MODULE 3 EXAM REVIEW
HFC-410A
A 50-50 blend of HFC-32 and HFC-125 produce ________.
Zeotropic
A ________ blended refrigerant never fully mixes chemically, and are not true compounds.
P-T chart
A _________ shows the pressure and temperature relationships at saturation for a specific refrigerant.
total loss of refrigerant
A leak in an evaporator coil, of a unit using a zeotropic blend, usually results in a _________.
CFC
A lot of ______ refrigerants are azeotropes, azeotropes are not compounds.
fully blended refrigerant / no harm
A small leak on the liquid line of a unit that operates around the clock, using a zeotropic blend, usually results in a loss of ________, and ________ is done to the remaining refrigerant.
temperature range / constant pressure
A zeotropic blended refrigerant evaporates and condenses over a ______, called the glide, and at a _________.
hygroscopic
All refrigerant oils are _______ to some degree, meaning that they can absorb moisture from the air.
HFC
An _______ refrigerant has an ODP of 0.
Azeotropic
An ________ refrigerant blend behaves like a pure refrigerant.
superheat
Any vapor temperature measured above the dew point would indicate ________
binary blends
Blends containing 2 refrigerants are called ______.
ternary bends
Blends of 3 refrigerants are called ________.
azeotrope
Charging charts and P-T charts that one equipment manufacturer uses for R-410A, a near-azeotrope, look identical (except for pressures) to charging charts for similar equipment using HCFC-22, an _________.
added
For a system using a fixed restrictor metering device, if the superheat calculated is higher than the required superheat for the system, refrigerant would have to be ________.
recovered
For a system using a fixed restrictor metering device, if the superheat calculated is lower than the required superheat for the system, refrigerant would have to be ________.
leak
Fractionation becomes a problem if a _______ occurs in the system.
Zeotropic
Fractionation is a problem with what classification of blended refrigerants?
pure refrigerant compound
From a technicians standpoint working with an azeotrope is like working with a _________.
Zeotropic
HFC-407C is an example of a _________ blended refrigerant.
near-azeotropic
HFC-410A is an example of what classification of blended refrigerants?
higher
HFC-410A operates at ________ pressures than HCFC-22, therefore it cannot be used in equipment designed for HCFC-22.
charged properly
If the system temperature, humidity, and required superheat are known for the equipment, then superheat can determine if a system is _________.
Fractionation
In a leaking system using a zeotropic blend of refrigerants; When the different refrigerants in the blend boil off at different rates, and leak at different rates, upsetting the blend proportions in the remaining refrigerant it is referred to as ________.
evaporates / condences
In an azeotropic refrigerant blend, the refrigerant ________ and _______at one given pressure and temperature
liquid
Like zeotrope blends, near-azeotropic blends should be charged into a system as a ________.
glide
Near-azeotropes have ________ characteristics, like zeotropes, but they are usually minimal and not a factor to technicians servicing the system.
pumped
Oil should always be _______ into a system to avoid the contamination from the air.
Vapor / liquid
On P-T charts for zeotropic blends that do not have a bubble point or dew point listed, the ______ column should be used for the dew point, and the ______ column should be used for the bubble point.
hygroscopic
PVE oil is not ________ giving it an advantage over POE and PAG oils.
temperature / subcooling
Subcooling can only determine if a system is charged properly if the __________ and required _________ of the equipment are known.
fixed metering device
Superheat can only be used to tell if a system is charged properly if the system uses a __________.
expansion valves
Systems with ________ must be charged based on subcooling values.
refrigerant gauge manifold
The __________ can serve as an expansion device during during the charging of a zeotropic blend.
compressor oil
The __________ must have a dielectric strength high enough so that it doesn't break down or arc under normal operating voltage conditions.
bubble point
The point at which refrigerant starts evaporating when heat is added to the refrigerant.
dew point
The point at which refrigerants ends evaporating when heat is added to the refrigerant.
HFC-410A
The refrigerant __________ is an example of a near-azeotrope.
liquid line pressure / liquid line temperature
The second step to calculate subcooling is to record the _________.
suction pressure / suction line temperature
The second step to calculating superheat is to record the _________ after the system has been turned on and ran for at least 10 minutes.
glide
The temperature range in which a zeotropic refrigerant blend evaporates and condenses is called the ________.
saturated temperature
The third step to calculate subcooling is to find the liquid line pressure on the P-T chart and record the corresponding _________.
suction pressure
The third step to finding superheat is to find the ________ on the P-T chart and record the corresponding saturated temperature.
leak location / volume lost / how much time the unit operates
To determine if a system using a zeotropic blend should be evacuated and recharged with new refrigerant after a leak has occured depends on what three things?
azeotropes / zeotropes / near-azeotropes
What are the 3 categories blended refrigerants fall into?
temperature at which the evaporator operates
What determines the type of refrigerant used in a system?
Refrigerant finishes condensing
What happens at the bubble point when heat is removed from the refrigerant?
Refrigerant starts condensing
What happens at the dew point when heat is removed from refrigerant?
red band
What indicates a flammability hazard on a refrigerant cylinder?
measured temperature-saturation temperature=
What is the formula to find superheat?
liquid refrigerants
What kind of refrigerant is a class 1 safety refrigerant?
low-pressure refrigerants
What kind of refrigerant is a class 2 safety refrigerant?
high-pressure refrigerants
What kind of refrigerant is a class 3 safety refrigerant?
flammable refrigerants
What kind of refrigerant is a class 4 safety refrigerant?
bubble point / dew point
What points are given on a P-T chart for a zeotropic refrigerant blend?
gauge manifold, electronic thermometer, P-T chart
What tools or instruments are needed to calculate superheat and subcooling?
POE
What type of oil is compatible with most of the HFC refrigerants, and is widely used in those applications.
mineral oil
What type of oil is required for systems using HCFC-22?
POE/PVE
What type of oil is required for systems using HFC-410A?
liquid state
When adding charge, zeotropic blends must always be in a _______, this ensures that they are in proper proportions to each other.
bubble point
When calculating subcooling with a zeotropic blend use the ______.
bubble point
When calculating subcooling with a zeotropic blend, use the ______.
dew point
When calculating superheat with a zeotropic blend use the _______.
dew point
When calculating superheat with a zeotropic blend, use the _______.
metering orifice / vapor state
When charge is added using a zeotropic blend to an operating system through the suction service port, the liquid must be passed through a ________ before it enters the unit to ensure that it is in a _________.
begins to evaporate
When heat is added to the refrigerant bubble point can be looked at as the point at which refrigerant __________.
Dew point / superheating
When heat is added to the refrigerant, the ________ can be looked at as the point at which the blend is finished evaporating, and _______ of the vapor begins.
condensed to a liquid
When heat is removed from refrigerant the bubble point can can be looked at as the point where all vapor has ________.
condense from vapor
When heat is removed from the refrigerant, the dew point can also be looked at as the point at which liquid refrigerant first begins to _______.
recovering refrigerant
When subcooling, _________ will increase the liquid line temperature
adding refrigerant
When subcooling, _________ will lower the liquid line temperature.
drop-in replacement
When using a ________ in a system, the compressor oil may have to be purged from the system and a new type of oil in its place, the system components such as the filter drier, metering device, and accumulators or receivers may need to be replaced.
liquid line near the exit of the condenser
Where do you attach the temperature probe to calculate subcooling?
suction line near the compressor
Where do you attach the thermometer to calculate the superheat?
liquid pressure
With zeotropic refrigerants, the bubble point is indicated by the ________ column on a P-T chart.
vapor pressure
With zeotropic refrigerants, the dew point is indicated by the ________ column on a P-T chart.
alkylbenzene
_____ oils are widely used in low-temperature applications and are not compatible with synthetic oils.
saturation
________ is the point at which a refrigerant is partially in its liquid state.
acid/oil
________ test kits are used to sample the compressor oil to check for contaminants.
superheat
_________ is the heat added to a refrigerant after it is fully vaporized.
subcooling
_________ is the heat removed from a refrigerant after it has fully condensed into a liquid.
PAG
_________ oil is used in automotive ac systems where HFC-134a is the refrigerant.
glide
_________ only has to be considered when dealing with zeotropic refrigerants.
dielectric strength
___________ is the ability of oil or any material to resist breaking down in the presence of voltages.
voltages
___________ of varying values exist inside shells of operating compressors.
contaminents
___________, such as water can lower the dielectric strength of oil and cause it to break down.
subcooling
any temperature measured below the bubble point would indicate _________.
drums
class 1 refrigerants have a normal boiling point of 68F and are typically packaged in _______, since their pressure is very low at normal temperatures.
3
class _____ refrigerants are compressed gases with a minimum cylinder pressure that exceed 500 psig.
4
class _____ refrigerants have a flammability rating of 2 or 3 in ANSI/ASHRAE standard 34.
2
class ______ refrigerants are compressed gases with a minimum cylinder pressure that does not exceed 500 psig.
saturated temperature-measured temperature=
what is the formula to calculate subcooling?
zeotropic
what type of refrigerant blend is fractation a problem?
