104 B Part B

Question 1

What does a controller do

Answer 1

-Sense changes in an control point or variable
-compares control variable with set point
-uses power to transmit a functional signal to the actuator of the controlled device

Question 2

Four main sensors

Answer 2

Temperature sensor
Pressure sensor
Humidity sensor
Flow sensor

Question 3

The four main sensors have what inside

Answer 3

Electromechanical sensor

Question 4

Types of electromechanical sensors include

Answer 4

A bimetal strip
A rod and tube
A remote bulb
An averaging element
A fast response element
A flexible diaphragm
A bourbon tube
A flow sensor
Bellows

Question 5

Electromechanicsl Temperature sensors include

Answer 5

Bimetal sensor
Rod and tube
Remote bulb
Averaging element
Fast response element

Question 6

Fast response element has a

Answer 6

Constant cut in

Question 7

How many bimetal strips do thermostats have

Answer 7

2
One for heating
One for cooling

Question 8

Must the thermostat be level so the mercury is always in setpoint balance

Answer 8

Yes always!!!!

Question 9

How many different types of thermostats are there

Answer 9

4
-two position adjustable spring
-anticipated multi stage heat and cool
-modulating or proportional
-combination fan limiting controls
-thermodisk or bimetal disk

Question 10

Bellows style thermostat uses

Answer 10

Uses a remote bulb sensor to see if temp is right, adjusts temperature if not the right temp

Question 11

A combination fan is used for

Answer 11

Natural gas heating appliances

Question 12

A combination fan limit controller does what two things

Answer 12

-Automatically starts and stops the furnace fan in response to the temperature
-has a high limit to stop heat(safety)

Question 13

When changing a fan limit controller make sure you

Answer 13

Pick the correct one or it will not work

Question 14

Fan cut out is at what temp

Answer 14

80-90°F

Question 15

Fan cut in is usually set at

Answer 15

120-140°F

Question 16

The high limit setpoint is usually set between

Answer 16

150-200°F

Question 17

What is a flexible diaphragm on a pressure sensor

Answer 17

Is a thin flexible membrane that stretches across the mouth of a bell shaped container which then entraps air pressure sensing it

Question 18

Another name for flexible diaphragm is

Answer 18

Combustion air proving control (more found in gas lines)

Question 19

What is a bellow

Answer 19

A stack of round diaphragm that join alternately at their outer and inner circumference

Question 20

High and low pressure controllers have two functions

Answer 20

-high pressure limit, protects from to high pressure
-operating controller, it cycles the condensing unit

Question 21

What happens when a Low pressure is on a high event

Answer 21

Cuts in

Question 22

What happens when a high pressure controller goes on a high event

Answer 22

Cuts out

Question 23

Encapsulated pressure controllers are

Answer 23

Inexpensive, have a fixed set point and fixed differential, reset as well