Final Study Guide Hvac Maisy Flashcards
if a resilient mounted motor develops a short to the frame the tech can simply cut the ground strap wire as a permanent repair
false
before testing a run or star capacitor with an ohmmeter the capacitor should be discharged with a 20,000 ohm a fully 5 watt resistor
true
the electrical components for a fully welded hermetic compressor are checked at the disconnect box for the compressor unit
false
A homeowner plans to build a house out in Las Vegas, Nevada, in the middle of the desert. It would be in his/her best interest to lower the “solar load,” to locate most of the windows on the _____.
north and south
On a package air conditioning system, which refrigerant lines must be field installed?
Condensing line, power & low voltage line
The solar load on a structure is the heat gain resulting from the _____.
radiation of the sun
The total heat content of infiltrated air of the same dry-bulb temperature may vary from one part of the country to another because of difference in _____.
humidity
More than one evaporator coil circuit is used when _____.
there will be an excessive pressure drop in the coil circuit.
A popular material combination used in air conditioning evaporators and condensers is _____.
Copper tube and aluminum fin
Fractionation occurs when
some of a blended refrigerant evaporates or condenses before the rest of the blend
Using a restrictor, liquid refrigerant can be charged into the low-side of the system with the system operating.
true
When charging a refrigeration system with a near-azeotropic mixture, what must be done to prevent liquid from entering the system?
Charge as a liquid through the low side using a restrictor.
Refrigerant in vapor form is normally put into the system through the
suction line
When charging a system with vapor refrigerant from a refrigerant cylinder, the cylinder will become
cold
A manufacturer’s charging chart may be used when available to determine the correct charge for a system.
true
Wear all your equipment including
Glasses
Hat
Boots
Gloves
The factory charge in a split system, using R-22, shows 6 lb. 8 oz. in the outdoor condensing unit and 2 oz. in the evaporator. The 3/8” liquid line contains 0.48 oz. per foot and the 7/8” suction line contains 0.10 oz. per foot. The refrigerant lines are 30’ long. What is the correct refrigerant charge for this system?
7 lb 11 oz.
When adding refrigerant in liquid form into the high-side of the system, the system motor/compressor assembly is running.
false
One good feature of an electronic charging scale is that it counts upward as refrigerant is removed, to tell the technician how much refrigerant was used.
true
Charging a refrigeration system refers to
adding refrigerant to a system
When charging liquid refrigerant from a single valve supply cylinder, the cylinder is placed
upside down
Refrigerant in liquid form is normally put into the system through the
liquid line
When your in customer home, you must give consideration to what issue?
Tarps
When adding refrigerant in vapor form to an operating refrigeration system, the refrigerant must be added to the low-pressure side of the system.
true
If 22 oz. of refrigerant are to be added to a refrigeration system and the supply cylinder weighs 24 lb. 12 oz. before any is added, what will be the supply cylinder weight after the system has been charged?
23 lb 6 oz.
If a critically charged refrigeration system is over charged, which of the following is a likely result?
Increased operating pressures.
If the tank is a reusable tank, there are no check valves and system refrigerant can enter the tank as long as the system pressure is higher than the pressure in the tank.
true
The quickest method to charge a system is to charge only vapor.
false
Air-conditioning equipment will perform at its best efficiency when running at full load.
true
High-efficiency condensers
have more surface area than standard condensers
In rotary compressors, the motor is cooled by
discharge gas from the compressor
The air temperature of the air off an evaporative cooler is
cooler than the entering air
The moisture content of the air in different locations of the country must be taken into account when selecting air-conditioning equipment.
true
If a residential split air-conditioning system has a compressor equipped with a start capacitor and relay, it is probably using a thermostatic expansion valve as a metering device.
True
In reciprocating compressors used in air conditioning, the motor is mainly cooled by
Air over the shell of the assembly
Suction gas returning to the compresser
A dirty condenser coil can lead to
reduced efficiency
If 30 oz. of refrigerant are to be added to a refrigeration system and the supply cylinder weighs 26 lb. 4 oz. before any is added, what will the supply cylinder weigh after the system has been charged?
24 lb 6 oz.
After being threaded many times, the screw holes in condenser cabinets may become oversized; if so, replace the screws with new ones of the same size.
false
If a structure has no attic, there should be sufficient insulation in the roof to minimize the heat gain in the occupied space.
True
The supply duct portion of an air handling system need to be insulated when run through an unconditioned space.
True
One drawback of using custom made, pre-measured duct sections is that ____.
a. if the measuring was not done correctly, the job may not go together
b. the sharp edges provide possible safety issues
c. altering a duct section at the job site is extremely cost-ineffective
What two fasteners are used with fiberglass ductboard?
staples and taps
A fitting used to change the size of a square or rectangular duct is called a _______.
Transition
What fastener is commonly used with round flexible duct?
Draw bands or self-tapping screws
A good way to fasten insulation to the inside of sheet metal duct is to use _____.
Tabs or adhesives(glue)
An auxiliary drain pan under the unit is recommended when the evaporator is installed _____.
above the conditioned space.
_____ used at the end of a metal duct run will help reduce any noise that may be traveling through the duct.
Flexible duct
A boot in a duct system is used _____.
between the branch duct and the register
A trap in the condensate line prevents _____.
A. air and foreign material from being drawn up into the drain line
B. additional cooling load from warm air being drawn up into the air handler
After refrigerant lines have been installed, they should be evacuated to a _____ vacuum.
deep
Most occupants will normally operate their systems at about_____ degrees F.
75
AHRI rates condensers with_____ degrees F air passing over them.
95
At what conditions are AC systems rated?
95 F outdoors - 80 F DB - 50% indoors
At typical operating conditions, the standard AC system will operate with an evaporator boiling point of _____ F.
40
A normal evaporator superheat at the evaporator outlet in a standard efficiency AC system operating under design conditions will be_____ F.
10
At typical operating conditions, the high efficiency AC system will operate with an evaporator boiling point of _____ F.
45
A more accurate rating system for AC equipment that takes into consideration operation during the complete cycle is the _____ standard.
SEER
The_____rating is a steady-state rating and does not account for the time the unit operates before reaching peak efficiency.
EER
Ratings that are not completely accurate are known as _____
Nominal ratings
As a rule of thumb, the air leaving the evaporator will be about_____than the air entering the evaporator.
17-20 degrees cooler
A service valve can be used to ____.
a. check the electrical service to the compressor
b. isolate the refrigerant so the system can be serviced
A typical evaporator superheat reading at the evaporator outlet for a central AC system on a 95 F day would be_____F
10-12
On a 95 F day, the R-22 refrigerant pressure on the high side should be about_____psig.
243
The liquid line temperature is used to determine the _____ of a condenser
subcooling
To accurately add refrigerant to a system, a condenser ambient temperature of_____ F should be simulated.
95
The instrument to use to check for a short in the compressor motor winding is a(n)_____.
ohmmeter
One purpose of a flexible duct connector in a duct system is to reduce the transmission of noise and vibration.
TRUE
Power to the control transformer is controlled by the conditioned area thermostat.
false
When hanging a horizontal air handler, it should be pitched toward the drain port for proper condensate removal.
false
The sun shining on the outdoor section of the AC system has a direct affect on the operation of the unit.
True
When installing a split AC system with a remote condensing unit, the line set may be altered if the standard length was incorrect for installation.
True
When removing rubber plugs from a line set, the hiss indicates that the tubing is not leaking before installation.
true
Since the evaporator absorbs both sensible and latent heat, humidity must be taken into account and considered part of the load on the evaporator.
true
High efficiency condensers can actually be too efficient on cool days.
true
With a rise in outdoor temperature, the head pressure will rise.
true
Superheat occurs in the condenser as well as the evaporator.
false
The best way to tell if a compressor’s discharge line is at the correct temperature is to grab hold of it.
false
Subcooling occurs in the evaporator as well as the condenser.
false
When checking the electrical circuits of an AC system, each parallel circuit should be isolated and checked separately.
true
If a compressor has a partially shorted winding, it could run for a while, overheat, and shut off.
True
When the length of quick-connect precharged line sets is altered, the charge will not normally have to be altered.
false
Application of acoustical lining to the interior of a duct is accomplished by using tabs, glue, or both.
true
Once the power has been connected to the condensing unit of a package air conditioner, it is a good idea to start the compressor immediately to make certain it runs.
false
The magnetic fields generated in the rotor and stator of a motor causes the rotor to be pushed around the shaft.
false
The heavier the load on an operating motor, the greater the amount of slip.
true
In order to change the direction of rotation of a split-phase motor, the technician must change the direction of current flow through the start winding.
true
The centrifugal switch mounted on the shaft of a split-phase motor has a normally closed contact.
True
an open winding in an electric motor means that
a wire in a winding is broken
Which of the following voltages are not safe for a 208-V motor to operate?
170 volt and 238 volt
If the voltage supplied to the motor is well below the motor rated voltage, the current draw will be _____ it should be.
higher than
The voltage tolerance of a standard electric motor is ___.
+10% -10%
The locked-rotor amperage is normally ___ times as great as the run-load amperage.
5
A direct-drive motor is usually connected to a load with a ___.
coupling
Which of the following statements are correct when referring to large refrigerant or nitrogen tanks?
a. The protective cap must be on
b. Safety Goggles or glasses must be worn when moving
c. Large Tanks should not be carried, but moved with an approved cart
An example of a pressure vessel is
a cylinder containing refrigerant
Which of the following tools is different from the rest with respect to the shape of the nut or screw that it turns
Hex Key
A wiring and crimping tool is used to _______
Cut and Strip Wire
Air conditioning and refrigeration reversible ratchet wrenches are used to
open and close refrigerant service valves
Flare nut wrenches are used to _______
tighten or loosen nuts on copper tubing
Tube cutters are used to ______
Cut copper tubing
A sling psychrometer is used to _______
measure the dry bulb and wet bulb temperatures of air
The halide leak detector ________
Detects refrigerant leaks in a refrigerant system
Variable speed reversible electric drills can be used to drill holes as well as tighten and loosen screws
True
The odd shape of a Torx type screw driver is the square shaft used to tighten or loosen screws
False
A programmable charging scale measures the volume of refrigerant flow into a refrigeration system
False
An instrument called a clamp on ammeter is so called because the tongs can be clamped around a single wire.
True
The tool used to create pipe threads on the outside of a pipe is called a ______
Die
The tool used to create internal threads is called a _____
Tap
A ________ is used to measure the amount of oxygen in flue products
O2 Indicator
What is the major advantage of an clamp-on ammeter?
You can measure the amp pule of a compressor while it is running without having to locate both ends
what does a VOM meter measure?
voltage, resistance and current
Mechanical refrigerant recovery equipment must meet specification establsihed by the 1993 ARI 740 standard.
True
When a technician works for a company in which the technician does not have a financial interest the technician does not have to be certified.
False
a clamp-on ammeter is designed to measure only alternating current
True
Mercury bulb-controlled thermostats require that they are installed perfectly horizontal. The tool used to accomplish this is called a __________
Level
After brazing a joint in a very tight location, the technician wold use an ________ ________ to determine of the joint is properly brazed
Inspection Mirror
Evacuating a system is accomplished with a __________ and helps to remove __________ and __________ from a system
Vacuum pump / Air / Moisture
A(n) __________ is used to measure the percentage of CO in flue products
carbon monoxide indicator
A(n) __________ is used to measure the amount of CO2 in flue products
Carbon Dioxide Indicator
A(n) __________ is used to measure the amount of O2 in flue products
Oxygen Indicator
The dial-type meter used to measure the pressure in a heating unit flue pipe is called a __________
Draft Guage
A vacuum pump removes ___________ and _________ from a refrigeration system
Air / Moisture
For what is a soldering gun usually used?
Solder Electrical Connections
Match the cutting tool to the material on which it would best be used.
Tubing shear - pvc pipe
Utility knife - plasterboard / fiberboard
Stripper and crimping tool plastic - copper wire
Tubing cutter - soft-drawn copper tubing
Hacksaw - metal stock
An R-22 cylinder containing enough refrigerant to have liquid refrigerant in it, is in a truck with a temperature of 120°F. What would be the psig pressure in the cylinder?
259.9 psig
A cylinder with 1,500 sq. in. of internal surface contains R-22 and is in a service truck body at 120°F. What is the total outward force of the refrigerant against the inner wall of the cylinder in tons of pressure?
194.92
A fusible plug is a metal fitting that has a hole drilled through it and the hole is filled with ____.
a. a metal alloy
b. material with a low melting point.
When transferring refrigerants form a cylinder to a refrigeration system or any other container, you should always wear.
goggles with side shield and gloves
electrical power should always be shut off at the _ panel before installing equipment.
distribution
a double insulated drill
has plastic case with electrical connections and motors
in electrical circuits, the _ wire protects the operator
ground
fires that involve ordinary materials like paper, cardboard, and wood are classified as
type A fires
fires that involve oil and gas are classified as
type B fires
Fires that involve electrical equipment are classified as Type __ Fires
Type C Fires
When it is necessary to preform work in an area that has a damp or wet floor, which of the following can be done to minimize the chance or electrical shock?
A place a rubber mat on the floor
b use a wooden ladder
c wear insulated gloves
Fire extinguishers that van be used on any type of fire generally contain a ______ to extinguish the fire
Dry Chemical Powder
When working in a machine room, safety glasses should not be worn because they can fog up and impede your eyesight.
False
As long as the torch is kept moving below the level of liquid refrigerant in the cylinder so as not to create a hotspot, it is ok to heat the cylinder in this manner.
False
It is possible that your hand would suffer frostbite if it comes in contact with liquid R-22 when accidentally releasing refrigerant into the atmosphere (an illegal procedure)
True
To ensure proper operation of an oxygen cylinder regulator, make sure no oil residue is present.
True
Aluminum ladders are safe to use around electrical equipment as long as they have insulation pads on the bottom of the rungs.
False
A necessary safety practice for a technician is to lockout panel with padlock and keep the key with you.
True
If you are a refrigeration technician, a warm coat and gloves should be in your truck, even in the middle of the summer.
True
Oil must never be used around a ______ cylinder.
Oxygen
Refrigerants from a refrigeration system that has a burned out motor-compressor assembly can be dangerous because it could contain a high concentration of ______.
Acids
A way to move equipment across a roof is to use rollers and _______ for a base.
Plywood
If a large pressurized tank falls over and the stem breaks off, why shouldn’t you try to stand up the tank?
The tank will start to fly around because the pressure inside the tank is so great.
Why should a technician not wear jewelry and metallic watches while working on a system?
To prevent you from getting shocked when working on a electrical box in tight areas. Also prevent the watch or jewelry from getting caught onto something and ripping your skin off.
If all else fails
Call for assistance
If all else fails, you can referred the manufactures installation instructions.
True
Besides maintaining pressure on the contacts for current carrying capacity, the pressure springs have a second important function. This is to ____________________________________________________.
help obtain equal contacts against the stationary contacts
When a contactor’s coil is energized, how much resistance should be measured between terminal “L1” and terminal “T1”? ________________________________________
zero ohms
To reprocess refrigerant to meet new product specifications is called ___.
reclaim
To remove the refrigerant from a system without any testing or processing and to be put back into the same system is called ___.
recovery
A graduated cylinder charging device is a device that ___.
A. measures refrigerant by volume for precise refrigerant charging
B. has a compensation dial for adjusting for the temperature of the refrigerant
C. often has a heater to keep the refrigerant temperature from dropping when refrigerant is released into the system
Refrigerants that have a low Ozone Depletion Potential (ODP) will, in turn, have a high “Total Equivalent Warming Impact” (TEWI)
False
The DOT-approved cylinder used for recovering refrigerant is gray and yellow
true
common practice in condensing units is to be able to use a contactor with only one set of contacts opening only one side of the power to the unit. This is to_____.
provide off-cycle heat to the compressor
Beside maintaining pressure on the contacts for current carrying capacity, the pressure springs have a second important function. This is to_____.
help obtain equal contacts against the stationary contacts
When a contactor’s coil is energized, how much resistance should be measured between terminal “L1” and terminal “T1”?
Zero ohms
Technician “A” says that if you take a voltage reading from terminal “L1” to terminal “T1” on a contactor whose coil is energized, you should read zero volts. Technician “B” says that the contactors can only have normally open contacts. Which of the following statements is correct
Technician “A” is correct. Technician “B” is incorrect
An inherent motor protector is a _____.
Thermally activated device in the motor winding
The service factor of an electric motor is determined by the
Motors reserve capacity.
Standards for motor overload protection are set by the ______.
National Electrical code
solder pot is part of a ____.
resettable circuit breaker
Which of the following overload devices is not affected by ambient temperature?
magnetic
The locked rotor amperage, LRA, of a motor is typically five times higher than the full load amperage, FLA, of the motor and can be as high as seven times the FLA.
True
A set of contacts are closed when the relay is energized. These contacts are classified as normally closed.
False
Auxiliary contacts are usually rated at a lower amperage than the contactor’s primary contacts.
True
Contactor contacts that are badly pitted can cause the motor to burn out.
True
A sure sign of contact failure is discoloration on the contact surfaces.
False
Bimetal and solder pot overload devices are thermally operated.
True
The sun shining on a distribution panel has no effect on the breakers in the panel.
False
Most electrical problems with an electrical motor are ___.
short circuit windings, open windings, and grounded windings.
What is the best method to repair a fractional horsepower motor that has a bad bearing?
Replace the entire motor
A technician needs to check a single-phase compressor. He labels the three terminals “A,” “B,” and “C” and takes resistance readings of the windings. He reads 10 ohms from “A” to “B,” infinity from “B” to “C,” and infinity from “C” to “A.” Identify the terminals.
Canot identify terminals: open winding
Technician “A” says that a shorted winding will result in in an increased current flow through the winding. Technician “B” says that if a motor is to be replaced, a motor with a lower horsepower rating should always be used. Which of the statements is correct?
Technician “A” is correct. Technician “B” is incorrect
Technician “A” says that while checking the windings of a compressor, a reading of 10 ohms or less from the common terminal to ground indicates that the motor is okay. Technician “B” says that the resistance of the start winding should always be less than the resistance of the start winding. Which of the statements is correct?
Technician “A” is incorrect. Technician “B” is incorrect.
An open winding in an electric motor means that ___.
a wire in a winding is broken
If the resistance of the run winding decreases, the (motor will) ___.
motor will draw too much current while running
Appearance is a major drawback with what type of air-conditioning equipment?
Ductless split systems
If a condenser fan motor grounds out, it will usually ___.
trip a circuit breaker to cut off the unit
If the cost of repairing the motor is close to the cost of replacing the motor, it would definitely pay to repair the motor if the new component carries a one-year warranty and the repaired motor carries only a 90-day guarantee.
False
If a normally operating motor draws 75 amps on startup, it will most likely draw 15 amps when running
True
It is always important to maintain a good work ethic to everyone except
Your mother (really ithats the answer)
A megger ____.
measure very high resistance
If a motor hums but does not start, there is a potential problem ____.
with starting components, with short supply voltage, with open winding
The recommended way to discharge a capacitor is to ____.
use a 20,000 ohm 5 watt resistor that has had insulated leads soldered to it
The wiring and connectors that carry the power to a motor must be in good condition. When a connection becomes loose, oxidation of the copper wire occurs. The oxidation ____.
act as the resistance and causing the connect to heat more
When referring to motors, to what does the “insulation class” relate?
the normal operating temperature of the motor
The motor that should be used in a potentially wet area is a(n) ____ motor.
drip proof
Why are explosion-proof motors not normally used on standard equipment?
they are too expensive
A motor’s speed is determined by ____.
number of motor poles
The starting device usually used on single phase, fractional horsepower motors requiring low starting torque is the ____.
current relay
The start windings have ____.
more turns than the run winding
Capacitors wired in series with the starting winding provide a(n) ____.
greater starting torque
Start windings are placed ____ with the run windings.
slightly out of phase
A permanent split capacitor (PSC) motor that is running and up to speed will have the start winding ____.
energized
The shaded pole motor ____.
has little starting torque
When a general duty split-phase motor reaches approximately 75% of its operating speed, the start winding is de-energized by a ____.
centrifugal switch
A split-phase has a ____ winding and a ____ winding.
start, run
A current magnetic relay opens and closes its contacts based on the ____.
current in the run winding
A permanent split-capacitor motor has a ____.
run capacitor only
A split-phase motor that has a current relay and a start capacitor is called a(n) ____ motor.
Capacitor Start, Induction Run CSIR
When a Capacitor Start, Capacitor Run (CSCR) motor initially starts, what is the total capacitance acting on the motor? (Assume the run capacitor is 5 microfarads and the start capacitor is 20 microfarads, if present.)
25 microfade
If a normally operating motor draws 75 amps on startup, it will most likely draw _____ amps when running.
15
When a Capacitor Start Induction Run(CSIR) motor is running and up to speed what is the total capacitance acting on the motor?(Assume the run capacitor is 5 microfarads and the start capacitor is 20 microfarads if present.)
5 microfarads
the positive temperature coefficient resistor start device is a type of
variable resistor
the positive temperature coefficient resistor start device is a type of
variable resistor
a sleeve bearing would typical be used in a motor that operates with a ______
light load and where noise is a factor
a slotted screw at the bottom of the bearing housing is called a
relief plug
a direct drive motor is usually connected to a load with a
coupling
grounding straps are required on a resilient mounted motors to
ground the motor in case of winding failure
the width of a drive belt is classified as
large or small ,narrow or wide
the alignment of a motor and the driven mechanism must be done at room temperature and
at operating temperature
the alignment of a motor and the driven mechanism must be done at room temperature and
at operating temperature
a motor can burn out if the supply voltage is either too high or too low
TrueTrue
one method a technician can employ to check a motor is to take amperage readings of a motor both on start up and after start up and compare them to the motors nameplate
True
the delta transformer has been popular in some locations in the past t or f
True
a drip proof motor is designed to prevent any lubricating oil from leaving any of the bearing
False
when oiling a permanently lubricated motor a 20 weight non detergent motor oil should be used
False
regardless of the type of motor or application the motor bearing require yearly lubrication
False
there is a definite relationship between the speed of the motor and the speed of the blower
true
magnetic overload devices are the most accurate type of device for electrical protection
True
if normally operating motor draws 75 amps on startup it will most likely draw ____ amps when running
15 amps
the best way to repair a defective relay is by
Replacing it
the most common material used on the surface of contacts is
sliver plated
Belt tension will not have any affect on the wear of the bearings
False
pulleys must be in proper aligment or belt and bearing wear will occur
True
open windings will not affect the resistance reading of the start winding as well as the resistance reading between the run and start terminals
False
if the resistance of the run winding is lowered the imbalance in magnetic fields between the start and the run winding will be increased and the starting torque of the motor will actually increase
True
if a resilient mounted motor develops a short to the frame the tech can simply cut the ground strap wire as a permanent repair.
False
before testing a run or star capacitor with an ohmmeter the capacitor should be discharged with a 20,000 ohm a fully 5 watt resistor
True
the electrical components for a fully welded hermetic compressor are checked at the disconnect box for the compressor unit
False
A homeowner plans to build a house out in Las Vegas, Nevada, in the middle of the desert. It would be in his/her best interest to lower the “solar load,” to locate most of the windows on the _____.
North and South side
On a package air conditioning system, which refrigerant lines must be field installed?
Condensing line, power & low voltage line
The solar load on a structure is the heat gain resulting from the _____.
radiation of the sun
The total heat content of infiltrated air of the same dry-bulb temperature may vary from one part of the country to another because of difference in _____.
Humidity
