1 exam prep intermediate mechanical study guide...
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1 Exam Prep – Intermediate Mechanical Study Guide 1
1 Exam Prep
Intermediate Mechanical Study Guide
Tabs and Highlights
These 1 Exam Prep Tabs are based on Intermediate Mechanical Study Guide.
Each Tabs sheet has five rows of tabs. Start with the first tab at the first row at the top of the page; proceed
down that row placing the tabs at the locations listed below. Place each tab in your book setting it down one
notch until you get to the last tab (usually the index or glossary). Then start with the highlights.
Special Note to our Students: If you are a 1 Exam Prep student, here is how to really get the most from
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outline of your appropriate module. Now locate and highlight several items listed in the outline just before
the topic, and just after. See how the topic fits in the outline and how it relates as a concept to the broader
concept spelled out in the outline. If you take a few minutes to do this, when you take the test key words in
the test questions will remind you of where the information is in the manual!
1 Exam Prep Tab Section
Contents I
Basic Electricity 03106-07
Introduction to Cooling 03107-07
Introduction to Heating 03108-07
Introduction to Hydronic Systems 03203-07
Alternating Current 03206-07
Introduction to Control Circuit 03208-07
Trouble Shooting
Troubleshooting Gas Heating 03209-07
Basic Installation and Maintenance 03212-07
Practices
Refrigerants and Oils 03301-08
Retail Refrigeration Systems 03304-08
Commercial Hydronic Systems 03305-08
1 Exam Prep – Intermediate Mechanical Study Guide 2
1 Exam Prep Tab Section
Steam Systems 03306-08
Water Treatment 03308-08
Troubleshooting Electronic Controls 03309-08
Construction Drawings and 03401-09
Specifications
System Startup and Shutdown 03406-09
Index 799
This concludes the tabs for this document. Please continue with the highlights below.
Section Highlight
03106-07 Basic Electricity
2.1.0 Electrical Power Generation and Distribution: Devices known as transformers are
used to step up the voltage down to lower levels as it reaches electrical substations and
eventually our homes, offices, and factories.
2.2.0 Current, Voltage, and Resistance: When a difference in the number of electrons exists
between two points, electrons …. Between the two points is called voltage.
In the common 12V car battery, a chemical reaction causes one of the poles to be
negative with respect to the other.
Current is expressed in amperes or amps (A), voltage is expressed in volts (V), and
resistance is expressed in ohms.
3.0.0 AC and DC Voltage: The kind of electricity produced by a battery is known as direct
current.
The electricity supplied by your local utility is alternating current (AC). Almost all
HVAC devices use AC … such units contain special circuits called rectifiers that convert
AC to DC.
1 Exam Prep – Intermediate Mechanical Study Guide 3
Section Highlight
4.1.0 Ohm’s Law
Figure 4: Ohm’s Law
4.2.0 Electrical Power: Power formula: Power (P) = voltage (E) x current (I).
5.0.0 Electrical Circuits: An electrical circuit is a closed loop that contains a voltage source, a
load, and conductors to carry current.
5.1.0 Series Circuits: A series circuit provides only one path for current flow. The total
resistance of the circuit is equal to the sum of the individual resistances.
5.2.0 Parallel Circuits: In a parallel circuit, each load is connected directly to the voltage
source.
7.2.0 Switches: Switches stop and start the flow of current to other control devices or loads.
The simplest type of switch is one that makes (closes0 or breaks (opens) a single
electrical unit … Figure 13 shows some of the common switch arrangements, including:
1-3.
7.2.2 Fuses and Circuit Breakers: Fuses and circuit breakers protect components and wiring
against damage from current surges or short circuits.
A problem known as a ground fault occurs when a live conductor touches another
conducting substance … are installed for such problems.
7.2.5 Transformers: A transformer is used to raise or lower a voltage … around a common
iron core.
8.1.0 The Effect of Current: Electrical current flows along the path of least resistance to
return to its source.
8.2.0 Safety Practices: Here are some general safety practices to o\follow whenever you are
working with electricity: (8 bullets).
9.0.0 Circuit Diagrams
9.2.0 Simplified Schematic Design
Figure 25 – Circuit diagram
Figure 26- Ladder Diagram
1 Exam Prep – Intermediate Mechanical Study Guide 4
Section Highlight
11.0.0 Electrical Measuring Instruments
11.1.0 Ammeter: Ammeters are often used to check motor circuits.
11.2.2 Resistance Measurements: An ohmmeter is used to check continuity in a circuit.
03107-07 Introduction to Cooling
2.1.1 Temperature: On the Fahrenheit scale water boils at 212 F and freezes at 32 F.
2.1.2 Heat Content: Btu is the amount of heat needed to raise the temperature of one pound of
water one degree Fahrenheit.
2.1.3 Sensible and Latent Heat: The increase in temperature from O F to 32 F registered by
the thermometer is called sensible heat … is called latent heat.
If we continue to add heat after all the water has been converted to steam … changed into
vapor.
Subcooling is the reverse of superheat.
Figure 4 – Change of state terminology.
2.2.0 Heat Transfer: Heat transfer is the movement of heat from one place to another, either
within a substance or between substances.
2.2.1 Conduction: Conduction is a means of heat transfer in which heat is moved from
molecule to molecule within a substance.
2.2.2 Convection: Convection is the transfer of heat by the flow of liquid or gas caused by a
temperature differential.
2.2.3 Radiation: Radiation is the movement of heat in the form of invisible rays or waves,
similar to light.
2.2.5 Rate of Heat Transfer: One ton of refrigeration is defined as 12,000 Btuh.
2.3.0 Pressure: Pressure is defined as force per unit area. This is normally expressed in pounds
per square inch.
2.3.1 Atmospheric Pressure: Atmospheric pressure can be measured with a barometer.
For this reason, it is often referred to as barometric pressure.
2.3.2 Gauge Pressure: Positive gauge pressures, those above zero are expressed in pounds
per square inch … in inches of mercury vacuum or in Hg vac.
1 Exam Prep – Intermediate Mechanical Study Guide 5
Section Highlight
2.3.3 Pressure/Temperature Relationships: the boiling temperature of a liquid will drop
as the pressure on it decreases.
2.3.4 Movement of Fluids: Differences in pressure cause the flow of fluids. This flow is
always from a higher pressure to a lower pressure.
2.4.2 Gauge Manifold Set: The compound pressure gauge is used to measure system low-side
(suction) pressures, including any vacuum that exists in a system.
Most gauge manifold sets and service hoses are color-coded. The low-pressure compound
gauge, hand valve, and low-pressure hose port are blue.
Red is the color used to mark the high-pressure gauge, hand valve, and hose port.
Four-valve manifolds and related service hose sets are color-coded as follows: Blue (low
pressure), red (high pressure), yellow (charging), and black (vacuum).
Figure 12 – Basic refrigeration cycle
3.1.0 System Components:
- Evaporator
- Compressor
- Condenser
- Metering device
The type of lines are:
- Suction line
- Hot gas line
- Liquid line
3.2.0 Refrigeration Cycle
3.2.1 Basic Operation: The refrigeration cycle is based on two principles: (2 bullets).
Figure 13 – Typical air conditioning cycle for HCFC-22 (R-22) refrigerant
4.0.0 Refrigerants
4.3.0 Fluorocarbon Refrigerants: Man-made (synthetic) refrigerants in popular use today are
fluorocarbons or a mixture of … changed molecule is called s halocarbon, short for
halogenated hydrocarbon.
Fluorocarbon refrigerants fall into three groups, CFCs, HCFCs, and HFCs, based on their
chemical structure.
1 Exam Prep – Intermediate Mechanical Study Guide 6
Section Highlight
4.5.0 Identifying Refrigerants
Table 3 – Color Codes for Common Refrigerant Containers
4.6.0 Refrigerant Safety Precautions
5.0.0 Compressors: Five types of compressors are commonly used in mechanical refrigeration
systems: (5 bullets).
5.1.0 Reciprocating Compressors: They use one or more pistons moving back and forth
within a cylinder.
5.2.0 Rotary Compressors: There are two types of rotary compressors: stationary vane and
rotary vane.
5.3.0 Scroll Compressors: achieves compression by the use of two spiral-shaped parts called
scrolls.
5.4.0 Screw Compressors: use a matched set of screw-shaped rotors, one male and one female
enclosed within a cylinder.
5.5.0 Centrifugal Compressors: use a high-speed impeller with many blades that rotate in a
spiral-shaped housing.
6.0.0 Condensers: Condensers are used for removing heat from the refrigeration system.
7.0.0 Evaporators: are used to extract heat from the conditioned space.
8.2.1 Thermostatic Expansion Valve: It is designed to maintain a constant superheat.
9.0.0 Other Components
9.5.0 Oil Separator: Their use is mainly in refrigeration and industrial systems.
9.9.0 Compressor Muffler: Mufflers are used most often in systems with open or semi-
hermetic reciprocating compressors.
10.0.0 Controls: Primary controls start or stop the refrigeration cycle either directly or
indirectly by sensing temperature, humidity, or pressure, or by measuring time.
Secondary controls regulate and protect the cycle and its components.
10.1.0 Primary Controls: Primary controls include the following: (4 bullets).
11.0.0 Piping
11.1.0 Basic Principles: Keep them simple and pitch horizontal lines in the direction of flow.
1 Exam Prep – Intermediate Mechanical Study Guide 7
Section Highlight
11.5.0 Insulation: The three major considerations in refrigerant piping layout are compressor
protection, oil return, and pressure drop.
Figure 49 – Piping layout
03108-07 Introduction to Heating
2.1.1 Conduction: Conduction is the flow of heat from one part of a material to another part
or substance in direct contact with it.
An example of conduction is the transfer of heat from the gas burners to the heat
exchangers in a furnace.
2.1.2 Convection: Convection is air motion due to the warmer portions rising and the denser,
cooler portions falling.
2.1.3 Radiation: Radiation is the transfer of heat through space by wave motion.
2.2.0 Temperature: There are times when it may be necessary to change from one scale to the
other. These conversions can be done using the following formulas: (Equation).
2.3.0 Heat Measurement: The unit of measurement of heat in the inch-pound system is the
British thermal unit (Btu). One Btu is the amount of heat required to raise the temperature
of one pound of water 1 F.
2.4.0 Combustion: Combustion is the burning of fuel to create heat.
2.4.1 Complete Combustion: Complete combustion takes place when carbon combines with
oxygen to form carbon dioxide.
2.4.2 Incomplete Combustion: Incomplete combustion results from lack of oxygen and
causes undesirable products to form.
2.4.4 Flames: Pressure-type oil burners burn with a yellow flame, while gas burners burn with
a blue flame that has a slight orange tip.
2.5.0 Fuels
2.5.1 Gaseous Fuels: There are three types of gaseous fuels: natural gas, manufactured gas,
and liquefied petroleum.
- Natural gas
- Manufactured gas
- Liquefied petroleum
1 Exam Prep – Intermediate Mechanical Study Guide 8
Section Highlight
2.5.2 Fuel Oils: There are six common grades of oil: Nos. 1, 2, 4, 5 and g. the lighter-weight
oils have a higher API gravity. (6 bullets).
3.0.0 Forced-Air Furnaces: In a forced-air furnace, cooled air-return air from the space being
… to the space through the supply ductwork.
3.2.0 Heat Exchangers: The heat exchanger is the part of the furnace where combustion takes
place.
3.3.0 Condensing Furnaces: Condensing furnaces are equipped with a secondary heat
exchanger made of stainless steel … looks like refrigeration condensing coil.
The latent heat removed by the condensing process is transferred to the conditioned air.
3.4.0 Fans and Motors
3.7.0 Humidifiers: Humidifiers are used to add moisture to outside air.
3.8.0 Installation
3.8.2 Safety Controls: Some of the furnace safety controls include the following: (4
bullets).
4.0.0 Gas Furnaces: In a gas furnace, gas fuel is supplied at low pressure into a burner head,
where it is mixed with the air required for combustion.
4.6.2 Manifold Pressure: One way to check the manifold pressure is to connect a manometer
to the pressure is to connect a manometer … It is calibrated in w.c.
5.0.0 Oil Furnaces: Electrodes located at the point where the oil spray enters the combustion
chamber provide a high-voltage spark that ignites the oil.
5.1.0 Oil Burner Operation: A high-pressure gun type burner forces oil through the nozzle
under pressure … Combustion air is supplied by a vane fan, creating turbulence and
complete mixing action.
5.1.4 Ignition System: The ignition system for high-pressure burners consists of a step-up
transformer connected to two electrodes.
5.4.0 Oil Safety Controls: Electric furnaces differ from fuel furnaces in that no combustion is
required.
6.1.0 Heating Elements
7.0.0 Hydronic Heating Systems: Another type of residential heating system heats water …
called a hydronic heating system.
1 Exam Prep – Intermediate Mechanical Study Guide 9
Section Highlight
03203-07 Introduction to Hydronic Systems
1.0.0 A hydronic system uses pipes to transport heated or cooled fluid.
2.1.0 Water: Water itself is non-corrosive to most materials used in hydronic systems.
Although nitrogen is relatively inert, the dissolved oxygen will cause corrosion and
rusting … These systems are no longer used.
2.3.0 Head Pressure: Head pressure (or head) is another measure of pressure … column of
water 2.31’ high will produce a pressure of 1 psi.
Figure 3 – Relationship of head pressure in feet to pounds per square inch
2.4.0 Static pressure: Static pressure levels in a system decrease as we move from the lowest
point … the static pressure is 0 psi.
3.0.0 Hot-Water Heating Systems
3.1.0 Gravity Hot-Water Systems: In a gravity hot-water system water contained in the boiler
is heated to the operating temperature needed for use in the system.
3.2.0 Forced Hot-Water Systems: When a zone thermostat calls for heat the system
circulating … through a zone control valve to terminal devices located in the zone.
4.1.0 Hot-Water Boilers: A boiler heats water using gaseous fuels, oil fuels, solid fuels, or
electricity.
4.1.2 Cast-Iron Boilers: cast-iron boilers are formed by assembling individual cast-iron heat
exchanger sections together … small residences up to large commercial systems of
13,000 MBh.
4.2.0 Boiler Operating/Safety Controls and Accessories
4.2.2 Pressure (Safety) Relief Valve: A pressure (safety) relief valve is used to protect the
boiler and the system … maximum working pressure of less than 30 psi, at which point
the valve is designed to be fully open.
4.2.3 Thermal/Electronic Probe/Operating/Safety Controls: Electronic probe-type controls
are also common. This device uses an electrode placed in water.
4.3.0 Expansion/Compression Tanks: An expansion tank, also called a compression tank, is
used to maintain system pressures.
These tanks are normally installed near the boiler.
1 Exam Prep – Intermediate Mechanical Study Guide 10
Section Highlight
4.4.0 System Air Control Devices
4.5.0 Circulating Pumps: On larger systems with high pump head, it is recommended that the
pump(s) be installed in the supply side … discharging away from the boiler and
expansion tank.
4.6.0 Valves
4.6.1 Gate, Ball, Globe, and Angle Valves: Gate valves are used to turn on or shut off the
flow of water or steam.
4.7.0 Heating System Terminals
4.7.1 Convectors: A convector is a heating device that depends mainly on gravity conductive
heat transfer.
5.0.0 Water Piping Systems
5.1.0 One-Pipe Systems: One pipe water systems are used primarily for hot-water heating
systems.
5.2.0 Two-Pipe Systems: Two-pipe systems are classified as either direct-return or reverse
return systems.
5.3.0 Hot Water Zoning
Figure 40 – Boiler piping zoned with valves
7.0.0 Water Balance
7.1.1 System Rate of Flow and Pump Selection
03206-07 Alternating Current
2.0.0 Transformers: The transformer is the key component in an AC-powered system. A
transformer generally consists of two or more coils … and is called the secondary
winding.
The output voltage of a transformer can be calculated by comparing the number of turns
of wire in the primary winding to the number of … This relationship is stated by the
formula: (Formula).
Figure 3 – Multiple-tap secondary winding
Figure 4 – Multiple-tap primary winding
1 Exam Prep – Intermediate Mechanical Study Guide 11
Section Highlight
2.3.0 Transformer Selection: Transformers are rated or sized according to the amount of
power the secondary … expressed in VA (voltage times amperage).
Figure 5 – Three-phase transformers
3.1.0 Sine Wave Generation
Figure 8 – Sine Wave Generation
Because the amplitude of the voltage wave-form varies between zero and peak … volts
produces a working voltage of 120 volts. (equation)
If you know the effective voltage and want to determine the peak voltage …which is the
square root of 2.
3.2.0 Frequency: The speed at which an armature rotates affects the frequency … so does the
frequency.
Figure 9 – Sine wave plot
3.3.0 Single-Phase Power: Power generated at the power station is transmitted as a very high
AC voltage … of a residence is usually about 240 volts.
An Edison hookup is a common wiring arrangement for a power transformer that delivers
power to a residence.
Figure 12 – Edison hookup
Figure 14 – 240V Branch circuits
Figure 15 – 120V Branch circuits
4.1.0 Resistive Circuits: The amount of power consumed by the load is determined by the
formula: P (power) = E (voltage) x I (current).
Figure 22 – Resistive circuit
4.2.0 Inductive Circuits: In a purely inductive circuit, the current waveform will lag the
voltage waveform by 90 degrees.
4.3.0 Capacitors: A capacitor is an electrical storage device that charges and discharges as the
applied voltage changes.
In a purely capacitive circuit, voltage lags the current by 90 degrees.
There are two common types of capacitors … be damaged if it is left in the circuit.
1 Exam Prep – Intermediate Mechanical Study Guide 12
Section Highlight
5.0.0 Induction Motors: AC induction motors are the primary load devices in HVAC
equipment.
5.1.0 Single-Phase Motors: The main components of a single-phase motor are the rotor and
the stator. The stator is fixed and the rotor turns.
5.1.1 Split-Phase Motors: In the split-phase motor an additional winding (Start winding) is
added to the stator … run winding which has fewer turns of the wire.
Split phase motors are used in pumps, oil burners, and other applications requiring 1/3
horsepower or less.
5.1.3 Capacitor-Start Motors: Their high starting torque makes them suitable for powering
and some refrigeration compressors.
5.1.4 Capacitor-Start, Capacitor-Run Motor: The capacitor-start, capacitor-run motor
(Figure 33) is used to drive refrigerant compressors.
5.1.5 Shaded-Pole Motor: Shaded-pole motors are used to drive small fans and pumps.
5.1.6 Multi-Speed Motors: The maximum speed at which a motor can run is known as its
synchronous speed.
5.2.0 Three-Phase Motors: Three-phase motors offer several important advantages over
single-phase motors: (4 bullets).
6.0.0 Testing AC Components
6.3.0 Megohmmeter (megger): Test voltages ranging from 50V to 5,000 V can be supplied by
the megohmeter, or meggar … There are three types of meggers: hand, battery, and
electric.
6.3.1 Safety Precautions: (4 bullets)
6.5.0 Checking Inductive Loads: The start winding of a single-phase motor will have a higher
resistance than the run winding, perhaps three to four times higher.
7.0.0 Safety: Practically all electric shocks are due to human error, rather than equipment
failure … all defects found by tests and inspections.
03208-07 Introduction to Control Circuit Troubleshooting:
2.1.0 Principles of Operation: Most residential and small commercial thermostats are of low
voltage (24 V) type … electrical shock and less chance of fire from short circuits.
1 Exam Prep – Intermediate Mechanical Study Guide 13
Section Highlight
2.2.0 Heating-Only Thermostats: To avoid the discomfort that this condition might cause, the
thermostat … space reaches the setpoint.
2.3.0 Cooling-Only Thermostats: Cooling thermostats contain a device called a cooling
compensator … has a much higher resistance that the switch contacts.
2.5.0 Heating-Cooling Automatic Changeover Thermostats: A thermostat contains a built-
in mechanical differential, which is the cut-in and cut-out points of a thermostat. The
differential is normally 2 F.
2.7.0 Programmable Thermostats: The following are some of the features available on
electronic thermostats:
- Better temperature control
- Installation versatility
- Override control
- Multiple programs
- Staggered startup for multi-unit systems
- Maintenance tracking
2.9.0 Thermostat Installation
2.9.1 Installation Guidelines: The thermostat should be installed in the space in which it will
be called upon to control the temperature … making the thermostat contacts chatter.
2.9.2 Thermostat Wiring
2.9.3 Checking Current Draw: The current draw is usually printed on the furnace nameplate
… R and W terminals of the existing wall plate or sub-base.
3.1.0 Relays, Contactors, and Starters
3.1.1 Relays: A relay operates to stop or permit the flow of electricity.
3.1.3 Contactors and Starters: A motor starter is used to stop and start motors and provide
overload protection.
3.3.0 Lockout Control Circuit: The purpose of the lockout relay in a control circuit is to
prevent the automatic restart of the HVAC equipment.
3.5.0 Compressor Short-Cycle Timer: A compressor short-cycle protection circuit contains a
timing function that prevents the compressor … Lockout periods are typically 2 to 5
minutes.
3.7.2 Limit Control
Figure 34 – Circuit diagram of a cooling / gas heating system
1 Exam Prep – Intermediate Mechanical Study Guide 14
Section Highlight
5.1.0 Customer Interviews: Talking to the customer prior to working on the equipment
is always valuable information on equipment … thereby eliminating unnecessary
equipment maintenance.
5.4.0 Use of Manufacturer’s Troubleshooting Aids
5.4.1 Label Diagrams: They normally show a component arrangement diagram, wiring
diagram, legend, and notes pertaining to the equipment.
5.4.3 Diagnostic Equipment and Tests
Figure 35 – Typical label diagram
6.0.0 Safety
6.1.0 Safety Practices: The following is a list of recommended safety practices: (8 bullets).
7.0.0 HVAC System Troubleshooting
8.0.0 HVAC Equipment Input Power, Load, and Control Circuits: Most HVAC
equipment can be divided into three functional circuit areas: (3 bullets).
10.3.0 Start Relay Checks: When the start relay is operating properly, the clamp-on ammeter
current indication should momentarily … is good because its contacts have opened.
10.5.0 Identifying Unmarked Terminals of a PSC/CSR Motor: First, the multimeter is used
to find the two terminals across
Figure 57 – Identifying unmarked terminals of a PSC/CSR motor.
12.0.0 Pneumatic Controls
12.1.0 Basic Components: P-E relays are simply pressure switches in which a pneumatic signal
causes an electrical change … switch differentials (the pressure change that causes the
switch to make and break).
13.0.0 HVAC Digital Control Systems
13.1.0 Direct Digital Control
Controlling Devices
03209-07 Troubleshooting Gas Heating
1 Exam Prep – Intermediate Mechanical Study Guide 15
Section Highlight
2.1.0 Natural-Draft Packaged Units: Government-mandated energy efficiency requirements
for gas furnaces cannot easily be met with furnaces using natural draft venting
technology.
Figure 1 – Natural Draft Gas Heating System
The basic operating sequence of any natural-draft unit is as follows: 1-5.
Induced-Draft Packaged Units
Figure 3 – Induced-draft gas heat/electric cool unit
2.3.0 Induced-Draft Gas Furnace
2.5.0 Low-and High-Intensity Infrared Gas-Fired Heaters: The basic purpose is to heat
objects, not air.
2.5.1 Low-Intensity Infrared Gas-Fired Heaters: Tubular heaters are available in either
vented or non-vented versions…by a blower in the burner assembly at the input to the
tube.
2.5.2 High-Intensity Infrared Gas-Fired Heaters: These non-vented units also called direct-
fired radiant burners, are used at high levels off the floor as spot or space heaters.
In some cases, the grids can also be closely covered by an optional wire screen, called
reverberator, that increases the infrared radiation when heated.
3.1.0 Troubleshooting Thermocouples: A thermocouple generates only enough voltage to
hold open the safety valve once … but operate at 18 to 25 millivolts under load.
3.2.0 Troubleshooting Pilot Resignation and Direct Ignition Devices: Pilotless systems uae
either a hot surface ignitor (HIS), which is made of ceramic material that glows when a
current flows through it, or a direct spark ignitor. Both ignite the gas at the burner.
3.2.1 Spark Ignitors: If there is no spark at all, the spark gap … is most likely in the ignition
module or the high-voltage wire to the ignitor.
3.2.2 Glow Coil Ignitors: A glow coil of platinum wire to ignite the pilot gas … so the voltage
drop across the glow coil is 11.5 to 12 volts.
3.3.0 Troubleshooting the Flame Sensor: The normal range is between 0.5 and 4.5
microamperes.
3.3.1 Testing a Combined HIS/Flame Sensor: The meter used must have a DC
microammeter range of about 10 microamps.
1 Exam Prep – Intermediate Mechanical Study Guide 16
Section Highlight
4.0.0 Air System: In addition to component failure, there are three general kinds of problems
that can occur in the supply and return system:
- Obstructed air flow
- Ductwork
- Blower motor
03212-07 Basic Installation and Maintenance Practices
2.1.1 Thread Designations: The three series are:
- Unified National Course
- Unified National Fine
- Unified National Extra Fine
2.1.2 Fastener Grade Designations
Figure 1 – Thread Designations
2.2.0 Types of threaded fasteners include the following:
- Set screws
- Machine bolts
- Flat and lock washers
- Nuts
- Thread-forming and thread-cutting screws
- Toggle and anchor bolts
- Inserts
2.2.1 Machine Bolts, machine Screws, Stud Bolts, and Cap Screws:
Machine bolts are used to assemble parts that do not require close tolerances.
Machine screws are used for general assembly.
Cap screws are generally used on assemblies that need a finished appearance.
Stud bolts are headless bolts, threaded either along the entire length or on both ends.
2.2.2 Set Screws: They are used to fasten pulleys and fan blades on shafts, and to hold collars
in place.
2.2.3 Flat and Lock Washers: Some common types of lock washers include the following:
- External
- Internal
- Internal-external
- Countersink
- Split ring
1 Exam Prep – Intermediate Mechanical Study Guide 17
Section Highlight
2.2.4 Nuts: Some special-purpose nuts include the following:
- Acorn nut
- Castellated (or castle) and slotted nuts
- Self-locking nut
- Wing nut
- Jam nut
- U-nuts and J-nuts
- Cage nut
2.2.5 Thread-Forming and Thread-Cutting Screws: Thread-forming screws are used mainly
to fasten light-gauge metal parts.
2.2.6 Toggle and Anchor Bolts: Toggle bolts are used to fasten a part to a hallow wall or
panel.
2.3.0 Non-Threaded Fasteners: This section describes the following types of non-threaded
fasteners:
- Retainer rings
- Pins
- Keys
- Rivets
2.3.2 Pins: Some common pins and their uses are as follows:
- Dowel pins
- Taper and spring pins
- Cotter pins
2.4.0 Installing Threaded Fasteners
2.4.1 Torqueing Steel Fasteners: When torqueing steel fasteners, you must first select the
proper type … to the recommended specifications.
Figure 14 – Torque Specifications
Torque is the resistance to turning or twisting force … the scale when the required torque
is applied.
The following terms, sometimes used in manufacturer’s service literature must be
understood when using a torque wrench:
- Break-away torque
- Set or seizure
- Run-down resistance
2.4.2 Flange Tightening Sequences: When tightening bolts on flanges and similar surfaces,
the bolts … in the fastener type, then tighten to the final torque.
1 Exam Prep – Intermediate Mechanical Study Guide 18
Section Highlight
2.4.4 Installing Anchor Bolts: When installing a non-expansion anchor bolt in hardened
concrete, it is installed … Also, the anchor bolt should extend out of the hole far enough
for the threads and a little of the unthreaded bolt to be above the surface level.
3.0.0 Gaskets: The basic function of a gasket is to create a seal between two fixed parts … and
compressor cylinder heads.
3.2.0 Installing and Removing Gaskets: When installing the new gasket, do not over tighten
the bolts because … should not be used with the gaskets unless specified by the
manufacturer.
5.0.0 Seals: Seals are devices used to prevent or control leakage between moving and fixed
parts … non-mechanical and mechanical.
5.1.0 Nonmechanical Seals: Nonmechanical seals are used both as static seals and dynamic
seals … Lip and oil-type seals are examples of seals used as dynamic seals.
5.1.1 O-Rings: O-rings are circular seals used as either static or dynamic seals.
5.1.2 Lip and Oil Seals: Lip seals are low pressure, positive-contact seals used with rotating
shafts.
6.0.0 Bearings: The following terms are commonly used when describing the operation of
bearings:
- Axial Load
- Journal
- Radial Load
- Thrust
6.1.0 Plain Bearings: Plain bearings are simple in construction, operate efficiently, and can
support heavy loads.
6.2.0 Anti-Friction Bearings: Anti-friction bearings are so named because they operate on the
principle of rolling motion, using either balls or rollers between rotating and fixed
surfaces.
6.2.1 Ball Bearings
6.2.2 Roller Bearings
6.4.0 Removing and Installing Bearings
6.4.2 Installing Bearings: The temperature mounting method used for interference bearings
can usually be performed … the bearing is still in the equipment.
1 Exam Prep – Intermediate Mechanical Study Guide 19
Section Highlight
When using this method, care must be taken not to overheat the bearing … The
maximum temperature to which a bearing should be heated is 250 F.
7.1.0 Oils
7.1.1 Viscosity: Viscosity is the thickness of a liquid or the ability of the liquid to flow at a
specific temperature.
7.2.0 Greases: Grease is not a liquid and cannot form a liquid film when it is initially applied
… grease releases some of its oil, allowing the lubrication action to begin.
8.0.0 Belts and Belt Drives
8.1.0 V-Belts
8.1.1 Fractional Horsepower Belts: Fractional horsepower (FHP) belts are light-duty belts,
usually used singularly.
FHP belts come in the following standard widths and heights: 2L, 3L, 4L, 5L
8.1.2 Standard Multiple Belts: Standard multiple belts are used for continuous service.
They are available in various lengths for each width size and in the following standard
widths and heights: A, B, C, D
8.1.3 Wedge Belts: The wedge belt is a multiple belt that has a smaller cross-section per
horsepower than the standard widths and heights: 3V, 5V, 8V
9.0.0 Couplings and Direct Drives
9.1.0 Coupling Types
9.1.1 Rigid Couplings: Rigid couplings provide a nonflexible connection between the driver
and driven shafts.
9.1.2 Flexible Couplings: Flexible couplings are much more common than rigid couplings
because they are usually easier to install and maintain and do not require precise
alignment.
9.1.3 Soft-Start Couplings: Soft-start couplings are used in applications where smooth, even
starts are needed.
9.3.0 Coupling Alignment: When aligning two coupling halves so that the shafts will be
aligned … This results in four basic ways the coupling must be aligned. (4 bullets).
1 Exam Prep – Intermediate Mechanical Study Guide 20
Section Highlight
9.3.1 Correcting Outer Diameter Alignment, Side View: In OD misalignment, one coupling
is higher than the other, and one of the units must be raised or lowered to align the
couplings.
9.3.2 Correcting Outer Diameter Alignment, Top View: In this type of misalignment, one of
the units must be moved to one side or the other to align the couplings.
9.3.3 Correcting Face Alignment, Side View: In this type of misalignment, one of the units
must be tilted on its base to align the couplings.
9.3.4 Correcting Face Alignment, Top View: In this type of misalignment, one of the units
must be rotated on its base to align the couplings.
10.0.0 Basic Maintenance Procedures
10.1.0 Measuring Devices
10.1.2 Calipers and Dividers: Calipers are used to measure the thickness or diameter of a piece
of work … compare and transfer work dimensions.
10.2.0 Supplemental Tools
10.3.0 General Guidelines for the Care and safe Use of Hand and Power Tools
10.4.0 Motor Lubrication: The most common problem with lubricating motor bearings is
over-lubrication. It can cause and increase in operating temperature and a decrease in
viscosity.
11.0.0 Documentation
11.2.0 Service Ticket/Invoice: At the completion of the service call, the technician fills in all
applicable portions of the form to provide a specific description of the work that … the
labor hours expended, and so on.
11.3.0 Commissioning Job Report: At the completion of most large commercial and industrial
HVAC installations, a commissioning process is used to document and verify … with the
design intent.
At the completion of the process, these checklists and reports are turned over to the
building owner or other designated authority.
11.4.0 Start-up Report: Forms are used to record a specific operating conditions and
parameters that exist at the time … or individual components of an HVAC system.
11.5.0 Warranty Ticket: HVAC equipment warranty forms or tickets should be filled out and
given to manufacturers to notify them that their equipment has been put into operation.
1 Exam Prep – Intermediate Mechanical Study Guide 21
Section Highlight
12.0.0 Customer Relations
12.2.0 Personal Habits, Behaviors, and Attitudes: The customer’s first glimpse of a
technician can determine that the customer’s opinion of the worker and the company the
technician represents.
12.3.0 Customer Relations: Handling Service Calls: The typical service call has three parts:
- The opening
- Servicing
- The closing
13.0.0 Customer Communication: Here are some simple yet effective tips: (4 bullets).
13.3.0 Showing Concern for Customers: Do this by:
- Being a good listener
- Talking in terms of the customer’s interests
- Keeping your personal problems to yourself
- Answering questions honestly, but positively
- Respecting your customers opinions
- Not socializing while on the call
13.4.0 Handling Difficult Customers
03301-08 Refrigerant Characteristics: In order to be: (5 bullets)
1.3.0 Common Refrigerant Applications: Different refrigerants are used in different
refrigerants available:
- HCFC-22
- HFC-410A
- HFC-407C
- HCFC-123
- HFC-404A
- HFC-134a
Table 1 Common Refrigerants
2.1.0 Refrigerants Classifications: Refrigerants fall into the following three major
classifications of halocarbons:
- Chlorofluorocarbons (CFCs)
- Hydrogentated chlorofluorocarbons (HCFCs)
- Hydrogentated fluorocarbons (HFCs)
2.1.1 CFC Refrigerants: Chlorofluorocarbon (CFC) refrigerants are the most damaging to the
environment because they contain more chlorine atoms in their structure.
1 Exam Prep – Intermediate Mechanical Study Guide 22
Section Highlight
2.1.2 HCFC Refrigerants: Hydrogenated chlorofluorocarbon (HCFC) refrigerants contain
chlorine …. Allowing them to be phased out over a longer period of time.
2.1.3 HFC Refrigerants: Hydrogenated fluorocarbon (HFC) refrigerants such as HFC-123
contain no chlorine atoms in … of the three classifications of halocarbon refrigerants.
2.3.0 Refrigerants and the Environment – Ozone Depletion: Refrigerants are listed
according to their ozone depletion potential (ODP). The lower the number, the lower the
ozone depletion potential.
Table 2: Ozone Depletion Potential of Refrigerants
3.0.0 Refrigerant Identification: (4 bullets)
3.1.0 Refrigerant Safety Classifications:
Table 3 Old Versus New Refrigerants
- Class I
- Class II
- Class III
- Class IV
3.1.1 Refrigerant Cylinder Identification
Table 4 Refrigerant Cylinder Color Codes
3.2.0 Refrigerant Cylinder Safety: Disposable cylinders are single-use cylinders.
Returnable/reusable cylinders are to be returned to the distributor and/or refrigerant
manufacturer for refilling after they become empty.
Recovery cylinders are special cylinders designed for use with refrigerant recovery
machines.
Generally, the maximum capacity of a recovery cylinder is 80 percent of the cylinder’s
gross weight (weight of cylinder and refrigerant).
4.0.0 Refrigerant Composition
4.1.0 Azeotropes
4.2.0 Zeotropes: A zeotropic blend never mixes chemically … and finishes condensing
(bubble point) when heat is removed from the refrigerant.
1 Exam Prep – Intermediate Mechanical Study Guide 23
Section Highlight
Figure 9: P-T chart for azeotropes
4.4.0 Using Pressure-Temperature (P-T) Charts: A pressure-temperature (P-T) chart shows
the pressure and temperature relationships at saturation for a specific refrigerant.
4.4.1 Calculating Superheat: Step 1 -4.
4.4.2 Calculating Subcooling: Step 1 -4.
5.0.0 Refrigerant Leaks
5.1.0 Finding Leaks: The following are some common leak sites: 4 bullets.
5.2.0 Isolating Leaks: Some of the uncommon methods used to isolate leaks include:
- Leak-detecting fluids
- Halide torch
- Leak-detecting dyes
- Electronic leak detectors
5.2.1 Pressurizing for Leak Detection: Use the following procedure to pressurize a system:
Step 1 -4. Step 4: If a leak detecting fluid is being used … No refrigerant is needed.
6.0.0 Lubricating Oils
6.1.0 Lubricating Oil Properties
6.1.1 Stability
6.1.2 Viscosity: Viscosity can be described as the resistance of a fluid to flow.
6.1.3 Pour Point: It can be defined as the temperature at which oil first starts to flow.
6.1.4 Dielectric Strength: Dielectric strength is the ability of oil or any material to resist
breaking down in the presence of voltage.
6.1.5 Floc Point: The floc point of oil is the temperature at which heated oil vapors burst into
flame.
6.1.6 Flash Point: The flash point of oil is the temperature at which heated oil vapors burst
into flame.
6.1.7 Material Compatibility
6.1.8 Foaming: caused by mechanical movement in the compressor and/or dissolved
refrigerant boiling … leading to mechanical wear or failure of the compressor.
1 Exam Prep – Intermediate Mechanical Study Guide 24
Section Highlight
6.2.0 Oil Types
6.2.1 Mineral Oils: Mineral oils have traditionally been used in the systems using CFC and
HFC refrigerants.
6.2.2 Synthetic Oils: the predominant synthetic oils are gycol-, ester-, ether-, or alklbenzene-
based.
Polyalkylene glycol (PAG) oil is widely used in automotive air conditioning systems
where HFC-134a is the refrigerant.
Polyolester (POE) oil is very compatible with most of the newer HFC refrigerants and is
widely used in those applications.
Polyvinyl ether (PVE) oil has properties similar to mineral oils but can be used with
HFC refrigerants.
Refrigerant compatibility with various refrigerant oils varies … and oil are best suited for
the application.
Table 5: Refrigerants and Oils
7.1.0 Refrigeration System Piping: During cold starts, the refrigerant/oil mixture in the
crankcase can foam are refrigerant boils … piping sections called risers.
7.2.0 Refrigeration System Contamination: Ideally, the only two substances that should be
inside a refrigeration system are refrigerant … and solid contaminants such as metal
particles.
8.0.0 Oil Handling Guidelines
8.1.0 Personal Protective Equipment: When handling refrigerant oils, wear oil resistant
gloves and eye protection.
8.2.0 Working with Oils: When working with synthetic oils, follow these guidelines:
(7 bullets).
9.0.0 System Conversion: With CFC and HCFC refrigerants being phased out, refrigerant
manufacturers have developed replacement refrigerants … less environmentally
damaging refrigerants.
1 Exam Prep – Intermediate Mechanical Study Guide 25
Section Highlight
9.1.0 Common Refrigerant Conversions: There are a variety of refrigerants available for
retrofitting systems from CFC and HCFC refrigerants to more environmentally friendly
refrigerants. Some of the more common ones include the following:
- CRC-11 retrofits
- CFC-12 retrofits
- HCFC-22 retrofits
HFC-410A is considered to be likely replacement refrigerant for HCFC-22 …. of its
much higher operating pressures.
03304-08 Retail Refrigeration Systems
2.0.0 Mechanical Refrigeration Systems
Figure 1 Basic Refrigeration System
Refrigeration applications are generally classified based on the required space
temperature for a given application … classified for duty based on these temperature
ranges:
- Above +60 F
- - 30F to +60 F
- - 40 F to -30 F
2.1.1 Medium-Temperature Refrigeration Cycle: Refer to Figure 2 for an example of a
typical medium-temperature refrigeration cycle using HFC-134a as the refrigerant.
Figure 2: Typical medium-temperature refrigeration cycle for HFC-134a
2.1.2 Low Temperature Refrigeration Cycle: Figure 3 represents a typical low-temperature
refrigeration circuit, such as that used in a reach-in freezer.
2.2.0 Primary Refrigeration Cycle Components
2.2.1 Compressors: Discharge line thermostats will also be incorporated into the controls to
further prevent compressor damage or failure from overheating. They are generally set to
open at 250F to 260 F.
2.2.2 Condensers: Regular condenser cleaning must be an integral part of retail refrigeration
systems maintenance.
2.2.3 Evaporators: Forced-draft, finned-tube evaporators are most commonly used in smaller
retail refrigeration fixtures and systems …. referred to as unit coolers, or unitary coolers.
Some units may also use the condensate to their advantage … The moisture is evaporated
back to the surrounding environment in the process.
1 Exam Prep – Intermediate Mechanical Study Guide 26
Section Highlight
To minimize dehydration of the product and maintain higher humidity levels, evaporator
coils … desired storage temperature and the refrigerant.
Unitary evaporator coils that operate at 30 F and below generally form frost and will
require some automated means of frost removal.
2.2.4 Expansion Metering Devices: The expansion device controls the flow of refrigerant into
the evaporator, performing the following two primary functions: (2 bullets).
2.3.0 Other Refrigeration Circuit Devices and Components
2.3.1 Receivers: Receivers are used only on systems with a TXV or other modulating metering
device.
2.3.2 Accumulators: The accumulator is basically a trap designed to capture liquid refrigerant
in the system suction line.
2.3.3 Crankcase Pressure Regulators: Crankcase pressure regulating (CPR) valves are
installed in the suction line just upstream of the compressor, as shown in Figure 13.
2.3.4 Evaporator Pressure Regulating Valves: The evaporator pressure regulating (EPR)
valve allows the evaporators serving the higher temperature areas to maintain proper
refrigerant … temperature of the refrigerant.
2.3.5 Refrigerant-Side Head Pressure Control: Refrigeration units installed in locations
subject to low ambient temperatures generally require a method of maintaining head
pressure … device may not be sufficient to ensure adequate refrigerant is fed to the
evaporator.
The most accurate and stable means of ensuring that an adequate head pressure is
maintained is by using a head pressure control valve.
3.0.0 Defrost Systems: In retail refrigeration applications, these are four primary defrost
methods:
- Off-cycle defrost
- Timed defrost
- Electric defrost
- Hot-gas defrost
3.1.0 Off Cycle-Defrost: Off cycle defrost is the simplest and most passive of the defrost
approaches … during the normal off cycle.
3.2.0 Timed Defrost: Systems that operate at slightly lower temperatures than those using
simple off-cycle defrost will require a longer … 32 F to 36 F often benefit from this
approach.
1 Exam Prep – Intermediate Mechanical Study Guide 27
Section Highlight
3.3.0 Electric Defrost: Electric defrost systems are prevalent for medium … in the retail
refrigeration class.
3.4.0 Hot-gas Defrost: Hot-gas defrost sends discharge gas from the compressor directly to the
evaporator, bypassing the metering device through the use of several solenoid valves.
4.0.0 Retail Refrigeration Equipment and Fixtures
4.1.0 Ice Merchandisers: Ice merchandisers are generally offered with two major options –
cold wall construction, which offers no automatic defrost function … and allowing it to
warm to ambient temperature.
4.2.0 Reach-In Coolers and Freezers: Medium-temperature units may incorporate either off-
cycle or timed defrost …. Units using HCFC-22, HFC-134a, or HFC-404A as a
refrigerant dominate the market at this time.
4.4.0 Commercial Ice Markers
4.4.1 Cubed-Ice Machines: Cubed-ice machines have four basic modes of operation: fill,
freeze, harvest, and drain-down.
An ice thickness sensor is typically used on a cubed-ice evaporator … reached proper
thickness, the harvest mode is initiated.
5.0.0 Common Refrigeration System Controls
5.1.0 Thermostats: Electronic temperature controls are also becoming very popular in the
industry … an 8-foot cooper or aluminum capillary tube through complex cabinet
components.
5.2.0 Pressure Controls: Pressure controls, sometimes called pressurestats, are also applied to
refrigeration systems in many different ways.
The following are some of the functions that pressure switches provide: (6 bullets).
5.3.0 Time Delay Relays: Time delay are used to delay a switching action or ensure that a
sequence of actions takes place at the proper time.
Most of the time delay relays used in refrigeration applications can be specified as one of
the following types:
- Delay-on make
- Delay-on-break
- Bypass duty
1 Exam Prep – Intermediate Mechanical Study Guide 28
Section Highlight
5.4.0 Solenoid Valves: Solenoid valves are used to stop or allow the flow of either liquids or
gases in refrigeration systems.
The following are some of the applications for solenoid valves: (4 bullets).
6.0.0 Troubleshooting
6.1.0 Troubleshooting and Maintenance of a Reach-In Freezer
Figure 40 Troubleshooting chart
6.2.0 Troubleshooting and Maintenance of Cubed-Ice Machines
Figure 42 Energized parts chart
3305-08 Commercial Hydronic Systems
1.0.0 Introduction: Hydronic systems provide several advantages over forced-air systems in
the commercial environment … medium must be transported, the more economy
hydronic systems offer.
2.0.0 Water Concept Review
2.1.0 Water: At sea level, water boils at 212 F and freezes at 32 F.
2.2.0 Water Pressure
2.3.0 Pressure Drop: Defined as the difference in pressure between two points, pressure drop
is an important factor in all hydronic systems.
The change in pressure drop resulting from a change in flow in gallons per minute (gpm)
can be calculated as follows: (Equation).
This information may be expressed in a variety of units, so the conversions below may be
helpful: (4 bullets).
2.4.0 Head Pressure: Head pressure is another measure of pressure, expressed in feet of water
…. simple calculations prove that a column of water 2.31 feet in height results in a
pressure of 1 psi.
Figure 1 Water pressure concepts
Figure 2 Relationship of head pressure in feet to pounds per square inch
3.0.0 Commercial Hot-Water Heating System Components
1 Exam Prep – Intermediate Mechanical Study Guide 29
Section Highlight
3.1.0 Commercial Hot-Water Boilers
Low-pressure hot water boilers can be built to have working pressures of up to 160 psi.
Low-pressure hot water boilers are limited to a maximum operating temperature of 250 F.
3.1.1 Copper-Finned Tube Boilers: With the copper-finned tube design, heat transfer is
greatly enhanced, providing for rapid recovery and eliminating the need for hot water to
be stored within the boiler itself.
3.1.2 Cast-Iron Boilers: cast-iron boilers are formed by assembling individual cast-iron …
The number of sections used determines the size of the oiler and its energy rating.
3.1.3 Steel Firetube and Watertube Boilers: Two types of steel boilers are the firetube boiler
and the watertube boiler … with the flue gases on the outside.
3.1.4 Steel Vertical Tubeless Boilers: In this boiler, the water vessel surrounds the
combustion chamber … the length of the furnace.
3.1.5 Electric Boilers: electric boilers use immersion resistance heater elements to heat the
water in the boiler. Heating results from the electrical current flowing through the heater
elements.
Boiler operation is controlled by an electric/electronic controller.
Another type of electric boiler, called an electrode boiler, relies … the amount of water
that comes in contact with the electrodes.
3.2.0 Boiler Operating/Safety Controls: Float operated; low-water fuel cutoff controls can
be used to protect boilers from damage … related electrical switch.
Copper-finned tube style units transfer heat effectively with no significant volume of
water contained on board … copper-finned tube units should be equipped with water
flow switches.
3.4.0 Air Management: Due to the greater volume of water and the potential for much larger
volumes of air to collect and create problems … equipped with an air separator, such that
shown in Figure 14.
This particular unit, available in sizes large enough to accommodate 36” pipe …. At
which the buoyancy of the air bubbles cause them to rise and they are no longer swept
along by the water stream.
3.5.0 Circulating Pumps
1 Exam Prep – Intermediate Mechanical Study Guide 30
Section Highlight
3.5.1 Centrifugal Pump Construction: A centrifugal pump operates by increasing the
velocity of a liquid.
Centrifugal pump parts, as shown in Figure 18, include the following primary parts:
- Pump casing
- Suction port
- Discharge port
- Pump shaft
- Bearings
- Impeller
- Impeller vanes or blades
- Impeller shrouds
- Wearing rings
- Packing gland
- Mechanical seal
Figure 18 Centrifugal pump components
3.6.0 Valves
3.6.1 Multi-purpose Valves: In larger systems, a multi-purpose valve is commonly installed in
the discharge side of the circulating pump.
3.6.3 Butterfly Valves: A butterfly valve has a round disc that fits tightly in its mating seat and
rotates 90 degrees in one direction to open and allow fluid to pass through the valve.
There are three common types of butterfly valves in use:
- Wafer-type
- Wafer lug
- Two-flange
3.6.4 Two-Way and Three-Way Valves: Two and three-way valves are used to control the
flow and/or temperature of hot water, chilled, water, or both.
3.7.0 Heating System Terminals: The following types of terminals are commonly used in
heating-only systems:
- Convectors
- Baseboard and finned-tube units
- Unit heaters, unit ventilators, and fan coils
- Heating coils
4.0.0 Chilled-Water Cooling Systems: The use of a chilled-water system eliminates the need
to circulate refrigerant through refrigeration system components installed in a building to
provide comfort cooling.
1 Exam Prep – Intermediate Mechanical Study Guide 31
Section Highlight
The chilled water produced is described as a secondary coolant, which is any liquid that
is cooled by a system refrigerant and is then used to transmit heat from the conditioned
space without a change in state.
5.0.0 Chilled-water System Components
5.1.0 Water Chillers: Water chillers fall into two classes: mechanical and nonmechanical.
Mechanical chillers use compressors to provide cooling.
Nonmechanical chillers do not have a compressor …This type of chiller is called an
absorption liquid chiller.
Three common types of mechanical chillers are reciprocating or scroll compressor liquid
chillers, centrifugal chillers, and screw liquid chillers.
5.1.1 Reciprocating and Scroll Liquid Chillers
5.1.2 Centrifugal Liquid Chillers: Purge units are another type of device used on centrifugal
chillers that operate with low-pressure refrigerants, such as HCFC-123 … A purge unit
must be used to remove the noncondensible gases and water vapor from the system.
5.1.3 Screw Liquid Chillers
5.1.4 Absorption Liquid Chillers
5.2.0 Chiller Operating/Safety Controls
5.3.0 Cooling Towers/Evaporative Condensers: Condensers are used to remove heat from
the chiller refrigerant system.
5.3.1 Cooling Towers
5.3.2 Evaporative Condensers: The evaporative condenser combines the functions of a water-
cooled condenser and cooling tower … removing about 1,000 Btu’s from refrigerant
flowing through the tubes.
5.4.0 Circulating Pumps
5.5.1 Fan Coil Units: Fan coil units are terminals that can be used for chilled-water cooling
only, or for both cooling and heating … and sometimes an outside air connection with a
manual damper.
The term fan coil unit generally refers to units that produce up to 2,000 cfm of airflow.
6.0.0 Dual-Temperature Water Systems
1 Exam Prep – Intermediate Mechanical Study Guide 32
Section Highlight
7.0.0 Commercial Water Piping Systems
7.4.0 Primary-Secondary Water Systems: Primary-Secondary hot water or chilled water
systems are used in applications that have peak and varying loads.
Figure 55 Simplified primary-secondary chilled water system
8.0.0 Water System Balancing
03306-08 Steam Systems
2.0.0 Fundamentals and Properties of Water: Sensible heat is heat that can be sensed by a
thermometer or touch.
Latent heat is the heat energy absorbed or rejected when a substance is changing state
without a change in the measured temperature.
It requires 144 Btus of latent heat to melt the pound of ice before the temperature began
to rise. This is 144 times as much heat as is needed to raise the temperature of water one
degree (specific heat).
- Latent heat of fusion
- Latent heat of vaporization
- Latent heat of condensation
- Superheat
- Subcooling
Figure 2 Change of State Terminology
3.0.0 Steam Cycle Principles of Operation: Steam traps are among the most important
devices used in the steam cycle … Traps also require the most attention and maintenance
to ensure their proper operation, because failure of a steam trap can create a number of
problems.
4.0.0 Steam Boilers, Boiler Controls, and Accessories
4.1.0 Steam Boilers: Steam boilers are divided into three broad categories; those that produce
low-pressure steam; those that produce medium-pressure steam; and those that produce
high-pressure steam … High-pressure boilers operate at pressures from 60 psi and up.
With the exceptions that follow, steam boilers operate in the same manner as hot-water
boilers: (3 bullets).
4.2.0 Boiler Operating/Safety Controls
1 Exam Prep – Intermediate Mechanical Study Guide 33
Section Highlight
4.2.1 Pressure Gauge: This gauge is installed at the highest point of the boiler’s steam space.
A siphon assembly is generally installed between the boiler and the gauge.
4.2.2 Water Gauge Glass/Water Column: The water gauge glass is used to check the water
or steam level in the boiler.
4.2.3 Low- and High-Water Cutoff and water Feeder Controls: Low-water cutoff controls
provide valuable protection for steam boilers by interrupting power to the heat source
when the water falls below the minimum safe level.
4.2.4 High-Pressure Limit and Other Controls: The high-pressure limit control, also known
as pressuretrol, is activated by a rise in boiler pressure.
4.2.5 Pressure (Safety) Relief Valve: A pressure (safety) relief valve is used to protect the
boiler and the system from steam pressures exceeding the pressure rating of the boiler or
the system.
5.0.0 Valves
6.0.0 Heat Exchangers/Converters: A heat exchanger is used to transfer heat from on
medium to another.
For added safety against contamination, most heat exchangers used to heat potable water
are of double-walled construction … required if conditioning chemicals have been added
to the steam system.
8.1.0 Mechanical Steam Traps: Mechanical steam traps respond to the difference in density
between steam and steam condensate.
8.2.0 Thermostatic Steam Traps: Thermostatic steam traps respond to temperature changes
in the steam line.
8.3.0 Thermodynamic Steam Traps: Thermodynamic steam traps use the heat energy in hot
condensate and steam to control the opening and closing of the trap.
8.4.0 Fixed-Orifice Steam Traps
8.5.0 Installing a Steam Trap: Two generally rules for steam-trap mountings are that they
should be lower than any line in the system, and that a strainer has to be upstream of the
trap.
The following is a list of general guidelines for proper steam-trap installation: (12
bullets). #12: When a bypass is necessary, a globe valve should be used to allow manual
balancing of condensate flow.
1 Exam Prep – Intermediate Mechanical Study Guide 34
Section Highlight
8.6.0 Maintaining Steam Traps
8.6.4 Bimetal Thermostatic Trap
9.0.0 Troubleshooting Steam Traps
9.1.0 Diagnostic Methods: Three basic diagnostic methods of reading a steam system are
sight, sound, and temperature. The criteria observed include pressure.
10.1.0 Condensate Pump and Receiver Tank: The receiver tank is also equipped with a float-
actuated makeup water feeder control … water to enter the receiver tank from the city
water supply.
10.2.0 Vacuum Pumps: Vacuum pump operation is similar to condensate pump operation in
that the vacuum pump … to flow to the receiver tank.
11.0.0 Flash Tanks: When hot condensate under pressure is released to a lower pressure, part of
it is re-evaporated and becomes flash steam.
Some of the condensate flashes into steam and flows along with liquid condensate
through the return lines back to the boiler.
12.0.0 Steam System Piping
12.1.0 One-Pipe Systems: When the return is above the boiler water line, it is called a dry
return … The section of return piping installed below the level of the water in the boiler
is called the wet return.
12.2.0 Two-Pipe Systems: Two-pipe systems can have either gravity or mechanical condensate
returns. However, most systems use a mechanical return.
A vacuum-return system is similar to a condensate return system, except thst s vacuum
pump is installed to provide a low vacuum in the return line to return the condensate to
the boiler.
Operating the return line in a vacuum, rather than at or slightly above at … lowered for
significant fuel savings and improved efficiency.
13.0.0 Steam and Condensate Pipe Sizing: Operating steam boilers at pressures significantly
lower than the boiler is designed for reduces the volume of space in the boiler that
normally … water droplet carryover is greatly increased.
Undersized piping causes high pressure drops and greater velocities increasing noise and
erosion of internal piping surfaces.
1 Exam Prep – Intermediate Mechanical Study Guide 35
Section Highlight
On the other hand, piping that is too large creates unnecessary heat losses and higher
installation costs.
13.1.0 Velocity Sizing: Figure 45 provides a steam velocity chart for pipe sizing.
Figure 45 Steam pipe sizing for steam velocity
13.2.0 Steam Line Pressure Drop: Steam lines are generally sized based on velocity … for
pressure drop in the system.
However, a system operating as low as 5 psig should probably … than 0.3 psig to
maintain the needed pressure downstream.
Figure 46 Steam pipe sizing for pressure drop
13.3.0 Condensate Line Sizing
14.0.0 Boiler Blowdown and Skimming
03308-08 Water Treatment
2.0.0 Water Characteristics and Analysis: Even though the quality of a water supply makes
it safe to drink … water is used untreated in HVAC systems.
The strength or relative amount of an element present in a water solution is commonly
referred to as its concentration … element that is dissolved in a water sample.
The amount of carbon dioxide in water can be either measured directly or estimated from
the water’s pH and total alkalinity… amount of pH reduction from the addition of acids.
Water above the pH value of 7.0 is considered to be alkaline.
The hardness of a water sample indicates the amount of dissolved calcium (limestone)
salts and/or magnesium in the water.
As the hardness level increases, the amount of scaling usually increases … solids are not
visible and consists mainly of calcium, magnesium, chloride, and sulfate.
The greater the concentration, the greater the potential for corrosion … individual
particles or give water a cloudy look.
3.0.0 Problems Caused By Water Using Untreated Water: External corrosion appears as
rust or oxidation. Internal corrosion can be caused by acids, oxygen, and other gases
present in the water.
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3.3.0 Biological Growth: A film composed of bacteria, other organisms, and slimes produced
by the microorganisms acts as an insulator.
4.0.0 Water Treatment in Open Recirculating Water Systems: acidic gases and other
contaminants in the air are absorbed into the water.
The range of pH in cooling tower water is typically maintained between 7.5 and 8.5.
4.3.0 Biological Growths: The water contact with air that occurs in a cooling tower or
evaporative condenser allows …. debris to be introduced into the system recirculating
water.
5.0.0 Water Treatment in Closed Recirculating Water Systems: Oxygen is one of the main
agents of corrosion.
5.1.0 Corrosion: Some localities prohibit the use of chromates, while others allow their use
only in closed systems.
6.0.0 Water Treatment in Steam Boilers and Systems: Fouling clogs nozzles and pipes with
solid materials, thereby restricting circulation and reducing the heat transfer efficiency.
6.1.0 Corrosion: To minimize corrosion, the boiler water pH should be maintained between 11
and 12 by an alkaline water treatment using soda ash.
7.0.0 Mechanical Water Treatment Equipment
7.1.0 Filtration Equipment
7.1.2 Cartridge Filters: They are commonly used to remove suspended particles ranging
between 1 micrometer and 100 micrometers.
Depth-type filters capture particles throughout the thickness of the filtering medium.
Surface-type filters are thin-media made from pleated paper or similar material … and
have a better removal efficiency than an equivalent size depth filter.
7.1.5 Centrifugal Separators: Generally good for removing suspended particles greater than
45 micrometers in size, they tend to be inadequate at removing smaller ones.
7.3.0 Water Softeners: Many water softeners use a sand-like substance called zeolite that is
saturated with sodium … as the supply of hard water filters through the zeolite, sodium is
released and calcium and magnesium are absorbed.
Through extender use, the sodium content of the zeolite bed gradually depletes, thus
preventing the unit from softening the water … periodically treating the unit with a strong
dose of salt solution.
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7.4.0 Deaerators: Dearators (Figure 11) are typically used in steam systems to remove air and
other noncondensible gases from the system feedwater.
8.0.0 General Water Treatment Procedures and Guidelines
03309-08 Troubleshooting Electronic Controls
2.0.0 Microprocessor Controls: Likewise, if a cooling thermostat calls for cooling, you
expect the compressor and fans to turn on. If they don’t, you know that something is
wrong.
3.0.0 Troubleshooting Microprocessor Controlled Systems
3.1.0 Troubleshooting Approach: Another reasonable assumption is that when the thermostat
is calling for heat or cooling, there will be 24V (or other specified voltage) applied to the
control board input.
4.0.0 External Causes of Failure
4.1.0 Environmental Conditions: Failures in electrically controlled equipment can result from
exposure to harmful environmental conditions… equipment terminals, cable
terminations, and relay contacts.
Dirt and other contaminants such as fumes, vapors, abrasives, soot, grease, and oils can
cause electronic devices to operate abnormally until they finally break down.
Equipment that is subjected to unusual amounts of dust and other airborne particles tends
to fail due to overheating caused by clogged … required to dissipate heat generated in the
unit.
Heat increases the resistance of circuits, thereby increasing the current. Heat causes
materials to expand, dry out, crack, and/or blister.
4.4.0 Electrostatic Discharge: Electrostatic discharges that occur at or near electronic
equipment can damage sensitive semi-conductor circuits and devices.
When subjected to ESD, a sensitive electronic component can experience a catastrophic
failure, meaning it is immediately damaged to the point at which it is totally inoperative
… in a poor system performance and eventual system failure.
4.4.1 Grounding: Always ground yourself before touching the PC board or components.
4.5.0 Thermistor Failure: the resistance of a thermistor itself can be tested with an ohmmeter.
5.0.0 Electronic Controls in Heating Systems: Following are the highlights of the operating
sequence for this unit. (4 bullets).
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Section Highlight
6.1.0 Cooling Systems
6.2.0 Heat Pumps
Figure 12 Input and output signals
03401-09 Construction Drawings and Specifications
2.0.0 Reading Drawings: Use this procedure to familiarize yourself with an available set of
drawings: Step 1 -14.
2.1.0 Site Plan: The site plan indicates the location of the building on the land site. It may
include topographic features such as contour lines, trees, and shrubs. It may also include
some construction features such as walks, driveways, curbs, and gutters.
Figure 2 Site Plan
On large commercial jobs, a utility site plan may also be included … power or
communication system cables, and other facilities.
2.2.0 Plan Views (Floor, Roof, and Ceiling Plans): It shows the length and width of the
building and the location of the rooms and other spaces that the building contains.
Figure 3 Floor plans for a building
2.3.0 Elevation Drawings: The elevation view of a structure (Figure 6) shows the exterior
features of that structure.
Figure 6 Elevation drawing
2.4.0 Schedules: They are tables shown on various drawings throughout the drawing set that
identify the types and sizes of items used by the different trades in the construction of a
building.
Schedules shown on the related plumbing plans and electrical plans may …. Shows
schedules typical of those found on mechanical plans.
Figure 7 Mechanical equipment schedules
2.6.0 Section Drawings: Section drawings are cutaway views that allow the viewer to see the
inside of a structure or how something is put together internally.
Figure 9 Section drawing showing building construction
2.7.0 Plumbing Plans: Plumbing plans show the layout of fixtures, water supply lines, natural
gas piping, and lines to sewage disposal systems.
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2.8.0 Mechanical Plans: mechanical plans show the heating, ventilation, and air conditioning
systems, as well as other mechanical systems for a building.
Figure 11 Sanitary plumbing plan
Figure 12 Plumbing legend
Details of the mechanical plan are usually overlaid on tracings of the various building
floor plans from which … Figure 13 shows an example of a typical HVAC mechanical
plan.
As appropriate, detailed views describing the installation of the HVAC equipment are
shown … and the pipe sizes for major items of HVAC equipment.
Figure 13 HVAC mechanical plan
Figure 14 Refrigeration piping schematic
Mechanical plans also normally include an HVAC legend listing the various symbols …
(Figure 16) and information about relevant HVAC system specifications (Figure 17).
2.9.0 Electrical Plans: For smaller construction jobs, the electrical plans are usually shown on
the architectural floor plans … information about the electrical system installation.
3.0.0 Request for Information: The general contractor then relays the RFI to the architect or
engineer.
Figure 16 Schedule of HVAC systems
4.0.0 Specifications
4.4.0 Format
4.4.1 CSI Format: The most commonly used specification-writing format used in North
America is the Master Format. This standard was developed jointly by the Construction
Specifications Institute) (CSI).
Figure 20 2004 Master Format. Note: Division 23: Heating, Venting, and Air
Conditioning
5.0.0 Shop Drawings: A second type of shop drawing (or submittal pertains to the purchase of
special items … out so that the architect or engineer responsible can correct the problem.
5.1.0 Cut Lists: After the shop drawings are complete, or as they are drawn (depending on the
workload) … matches the numbers on the shop drawings.
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5.1.0 Cut Lists: After the shop drawings are complete or as they are drawn (depending on the
workload) … matches the numbers on the shop drawing.
6.0.0 Submittals: Submittals are documents that illustrate special pieces of equipment or
accessories that are to be furnished and installed by the subcontractor.
7.0.0 As-Built Drawings: As-built drawings must be made on alteration or addition jobs, on
jobs where modifications must be made to make way for other mechanical trades, or to
alter the location of a component.
8.0.0 Takeoffs: The takeoff procedure involves surveying, measuring, and counting all
materials and equipment … should be taken off in the following order: 1-10.
8.1.0 Takeoff Tools and Materials: The following materials will make the measuring,
counting, and calculating tasks easier. (8 bullets) #3: An electronic wheel scaler or
similar device for measuring duct and piping runs (should have scales of 1/8”, ¼”, and
½”.
8.2.0 Selecting Equipment and Materials
8.2.1 Ductwork: The materials commonly used in duct run system construction are the
following: (9 bullets). Duct construction is classified in terms of operating pressure and
air velocity. The common classifications are shown in Table 1.
Table 1 Pressure and velocity
8.2.2 Duct hangers: Ductwork must not be hung from overhead piping or ceiling hanger irons
… Trapeze-type hangers are recommended for large ducts.
Duct sizes are determined according to airflow rates (cfm), velocity (fpm), and duct
friction losses.
03406-09 System Startup and Shutdown:
2.0.0 Steam/Hot water Boilers and Systems
2.1.0 Shutdown: Unless proper procedures are followed before taking boilers off line, severe
corrosion … to produce extensive pitting of metal surfaces.
2.1.1 Boiler Shutdown Concerns: Corrosion that could occur during the layup period can be
greatly reduced by thoroughly … from the boiler’s fire-side components immediately
after shutdown of the boiler.
2.1.2 Boiler Preparation for Dry Storage: Dry storage of a boiler is typically done when the
boiler is subjected … or when it will be out of service for more than a month.
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Section Highlight
2.1.3 Boiler Preparation for Wet Storage: The following procedure outlines the preparation
of the typical oil-fired steam boiler for wet storage. Step 1 -8.
Step 2: valve the boiler off from the rest of the system, and then refill it to overflowing
with treated water.
Step 3: Add the water treatment chemicals needed to condition the added amount of
water that is now above the boiler’s normal water line.
2.2.0 Steam Boiler System Start-up: The start-up procedure typical of that used with an oil-
fired steam boiler is outlined here. Step 1 -16.
Step 4: Make sure that the main steam stop valve is closed.
Step 7: The boiler burner and control system should allow the boiler water to warm …
position and the MANUAL FLAME control to the LOW-FIRE position.
Step 9: When the steam gauge shows pressure in the boiler, blow down the gauge glass,
water column, and low-water cutoff as applicable.
2.3.0 Hot-water Boiler Startup
2.3.1 Filling and venting a Hot-water System: Because a hot-water boiler is completely filled
with water, the hot-water outlet usually … the expansion tank where the air is properly
released.
2.3.2 Hot-water System Operating Temperatures: The minimum boiler water temperature
recommended for hot-water boilers is 140 F.
Figure 4 Typical hot-water boiler circulation chart
3.0.0 Reciprocating Chillers and Water Systems
3.1.0 Startup: Step 1 -17.
Step 6: Check the pH of the chilled water to determine its acidity or alkalinity … A pH of
7 is considered neutral.
4.0.0 Centrifugal Chillers and Water Systems
4.1.0 Startup
Figure 9 Typical centrifugal/screw chiller sequence of operation
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Section Highlight
The chilled water temperature is compared to the chiller’s leaving (or enetering) water
temperature control point and deadband … For example, a 1 F deadband controls the
water temperature to within + 0.5 F.
4.2.0 Normal Shutdown: When a stop command occurs, the automatic sequence for the
shutdown … events F and G in Figure 9 and described below:
- Event F
- Event G
4.3.0 Extended Shutdown
5.0.0 Screw Chillers and Water Systems
6.0.0 Cooling Tower and Water Systems
6.1.0 Startup: Step 1 -10.
Step 9: Adjust the bleed-off rate to match the rate set by the system water treatment
program … small amount of the water circulating in a system.
6.2.0 Periodic Maintenance After Startup: Cooling towers are highly susceptible to the
growth of algae, bacteria, and other living organisms … if manufacturer information is
not available, table 5 can be used as a guide.
6.3.0 Winter Operation: When a cooling tower is used in subfreezing temperatures … need to
winterized.
Table 5 Cooling Tower/Open Recirculating Water System Maintenance
6.4.0 Shutdown
7.0.0 Air handling Unit/Air Distribution System
7.1.0 Startup
7.1.1 Preliminary Checks: Step 1-8.
Step 4: Inspect the complete supply air system from the supply air fan … verify that: a-c.
7.1.2 Startup and Air Distribution System Balance: Step 1 – 10.
Step 7: Use the values of supply fan rpm and total static pressure measured in Steps 5 and
6 … static pressure is 1.40 in. w.g. and the fan is running at 900 rpm.
Figure 14 Example of a typical fan curve chart
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Section Highlight
Step 10: b. Use a velocity pressure/velocities chart (Figure 16) to convert each of the …
velocity in feet per minute (fpm).
Figure 16: Velocity pressure/velocities chart
7.2.0 Shutdown: Clean duct using portable and/or truck-mounted … to dislodge dirt and
debris in the ductwork.
8.0.0 Packaged Year-Round Air Conditioning Units
8.1.0 Start-up
8.2.0 Shutdown