HVAC: EPA 608 Certification Study Guide

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