Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Level 2 > HC 221 heating and cooling systems > Flashcards

HC 221 heating and cooling systems Flashcards

You may prefer our related Brainscape-certified flashcards:
Certified Sommelier Exam (CMS 2) flashcards
1
Q

thermal comfort is affected by what things

A

-air temp
-humidity
-air movement
-heat loss/gain
-ratiation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what is heat loss and gain caused by

A

conduction or radiation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what will improve air quality in an HVAC system

A

-propper filtration
-ventalation
-humidity control

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what is convection

A

the transfer of heat by air currents OR water current. air temp huumididty and speed play factors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what are the 3 ways heat is transfered

A

-convection
-conduction
-radiation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

___________ refers to heat transfered by natural currents. if the air is cool it absorbs heat from the skin and because its able to move the heat is then carried away

A

convection

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

the amt of heat gained or lost by convection depends on what

A

-temoerature and humidity of the air and the rate that it moves

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

heat gained or lost through ______________ loss required direct physical contact

A

conduction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

warm air can hold __________ moisture

A

more

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

cold air heated will be ____________ dry

A

more

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

____________ is the transfer of energy across some distance without a conducting or convecting medium

A

radiation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what is absolute zero

A

the temperature that atoms stop moving (0 degrees kalivin) ( -273 degrees celicus)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

why does moist air carry more energy than dry air

A

-because of energy stored in the water vapour. takes more energy to raise a temoerature of a colume of ait that is moist than it does if the air is dry

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

moist air feels warmer than dry air due to the extra _____ energy it contains

A

heat

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

how is humidy measured

A

relative humidity (RH)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

does an RH of a given volume of air change if the temperature changes

A

yes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

RH __________ as the air is heated

A

drops

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

RH __________ as the air is cools

A

rises

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

for general human health what is the ideal relative humidity (RH)

A

30-70%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

RH levels _______________ during heating season for comfort and increase the________ during hot weather

A

increase
discomfort

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

_______ RH causes irriatation in lings and throat

A

low

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

RH also affects the build up of _________ electricity

A

static

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

when does static energy builf up in relation to RH levels

A

when they are low

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

static is not a problem if the RH is not less than ___________-%

A

45%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what can air quality be reduced by

A

-particles like smoke dust pollen
-chemical pollutants like gas
-oxygen depletion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

how can you improve air quality

A

-controlling source of pollutants
-using filters
-replenish indoor oxygen supply

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

residential furnaces use extended plenums to distribute conditioned ____________- air to ducts and draw ______ air from the house back through the furnace

A

supply
return

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

combustion and ventalation air both have to come from ____________

A

outdoors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

how is combustion air provided

A

-natural building leakage
-vents to outside
-combustion air ducts that are brought near the furnace but not connected to
-combustion air ducts that return to the plenum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

older furances reply on _________— for ventalation

A

natural draft

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

modern instilations (mid efficent) for burners have what for ventalation and combustion

A

-combusion air duct terminated beside the furnace AND a second ventalation air intake duct that is terminated in the return air plenum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

what is a standing piolet ignition

A

-a continuously burning flame

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

in a mid-efficent furnacew when do vents need to be active

A

when the burner is running

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

what does the second heat exchanger do in a high-efficiency furnace

A

-cools the exaust gasses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

what do secondary heat exchanger and drains have to made from on a high efficency furnace and why?

A

-corrosion resistant materia;
-condensate liquid is very high

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

__________ burners are closed systems with a dedicated combustion air intake line and a vent that isnt shared with any other appliances. what are these intake and vents made from?

A

high efficiency
plastic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

what material is never used with high efficency furnaces

A

metal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

what does a condensor unit do

A

-takes a gas and turns it into a liquid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

can a Air conditioning compressor unit compress a liquid

A

no it would blow up and youd fuck it up

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

A compressor unit is linked to the A-coil by 2 copper lines. what do they do?

A
  1. carrying high pressure liquid refridgerant from the condesor to the evaperator.
  2. for the low pressure vaporuized refridgerant that is returned to the compressor
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

what happens when the compressor pumps refridgerant vapour into the condenser

A

-loses its excess heat and liquifies

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

the liquif refridgerant is delivered under pressure to the ____________ where it is released at a controlled rate

A

evaporatior

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

the air-conditioning unit has its own ______ volt supply but its controlled by a _______ volt cct from the thermostat

A

240v
24v

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

what is an HRV

A

heat recovery ventalator

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

what does the HRV do

A

-acts as the central exuast fan, but uses warm exaust air to preheat the incoming ventilation air

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

What does a energy recovery ventalator do? (ERV)

A

-transfers heat an dhumidity from one air stream to another

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

an air-conditioning system can be used to reduce both of what

A

-RH
-temperature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

what does a de-humidistat do?

A

-used to start the ventilation fans where the humidity is too high

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

if humidity is too low due to building leakage what is used to bring the humidity up

A

humidifier

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

what happens without air circulation

A

hot air rises
cold air settles to the floor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

what is the benifet to using the furnace fan as constant circulation

A

-air is constantly filtered
-reduction of cold drafts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

where is an air filter on a furnace found

A

-between return air duct and fan chamber

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

what does a conventional media filter do best

A

-clean air well enough to protect the heat exchanger

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

what type of filter is the more efficent than a disposable

A

HEPA (high effiency media filters)
- trap a higher % of the airborn material

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

how do electronic air cleaners work

A

use a high voltage DC supply to charge a fine wire grid with one polarity and a set of collection plated with the opposite polarity.
-air passes throuhg at one polarity then is drawn to the collection plate because it has the opposite polarity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

what air filter for a furnace is the MOST efficient

A

electrinuc air cleaner

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
54
Q

when is an upflow furnace used

A

-in a basement where the cold air entres the bottom of the furnace and is blown out the top into the extended phlenum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
55
Q

when is a downflow furnace used

A

houses without a basement or mobile homes
- cold air return is taken to the top of the furnace and the conditioned air is blown out the bottom unto the plenum and into the distrubuting ducts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
56
Q

why do horizonal and downflow furnaces have more temoerature limits built into them

A

-more hotspots in different spots if the fan fails to operarte

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
57
Q

why are propane fired furnaces different than natural gas

A

-smaller holes to reduce the gas flow into the burners

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
58
Q

in a propane furnace the size of the holes depend what

A

the rate gas is burned

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
59
Q

how do oil furnaces work

A

-have a “gun type” burner
-fuel pump and combustion air blower driven by a small burner motor
-blower creates air stream down the barrel of the burner gun and the pressurized fuel oil is fef into the centre of it by a nozel
-when transformer is energized it lights a spark to light the fuel and air mixture

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
60
Q

what are heat pumps

A

reversible air conditioners

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
61
Q

how does a heat pump work

A

during heating season the heat pump extracts heat from the outdoor air and releases it into the heat exchanger inside. heating elements used during defrost cycles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
62
Q

in a residental heating boiler system how is the system broken into

A

-several zones each with their own thermostat

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
63
Q

what does each zone of a residential boiler system have

A

-a normally open contact called an end switch that is wired into the circulating water pump control

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
64
Q

how do end switches for a residential boiler system work

A

-contacts are in //
-pump starts when the first zone valve opens
-shuts down when all the zone valves are closed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
65
Q

what is the burner controlled by in a residential hot water boiler system

A

an aquistat (responds to warer temoerature in the boiler)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
66
Q

advantages of hot water heating systems for residential

A

-building heated effectivley without stirrin gup allergens in ducts
-easier to zone than force air
-dont need a seperate water heater for water in the taps

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
67
Q

disadvantages of hot warer heating systems in residential

A
  • higher inital cost
    -higher water bill
  • NO SHARED EQUIPMENT FOR ADDING CENTRAL AIR CONDITIONING
  • cant filter air
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
68
Q

what do you use limit switches for

A

-dampers
-valves

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
69
Q

for boilers what are limit switches used for

A

-high pressure limits, shuts down burner if pressure gets too high
-low water cut off, shuts down the burner if the water gets too low

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
70
Q

what are on delay timer contacts

A

-have a delay period that starts with when the timer is activiated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
71
Q

what are off-delay timer contacts

A

-have a delay period that starts AFTER the timer is deactivated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
72
Q

what is an anticipator

A

-stores energy
-prevents swings in temperature by turnin gburner off slighly before set point is reached by anticiaptin git will be reached soon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
73
Q

what is aquistat

A

a thermostat that responds to changes in liquid temperaturs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
74
Q

what is a cut in/cut out switch

A

one will turn on the furnace and one will cut in/out

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
75
Q

what is a differiential

A

control with a differential that is too narrow will short cycle equipment which reduces efficency of burners

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
76
Q

direct spark ignition

A

electric spark to light the main flame and HAS NO PIOLET FLAME

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
77
Q

what is a direct vent

A

directly vents the firnace outside

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
78
Q

what is a fan control

A

-cycle the circulating air blower of a heateing unit like a furnace

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
79
Q

What is flame roll out protection

A

-manual reset disk with a red button
-looks for flames where they shouldnt be and if there is flames where they shouldnt be it will shut down

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
80
Q

what is a high limit or limit control

A

shuts off the furnace burner if a phlenum gets too hot

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
81
Q

what is the hot surface ignition

A

-uses a high temperature electric heating element to light the burner
-safter than a piolet light because there is no spark and a slower heat time. NO PIOLET FLAME

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
82
Q

What is an intermittent piolet ignition

A

-piolet lights and stays lit while the burner is running and shuts off at the end of each burner cycle and doesnt shut off untul the main burner is shut off

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
83
Q

what is interuppted piolet ignition

A

-shuts off the piolet light when the burner is running
-uses a piolet flame to light the main burner and shuts the piolet off when the main flame is operating normally.
-the burner control lights the piolet first then uses it to light the main burner then shuts off and runs on the main burner alone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
84
Q

what is a PSC motor

A

acts as a current limiting reactance and then tapped to provide different operating speeds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
85
Q

what is a standing piolet ignition

A

uses a continuous piolet to light the main burner and stays lit. is no longer used in residential homes for saftey reasons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
86
Q

What is a thermocouple

A
  • coupling of 2 dissimilar metals and when we heat them they create 30mV. used as a saftey shut off for standing piolets and gas burners
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
87
Q

what is the output of a thermocouple

A

30mV

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
88
Q

what is a thermopile

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
89
Q

what is the output of a thermopile

A

750mV

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
90
Q

what is a thermostat

A

converts change in temoerature into an output signal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
91
Q

What is a vent limit

A

a temperature operated contact that monitors the temperature of the flue gas at the bent in a gas furnace. opens if temoerature is too high

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
92
Q

what is the primary hazard with gas burning appliances

A

-failing to light the gas when its admitted to the burner

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
93
Q

where is a thermocouple mounted

A

with the tip in the piolet flame

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
94
Q

what happens to the thermocouple if the piolet goes out

A

it cools off and the saftey valve closes to shut off the gas

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
95
Q

in standing piolet gas burners how does the saftey valve coil get reset

A

must be opened manually with a push-to-light button

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
96
Q

how does a standing piolet gas burner work

A

to start the burner-manual valve must be turned to the piolet position and then the saftey valve opened with the push to light feature. button cant be released until thermocouple gets hot enough to hold the vavle open then it will keep running

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
97
Q

when will the gas flow in a standing piolet gas burner

A

-In the PIOLEt position the push to lught feature can work byt the gas is shut off ahead pf the main burner valve
-once the saftey valve is open the gas can only flow to the piolet burner
-in the on position the manual valve is opnen=ed and the gas flow is controlled by the saftey flow anf the main valve
-as long as the saftey calve is open the piolet recueves gas and the main burner gets gas

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
98
Q

when will the main valve open in a standing piolet firnace on a 24vac system

A

-thermocouople has proved a flame to the value of 30mV
-thermostat calls for heat
-high limit switch is closed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
99
Q

what happens if the high limit switch opens in a standing piolet firnace on a 24vac system

A

-control cct and transformer de-energize

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
100
Q

when will the saftey valve close in a standing piolet firnace on a 24vac system

A

wgeb tge thermocouple senses flame of 30mV

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
101
Q

when does the fan motor operate in a standing piolet firnace on a 24vac system

A

whyen phlenem gets to a rated temperature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
102
Q

what does a murcury switch have

A

-glass bulb with 2 small probes in one end and a blob of mercery inside

103
Q

what does dial setting determine in a mercery thermostat

A

-initial tilt of the bulb and changes in temperature bend the bimetal and tip the bulb to the left or right

104
Q

what does an adjustable series resistor called a heat inticipator do

A

acts as a switch in the gas valve cct

105
Q

what would happen if there wasnt a heat anticipator

A

temp would overshoot the set point

106
Q

the anticipator resistor is not a current limiting device it is a ____________

A

adjustable heater

107
Q

in a heat anticipator increassinf the amt of the resitor that is in the cct will __________- the heat output and _____ the cycles

A

increase
shorten

108
Q

What do the R,C,W,Y,G terminals mean on a heating and cooling thermostats

A

R-power
C-common
W-heat (gas valve)
Y-cooling
G-fan

109
Q

power is supplied to the _______ terminal from one side of the crontrol transformer

A

R

110
Q

the gas valve or burner control is connected to the terminal marked with _______

A

W

111
Q

what is a fan center

A

a transformer with a relay to turn one speed to another
-called a control centre

112
Q

if a combination fan/limit control is used what has to be done to the jumoer and why

A

-jumoer removed to isolate the limit from the fan control

113
Q

if the limit for a standing piolet mV system is part of a fan/limit conteol what must be done to isolate the 2 systems

A

remove the jumper

114
Q

what are advantages of a mV sytem compared to a 24V system

A

-can run during a power outage

115
Q

in what ways are the saftey shut off valve in a mV system the same and diffrent as a 24V ac main valve

A

same- if piolet goes out the main gas valve doesnt get gas
different-different voltages used, 750mV and 24V

116
Q

mv systems are bad for intermittent problems caused by poor connections whats the reason

A

-poor or loose connections
-voltage drops

117
Q

what does a CAD cell do

A

senses light

118
Q

a furnace oil burner cycles on and off according to the demands of the thermostat and the flame must be lit how often

A

lit every time the burner starts

119
Q

how is an oil burner monitored

A

-automatic flame detector and the burner motor will shut off if there isnt a flame

120
Q

what is a stack control

A

bimetal detector

121
Q

how does a CAD cell work

A

changes its resistance when exposed to light, light from flame reduces resistance and the control cct usees that change to operate the flame relay

122
Q

why must a CAD cell be stored in total darkeness prior to the burner startiing

A

any light leakage could interfere with the propper flame detection and cause a false flame

123
Q

what is the 1K relay

A

main relay, shuts off gas valve

124
Q

what is the 2k relay

A

flame relay or change when it sees flame

125
Q

what does a line voltage high limit do

A

shuts down ebverytning on high limit

126
Q

what does a thermostat control

A

controls power to the low voltage side of the burner control

127
Q

what does an oil valve do

A

a solenoid valve that shuts off the fuel supply

128
Q

what does the burner motor do

A

motor that operates the oil pump and combustion air blower

129
Q

what does the ignition transformer do

A

supplies voltage to spark the electrodes to light the fuel

130
Q

what does the control transformer do

A

supplies power to the control cctg

131
Q

what happens if there is a false flame in an oil burner control

A

2k relay will be picked up and the 2kI NC will open if there is no flame detected it wont pick up

132
Q

how does a power humidifier work

A

-picks up water as the sylinder rotates and picks up the water from the tray and the hot air passing through the wet foam picks up and adds more moisture.
-humidified air passes through furnace through the cold air return and is distributed through the building

133
Q

How does an oil burner cct work

A
  • thermostat calls for heat which energizes 1k
    -Ik2 energizes rhw burner/ignition/oil valve
    -Ik1 contact closes in // with 2K1
    -burner lights
    -light from flame reduces resistance in CAD cell which enrgizes 2K contact
    -2k1 NC opens and 2k1 No opens which bypasses the ss heater to advoid lockout
    -burner runs until meets the heat demands then de energizes K1 which deenergizes the system
134
Q

the humidistat starts and stops at the ___________V humidifier motor

A

24V

135
Q

Humidifiers usually connected to the main furnace fan control cct. When does the humidifier run?

A

-when the fan is running

136
Q

why must electronic air cleaners have to be interlocked with the main furnace fan

A

they are only energized when the fan is running

137
Q

what is a sail switch

A

has a lightweight paddle that extends to the air stream
-A pressure on the airflow switch uses direct or differential pressure to operate the contacts

138
Q

how do programmable thermostats that steal power work

A

-steals power from the 24V cct without a connection to the 24V common

139
Q

why arnt most modern or high end thermostats not enterchangable

A

custom electronic so interchange with conventional thermostats

140
Q

Can a class 2 power supply be connected in series or parallel with another class 2 power supply?

A

no

141
Q

what kind of cable do you have to use for heating devices

A

FT4 rated cable

142
Q

for a gas furnace you need a diconnect or any arching/sparking devices within _________. For propane its _______

A

1m
3m

143
Q

how do you remove a blower fan in a furnace

A

remove jumper cable which attaches the cct board to the furnace wirings

144
Q

what happens if you dont propperly tighten the bolts on a blower motor

A

-mounts wont be able to absorb vibration witch will cause lots of noise

145
Q

how often must you lubricate low energy efficent furnaces

A

once or twice each year

146
Q

what happens if you over lubricate an electric motor

A
  • excessive oil will accumulate and dust and dirt will stick to it which interfears with cooling an dshorterns the life of the motor
147
Q

how tight should a blower motor belt tension be

A

one inch of movemebt

148
Q

A large diameter motor pulley will drive the fan at a __________- speed without a change in the motor speed

A

higher

149
Q

Gas supply to mid and high efficient furnaces comes through a __________

A

solenoid valve

150
Q

Is a high efficient furnace condensing or non condensing

A

condensing

151
Q

Is a mid efficient furnace condensing or non condensing

A

non-condensing

152
Q

In a mid or high efficient furnace what happens if the exuast fan isnt running

A

gas shuts off

153
Q

Is a service switch a disconnect

A

no
a breaker would be

154
Q

what is an HSI element

A

hot surface igniter

155
Q

what happens if you touch an HSI element with your hands

A

destroyed by chemicals on your hands

156
Q

What can depressurization cause

A

gasses to spill back into the buildings

157
Q

The safe limit for depresurizartion is ________kPa of negatice pressure

A

5

158
Q

in a forced-air heating system what does the furnace fan and duct do. when does the furnace fan run

A

supply fresg air through the building
-runs when the exaust fan is operating

159
Q

in a forced air heating system how is fresh air brought in

A

through an outdoor air duct that connects to the return air plenum of the furnace

160
Q

in forced air heating systems does it need a seperate combustion air supply

A

yes

161
Q

in a hot water heating system what does a supply fan with an outdoor intake do

A

provides fresh air

162
Q

in a hot water heating system when does the supply fan run

A

when the exaust fan is on

163
Q

in a hot water heating system what is used to distrubute fresh air to every room

A

ducts

164
Q

if the burner is gas for a boiler there will be a __________ combustion air duct

A

seperate

165
Q

what is the preferred fan speed

A

lowest one

166
Q

what is the most common ignition system

A

electric spark that lights a piolet flame

167
Q

What is an intermittent piolet

A

-ignited at the start of the burner cycle and burns continiously until the main burner is shut down

168
Q

what is an inturrupted piolet control

A

lights the piolet, proves it with a flame detector and then lights the main burner then the piolet shuts off

169
Q

What type of ignition do oil burners use

A

electrical sprak ignition

170
Q

Resdiential oil burners use what as a light sensitive cell

A

CAD

171
Q

What do commerical or industrial burners use for flame light detection

A

-infared
-rectifying photo cells
-ultra violet

172
Q

Large burners have regulators byt they also monitor ______________– to be sure its in the right limits

A

gas pressure

173
Q

The contacts from the gas pressure switch are used as _______________- or limits in the main burner control

A

interlocks

174
Q

what is an air proving contact

A

interlock or limit in the burner control cct

175
Q

Residential and commercial forced air units use one or more_________to monitor the temperature of the heat exchanger and may have other limits to protect against high vent temperature

A

high limits

176
Q

How are commercial forced air system divided

A

Separately controlled zones

177
Q

How do you zone thermostats work

A

Operate a damper mounted into a duct

178
Q

A hot water boiler has a high limit what does it do

A

Detects a dangerous over temperature. and a low water cut off that shuts the burner down. If the boiler waterfalls below the safe operating level.

179
Q

What does a two stage gas valve do

A

Reduce the number of operating cycles

180
Q

What is a pressure troll

A

Monitors and measures pressure of steam in a boiler

181
Q

Why do steam boilers have a pressure operated high limit?

A

To protect against over pressure and low water cut off, to shut down the burner if the water level falls too low

182
Q

What do auxiliary pumps do

A

Return the collected contensate.

183
Q

What components does a boiler have

A

Pressure troll, water cut off ,water level control float.

184
Q

What does a water level control do in a boiler

A

Used to control the boiler feed pump or feed water supply valve that adds returned condensate to the boiler to replenish the water that is continuously being boiled into steam

185
Q

Why do residential burners with induced draft blowers have a brief purge delay?

A

To allow the boiler to exhaust any combustible gases that may be left in the heat exchanger

186
Q

In a residential burner what happens after the pre purged period is over

A

A residential burner with a pilot will energize.

187
Q

What are three types of burners

A

Atmospheric, natural draft, forced air.

188
Q

How does the atmospheric burner work

A

Gas comes out and mixes with air and burns. It is not pressurized

189
Q

How does a natural draft burner work

A

A fan blows air in the direction and gas is pushed and it ignites. The gas is released into the air flow and is pushed by a fan

190
Q

How does a forced air draft burner work

A

The fan blows air and it’s pressurized and it pushes into the air flow

191
Q

Residential and like commercial style burners operate with an input of how many Btuh

A

400,000 or less

192
Q

In residential and like commercial style burners what is the flame failure response time

A

No more than three minutes

193
Q

In commercial style burners what is the B T U rating

A

Over four hundred thousand B T U

194
Q

In commercial style burners what is the flame failure response

A

No more than 4 seconds

195
Q

What do flame rectification (flame rods) react to. is it polarity sensitive

A

React to D C current
yes

196
Q

What do rectifying photo cells which are visible light detectors what’s the input what’s the output? is it polarity sensitive?

A

A C input D C output
yes

197
Q

Are u v detectors polarity sensitive

A

yes

198
Q

Is an infrared which uses lead sulfide cells that are sensitive to infrared radiation Polarity sensitive and what does it react to

A

Reacts to more than just heat and is not polarity sensitive

199
Q

What type of flame detector is not polarity sensitive

A

Infrared

200
Q

when are Flame Rods used with what type of burners

A

Gas burners

201
Q

a flame is an envolope of __________ gasses

A

ionized

202
Q

How does a flame rectification or a flame rod work

A

-First the electronic circuit automatically pre-checks the flame rod and will not allow the burner to light if a false flame condition exists.
- Second the flame circuit is used as a rectifier instead of Just a high resistance conductor
- The DC component is in the range of a 2-4 micro amps. The AC portion is quite a bit higher but the electronic circuit ignores it. The DC signal is amplified and is used to energize a flame relay
-200VAC converts to 2-4 microAmps

203
Q

The D C flame rectifier current is a good indicator of what

A

general health Of the flame rod circuit

204
Q

How does a rectifying photo cell work

A

Once it sees the flame it will turn AC into DC.
- It’s a small vacuum tube that has a large curved collector plate and a smaller second terminal. When the light strikes the material it emits electrons which results that the cell response to visible light like the flame rod

205
Q

Why are rectifying photo cells not used for gas burners

A

The blue flame of the gas burner does not provide enough visible light

206
Q

How does A UV flame detector work

A

There are two electrodes. The anode and the cathode. when the cathode is exposed to UV radiation it emits electrons that ionize the gas in the tube this causes the tube to fire and generate a visible glow inside the tube

207
Q

How much do uv detectors be placed

A

Have to have a clearview of the flame but they must not be able to see the spark from the igniter because the electric Spark can be mistaken for a flame

208
Q

Are u v detectors polarity sensitive

A

Yes

209
Q

What type of cell does the infrared detector use

A

Lead sulfide cell

210
Q

Is an infrared detector polarity sensitive

A

No

211
Q

How does an infrared cell work

A

Detects a flame in a firebox that is glowing with radiant energy

212
Q

What type of burners are non-programming used for

A

Lower B T U burners

213
Q

What type of burners are programming burner controls used for

A

Higher B T U burners

214
Q

How does a non-programming control Self check to protect against unsafe controller failures

A

Start self check or dynamic self check

215
Q

How does a start self check system work in a non-programming control

A

Self check systems will refuse to start the burner if a flame or flame stimulating condition exists when the controller is first energized It basically checks for a flame

216
Q

How does a dynamic self check system work in a non-programming control

A

It continuously monitors their internal circuits and will shut down on an internal failure. It’s checking for flames while it started

217
Q

In a non-programming control what is the sequence the burner motor, ignition transformer,. Pilot and main valves

A

Models with the pre purge have internal timers or plug in timer modules to provide this function models without preparation may require external perge times

218
Q

In a non-programming control how does it monitor the flame and respond to flame failure

A

Each controller has a built in amplifier or a plug in amplifier. They can use recycling controllers or non recycling controllers

219
Q

How do recycling controllers in a non-programming control work

A

they will attempt to relate the burner if there is still a failure while the burner is running used in smaller B T U units and in residential

220
Q

In a non-programming control how does non-recycling controls work

A

They will lock out if a flame failure occurs when the burner is running they’re used for higher BTU units like commercial and it starts at the beginning every time there’s a flame failure

221
Q

How are the limits for a non-programming controls connected

A

In series in the power supply ahead of the burner control

222
Q

In a programming control why does it self check and why is it the first thing it does

A

Protects against unsafe controller failures

223
Q

Why won’t boiler start in the high fire

A

Too much gas and there started in low fire

224
Q

Why are limits connected in a programming control

A
225
Q

Why does the burner controller pre purge with the maximum air flow

A

Ensure the fuel combustion error are set to low fire before any ignition attempt

226
Q

In a programming control what happens if you don’t pre purge

A

Cause an explosion in the firebox. A programming controller provides a time to preparge to ensure that’s done properly each time the burner is lit

227
Q

A programming controller may also use a __________________- to provide timed main burner ignition

A

Interrupt pilot

228
Q

What are the two relays used in the RA 890 controller?

A

Non-programming burner and recycling controller

229
Q

what is a fire tube

A

Fire in the tube and the water is in the container

230
Q

Most heating boilers operate at low pressure what is the P S I

A

Fifteen p s i or less

231
Q

in a steam boiler what happens if there is an ineffective purge or an undetected flame failure

A

Can become an explosion in a fire

232
Q

In a steam boiler what does the pre purge do

A

Get rid of dirty air or leftover gas from chamber

233
Q

How does a two pass fire tube heating boiler work

A

Flame travels down a large central tube that is surrounded by water then the returns through a large number of smaller tubes arranged in a rows around it

234
Q

What does the blank Section at the top of a steam boiler do

A

portion that only has steam in it

235
Q

In a steam Boiler what happens as the water boils into steam

A

Feed water which is mostly condensate is added into the bottom of the boiler vessel.

236
Q

In a steam boiler the pump Or valve is controlled by the what

A

Water level control (WLC)

237
Q

What point in a boiler must the water never be allowed to drop

A

Can’t be dropped so low that it exposes any of the Fire tubes if this happened these two would overheat and be damaged

238
Q

The water level in a boiler is monitored by what

A

A low water limit called the water cut off (LWCO)

239
Q

Why do all boilers need to have a low water cut off (LWCO)

A

To shut down the burner in case the water level falls too low steam boilers also need a water level control (WLC) that works in conduction with the pump or valve

240
Q

In a boiler what does a water level control do

A

Controls the amount of water the boiler receives

241
Q

What kind of controls are used for low water cut off

A

Float controls

242
Q

The LWCO contact is normally _________ and the WLC is normally ______

A

-closed
-open

243
Q

How is a low water cut off and a water level control adjusted

A

Independently

244
Q

Probe controls depend on what complete a circuit from one probe to another

A

The conductivity of water

245
Q

How does a probe operated water level control work

A

The water moisturize to the upper which is the shorter probe to energize the relay coil. This energizes the really and closes the seal in contact between the two probes. Both probes now in connected into the relay circuit the water level must fall below the tip of the lowest probe before it will be de-energized

246
Q

How does a probe type low water cut off work

A

The burner controllers shut down immediately on failures such as an open limit. The energizes the main gas valve to eliminate any potential hazards. It will restart automatically when the limit contact closes again

247
Q

What happens when you add a connection to blue in a two position mechanical valve actuator

A

Opens air and gas

248
Q

What happens when you add a connection to white in a two position mechanical valve actuator

A

Closes air and gas

249
Q

What is the acronym for a two position mechanical valve actuator

A

ARWOBC. Stands for add resistance white opens And blue closes

250
Q

How does a two stage fluid power valve actuator work

A

When the solenoid valve is energized to close the oil return port operating the motor driven hydraulic pump will force oil into the diaphragm chamber. The diaphragm is driven downward to open the spring loaded valve. A limits which shuts off the motor when the valve is fully operated.

251
Q

When the solenoid valve is the energized in a two stage fluid power valve actuator what happens

A

The oil returns from the diaphragm chamber into the motor case, and the valve closes

252
Q

What is the sequence of operation in a two stage fluid power valve actuator

A

A C B

253
Q

Can non-programming controls restart

A

yes

254
Q

Can the programmable control restart

A

No it has to go through all the steps which makes it recycle

255
Q

What are the four steps in a programmable control

A

Step one prepare \
Step two ignition
Step three running stage
Step four post purge

256
Q

What is the purpose of a thermistor in a non-programming control

A

Delays 1k relay

257
Q

What does the 2 k relay do in a non-programming control

A

Sentence Flame if it detects a flame it will open which will make it all de energized

258
Q

what is the purpose of an LS heater

A

It locks out the circuit if it doesn’t light properly and energizes an alarm

Level 2 (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions