IP Prep Flashcards
Liquid recirculation pump used in an ammonia system is located between
a) compressor and receiver
b) low press receiver and high press receiver
c) low press receiver and evap
d) high press receiver and evap
c
boiling point of r717 ammonia is
a) -28c
b) -27.6c
c) -28f
d) -27f
c
When installing globe valves in any system for component isolation. How should they be installed on horizontal line runs
a) valve stem vertical to line run
b) stem horizontal to line run
c) stem any position so long as high pressure side of system is exerted on seat
d) stem should be at right angles
d
What component is not normally required in cascade systems?
a) condesner
b) receiver
c) refrigerant flow control on secondary coil
d) low stage condenser
b
Which type of intercooler is not suitable for ammonia compression systems?
a) dry type
b) shell and coil
c) open type
d) any above are fine
A
Multi-stage or booster systems used for very low temp are usually required when compression ratios of a single system exceed
a) 20:1
b) 10:1
c) 3:1
d) 5:1
B
Multi stage compression systems can be divided into two major groups which are
a) cascade or extra low
b) cascade or multi stage
c) cascade or direct
d) any above correct
C
An ammonia receiver has the following dimensions 3ft x 60inches long. find correct prv
a) 90cuft/min
b) 90lbs/min
c) 7.5cuft/min
d) 7.5lbs/min
The corrosiveness of a brine and eutectic mixture should maintain between ____ and ___ and can be determined by a ph tester
a) 7 and 6.5
b) 7 and 7.5
c) 7 and 8.5
d) none
d
Normal temp drop through low temp chiller is
a) 2 degC at flow rate of 10-15gal/ton
b) 2degF at flow rate of 10-15gal/ton
c) 10degf at flow rate of 2gal/ton
d) 10degc at flow rate of 2gal/ton
c
Normally ice temperature is controlled by a brine thermostat (return temp). If your saturated
suction temp is 8 degF what should ice temp be?
a) 18deg f
b) 18deg c
c) 28f
d) 28f
b
Centrifugal pumps are widely used, what device can be found in the stuffing box of a pump
a) sleeve bearing
b) ball type bearing
c) mechanical seal
d) packing gland
d
Blank
Blank
When moisture is present in a refrigeration system, it will react with the refrigerant and the oil to form
a) co2
b) acid
c) co
d) all
b
Which of the following represents the lowest vacuum
a) 10psia
b) 5” hg vac
c) 5psig
d) 1000microns
d
A compound gayge
a) indicates pressure above 14.696psia
b) indicates pressures in inches hg below atmospheric
c) is one of two gauges on typical manifold
d) all of the above
d
A micron gauge is used to measure
a) atmospheric pressures at high altitudes
b) atmospheric pressures at sea level
c) absolute pressure below 1mm hg
d) high pressure in refrigeration system
c
Best method of leak checking is when the refrigeration system is
a) in a vacuum
b) open to atmosphere
c) operating with all fans on
d) standing with dry nitrogen pressure as set in b52
d
Non0condensables gases
a) are desirable
b) undesirable
c) condense readily under normal atmospheric conditions
d) help in pulling in a vacuum
b
What Is the most accurate instrument for reading a deep vacuum?
a) compound gauge
b) mercury u tube manometer
c) mercury barometer
d) electronic vacuum gayge
d
To insure accurate testing, best material to use for connecting lines to the vacuum pump and gauge set is
a) light flexible hoses
b) heavy duty rubber gauge line
c) copper tube
d) garden hose
c
Multiple evacuation means that
a) you connect there pumps simultaneously
b) pull a vacuum on 3 diff systems
c) pull vacuum on same system more than once with nitrogen purging between each
c
Moisture in a liquid state must be _____ before it can be removed with a vacuum pump
a) vaporized
b) condensed
c) cooled
d) solidified
a
Which of the following refrigerants is a CFC-type refrigerant
a) r22
b) r-123
c) r-134a
d) r-12
d
Which of the following is an example an HCFC refrigerant
a) r12
b) r402
c) r22
d) r-134a
c
To re-process refrigerant to meet new product specs is called
a) recovery
b) renew
c) reclaim
d) recycle
c
Refrigerants that are made up of two refrigerants that when blended in the right proportions , combine to make a third stable refrigerant, are called
a) blends
b) azeotropes
c) near azeotropes
d) mixtures
b
If a critically charged refrigeration system is over charged , which of the following is a likely result
a) increased cooling capacity
b) reduced compressor discharge temp
c) increased system efficiency
d) increased operating pressures
d
Fractionation occurs when
a) some of a blended refrigerant evaporates or condenses before the rest of the blend
b) fraction of total charge is added
c) operating pressures of a system increase
d) both a and c
a
When charging with a near-azeotropic mixture, what must be done to prevent liquid from entering the system?
a) charge only as vapour through high side
b) charge only liquid through high side
c) charge as liquid through low side using a restrictor
d) charge as a vapour through the low side using a restrictor
c
Charging a refrigeration system refers to
a) removing refrigerant from system
b) adding refrigerant to a system
c) cleaning the refrigerant
d) vaporizing the refrigerant
b
if 22oz is to be added, and supply cylinder weighs 24lb 12oz, what will supply cylinder weigh after?
a) 23lb 12oz
b) 23lb 6oz
c) 22lb 8oz
d) 22lb 6oz
d
if 30oz is to be added to system and cylinder weighs 26lb 4oz before any added. what will supply cylinder weigh after?
a) 22lb 80z
b) 24lb 60z
c) 24lb 80z
d) 22lb 6oz
b
Refrigerant in liquid form is usually put into the system through
a) liquid line
b) suction line
c) hot gas line
d) liquid return line
a
refrigerant in vapour form is usually put into the system through the
a) liquid line
b) suction line
c) hot gas line
d) liquid return line
b
when charging refrigerant system with vapour from a cylinder, the cylinder will become
a) cold
b) very warm
c) same temp as ambient
d)
a
When charging liquid refrigerant from a single valve supply cylinder, the cylinder is placed
a) upside down
b) right side up
c) on its side
d) in any position
a
a graduated cylinder charging device is a device that
a) measures refrigerant by volume for precise charge
b) compensation dial for adjusting temp of freon
c) heater keeps freon temp from dropping when released into system,
d) all of the above
d
Factory r22 split shows 6lb 8oz in outdoor condensing unit and 2oz in evap. The 3/8 liquid line contains .48oz per foot and 7/8 suction line contains .10oz per foot . Lines are 30ft long. What is correct charge?
a) 6lb 10oz
b) 6lb 15oz
c) 7lb 7oz
d) 7lb 11oz
d
to pull a vacuum means to
a) raise pressure in refrigeration system
b) lower pressure in refrigeration system
c) lower pressure in refrigeration system below atmosphere
d) condense gases
c
liquid freon charging should be done when refrigeration system is
a) off and introduced through SSV
b) very low on freon
c) on and introduced through compressor service valves as long as they are front seated
d) off and introduced through the king valve on liquid receiver
d
TW=20lb and WC=35lb. How much freon can be recovered to tank if you used liquid lift recovery method without oil separation.
a) 33lb
b) 21lb
c) 28lb
d) 35lb
c
When using a recovery unit on a system needing repair, normal sequence goes
a) recover, repair, evacuate, recharge
b) recover, repair, pressure test, evacuate, recharge
c) recover, repair, evacuate, pressure test, recharge
d) any combo
b
Best way to determine charge on unit with no gas and no sight glass is
a) using two lb per ton design cooling
b) pressure method of charging
c) superheat method
d) old ads equipment log if available
d
control can be which of the following?
a) electrical
b) mechanical
c) electrical and mechanical
d) all of the above
d
example of a power consuming device would be a ____ while an example of a non-power consuming device is a ____
a) SPST switch, light bulb
b) light bulb, elec motor
c) elec motor, light bulb
d) light bulb, SPST switch
d
Air con system turned on but no major components turn on; comp, fans, etc. Check first
a) compressor wires
b) indoor fan relay
c) condenser fan motor capacitor
d) power being supplied to system
d
Transformers are rated using
a) volt-amperes
b) volt-ohms
c) amperes-ohms
d) volt-resistance
a
Air con system calling for cooling and comp is running but indoor fan is not. Which terminal on stat do you check first?
a) Y
b) G
c) R
d) W
b
An electrical power consuming component is usually
a) wired in series
b) to pass power to another component
c) often a basic switch
d) uses power and is wired in parallel
d
line side of a switch is
a) side load is connected to
b) neutral side of circuit
c) side of power source
d) side with white wire
c
continuity through a heat relay is checked with
a) ohmeter
b) voltmeter
c) clamp on meter
d) micron gauge
a
a ten wrap amperage multiplier is used with a
a) volt meter
b) clamp on ammeter
c) ohmmeter
d) megger
b
A ________ is the easiest diagram to use to follow a cct. circuit function is obvious
a) pictorial
b) ladder
c) layout
d) oblique
b
An electrical diagram showing the approx location of components is called a
a) pictorial
b) ladder
c) layout
d) oblique
a
Process of ice making usually occurs in what temp range?
a) 0-5f
b) 5-20f
c) -10 - 0f
d) 20-30f
b
If an air cooled condenser is located on a 95F roof and con sat temp is 150f, which of following is likely
a) overcharge
b) condenser clogged
c) system undercharged
d) both a and b correct
d
An air cooled R12 operating good with 25psig suction and 136psig head. which represents possible pressures if condenser fan motor burns out
a) high side 136 low side 25
b) high side 100 low side 15
c) high side 200 low side 20
d) high side 180 low side 35
d
In a waste water system the water in the condenser is 85f and leaving is 105f. Which is logical explanation for conditions above
a) reduced water flow through con
b) scale build up in water
c) excess water through con
d) Both a and b
a
In a waste water system the water in the condenser is 85f and leaving is 90F. Which is logical explanation for conditions above
a) reduced water flow through con
b) scale build up in water
c) excess water through con
d) Both b and c
d
Ref cabinet temp of a high temp fridge unit ranges from
a) 75-95f
b) 60-75f
c) 45-60F
d) 25-45f
c
high temp ref unit the boiling point of freon in the coil is normally ______ lower than the cabinet temp
a) 10-20f
b) 25-35f
c) 35-46f
d) 5 - 15f
a
Medium temp ref cabinet range from
a) 5-20f
b) 20-35f
c) 35-50f
d) 30-45f
d
condensing units located outside that operate year round
a) larger fan motors
b) cpr valves
c) all weather protection
d) head pressure control
d
with entering air to condenser above 70f, the td between outdoor air and condensing temp on standard units will be?
a) 10-15f
b) 15-20f
c) 20-25f
d) 25-30f
d
When the comp in a system using cap tubes is sweating it is a sign of
a) overcharge
b) dirty evap
c) evap blower motor problem
d) any above
d
In a waste water cooled system, the diff between condensing temp of freon and leaving water is approx
a) 10f
b) 20f
c) 30f
d) 40f
a
in a water cooled condensing unit/ cooling tower combo, the td of water through the condenser will be approx
a) 10f
b) 20f
c) 30f
d) 40f
a
approach of a cooling tower is
a) diff between entering and leaving wet bulb temperatures
b) number of degrees water is cooled in the tower
c) diff in temp between the entering air wet bulb and sump water temp
d) diff in temp between the entering air wet bulb and water entering tower
c
Completely clogged driers can lead to?
a) low evap fan amperage
b) compressor damage
c) evap ice formation
d) all of the above
d
if the blades of a forward curved centrifugal (evap) blower become clogged with dirt, what is likely
a) evap could freeze
b) suction pressure drops
c) head would rise
d) both a and b
d
Standard air con system will operate with an evap boiling point of
a) 40
b) 45
c) 50
d) 55
a
in a system using cap tube or orifice , when the air filters become clogged, SH will
a) increase
b) decrease
c) remain same
d) swing back n forth
b
in a system using a txv , when air filters become restricted, SH will
a) increase
b) decrease
c) remain same
d) disappear
c
when is it beneficial to pump down a system before servicing?
a) when comp needs to be changed
b) when txv needs changing
c) when condenser needs cleaning
d) condenser coil needs replacing
b
As a rule of thumb: air leaving evap will be about ______ than air entering
a) 17-20 warmer
b) 10-15 warmer
c) 17-20 cooler
d) 10-15 cooler
c
if compressor motor locks up it will_____
a) not start
b) hum then turn off
c) draw RLA
d) all of the above
d
A service valve can be used to
a) check electrical service to comp
b) isolate ref so system can be serviced
c) check air flow across evap
d) ambient air check
b
on a 95f day, r22 pressure on high side should be about
a) 182
b) 108
c) 297
d) 243
b
liquid line temp is used to determine _____ of condenser
a) superheat
b) low side press
c) suction pressure
d) sub cooling
d
to accurately add freon, condenser ambient temp of about ______f should be simulated
a) 75
b) 85
c) 95
d) 100
c
instrument used to check for a short in the compressor winding is called a
a) ohmmeter
b) ammeter
c) voltemeter
d) milliamp meter
a)
problems in refrigeration portion of the system are caused by
a) refrigerant quantity
b) ref flow
c) contaminents
d) any of above
d
typical evap superheat reading at evaporator outlet for central air on a 95f day would be
a) 5-7
b) 8-10
c) 10-12
d) 12-15
c
After repairing a system that has had an electrical motor failure (comp burnout). It is good field practice to re-use the recovered refrigerant in that system?
a) true
b) false
false
air entering a refrigerant system can eventually lead to compressor failure
a) true
b) false
true
clearance tolerances are such that the ordinary clean refrigerant oil can be used satisfactorily in a vacuum pump
a) true
b) false
false
while under deep vacuum , any liquid water under oil in the motor compressor assembly can be removed by operating compressor motor for several seconds without any adverse affect on system
a) true
b) false
false
rec max pressure for leak testing is 150psig
a) true
b) false
false
s it possible to have a leak free system when under a vacuum but still leak when the system pressure is above atmospheric
a) true
b) false
true
pressure test of 100 microns has been reached with vacuum pump on. pump is turned off and gauge reading rises above 500 microns, this indicates a leak
a) true
b) false
true
Azeotropic mix will separate into its components and have specific separate boiling points. A near azeo mix will not separate readily. This causes glide. Near mixtures must be removed from their container n the liquid form to prevent fractionalization
a) true
b) false
false
Fractionalization is when parts of (refrigerants) of a nearazeotrpic mixture condense and or evaporate at different rates
a) true
b) false
true
Glide is the range of pressures/temperatures in which a blended refrigerant will condense
a) true
b) false
true
one god feature on an electric charging scale is that It counts upwards as refrigerant is removed , to tell the technician how much was used
a) true
b) false
true
quickest method to charge is doing vapour only
a) true
b) false
false
when adding freon in vapor form to a ref system, system motor/comp is running
a) true
b) false
true
when adding freon in liquid form into the high side, system compressor/ motor is running
a) true
b) false
false
using a restrictor, liquid freon can be charged into low side of system with system on
a) true
b) false
true
manuf charging chart may be used when available to determine correct charge for a system
a) true
b) false
true
a deep vacuum involves reducing pressure in system to approx 50-100 microns. with a field acceptable level of 500
a) true
b) false
true
Nitrogen is an inert gas used to test refrigeration systems for leaks
a) true
b) false
true
freon driers are commonly used to remove any moisture left in system after install r servicing has been performed . a type of desiccant used in these driers is silica gel which is an adsorbent?
a) true
b) false
false
when referring to vac depth “deep and high” vacuum mean the same thing
a) true
b) false
true
when adding oil to a refrigeration compressor w/ a sight glass, oil level upon completion should be 3/4 way up with comp off according to manuf rec
a) true
b) false
true
a halide leak detector can be used with a mixture of nitrogen and sulfur hexafluoride to indicate leaks
a) true
b) false
false
when servicing a ref system when it is short of both freon and oil, ref should be added first then top up oil as req’d
a) true
b) false
true
if line one of a circuit had a potential of 120v and line two was neutral , the potential voltage between line on and two would be zero volts
a) true
b) false
false
heating anticipator in a thermostat is usually of the adjustable type
a) true
b) false
true
cooling anticipator is usually of the adjustable type
a) true
b) false
false
when checking thermostat circuits an insulated jumper wire is a handy tool
a) true
b) false
true
a 120v/24v control transformer has a VA of 20 . Max amp the transformer will put out is .8 amps
a) true
b) false
true
regardless of what load is on sec side of transformer, output voltage remains the same
a) true
b) false
false
when using a ten -wrap multiplier, reading on the meter must be multiplied by ten
a) true
b) false
false
while troubleshooting a 24v circuit w thermostat, press control, contactor coil, tech reads 24v across stat, 0v on press control, 0v across coil. technician says this
- transformer burned out
- stat is open
- contactor coil is energized
a) true
b) false
false
since any new replacement refrigerants are being used, a tech should rely on system temperatures to ease troubleshooting
a) true
b) false
true
a txv capacity will drop if if pressure drop across the valve increases
a) true
b) false
false
high comp ratios lead to lower compressor discharge temps
a) true
b) false
false
bubbles in sight glass always indicates low charge
a) true
b) false
false
best place for liquid line sight glass is the inlet of expansion device
a) true
b) false
true
Low density vapours entering the compressor mean low refrigerant flow through compressor
a) true
b) false
true
because of low freon flow through compressor and low charge, the 100% saturated vapour point in condenser will be very low, causing low SC
a) true
b) false
true
dirty condenser coils are often the cause for inefficient compressors
a) true
b) false
true
if the evap and compressor are starved, condenser will also be starved
a) true
b) false
true
since evap absorbs both sensible and latent heat, humidity must be taken into account and considered as part of the load on the evap
a) true
b) false
true
high eff condensers can actually be too efficient on cool days
a) true
b) false
true
temp drop in air through evap responds in reverse to a change in cfm through the evap
a) true
b) false
true
best way to tell if a comp discharge line is correct is to touch it
a) true
b) false
false
if metering device malfunctions and gets stuck in the closed position, compressor could overheat
a) true
b) false
true
if a compressor has partially shorted winding it could run for a while, overheat then shut off
a) true
b) false
true
when checking elec circuits of an air con system, each parallel circuit should be isolated and checked separately
a) true
b) false
true
with a rise in outdoor temp the head pressure will rise
tru
superheat occurs in condenser as well as evaporator
a) true
b) false
true
subcooling occurs in evap as well condenser
true
false
false
a suction line filter drier should always be installed with a compressor changeout
true
false
false
