HVAC EPA 608 Certification Study Guide questions
and answers with solutions 2025
Are there drop-in replacements for R-12 systems? Why or why not? - ANSWER 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? - ANSWER Ester based oils and
they do not mix with other oils
What type of lubricant is used with HCFCs? - ANSWER Alkylbenzene lubricant
What is difference b/w ternary blend a azeotropic blend? - ANSWER 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? - ANSWER It absorbs (takes on) moisture
What is temperature glide and what type of blend won't have it? - ANSWER Temp. blend is the
difference between the dew point and the bubble point
Dew Point - ANSWER Occurs when saturation temp in evaporator causes refrigerant to change
from liquid to vapor
Bubble Point - ANSWER 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? - ANSWER No because
different refrigerants in blend have different vapor pressures, causing them to leak at uneven
rates
, Refrigeration Process - ANSWER transfer of heat from one place to another
Evaporator - ANSWER 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 - ANSWER Takes low pressure, low temp vapor and changes it to a high-temp, high-
pressure, superheated vapor and delivers it to the condenser
Condenser - ANSWER Rejects heat from system and changes refrigerant from high-temp, high-
pressure vapor into high-pressure, high-temp liquid
Metering Device - ANSWER reduces pressure of refrigerant and changes the high-pressure, high-
temp liquid into low pressure, low temp liquid.
Compound Gauge - ANSWER Typically blue and measures low pressure (psig) and vacuum
(inHg).
High Pressure Gauge - ANSWER Red and measures high side (discharge) pressure. 0 to 500 psi
What does a compressor compress? - ANSWER Vapor
Why will refrigerant migrate to the crankcase in a compressor? - ANSWER Because of the vapor
pressure difference between refrigerant and oil
What color is the high pressure gauge? - ANSWER Red
and answers with solutions 2025
Are there drop-in replacements for R-12 systems? Why or why not? - ANSWER 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? - ANSWER Ester based oils and
they do not mix with other oils
What type of lubricant is used with HCFCs? - ANSWER Alkylbenzene lubricant
What is difference b/w ternary blend a azeotropic blend? - ANSWER 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? - ANSWER It absorbs (takes on) moisture
What is temperature glide and what type of blend won't have it? - ANSWER Temp. blend is the
difference between the dew point and the bubble point
Dew Point - ANSWER Occurs when saturation temp in evaporator causes refrigerant to change
from liquid to vapor
Bubble Point - ANSWER 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? - ANSWER No because
different refrigerants in blend have different vapor pressures, causing them to leak at uneven
rates
, Refrigeration Process - ANSWER transfer of heat from one place to another
Evaporator - ANSWER 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 - ANSWER Takes low pressure, low temp vapor and changes it to a high-temp, high-
pressure, superheated vapor and delivers it to the condenser
Condenser - ANSWER Rejects heat from system and changes refrigerant from high-temp, high-
pressure vapor into high-pressure, high-temp liquid
Metering Device - ANSWER reduces pressure of refrigerant and changes the high-pressure, high-
temp liquid into low pressure, low temp liquid.
Compound Gauge - ANSWER Typically blue and measures low pressure (psig) and vacuum
(inHg).
High Pressure Gauge - ANSWER Red and measures high side (discharge) pressure. 0 to 500 psi
What does a compressor compress? - ANSWER Vapor
Why will refrigerant migrate to the crankcase in a compressor? - ANSWER Because of the vapor
pressure difference between refrigerant and oil
What color is the high pressure gauge? - ANSWER Red
