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NORA Oilheat Technicians Manual

• Make sure the motor is aligned with the driven device and the coupling is tightened. • Make sure the motor is operating within the proper amp ratings. • Make sure voltage and rotation are correct. When choosing a new motor Generally, heating system motors are designed to be non-serviceable items that must be replaced when they fail. When replacing a motor, look for the following: 1. Correct voltage. 2. Correct rotation. Some motors have reversible rotation. Change if necessary. Run the motor without the load to verify rotation is correct before connecting the load. 3. Frame designation, size, and mounting type. Example: most standard 1725 RPM burner motors are frame type 48N and most 3450 burner motors are 48M frame. 4. Is the speed of the new motor the same as the old? 5. Horsepower is at least the same as the old. 6. Shaft diameter and length must be the same as the old, or at least long enough and the proper diameter to securely couple to the driven device. Bushings are sometimes used to increase the diameter of the shaft. 7. Rated amperage must be at least as high as the driven device will require. Replacing an oilburner motor The specified motors for most oilburners either are the closed-end type or models with small cooling openings in the shaft bell at the motor shaft end. The small openings Chapter 10 Motors Figure 10-16: Beckett AFG motor are satisfactory as long as they are covered once the fan wheel is installed onto the motor. The back plate of the fan wheel must be positioned close to the motor end bell according to the manufacturer’s gap setting for maximum efficiency and output. See Figure 10-16. Use of a motor with cooling openings that are not covered will cause a loss of static pressure at the burner retention head due to air leakage and turbulence. Use a thickness feeler gauge to measure the gap between the motor and the blower wheel. Place the gauge on top of the motor and bottom of the blower wheel. The setscrew must be centered on the flat of the motor shaft. Then tighten the setscrew. Burner couplings Motor A flexible burner coupling is a mechanical device used to connect two rotating shafts. It permits a small amount of misalignment between shafts. The “Nylo- FlexTM” coupling, see Figure 10-17, fits most burners, thereby reducing truck inventory. These couplings are made up of two plastic ends and a center piece that is cut to size. The molded ends are designed to slip over the motor and pump shafts and do not require setscrews. They can be purchased with a variety of ends to match the various pump shaft sizes. With this type of coupling, it is important to slide the ends on the shaft to the end of the flat portion or the coupling will move. Measure the length needed for the center piece and cut it exactly to that measurement. The center piece is hollow and will slide over any portion of the shaft extending beyond the end piece. Be sure the motor and the pump Figure 10-17: Flexible coupling Chapter 10—Motors 10-13 Blower Wheel 0.030" (1/32") Feeler Gauge Available From Automotive or Hardware Stores Note: Do Not Use Motors That Have End Bell Openings Outside the Blower Wheel Circumference Reprensented by the Dashed Lines


NORA Oilheat Technicians Manual
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