practice questions Flashcards
The evaporator in a refrigeration system:
Is the component where refrigerant boils and absorbs heat.
The purpose of the compressor is to change ___________.
Low-pressure, low-temperature vapor to a high-pressure, hightemperature vapor
A common refrigerant leak detection device is the:
Halide torch
Copper-plating of compressor parts is:
Caused by contaminants in the system
If not properly installed, a hot-gas muffler might trap:
Oil.
Unit ventilators are usually equipped with outside air dampers to
A. Partial Correct: Provide ventilation air during building occupancy
B. Partial Correct: Comply with most local or state codes
Face and bypass dampers should be adjusted to provide:
Tight shut off to reduce the possibility of overcooling or overheating
With belt driven equipment, alignment of the motor and driven equipment pulleys
Is accomplished using a string or straight edge.
To assist consumers in making an informed choice when purchasing unitary air conditioning equipment, the efficiency of such units is expressed as Energy Efficiency Ratio (EER or SEER) the units of which are:
Btuh/watt
Firestats located in the air stream of air handling units:
A. Partially Correct: Are required in both the supply and return air streams
B. Partially Correct: Should be the manual reset type
C. Partially Correct: Should be nonadjustable
A sleeve bearing would typically be used in a motor that:
Operates with a light load and where noise is a factor
A bearing used on the bottom of a motor where the shaft is positioned vertically is called a ____________ bearing.
Thrust
To produce electromagnetism, relative motion is required between a magnetic field and a/an:
Conductor
Materials which do not allow their electrons to spin out of orbit easily are called:
Insulators
A battery is an example of a/an ____________ source
Direct current
. “Current flowing through a conductor in one direction for a split second, then in the opposite direction for a split second” would be a good definition of:
Alternating current
If a pressure gauge reads five psig at sea level elevation, the corresponding absolute pressure is ___________ psia.
- 7
5. 0 psig + 14.7 = 19.7 psia.
Solar ________ is the amount of solar thermal energy produced divided by the water heating energy demand of the building
Fractional
The portion of the electromagnetic spectrum to which solar collectors respond is _____ and near-infrared radiation.
Visible light
During winter, ________.
Daylight is shorter and the Northern Hemisphere is angled away from the sun
Unless equipped with OSHA or Canadian Standards Association (CSA) approved ground-fault circuit interrupters, portable electric lighting used in wet and-or other conductive locations as, for example, drums, tanks and vessels, shall be operated at ______ volts or less.
12
Receivers are usually required in systems having:
Evaporative condensers
An important feature of a refrigerant receiver, in the case where the liquid line to the evaporator comes out of the top of the receiver, is a
Dip tube
A pressure regulator is constructed so that a rise in ____________ steam pressure reduces off the inlet flow of supply steam.
Downstream
A vacuum breaker is used to avoid which of the following:
Negative gauge pressure
Lock-out relays are used in air conditioning systems to:
Prevent compressor short-cycling
When measuring the winding resistance of a split-phase compressor motor, the smallest value will be measured between the:
The run terminal and the common terminal
Cavitation in a pump pumping hot water:
A. Partial Correct: Makes a pump noisy
B. Partial Correct: Is the result of water boiling into the steam
C. Partial Correct: Is the result of insufficient NPSH
D. Correct: All of the above
The amount of heat removed to lower the temperature of 15 lbs. of water from 48 degrees F to 39 degrees F is:
Correct: 135 Btu. Heat = Weight (lbs.) x Specific Heat (Btu/lb. per degree) F x Temperature (degrees F) = 15 x1 (48-39) degrees F = 15 x 1 x 9 = 135 Btu
Atmospheric pressure at sea level is:
14.7 psi
A dual-element fuse has:
A thermal cutout and a normal fuse link
A single-phase motor in which the run capacitor remains connected when the motor runs is called a:
Permanent-split capacitor motor
Refrigerant leaves the compressor through the ___________ line
Discharge
The symbol below would be used to indicate a ______ switch.
Temperature-actuated
A refrigeration system has a hand-operated needle valve for the refrigerant expansion device. If refrigeration load and suction pressure remain constant, a decrease in condensing temperature will:
Result in reduced refrigerant flow unless the valve is opened.
A full voltage starter has:
One contactor
The voltage rating of motor controller holding coils is:
Not necessarily the same as the motor supply voltage
A lock-out relay should drop out when:
An overload relay opens
In starting up a chilled water system, the first piece of equipment to start should be the:
Chilled water pump
In a gas-fired warm air furnace, the furnace fan should
Be controlled by furnace bonnet temperature
A damper that must throttle air flow should have:
Opposed blade operation
. A pressure regulator is constructed so that a rise in ____________ steam pressure reduces off the inlet flow of supply steam.
Downstream
A vacuum breaker is used to avoid which of the following:
Negative gauge pressure
If the R value on a section of insulation is 8, what would the value be when saturated with water?
0
In a RTD (resistance type device), as temperature increases, resistance will:
Increase linearly
Why is a surge suppressor used on a contactor coil?
To prevent damage to the control circuit
A minimum evacuation level for an air conditioning system is:
500 microns
One horsepower is the same as
746 watts
One watt is equivalent to
3.413 Btu
One kilowatt is equivalent to
1,000 watts
The purpose of the external equalizer line used with a thermostatic expansion valve is to compensate for:
Refrigerant friction through the evaporator
Cleaning refrigerants to ARI 700 standards is called:
Reclaiming
The unit of measure for the specific volume of air is:
FT 3/LB
The amount of heat removed by evaporating one pound of water in an evaporative cooling tower is approximately:
1000 btu
Which of the four lifting sling configurations shown below creates the greatest amount of load strain on the sling?
C- 45 degree strain
The components marked “B” would be called the
Motor contacts
__
__
Which of the following plans are typically NOT supplied in a complete set of Building Plans?
As built
Common Relay configurations are
A. (SPST) Single Pole Single Throw
B. (DPDT) Double Pole Double Throw
The __________ is a device that allows the use of a low voltage power source to operate a high Current load powered device
Contactor
When troubleshooting a contactor in a system. One should check the contact surfaces for
B. Pitting
C. Wear due to Arcing
Terminals “A” would be labeled
O O O
L1, L2, L3
The terminals marked “D” would be labeled
O O O
T1, T2, T3
. Pushing P1 down energizes
M1 first
Pushing P1 down energizes R1 relay coil, closing R1 normally open contacts, energizing TDR relay coil and R1 normally open contacts energizing M1 coil first. After TDR (Time Delay Relay) times out M2 coil energizes second
A (VFD) Variable Frequency Drive controls all but?
Motor life
Three general categories of motor starter problems include all except:
Sizing
VFD’s can be tested when ___________ by means of __________ Measurements for various sections.
Energized, Voltage
If the value of R1 is lowered, the current
Increases
lower resistance current increases
If resistor R2 burns open, the current
Goes to zero
If the value of R3 is raised, the current
Decreases
resistance increases current decreases
All Screw compressors consist of 2 Rotors:
One male and one female rotor
Capacity control for a helical screw compressor is done by?
A. The slide valve
B. Motor speed
If resistor R3 is shorted out the current
Increases
short to ground blows up
If the voltage goes up, the current
Increases
If you find yourself at odds with a confrontational customer, you should
Keep your cool, learn as much as possible, but call your supervisor to report the incident
For applications where quiet operation and light axial load characteristics are found, the type of bearing normally used is the:
Sleeve bearing
Sleeve bearings with the oil port lubrication system must be lubricated with the proper oil because
A. Oil that is too thin will allow the shaft to run against
the bearing surface.
B. Oil that is too thick will not run into the clearance
between the shaft and the bearing surface.
C. The correct oil allows the motor shaft to float on a film
of oil between the shaft and bearing surface.
D. Correct: All of the above.
Too much grease in grease lubricated ball bearing
Causes overheating.
A ladder must extend above the edge of a roof by at least ______ ______.
Three feet.
The proper angle for a ladder is achieved when the distance of the ladder from the building at the base is about __________ the working length (height) of the ladder.
One fourth
Air handling systems that employ economizers which permit outside air “free cooling”
Are most economical when controlled by an enthalpy controller
When face and bypass dampers are used on systems with direct expansion cooling coils:
Compressor capacity control is required
The rate of flow of electrons in a circuit is termed:
Amperage
“Pressure” differential in an electrical resistance is the:
Voltage
The unit used to measure electrical resistance is the:
Ohm
The four essential parts of the vapor compression cycle compressor, condenser, evaporator and
Expansion device
How is an anticipator connected to a single contact cooling thermostat?
In parallel with contacts
The process of removing moisture from air is called:
Dehumidification
Basic types of air supply outlets are
Grilles
With reference to copper tube, what is meant by the letters ACR?
Air conditioning and refrigeration tube
How is the heat anticipator wired in with heating contacts on a 24 volt space thermostat?
Series
A piece of ice weighs 20 LBS and its specific heat is 0.49. It will require __________ Btu to heat the piece of ice from 27 degrees to 31 degrees F
39.2 Solution: Use for Formula: Heat (Btu) = Weight (pounds) x Specific Heat (Btu per LB per degree F) x Temperature Difference (degrees F) = 20 x 0.49 x (31-27) degrees F = 20 x 0.49 x 4 = 39.2 Btu
Given a rate of air flow of 2250 cfm in a duct having a cross-section 18 inches by 18 inches, the duct velocity should be ___________ fpm.
1000
V = 144 x cfm divided by a
= 144 x 2250 (324,000) divided by 18 x18 (324) = 1000 fpm
If a refrigerant sight glass shows bubbles, you know
There is gas in the liquid
A liquid refrigerant receiver has two liquid level test cocks, one near the top of the receiver and one near the bottom. If the system contains enough refrigerant, when the lower cock is opened:
The test cock should discharge liquid refrigerant
Desiccants are used in
Driers
Only __________% of the direct radiation at the edge of Earth’s atmosphere reaches the Earth’s surface
51
Collectors should face as close as possible to ___________?
true South
_________ occurs in a Solar Thermal System when the heated transfer fluid within the absorber piping rises within the collector and is replaced by cooler fluid
downstream
Convection
A (n) ___________ system uses a Heat Transfer Fluid and heat exchanger to transfer heat to the Domestic Hot Water without the use of mechanical means to
circulate the HTF
Passive indirect
Self-pumping Systems are _________ systems.
Passive direct
The vacuum pump used in vacuum steam heating systems that creates a vacuum using high velocity water is the
Jet type pump
Vacuum pumps used in vacuum steam heating systems can be destroyed if they are made to pump
Air and Steam
If a vacuum pump in a vacuum steam heating system burns out, a very common cause is
A failed steam trap
Effective recovery of condensate reduces the following cost of making steam
Fuel/energy costs associated with producing steam.
Boiler water make-up and sewage treatment.
Boiler water chemical treatment
A symptom of a failed steam trap is
A trap that is warmer than condensate temperature
When entering a customer residential premises you should always
Place a clean pair of disposable covers over your shoes
If the technician is on a service call and notices another potential problem not related to the current work order, what should the technician do?
Discuss what you have with the customer and your supervisor so that the customer can decide whether to authorize the additional repair
Which of the following is required part of the work order?
B. Form completed in legible hand writing
C. Complete list of materials used and amount of time spent on the job
Getting the customer to sign the work order should be
The last thing that you should do before leaving the job
Which of the following is a part of your responsibility relative to your work crew?
Working safely on the worksite
The maximum desirable operating temperature of a ball bearing is
180 degrees F.
Shaft runout can be measured with
A. A dial indicator.
B. A runout gage.
The seal in a compressor is necessary to prevent
Refrigerant from leaking out the rotating shaft.
Oil from leaking out at the rotating shaft
The mating seal surfaces on a sleeve type rotary bellows seal are
Polished steel surfaces and a carbon ring
With belt driven equipment, alignment of the motor and driven equipment pulleys
Is accomplished using a string or straight edge
A lock and tag may only be removed by the employee that applied it, unless the employee is absent from the workplace, then the lock or tag may be removed
by a qualified person designated by the employer to perform this task provided that the employer ensures that ___________________________________
The employee who applied the lock or tag is not
available at the workplace
The employee who applied the lock or tag is aware that it has been removed before he or she resumes work at that workplace
Section 608 of the Act prohibits you from knowingly venting ozone-depleting compounds used as refrigerants into the atmosphere while maintaining,
servicing, repairing, or disposing of air-conditioning or refrigeration equipment (appliances). The prohibition went into effect on ____________.
July 1, 1992
When working on a HCFC-22 appliance, or isolated component of such appliance, normally containing 200 pounds or more of refrigerant and using
recovery or recycling equipment manufactured or imported on or after November 15, 1993, you are required to evacuate to a level of
10 in. Hg
If a compressor burn has occurred, the refrigerant must be ____________.
Recovered.
Reclaimed
An advantage of the inverted bucket trap is that
It also vents air and carbon dioxide continuously at steam pressure.
Flash steam is caused by:
Pipe friction
Reduced pressure.
A vertical rise in a condensate line
The purpose of a drip leg in a steam line is to
Let condensate escape by gravity from the fast-moving steam
Store condensate until it can be discharged through the steam trap
Inadequate trapping of steam mains often leads to
Water hammer and damaging slugs of condensate
Pressure in a vertical position condensate pipe will drop 1 psi for every ______ feet in elevation. This is an important factor, since boiling temperature drops as pressure drops. When elevating condensate, this drop in pressure can cause flash steam
2.31
When using a listening device to test a steam trap, what would the technician listen for that could indicate a problem
High velocity sound
If an inverted bucket steam trap is blowing live steam, what might the trouble be?
The valve may have failed to seat because of wear or a piece of dirt or scale
The trap may have lost its prime
The bucket is stuck or has a hole in it
The ____________ drains the condensate from the steam header and returns it to the boiler below the water line while preventing the boiler water from flowing out of the boiler into the return line main
Equalizing line
The ____________ is designed to protect boilers against the loss of water due to leaks in the return line
Hartford Loop
The control valve in a sub-atmospheric steam heating system is limited to approximately ______ % change per minute
3
When the discharge of one compressor is piped into the suction of another compressor, it is called a
Two stage system
What is the most common cause of valve noise?
Valve piped incorrectly
If too much refrigerant is being fed to the evaporator ____________.
The superheat will be low
The low pressure cap tube of an oil failure switch should be connected to the
Compressor crankcase
When copper tubing is being brazed, nitrogen gas can be purged through the system to prevent
Oxidation inside the tubing
In an economizer, an enthalpy control regulates the use of outdoor air on the basis of the air’s
Humidity and temperature
When removing the gauge port plug from a compressor discharge service valve, the valve should be
Back seated
An acid test kit is used to test acidity of
Oil
The TXV sensing bulb is mounted
On the suction line as it leaves the evaporator
In an air cooled system with capacity control, compressor unloading will cause the
Suction pressure to rise and the discharge pressure to fall
A lamp has a source voltage of 110 volts and a current of 0.9 amperes. What is the resistance of the lamp?
122.2 Solution: Ohms Law
R=E divided by I
110 divided by 0.9 = 122.2 ohms
The amount of heat removed to lower the temperature of 15 lbs. of water from 48 degrees F to 39 degrees F is
135 Solution: Heat = Weight (lbs.) x Specific Heat (btu/lb. per degree) F x Temperature Change (degrees F) = 15 x 1 (48-39) degrees f = 15 x 1x 9 = 135 Btu
A belt-driven fan is to turn at 580 rpm. If the fan is driven by a 1740 rpm motor and the motor has a pulley with a three-inch pitch diameter, the fan pulley should have a pitch diameter of ___________ in.
9 Solution: RPM x D = rpm x d
580 x D = 1740 x 3 (5220)
D = 1740 x 3 (5220) divided by 580
= 9 in.
