11

HVAC&R CONTROLSHVAC&R

CONTROLSby

Jayson Goff, CM12/12/2012

byJayson Goff, CM

12/12/2012

2

OBJECTIVES• Understand the operation of relays and

contactors

• Explain how to test relays and contactors

• Learn the selection and application of transformers

• Find out how to troubleshoot pressure controls

• Understand the operation of solenoids

3

Basic Relay Parts

4

Common Relay Faults

•Stuck armature•Shorted coil•Open coil•Burned or welded contacts

5

Testing the Contacts

6

Contactors

7

Testing Contactors

8

Magnetic Starters

9

Transformers

10

Transformer Types

Transformer Types

• Boost-and-buck transformers

• Control transformers

• Auto-transformers

• High-current secondary transformers

“Boosting” transformer

“Bucking” transformer

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Pressure Controls

12

Setting the Low-Pressure Control

Step 1. Set HIGH EVENT by adjusting range screw.All-Range Controls:

•Turn screw clockwise to raise high event.Micro-Set Controls: •Turn screw clockwise to lower CUT IN setpoint.

Step 2. Adjust the differential screw.All-Range Controls: •turning the differential screw changes theLOW EVENT

•Turn screw clockwise to raise low eventMicro-Set Controls: •Turning the differential screw changes the differential setting.•Turn screw clockwise to increase differential

DifferentialScrew

Range Screw

Visible Pressure Scale

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Solenoid Valves

14

M.O.P.D.

15

Transformer Selection

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1.Coil Burnout

2.Failure to open

3.Failure to close

Typical Malfunctions

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HVAC&R CONTROLSHVAC&R

CONTROLSEND OF LESSONEND OF LESSON