Deck 15: Flow Switches

Question 1

Explain how a snap action micro switch for an air flow switch works.

Answer 1

A metal arm is attached to the micro switch. A piece of thin metal or plastic is connected to the metal arm. The thin piece of metal or plastic has a large surface area and offers resistance to the flow of air. When a large amount of air flow passes across the sail, enough force is produced to cause the metal arm to operate the contacts of the switch.

Question 2

Figure 15-2
In the accompanying figure, a circuit like one for refrigeration or air conditioning is shown. When the thermostat contact closes what happens?

Answer 2

When the thermostat contact closes, control relay CR energizes and closes all CR contacts. This energizes both the condenser fan motor (CFM) relay and the evaporator fan motor (EFM) relay.

Question 3

Figure 15-6
In the above diagram, a(n) ____________________ controls the operation of the compressor.

Answer 3

pressure switch

Question 4

Figure 15-6
In the accompanying diagram, the circuit is designed to control the operation of a(n) ____________________.

Question 5

Figure 15-2
In the accompanying figure, what happens when the pressure switch contact closes?

Question 6

Flow switches are used to control high current loads.

Question 7

Air flow switches are often called ____________________.

Question 8

The air flow switch is constructed from a(n) ____________________ micro switch.

Question 9

Why are air flow switches often used in air conditioning and refrigeration circuits?

Question 10

The air flow switch is constructed from a snap action micro switch.

Question 11

Regardless of the type of flow switch used, a single pole double throw micro switch is generally contained.

Question 12

Regardless of whether a flow switch is intended to detect the movement of air or liquid, the NEMA symbol for both is the same.

Question 13

Figure 15-6
In the accompanying diagram, the red light indicates the flow of oil.

Question 14

Flow switches are used to detect the ____________________ of air or liquid through a duct or pipe.

Question 15

Figure 15-2
In the accompanying figure, why is there a dashed line around the condenser fan motor and overload symbol, and around the evaporator fan motor and overload symbol?