NEMA Motor Frame Comparison Tool
Pick the frame on the old motor's nameplate and the frame on the one you're looking at. Both footprints are drawn to scale, one over the other, so you can see whether the bolt holes, the shaft height and the shaft diameter line up before you order. The amp check below catches "5 HP" motors that aren't.
In stock in frame --
Motors we carry in frame B, so the drawing above is the one that would actually arrive. Where B has the same shaft height as A and the holes differ only front to back, a slotted base usually covers it.
| Motor | HP | RPM | Frame | Voltage | Price |
|---|
What the frame number tells you, and what it doesn't
The first two digits are the shaft height in sixteenths of an inch: a 184T sits 4 1/2 inches from the foot to the shaft center, a 213T sits 5 1/4. Frames that share those digits share shaft height, hole spacing across the motor, and shaft diameter. The third digit changes only the hole spacing front to back, which is why a 182T and a 184T both mount on most compressor bases, and a 143T often replaces a 56 with a slotted base and a different pulley bore.
The letter matters as much as the number. T frames, the standard since 1964, carry a bigger shaft than the U frames they replaced. A 184U has a 7/8 inch shaft; a 184T has 1 1/8. Same holes, same height, your pulley won't go on. The compressor-duty 56HZ is the other trap: a 56 footprint with the 7/8 shaft and the extra 143/145T holes, so it swaps into both families.
None of this is the enclosure, the voltage, the service factor or the rotation, and a frame match says nothing about whether a motor is rated for the start-stop life of a compressor. Which is why the amp check sits on this page: a motor whose nameplate claims 5 HP at 15 amps on 115 volts is drawing 1.7 kilowatts, and 1.7 kilowatts is about 2 HP, whatever the label says.
Dimensions are NEMA MG1 nominals and are consistent across manufacturers, but confirm against the dimension sheet on the product page before cutting a base. The amp estimate assumes 0.85 power factor and 88 percent efficiency for three phase, 0.9 and 80 percent for single phase. Full range in the motor collection, and the running cost calculator settles premium versus standard once you've found a frame that fits.
- V-Belt LengthPulley diameters and center distance to belt length, with the belts we stock near it.
- Belt Center DistanceYou have the belt. Where does the motor go, and how far must the base travel.
- Pulley Size and RPMSolve pump speed, motor pulley or compressor pulley from the other two.
- Pump-Up TestTime the tank between two pressures and find out if the pump is worn.
- Motor Lifetime CostPremium against standard, purchase plus ten years of power, with the breakeven.
- Unit Converterpsi, bar, CFM, l/min, HP, kW and the rest, with a ruler.
- Dryer CFM SizingCorrect dryer capacity for inlet temperature, pressure and ambient.
- Moisture in AirHow much water the compressor pulls in and how much a dryer removes.
- Air Motor SelectionPick a pneumatic motor by torque, speed and power, in SI or imperial.
- All calculatorsThe whole set on one page, with what each one is for.
