Refrigeration & Air Conditioning Technology, 8e - xvii

using the
for eLe
amperage
result. The vibration of the compressor will vibrate the conC. using
of the
CtriC H
th
trol tube and rub a hole in the tube or one of the refrigerantcircuit. e total of the highfa-vnolmotor.
eAt
Electric
FLOOR
heat may
tage ampe
D. using
involve
ai
DRAIN
r
rage in th
systems.
th
lines if they are not kept separate.
ei
e
th
vo
er boiler
lt
T
e
age at th
8. The se
he discus
concerne
systems
e limit co
quencer
sion in th
d with fo
or
ntrol.
uses
forcedPreface
xvii
is te
The electrical section of the control will usually havepow
aer to
rc
m
ed
on
-a
(h
ir
.
These fo
systems as xt has primarily
9. True or start and stop th igh or low) voltag
rc
been
ed-air sy
they are
system or
set of contacts or a mercury switch to stop and start some False: A pa
e electric
e
st
th
co
ems
em
ntrol
th
heater
ckage sequ
one stage
pumps. T e secondary heat may be the prim ost comencer can s.
of strip he
ing system
ary heat
he
component in the system. The electrical contacts are often
te
30
psig
BOILER
GAUGE
ch
ni
start or st
at.
ing
ci
for sympt
when used
an should
op only
oms. The
enclosed and cannot be viewed, so visual inspection is not
customer always listen to th with heat
of the pr
oblem w
ca
e
n often le
cu
ith a sim
is perfor
ad you to stomer
Problem
ple descri
possible. When a problem occurs, look for frayed wires
ming.
no heator
the cause
ption of
-therm
how the
ostat calli
system
ng for he
burned wire insulation adjacent to the control. The mercury
Possible
at
Cause
open di
sconnect
in mercury switches may be viewed through the clear glass
sw h
open fu the valveitcis
is 30 psig. No wonder
relieving the pressure; itPossib
se or brea
le repair
enclosure. If theCharts
mercury becomes dark, the tube is allowlose disc tell
r the technician C
Diagnostic
is too high. The boiler is hot, ke
but
cannot
onnect sw
itch.
replace
ing oxygen to enter the space where the mercury makes and
High-tem
fuse or re
if it is too hot. The burner
isfunot
operating,
so
the
techniperature
set breake
determin
se link op
Diagnostic
Charts are
included
the
e why it
breaks the electrical
contact
andatoxidation
is occurring. In
en circ
uit
cian decides that
this may be a pressure
problem
instead
of opened. r and
tighten
faulty hi
lo
end
of
many
units.
These
charts
include
gh
os
-v
e
this case, the switch should be replaced because the switch
connectio
a temperature problem. oltage wiring or co
causing
n at fuse
heat.
nnections
link
material
on troubleshooting
and diagnosis.
may conduct
across the oxidation
and so be closed at all
repair or reguConlooks
The technician
for and finds the water
pressure
trol-volta
re
pl
ace faulty
ge power
co
nn
w
su
ections. the
iring or
pply water
times. This could prevent a boiler from shutting off, allowing
lating valve, which is in the supply
line entering
off
Check co
faulty co
ntrol-vol
ntrol-volkeeps the supply water
boiler. Actually,co
this valve
pressure
overheating to occur.
tage fuse
tage w
device
nn
ec

iri

s.

s and sa
ng or
ns
fety
from reachingHea
the tio
boiler
and feeds
water into
the system
repair or
ting em
replace fa
ent burndue to a leak. The
when there is Po
a rtloss el
of water
cosupply
ulty wiring
nnections water
ed, open
or
ion of
.
circuit
s orpsig
pressure could
easily he
beater75
more.
The re
boiler
working
limits or
place he
Low
open
ating elem
voltage
circuit
en
t-
check ai
pressure is 30 psig with a relief valve setting ofSe30
e abpsig.
ove. if the
rflow.
Correct voit would
supply water were allowed directly into the boiler,
ltage.
push the pressure past the design pressure of the system,
which must be less than 30 psig. if the pressure were above
this, it would cause the pressure relief valve to relieve the
pressure and dump water from the system until the pressure
SERVICE CALL 1
is lowered.
A customer calls indicating that the boiler in the equipment
The technician shuts off the water valve leading to the
room at a motel has hot water running out and down the
boiler makeup system and bleeds some water from the sysdrain all the time. Another service company has been pertem until the pressure at the boiler is down to 15 psig. He
forming service at the motel for the last few months. The
then adjusts the water regulating valve to a lower pressure
problem is that the water-regulating valve (boiler water feed)
and opens the supply water valve to allow water to enter
is out of adjustment. Water is seeping from the boiler's presthe system. The technician can hear water entering through
sure relief valve, Figure 14.66.
the water regulating valve. in a few minutes, the water stops
The technician arrives at the motel, parking alongside the
entering. The pressure in the system is now adjusted to
building so as not to block the Section
front 1door
or the motel's reg18 psig and all is well.
28
Theory of Heat
istration parking areas. When the property manager comes
in this example the problem is that a mechanical automatic
into the
office
greet
the
technician,
the
technician
introFigure 1.25
This gauge
reads to
50 psig.
To convert
this gauge
reading to
Figure 1.26
Digital gauges.
The compound gauge on
the left reads
control
isprescausing another control to show that the system has
psia, add 15 psi (atmospheric pressure) to 50 psig to get 65 psia.
sures above and below atmospheric pressure. The high-pressure gauge on
duces himself and hands him his company's
business
problems.
if left unexamined, the problem might seem to be
the right will
read pressurescard.
up to 800 psi. The center
gauge is a vacuum
which is used for system evacuation (see Unit 8 for more on this
After asking some preliminary questionsgauge,
about
the system,
that the relief valve is defective because water is seeping out
topic).
the technician
and the manager
of it. This is not the case; the relief valve is doing its job. The
Service
Technician
Callsgo to the boiler room. Once
there, the tech notices that, as the customer said, water is
water regulating valve is at fault.
In seeping
many units,
practical
examples
ofthat
service
technician
out of
the relief
valve pipe
terminates
in the
The technician shows the motel manager what the probcalls
areThis
presented
a down-to-earth
format.
drain.
is heatedin
water,
causing a very situational
inefficient situation
lem was, how it was corrected, and completes the paperwork
These
are realistic
situations
technicians
The needle
on theservice
boiler gauge
is in in
thewhich
red; the
pressure
before leaving for another call. The technician makes a point
insufficien

t heat

may find themselves. In many instances, the solution is
provided in the text, and in others the reader must decide
what the best solution should be. These solutions are
provided in the Instructor's Manual. The Service Technician
Calls will now incorporate customer relations and technior reference point. If you want to know what the absolute
cian
pressuresoft
is, youskills.
must add the atmospheric pressure to the
gauge reading. For example, to convert a gauge reading of
50 psig to absolute pressure, you must add the atmospheric
pressure of 14.696 psi to the gauge reading. Let us round off

Gauges provided by Appion Inc. Photo by Eugene Silberstein

14.19 SERViCE TECHNiCiAN
CALLS

14.696 to 15 for this example. Then 50 psig 1 15 5 65 psia
(pounds per square inch absolute), figure 1.25. New generation gauges are of the digital variety, figure 1-26.

SUMMaRy
●●

●●

●●

●●

●●

●●

●●

Thermometers measure temperature. Four temperature scales are Fahrenheit, Celsius, Fahrenheit absolute
(Rankine), and Celsius absolute (Kelvin).
Molecules in matter are constantly moving. The higher the
temperature, the faster they move.
The British thermal unit (Btu) describes the quantity of
heat in a substance. One Btu is the amount of heat necessary to raise the temperature of 1 lb of water 1°F.
The transfer of heat by conduction is the transfer of heat
from molecule to molecule.
The transfer of heat by convection is the actual moving of
heat in a fluid (vapor state or liquid state) from one place
to another.
Radiant heat is a form of energy that does not depend on
matter as a medium of transfer. Solid objects absorb the
energy, become heated, and transfer the heat to the air.
Sensible heat causes a rise in temperature of a substance.

●●

●●

●●

●●

●●

Latent (or hidden) heat is heat added to a substance
that causes a change of state and does not register on a
thermometer.
Specific heat is the amount of heat (measured in Btu)
required to raise the temperature of 1  lb of a substance
1°F. Substances have different specific heats.
Pressure is the force applied to a specific unit of area. The
atmosphere around the earth has weight and therefore
exerts pressure.
Barometers measure atmospheric pressures in inches of
mercury. Two of the barometers used are the mercury and
the aneroid.
Gauges have been developed to measure pressures in
enclosed systems. Two common gauges used in the airconditioning, heating, and refrigeration industry are the
compound gauge and the high-pressure gauge.

REVIEW QUESTIoNS
1. Temperature is defined as
A. how hot it is.
B. the level of heat.
C. how cold it is.
D. why it is hot.

2.
3.
4.
5.

State the standard conditions for water to boil at 212°F.
List four types of temperature scales.
Under standard conditions, water freezes at _____°C.
Molecular motion stops at _____°F.

Summary
The Summary appears at the end of each
unit prior to the Review Questions. It can be
used to review the unit and to stimulate class
discussion.

Review Questions
Review Questions follow the Summary in
each unit and can help to measure the
student's knowledge of the unit. There are a
variety of question types-multiple choice,
true/false, short answer, short essay, and
fill-in-the-blank.



Refrigeration & Air Conditioning Technology, 8e

Table of Contents for the Digital Edition of Refrigeration & Air Conditioning Technology, 8e

Contents
Refrigeration & Air Conditioning Technology, 8e - Cover1
Refrigeration & Air Conditioning Technology, 8e - Cover2
Refrigeration & Air Conditioning Technology, 8e - i
Refrigeration & Air Conditioning Technology, 8e - ii
Refrigeration & Air Conditioning Technology, 8e - iii
Refrigeration & Air Conditioning Technology, 8e - Contents
Refrigeration & Air Conditioning Technology, 8e - v
Refrigeration & Air Conditioning Technology, 8e - vi
Refrigeration & Air Conditioning Technology, 8e - vii
Refrigeration & Air Conditioning Technology, 8e - viii
Refrigeration & Air Conditioning Technology, 8e - ix
Refrigeration & Air Conditioning Technology, 8e - x
Refrigeration & Air Conditioning Technology, 8e - xi
Refrigeration & Air Conditioning Technology, 8e - xii
Refrigeration & Air Conditioning Technology, 8e - xiii
Refrigeration & Air Conditioning Technology, 8e - xiv
Refrigeration & Air Conditioning Technology, 8e - xv
Refrigeration & Air Conditioning Technology, 8e - xvi
Refrigeration & Air Conditioning Technology, 8e - xvii
Refrigeration & Air Conditioning Technology, 8e - xviii
Refrigeration & Air Conditioning Technology, 8e - xix
Refrigeration & Air Conditioning Technology, 8e - xx
Refrigeration & Air Conditioning Technology, 8e - xxi
Refrigeration & Air Conditioning Technology, 8e - xxii
Refrigeration & Air Conditioning Technology, 8e - xxiii
Refrigeration & Air Conditioning Technology, 8e - xxiv
Refrigeration & Air Conditioning Technology, 8e - 1
Refrigeration & Air Conditioning Technology, 8e - 2
Refrigeration & Air Conditioning Technology, 8e - 3
Refrigeration & Air Conditioning Technology, 8e - 4
Refrigeration & Air Conditioning Technology, 8e - 5
Refrigeration & Air Conditioning Technology, 8e - 6
Refrigeration & Air Conditioning Technology, 8e - 7
Refrigeration & Air Conditioning Technology, 8e - 8
Refrigeration & Air Conditioning Technology, 8e - 9
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Refrigeration & Air Conditioning Technology, 8e - 11
Refrigeration & Air Conditioning Technology, 8e - 12
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Refrigeration & Air Conditioning Technology, 8e - 27
Refrigeration & Air Conditioning Technology, 8e - 28
Refrigeration & Air Conditioning Technology, 8e - 29
Refrigeration & Air Conditioning Technology, 8e - 30
Refrigeration & Air Conditioning Technology, 8e - 31
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Refrigeration & Air Conditioning Technology, 8e - 40
Refrigeration & Air Conditioning Technology, 8e - 41
Refrigeration & Air Conditioning Technology, 8e - 42
Refrigeration & Air Conditioning Technology, 8e - 43
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Refrigeration & Air Conditioning Technology, 8e - 45
Refrigeration & Air Conditioning Technology, 8e - 46
Refrigeration & Air Conditioning Technology, 8e - 47
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Refrigeration & Air Conditioning Technology, 8e - 50
Refrigeration & Air Conditioning Technology, 8e - 51
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Refrigeration & Air Conditioning Technology, 8e - 53
Refrigeration & Air Conditioning Technology, 8e - 54
Refrigeration & Air Conditioning Technology, 8e - 55
Refrigeration & Air Conditioning Technology, 8e - 56
Refrigeration & Air Conditioning Technology, 8e - 57
Refrigeration & Air Conditioning Technology, 8e - 58
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Refrigeration & Air Conditioning Technology, 8e - 60
Refrigeration & Air Conditioning Technology, 8e - 61
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Refrigeration & Air Conditioning Technology, 8e - 63
Refrigeration & Air Conditioning Technology, 8e - 64
Refrigeration & Air Conditioning Technology, 8e - 65
Refrigeration & Air Conditioning Technology, 8e - 66
Refrigeration & Air Conditioning Technology, 8e - 67
Refrigeration & Air Conditioning Technology, 8e - 68
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Refrigeration & Air Conditioning Technology, 8e - 70
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Refrigeration & Air Conditioning Technology, 8e - 81
Refrigeration & Air Conditioning Technology, 8e - 82
Refrigeration & Air Conditioning Technology, 8e - 83
Refrigeration & Air Conditioning Technology, 8e - Cover4
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