System controls and Schematics 4th year

Question 1

Define Relay.

Question 2

When looking at a schematic of a relay, it is showing it with voltage or no voltage?

Question 3

When the schematic is showing the contacts for a relay, they are said to be:

Question 4

List the parts of the relay.
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Question 5

NO contact means:
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Question 6

NC contact means:
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Question 7

What type of field is created from the relay coil when energized?
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Question 8

Why were Timed Delay Relays developed?
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Question 9

Why are Capacitors used?
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Question 10

Are capacitors mainly used for 3 phase motors?
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Question 11

What are the two types of capacitors?
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Question 12

Which type of capacitor is more commonly used for standard single phase motors?
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Question 13

Which type of capacitor is more commonly used for compressors?
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Question 14

Define Capacitance.
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Question 15

What is the symbol for a micro farad?
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Question 16

Which capacitor is designed for continuous duty?
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Question 17

What must be done before testing the capacitor?
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Question 18

What are some methods for discharging a capacitor?
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Question 19

List the available safeties in a forced air furnace.
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Question 20

Draw the symbol for a pressure switch.
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Question 21

When does the pressure switch prove?
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Question 22

The micro switch in the pressure switch is connected to what next?
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Question 23

Where is the induced draft motor located, in comparison to the burners for a mid efficient
furnace?
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Question 24

What does the IDM do for the flue gasses?
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Question 25

The vent motor draws a designed amount of air (products of combustion) through the heat
exchanger, what kind of pressure would then be in the heat exchanger?
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Question 26

Draw the symbol for a roll out switch.
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Question 27

Where is the roll out switch located in the furnace?
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Question 28

Why is there a manual reset for a roll out switch?
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Question 29

Can a high limit switch be adjusted for a mid to high efficient furnace?
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Question 30

What is the range of temperature a high limit will be?
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Question 31

The high limit is normally located where in the furnace? Choose (Inside the heat exchanger
itself or in the heat exchanger area).

Question 32

If the high limit should continue to open during normal operation, it is a good idea to by-
pass it for less nuisance calls. (True/ False]

Question 33

When the high limit opens in a furnace, what is then energized and de-energized inside the
furnace?

Question 34

List the two different types of hot surfaces igniters that are available. (What they are made
of).
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Question 35

What is the average temperature of HSI when energized?

Question 36

What is one test performed to check whether the hot surface igniter will work or not?
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Question 37

Define flame rectification.
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Question 38

Why are CPU’s used in most furnaces?
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Question 39

If the CPU is faulty or defective what should be done?
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Question 40

What type of system is the High pressure and low pressure switch used in (Fig. 14 and 15)?
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Question 41

Why is a TDR used in a split system or refrigeration system with regards to the compressor?
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Question 42

List the different types of wiring diagrams.
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Question 43

A ladder diagram identifies what easily?
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Question 44

When troubleshooting cooling equipment, what is the main voltage in the condensing unit?
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