HCC

Question 1

a set of contacts close after a valve has completely opened and starts the circulating pump

Answer 1

end of travel switch

Question 2

most common type of low water cut out (lwco)

Answer 2

float switch

Question 3

hot surface ignition requires voltage
true or false

Answer 3

false

Question 4

direct spark requires

Answer 4

high voltage

Question 5

what happens when a flame is detected by a cad cell

Answer 5

the cell resistance decreases

Question 6

purpose of a circulating pump

Answer 6

to circulate water through the zones and boiler

Question 7

purpose of the refrigerating

Answer 7

is to act as the working medium in the compressing and evaporating cycle

Question 8

state of refrigerant as it exits the compressor

Answer 8

hot, high pressure vapour

Question 9

purpose of the condenser

Answer 9

to cool hot refrigerant vapour by dissipating heat to the outside air

Question 10

2 basic types of hydronic heating systems

Answer 10

gravity systems and forced flow systems

Question 11

the electrical supply for a boiler must have a ?

Answer 11

disconnect switch on it’s on circuit

Question 12

purpose for microprocessor

Answer 12

can control indicator lights that show the operational state or motors, valves, pumps.

Question 13

what is a HTU

Answer 13

heat transfer unit

Question 14

what device transfers energy from a fuel source to water in a hot water heating system

Answer 14

boiler

Question 15

what voltage are zone valves

Answer 15

24v supplied by a class 2 transformer

Question 16

purpose of safety flow controller

Answer 16

sense the velocity of the water in the hydronic heating system and interrupts the heating circuit of the velocity is to low

Question 17

what safety device prevents damage if the pressure in a hot water heating system reaches dangerous levels

Answer 17

pressure relief valves (PRVs)

Question 18

2 styles of heat exchangers in hydronic heating boilers

Answer 18

cast iron, direct vent

Question 19

4 stages of a cooling cycle

Answer 19

evaporation
compression
condensing
metering

Question 20

what cools the reusing liquid as it passes through the metering device

Answer 20

flash gas

Question 21

what cools the reusing liquid as it passes through the metering device

Answer 21

flash gas

Question 22

what is short cycling protection

Answer 22

prevents a refrigeration system from operating when it tries to start and stop more frequently than it should

Question 23

what is the receiver

Answer 23

a pressure tank located after the condenser, collects liquid refrigerant

Question 24

A 3 wire zone valve is energized to ?

Answer 24

open or close

Question 25

purpose of a circulating pump in a hot water heating system

Answer 25

to circulate water through the zone and boiler

Question 26

aquastats are designed to be

Answer 26

fail-safe

Question 27

2 types of expansion tanks

Answer 27

compression and Diaphragm

Question 28

What is a compressor crankcase heater

Answer 28

Prevents refrigerant migration by keeping the crankcase oil warmer then the ambient temp, installed on the crankcase of a split air conditioner system compressor

Question 29

Difference between laten heat and sensible heat

Answer 29

Laten heat causes a change In state Sensible heat causes a change in temperature

Question 30

3 types of main burner ignition devices

Answer 30

A standing pilot, direct ignition, hot surface ignition

Question 31

Flame proving devices

Answer 31

Thermocouples, flame rods, pyrostats, cad cells

Question 32

What is the boiler temperature controlled by

Answer 32

An aquastat on the boiler

Question 33

What is a pop-test or a try-test

Answer 33

Testing of a pressure relief valve (prvs)

Question 34

A four wire zone valve contains witch electrical components

Answer 34

A motor and end of travel switch

Question 35

2 types of aquastats

Answer 35

High limit, reverse acting

Question 36

What can class 2 transformers be loaded to

Answer 36

80%

Question 37

a pyrostat senses

Answer 37

the heat of the flame

Question 38

what happens to the safety switch when the pilot light fails, what is the hazard with this switch.

Answer 38

it doesn’t stop gas flow to the pilot burner

Question 39

what 2 control devices are typically found in one common control switch

Answer 39

high limit switch and fan control

Question 40

when combustible fan is running what will cause the air prove swith to remain open

Answer 40

blocked flue

Question 41

how many roll out switches are used in a domestic furnace

Answer 41

2

Question 42

a roll out switch is typically a

Answer 42

single pole- single throw

Question 43

what is a pryomter consist of

Answer 43

a focusing lens and a sensitive thermocouple- can measure from a distance and up to 4000°

Question 44

what type of of heating unit can be used in either passive or forced air

Answer 44

resistive heating

Question 45

main disadvantage of thermocouples

Answer 45

slow response time

Question 46

what is a solenoid gas valves

Answer 46

is controls the flow of gas by an electrically operated plunger- downstream

Question 48

safety gas valve

Answer 48

provides for 100% shutdown, is located upstream of gas valve

Question 49

what is a faster safety gas valves device? solenoid or diaphragm

Answer 49

solenoid

Question 50

what is a flame roll out switch

Answer 50

is a high temperature limit that prevents the furnace from firing when the flame roll out condition exist

Question 51

RTD

Answer 51

resistance temperature detector and positive increase in temp causes increase in resistance

Question 52

thermosister-define

Answer 52

stolid state temp device that has a negative temperature coefficient and increase in temp causes a decrease in resistance