A/c stuff we learned in class.
based on the information in this chapter which of the following would be an incorrect air gap between the faces of the compressor clutch armature and pulley
.010 (.025 mm).
schrader valves on R-12 systems built after ? have different size high and low fittings
1986
each cycle through the evaporator absorbs at least? of heat from the air blowing across it
25 fereinheit
on hot days, condenser pressures can be as high as
400 psi
most air discharge specifications are between 35 f and
55 F
the ? compressor with a swash plate uses pistons that are double ended so they can pump in each direction
Axial
a refrigeration system using R-12 is one pound .45kg low. which of the following could be legally added to raise the refrigerant level to normal
R-12
all of the following is used to flush a refrigeration system except
R-12
what refrigerant is a CFC
R-12
all of the following statements about R-134a and R-12 are true except
R-12 condenses at a slightly higher pressure than R 134a
which of the following desiccants can be used with R-134a only
XH-7
desiccant is placed in a porous bag inside the
accumulator receiver and drier
what two devices are never found on the same refrigeration system
accumulator and receiver drier you either have one or the other but not both on the same system.
all of the following statements about condensers are true except
all condensers have a single serpentine tube
which of the following is the best description of the purpose of the accumulator oil return hole
allows oil to return to the compressor
which of the following is/are true about cycling/clutch orffice tube air conditioning systems
an accumulator is installed in the low pressure side of the system the accumulator supplies refrigerant vapor to the compressor
which of the following is/are true about steam
at sea level both water at 212 ferheinhet and steam are the same temperature
what does the expansion valve equalizer passage prevent
being flooded with fluid refridgerant when vehicle operating low speeds on a hot day.
all of the following statements about tube and fin coils are true except
bending the fins makes them weaker
tech A says PAG oil can be used with R-134a. tech B says PAG oil cannot be used with R-12 who is right.
both
tech A says heat always travels from a warmer object to a colder one. tech B says when all objects in an area are at the same temperature, no heat transfer would occur. who is right
both
tech A says if pressure is held constant, a substance will have different vaporizing and condensing temperatures. technician B says higher pressures cause higher boiling points. who is right
both
tech A says some refrigerant blends contain R-134a tech B says some fridge rant blends contain R-22 who is right
both
Evaporators with expansion valves are being discussed. tech A says the sensing bulb is located at the outlet tube of the evaporator. tech B says the bulb can be clamped to the tube exterior and covered with insulation. who is right
both A and B
tech A says that PAG oil absorbs moisture when exposed to air. tech B says that too much oil in the refrigerant reduces cooling efficiency
both A and B
all of the following statements about scroll compressors are true except
both scrolls can move
how is latent heat measured
british thermal units or calories
the sight glass is used to determine the refrigerant
charge level
in science there is no such thing as
cold
which of the following is/are true about the air distribution system
cold air coming from the defroster ducts when engine is warm indicates a problem
the spring lock coupling contains all of the following parts except
compression nut
A high pressure switch cuts off the ? if the pressure becomes too high
compressor
most refrigeration system gaskets are found on the
compressor
refrigerant is a high pressure liquid when it leaves the
condensor
what is the name of the part in front of the radiator that carries heat away from the refrigerant
condensor
heat transfer by direct contact
conduction
what is the purpose of refrigeration system hoses and lines
connect major parts of the refrigerantation system.
heat transfer occurs by ? radiation or evaporation
convection
how chicken is cooked over a barbecue pit
convection
heat always travels to an object ? than its surroundings
cooler
which of the following fittings requires a special machine to install
crimp
the thermostatic expansion valve is a refridgerant ? control device
flow
liquid refrigerant will fall to the ? of the receiver drier
desiccant
what type of valve does a scroll compressor have
discharge reed valve.
what is the name of the material that absorbs water in the air conditioning system
dissicant
when the compressor clutch is ? the compressor is operating
engaged
an expansion valve must have an opening between the high side line and the
evaporator
which of the following is a heat exchanger
evaporator and condensor
the accumulator is located close to the
evaporator outlet
when the outlet of the evaporator is warm, the gas in the sensing bulb causes the flexible diaphragm is to
expand
which of the following refrigeration systems devices restricts the flow of refrigerant into the evaporator
expansion valve
sensible heat can be
felt or sensed
after a compressor failure a ? is usually installed in a line after the condenser
filter
when there is a restriction in a line or part what will commonly appear downstream of the spot
frost ring
no bubbles in a receiver drier sight glass meant the system was
full or completely empty
which o rings are used on R-134a systems
green and blue
the usual way to cause change of state is by adding or removing
heat
what is the name of the device that engine coolant flows through to heat the cars interior
heater core
the refridergerant leaves the condensor as a
high pressure high temperature liquid
comfort depends on temperature ? and air movement
humidity
the amount of water vapor in the surrounding air is called the
humidity
raising pressure will ? the temperature at which a change of state takes place
increase
list three ways to measure o ring
inside diameter, outside diameter, and thickness
accumulator fixed orifice cycling clutch orifice tube system
is commonly used on modern refrigeration systems. the fixed orifice is a small tube which creates a narrow passage allowing refrigerant to enter the evaporator in controlled amounts. the size of the passage is non adjustable and controlling compressor operation controls evaporator pressure
what is used to ensure the armature plate does not spin on the crankshaft
key and keyway
what is the name of the type heat that is required before matter can actually change its state
latent heat
which of the following air conditioning lines should feel cold to the touch
low side
the refrigerant enters the compressor as a
low temperature low pressure vapor.
all of the statements about metal refrigerant lines are true except
metal lines are more expensive than hoses
a musty smell inside of the vehicle may be caused by ? on the evaporator
mold
how do HVac manufactures compensate for the use of R-134a instead of R-12
most manufactures compensate for the use of R-134a by using a slightly larger condenser or by increasing airflow through the condenser with dual electric fans.
what gas is produced when R-12 is exposed to flame
nerve gas phosgene
orifice tube systems have no
no receiver drier and vapor could reach the evaporator if there is no sub cooling.
because of the danger of leaks, refrigerants used in vehicles should be ? and ?
non flammable and non poisons
compression fittings always use ? as a seal
o rings
some ? is carried along with the refrigerant
oil
manual service valves are found on ? vehicles
older
the expansion valve sensing bulb is located on the ? side of the evaporator
outlet
what is the name of the substance that is a pollutant at ground level but when in the stratosphere protects the earths surface from uv rays
ozone layer
in an axial compressor the cylinders are ? to the crankshaft
parallel
? can be used with R-134a and R-12
polyester oil
which compressor type resembles an aircraft engine
radial compressor
how the sun heats the earth
radiation
makes use of infrared rays
radiation
systems with expansion valves have a
receiver drier between the condenser and expansion valve. the receiver is designed to separate vapor from liquid refrigerant.
expansion valve
receiver drier expansion valve system
leak detector dye is usually colored
red green orange
a movable flap that closes an opening in the compressor is a
reed valve
describe a multiple pass evaporator
refrigerant enters through the top and passes through three or four of the plates before being redirected upward through the next set of plates.
a reed valve is opened and closed by
refrigerant pressure
on a rotary vane compressor which of the following parts does the crankshaft drive
rotor
a rotary vane compressor consist of a ? mounted off center inside of a large ? casing
rotor round
when the air is totally saturated with moisture this is called 100 percent
saturated
all of the following statements about making replacement hoses are true except
screw clamps should be used to attached the hose to metal lines
? keep the air from bypassing the condenser
seals
? are used to connect the refrigeration system to the service hoses
service fittings
leak detector dye is put into the refrigerant systems through one of the
service ports
SNAP
significant new alternatives policy under the clean air act the EPA examines any and all R-12 substitutes.the procedure used to review potential replacement refrigerant is called the significant new alternatives policy or SNAP program. using the guidelines outlined in the SNAP program, the EPA examines replacement refrigerant for the following characteristics. Ozone depletion Global warming flammability toxicity acceptable refrigerants are subject to fitting, labeling, and shut off switch conditions. The EPA has determined several refrigerants that are acceptable for use as approved by the SNAP program for use in R-12 auto air conditiong. any refrigerants found to have high global warming potential or is ozone depleting flammable or toxic are classified as unexceptable not allowed. using refrigerants found unacceptable under SNAP is a violation of clean air act. however SNAPS evaluation does not determine how the replacement refrigerant will perform. some SNAP approved refrigerants are actually approved only for use in stationary equipment such as room air conditioning vending machines and water coolers. EPA law allows these refrigerants to be sold. they can even be advertised for use in vehicles however it is illegal to use them in a vehicle refrigeration system.
the three states of matter are
solid,liquid,gas
what is used for flushing a system
solvent
what are two names for scroll compressor
spiral and orbital
define superheat
super heat is any heat added after the change to a higher state.
hoses are made of a type of
synthetic rubber
compressor shaft lip seals are being discussed. tech A says the seal lip is held against the shaft by a garter spring. tech B says refrigerant pressure holds the lip against the shaft. who's right
tech A
tech A says barrier hoses are used on all refrigeration systems originally equipped with R-134a. Tech B says barrier hoses must be installed on all systems retrofitted from R-12 to R-134a. who is right
tech A
tech A says only liquid can change state up or down. tech B says a chemical change can also be a change of state. who is right
tech A
tech A says screw type hose clamps are easy to install. tech B says screw type hose clamps provide uniform pressure all the way around the hose and fitting. who is right.
tech A
tech A says that a bad expansion valve can cause low pressures on both sides of the system. tech B says that the accumulator must be replaced when the expansion valve is replaced. who is right
tech A
tech A says that a low pressure cutout switch will open the circuit to the magnetic clutch if refrigerant level is low. Tech B says that a high pressure cutout switch shuts off the compressor if discharge pressure drops too low.
tech A
tech A says that air temp should drop by at least 20 F as it passes through the evaporator. tech B says that the higher the temp of ambient air the more it cools as it passes through the evaporator
tech A
tech A says that evacuating a system will result in more efficient cooling. tech B says that water can be boiled at room temp by pressurizing it
tech A
tech A says that when refrigerant is pumped from the compressor it is a high pressure gas. tech B says that when refrigerant enters the compressor it is a liquid.
tech A
tech A says R134a has no effect on global warming. tech B says R134a has no effect on the ozone layer who right
tech B
tech A says a multiple pass plate and fin evaporator can be spotted by the use of an oil return line. tech B says the multiple pass plate and fin evaporator has been replaced by a later design. who is right
tech B
tech A says double ended pistons are used on radial compressors. tech B says reed valves are used on all piston compressors. who right
tech B
tech A says the capacity control valve is operated by pressure signals from the crankcase. tech B says the capacity control valve is operated by pressure signals from the low side of the refrigeration system who right
tech B
evaporator is called a heat exchanger because
the contact between the evaporator metal and the air transfers exchanges heat in air to the evaporator, which is then absorbed by the refrigerant. for this reason, the evaporator is often called a heat exchanger.
what is the purpose of the rubber flap at the evaporator case drain.
the flap seals against the entry of dirt, insects, and outside air.
what is meant when we say a refrigerant should be environmentally friendly
they should not harm the ozone layer
what is the purpose of evaporator surface cleaners
to kill organisms and dislodge them from the evaporator service to get rid of the musty smell.
some flushing agents are
toxic flammable damaging to the ozone layer
the flow control device can be either an orficie ? or expansion valve.
tube
when refilling from the low side should the can be upside down or right side up
upright right side up
an air conditioning compressor is designed to pump
vapor
hoses that carry refrigerant ? must have large internal diameter
vapor
refrigerant enters the condenser as a high temperature high pressure
vapor
the refrigerant leaves the compressor as a high pressure high temperature
vapor
if the heater has a control valve and its open the hoses should both be
warm
cooling phase operation
we will begin the basic refrigeration cycle at the evaporator -the evaporator is the place where heat is transferred from the air to the refrigerant. -the refrigerant enters the evaporator as a low pressure low temperature liquid -warm air passes through the evaporator -heat from the air is transferred to the evaporator metal by convection. -the heat passes from the evaporator metal to the refrigerant by conduction -since the pressure is low the heat causes the refrigerant to turn to gas or vaporize -as the refrigerant vaporizes it absorbs heat from the air -this heat becomes latent heat in the refrigerant vapor. the cooled air enters the passenger compartment. -the refrigerant leaves the evaporator as a low pressure low temperature vapor -the lines and accumulator will be cold to the touch -the vaporized refrigerant travels to the accumulator on its way to the compressor -the refrigerant vapor is drawn from the accumulator into the compressor. -in the compressor the refrigerant is packed or compressed into a smaller space -forcing the refrigerant vapor to occupy a smaller space does two things -it increases the pressure of the refrigerant -it forces the heat in the vapor into a smaller area -the refrigerant enters the compressor as a low pressure low temperature vapor. -and leaves as a high temperature high pressure vapor -from the compressor the high pressure vapor travels to the condenser. -the refrigerant leaves the condenser as a high pressure high temperature liquid - even though the liquid refrigerant is still hot it has changed to a lower state and is now ready to be reused in the evaporator. -the liquid refrigerant tries to enter the evaporator but is stopped by the flow restrictor. the action of the flow restrictor is similar to the nozzle of a water hose -it sprays the liquid refrigerant in a sheet or mist of atomized particles breaking the refrigerant into small particles helps it to vaporize easily. -the flow restrictor also works with the compressor to control the evaporator pressure. the compressor is always trying to draw refrigerant from the evaporator -the restrictor controls evaporator pressure by controlling the amount of refrigerant entering the evaporator. since the pressure is low the refrigerant in the evaporator vaporizes beginning the cycle again.
receiver and drier
when a receiver and drier is used it is located between the condenser and expansion valve.
Accumulator
when an accumulator is used it is located between the evaporator and the compressor.
which of the following driving conditions uses more fuel at highway speeds
windows down and air conditioner off