HVAC: EPA 608 Certification Study Guide 2024
Are there drop-in replacements for R-12 systems? Why or why not? -Correct Ans-No
because the new refrigerants are incompatible with the oils and lubricants used in R-12
systems.
What type of oil is used in R-134a and what oils will it mix with? -Correct Ans-Ester
based oils and they do not mix with other oils
What type of lubricant is used with HCFCs? -Correct Ans-Alkylbenzene lubricant
What is difference b/w ternary blend a azeotropic blend? -Correct Ans-Ternary blends
are three-part mixtures whereas azeotropic blends are blends of two or more
compounds that act like a single compound.
What is the trait of a hygroscopic lubricant? -Correct Ans-It absorbs (takes on) moisture
What is temperature glide and what type of blend won't have it? -Correct Ans-Temp.
blend is the difference between the dew point and the bubble point
Dew Point -Correct Ans-Occurs when saturation temp in evaporator causes refrigerant
to change from liquid to vapor
Bubble Point -Correct Ans-Occurs when saturation temp in condenser changes
refrigerant from vapor to liquid
Will the gases in a ternary blend leak at the same rate? Why or why not? -Correct Ans-
No because different refrigerants in blend have different vapor pressures, causing them
to leak at uneven rates
, Refrigeration Process -Correct Ans-transfer of heat from one place to another
Evaporator -Correct Ans-Absorbs heat into system from space to be cooled. Absorption
of heat causes refrigerant to boil. Upon leaving, refrigerant changed to low pressure,
low temperature vapor
Compressor -Correct Ans-Takes low pressure, low temp vapor and changes it to a high-
temp, high-pressure, superheated vapor and delivers it to the condenser
Condenser -Correct Ans-Rejects heat from system and changes refrigerant from high-
temp, high-pressure vapor into high-pressure, high-temp liquid
Metering Device -Correct Ans-reduces pressure of refrigerant and changes the high-
pressure, high-temp liquid into low pressure, low temp liquid.
Compound Gauge -Correct Ans-Typically blue and measures low pressure (psig) and
vacuum (inHg).
High Pressure Gauge -Correct Ans-Red and measures high side (discharge) pressure. 0 to
500 psi
What does a compressor compress? -Correct Ans-Vapor
Why will refrigerant migrate to the crankcase in a compressor? -Correct Ans-Because of
the vapor pressure difference between refrigerant and oil
What color is the high pressure gauge? -Correct Ans-Red
Are there drop-in replacements for R-12 systems? Why or why not? -Correct Ans-No
because the new refrigerants are incompatible with the oils and lubricants used in R-12
systems.
What type of oil is used in R-134a and what oils will it mix with? -Correct Ans-Ester
based oils and they do not mix with other oils
What type of lubricant is used with HCFCs? -Correct Ans-Alkylbenzene lubricant
What is difference b/w ternary blend a azeotropic blend? -Correct Ans-Ternary blends
are three-part mixtures whereas azeotropic blends are blends of two or more
compounds that act like a single compound.
What is the trait of a hygroscopic lubricant? -Correct Ans-It absorbs (takes on) moisture
What is temperature glide and what type of blend won't have it? -Correct Ans-Temp.
blend is the difference between the dew point and the bubble point
Dew Point -Correct Ans-Occurs when saturation temp in evaporator causes refrigerant
to change from liquid to vapor
Bubble Point -Correct Ans-Occurs when saturation temp in condenser changes
refrigerant from vapor to liquid
Will the gases in a ternary blend leak at the same rate? Why or why not? -Correct Ans-
No because different refrigerants in blend have different vapor pressures, causing them
to leak at uneven rates
, Refrigeration Process -Correct Ans-transfer of heat from one place to another
Evaporator -Correct Ans-Absorbs heat into system from space to be cooled. Absorption
of heat causes refrigerant to boil. Upon leaving, refrigerant changed to low pressure,
low temperature vapor
Compressor -Correct Ans-Takes low pressure, low temp vapor and changes it to a high-
temp, high-pressure, superheated vapor and delivers it to the condenser
Condenser -Correct Ans-Rejects heat from system and changes refrigerant from high-
temp, high-pressure vapor into high-pressure, high-temp liquid
Metering Device -Correct Ans-reduces pressure of refrigerant and changes the high-
pressure, high-temp liquid into low pressure, low temp liquid.
Compound Gauge -Correct Ans-Typically blue and measures low pressure (psig) and
vacuum (inHg).
High Pressure Gauge -Correct Ans-Red and measures high side (discharge) pressure. 0 to
500 psi
What does a compressor compress? -Correct Ans-Vapor
Why will refrigerant migrate to the crankcase in a compressor? -Correct Ans-Because of
the vapor pressure difference between refrigerant and oil
What color is the high pressure gauge? -Correct Ans-Red
