Blowers, Motors and Belts

1
Blowers,Motorsand Belts
2
This power point presentation will review Section
C2 in the Student Handout Packet. You may also
need to refer back to the basic Electric Wiring
course information on motors.
3
Blower Motors Belt Drive

1. Motor and blower are two separate devices
   connected with a belt(s) and pulleys.
2. Most likely 1725 or 1750 RPM
3. 1/3 HP or less HP
4. Split Phase or Capacitor Start Motor
5. Generally an open drive housing using a
   Centrifugal Switch

4
Blower Motors Direct Drive

1. Blower wheel is mounted on the motor shaft.
2. Motor is mounted on blower housing.
3. Shaded Pole, PSC or ECM motor
4. These motors are multispeed
5. Lower HP for shaded pole motor
6. Higher HP for the PSC and ECM

5
The C2 section material does NOT deal with the
ECM motor. The ECM is covered as separate
material.
6
Blower Speed Adjustment

• The blower speed can be changed either by
  changing the wire taps on the direct drive
  system, or by changing the size of the drive
  (motor) pulley on the belt drive system.

7
Blower Speed Adjustment

• Why do we need to adjust the blower speed?
  Heating requires one speed and cooling requires a
  different speed.

8
Blower Speed Adjustment

• The heating speed is determined by the
  temperature rise. The cooling speed is
  determined by the temperature drop. The speed of
  the ECM motor is determined electronically by the
  manufacturer of the heating equipment. Reference
  the ECM material.

9
Temperature Rise

• The temperature rise procedure is found in your
  textbook as well as page C2c. Be sure to review
  it. Pay particular attention to what you do if
  the rise is too high or too low.

10
Temperature Rise

• Formula
• Temperature Rise Supply Air Return Air

11
Temperature Rise

• If the rise is too high or too low, the solution
  is rather simple. If the rise is too high, RAISE
  the blower speed. If the rise is too low, LOWER
  the blower speed. In simple words, do to the
  blower speed what the rise is. Rise high, speed
  up blower. Rise low, slow down blower.

12
Temperature Drop

• Formula
• Temperature Drop Return Air Supply Air
• Remember this formula for this course, but more
  information will be provided during the air
  conditioning course, since temperature drop is
  for air conditioning.

13
Blower Speed

• The blower speed can be changed in one of three
  ways.
• Wire taps on the motor direct drive blowers
• Adjust pulley on the motor belt drive blowers
• Follow manufacturers directions for the ECM
  motor/blower arrangement.

14
Pulleys

• The pulley on a motor may either be of a fixed or
  adjustable design. Another name for a pulley is
  sheave.

15
Pulleys

• When an adjustable sheave is open, the belt will
  ride LOW in the pulley and the blower speed will
  be slower. When an adjustable sheave is closed,
  the belt will ride HIGH in the pulley and the
  blower speed will be faster.

16
Pulleys

• The sheave should never be adjusted open so far
  that the bottom of the V groove in the belt is
  off the slope of the groove. Nor should the
  sheave be adjusted closed so far that the top of
  the belt is above the top of the pulley. In
  either situation, the belt will not be in proper
  contact and will result in improper belt wear,
  slippage of the belt and improper pulley groove
  wear.

17
Belts

• Belts are sized in two ways
• Manufacturer and part number as identified on the
  belt.
• Width at the TOP of the belt and its length
  (circumference).

18
Belt Tension

• Page C2e indicates the belt should deflect ¼ per
  foot of belt span with 2 3 pounds of force.
  This is great when you have a belt tensioning
  tool. Unfortunately, most technicians do not
  have this tool. Most go by experience.

19
Belt Tension

• What does experience teach you? The belt
  deflection should be about ¼ per foot of free
  span with a slight amount of tension. Remember
  the 2 3 pounds of force? This is what is
  described as a slight amount of force.

20
Belt Tension

• If the belt tension is too tight it will lead to
  premature failure of the belt. There will be a
  greater amount of friction and this will produce
  heat. The heat will go from the pulley to the
  motor and fan bearings and shorten their life.
  If the belt is too loose, friction will be less
  and there will be a power loss and the fan may
  not operate at correct speed.

21
Lab. Time

• There are several lab. assignments that relate to
  blowers, motor and belts. It would be important
  for you to complete the following as soon as you
  can. In fact, you may need to review the
  information even after you have completed it one
  time.

22
Lab. Time

• Watch the video Belt Drive Tips
• Power Point Presentation ECM-CCAC
• Video the ECM GE Blower Box
• The three items listed above are critical to you
  moving forward in the lab. relative to blowers,
  motors and belts.

23
Additional Tip

• It is highly recommended that you return to the
  material from the Basic Electric Wiring course
  and review information on motors and capacitors.
  As part of that process, it would be wise for you
  to review the Motors and Relays exam from that
  course.

24
This concludes this review ofblowers, motors and
belts.
25
THE END