48 frame, 48/16th or 3"; 56 frame, 56/16th or 3-1/2". Letter suffixes are often added to a standard NEMAframe size to pro- vide information on additional mechanical features, such as mounting or shaft dimensions. The most common stan- dardized suffixes are:

D

"J"-- Mounting flange with 4-1/2" rabbet and a threaded shaft Most commonly used in pump applications

"C" -- Mounting flange with 4-1/2" rabbet, 5/8" keyed shaft. Most commonly used for gearboxes.

"N"-- Mounting flange with 6-3/8" rabbet, 1/2" shaft with setscrew flat. Usually an oil burner motor.

"M"-- Mounting flange with 5-1/2" rabbet, 1/2" shaft with setscrew flat. Usually an oil burner motor.

"Z"-- Motor with a non-standard shaft size for its frame size

"Y"-- Motor with a non-standard mounting, such as hub mount used on sump or carbonator pumps.

General Information Nominal Air Flow:

• Cooling 400 CFM per ton • Heating 12 CFM per 1000 BTU input

Gas Pressure: (inches of water to ounces) 1"W.C. = .58 oz. 1.73"W.C. = 1 oz. 3.5"W.C. = 2 oz. 10.5"W.C. = 6.1 oz. 27.71"W.C. = 1 lb.

Approx. Heat Values: (BTU’s)

Fuel Oil / Gal. #1 = 135,800 #2 = 139,400 #3 = 141,800

Gas Cu/ft. Nat. = 1,000 Propane = 2,550

Gas Gallon Propane = 91,500 Butane = 102,600

Watts of Heat, 1 Watt = 3.412 BTU. BTU = Watts x 3.412

Temperature Conversion • Fahrenheit and Centrigrade

• To convert Fahrenheit to Celsius (Centigrade) .556 x (˚F -32) = ˚C • To convert Celsius (Centigrade) to Fahrenheit (˚C x 1.8) +32 = ˚F C˚

F˚

-30 -25 -20 -15 -10 -5 0 5

10

-22 -13 -4 5

14 23 32 41 50

C˚ 15 20 25 30 35 40 45 50 60

F˚ 59 68 77 86 95

104 113 122 140

C˚ 65 70 75 80 85 90 95

100 105

F˚

149 158 167 176 185 194 203 212 221