HVAC: EPA 608 Certification Exam Study Guide 2024

Are there drop-in replacements for R-12 systems? Why or why not? - 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? - Ester based oils and they do not mix with other oils What type of lubricant is used with HCFCs? - Alkylbenzene lubricant What is difference b/w ternary blend a azeotropic blend? - 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? - It absorbs (takes on) moisture What is temperature glide and what type of blend won't have it? - Temp. blend is the difference between the dew point and the bubble point Dew Point - Occurs when saturation temp in evaporator causes refrigerant to change from liquid to vapor Bubble Point - 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? - No because different refrigerants in blend have different vapor pressures, causing them to leak at uneven rates Refrigeration Process - transfer of heat from one place to another Evaporator - 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 - Takes low pressure, low temp vapor and changes it to a high-temp, high-pressure, superheated vapor and delivers it to the condenser Condenser - Rejects heat from system and changes refrigerant from high-temp, high-pressure vapor into high-pressure, high-temp liquid Metering Device - reduces pressure of refrigerant and changes the high-pressure, high-temp liquid into low pressure, low temp liquid. Compound Gauge - Typically blue and measures low pressure (psig) and vacuum (inHg). High Pressure Gauge - Red and measures high side (discharge) pressure. 0 to 500 psi What does a compressor compress? - Vapor Why will refrigerant migrate to the crankcase in a compressor? - Because of the vapor pressure difference between refrigerant and oil What color is the high pressure gauge? - Red What color is the low pressure gauge? - Blue What needs to happen if oil has been contaminated by burnout? - Triple evacuate system, install permanent filter-drier, conduct deep vacuum before recharging What are three Rs of refrigeration? - Recover, recycle, reclaim Recover - to remove any refrigerant in any condition from system and store in external container without necessarily testing or processing in any way Recycle - To clean refrigerant for immediate reuse by separating oil from refrigerant and removing moisture and acidity from refrigerant by use of products like filter driers Reclaim - To process refrigerant to level of new product specifications as determines by chemical analysis What standards must refrigerant recovery equipment meet and what components must all Type I and Type II refrigerant systems have? - EPA-approved equipment testing organization. Service aperture or process stub System-Dependent Devices - Capture refrigerant with assistance of compressor and/or pressure of refrigerant in appliances from which refrigerant is being recovered Self-contained Devices - Have independent means to draw refrigerant out of appliances What is nitrogen and a filter-drier used for after recovery? - Use nitrogen to flush debris out of system after recovering refrigerant. Filter-drier should be installed to trap any debris that may cause damage to new compressor What must be done before starting an evacuation? - Recover all refrigerant and attain the mandated vacuum level ASHRAE Standard 15-1994 - Requires refrigerant sensor that will sound alarm and automatically start ventilation system in occupied equipment rooms where refrigerant from leak will concentrate How often should refillable cylinders be hydrostatically tested? - 5 years What are the three ways you can control fill level of refillable cylinder? - Mechanical floats, electronic floats, or weight What is the EPA definition of a small appliance? - One that is manufactured, charged, and hermetically sealed in factory and contains five lbs. or less of refrigerant What standards must recovery equipment manufactured before Nov. 15th, 1993 meet? - Capable of recovering 80% of refrigerant whether or not compressor is operating or achieve a 4-inch vacuum under conditions of ARI 740 What standards must recovery equipment manufactured AFTER Nov. 15th, 1993 meet? - Capable of recovering 80% of refrigerant without compressor operating or achieve 4-inch vacuum under conditions of ARI 740; be capable of recovering 90% of refrigerant with compressor operating or achieve 4-inch vacuum under conditions of ARI 740; and must be approved by EPA approved third-party laboratory Low-loss Fittings - Can be manually or automatically closed when disconnecting hoses in order to prevent refrigerant loss Service Aperture - Typically straight piece of tubing that is entered with piercing access valve Find the pressure for R-12 at 80 degrees F. - 84.4 psi Find pressure for R-22 at 70 degree F. - 121.4 psi R-134A at 90 degree F - 104.3 psi What might happen if cylinder containing mixed refrigerants is given to reclamation center? - Refuse to process it and ship back to sender or destroy it for a substantial fee What is difference between self-contained recovery tank and system-dependent recovery tank? - A self-contained recovery tank uses its own power to recover refrigerant from systems and is capable of reaching required recovery rates with or without compressor operating. Stores in pressurized tank. A system-dependent recovery tank captures refrigerant into a non-pressurized container. Uses system's compressor, an external heat source, or vacuum pump to recover refrigerant. What are two things that can cause high discharge pressures? - Not opening tank inlet valve or having excess air will cause higher discharge pressures How can you check if a tank contains excess air or non-condensables? - Check pressure inside recovery tank after allowing temp of cylinder to stabilize to room temperature What type of system can a vacuum pump be used on for recovery? - A vacuum pump can only be used on a recovery device in combination with a non-pressurized container and can not be used with self-contained recovery equipment (pressurized container) When using a system-dependent recovery system with an operating compressor, where should the refrigerant be recovered from? With a non-operating compressor? - When using a system-dependent recovery process with an operating compressor, run the compressor and recover from the high side of the system. When using a non-operating compressor, it may be necessary to access both low and high side of system to achieve required recovery level and it will speed the recovery How can you release trapped refrigerants in the oil? - Necessary to heat and tap compressor with mallet several times or use vacuum pump How will activating a defrost timer aid in recovery process? - Help vaporize any trapped liquid refrigerant When should piercing type valves be used? What is a common problem with these valves? - Copper or aluminum tubing only. Tend to leak over time What are some other small refrigeration systems that contain other types of refrigerants? Should these refrigerants be recovered with standard EPA equipment? - Ammonia, hydrogen or water and therefore, should not be recovered using current EPA-approved recovery devices. Similarly, systems built before 1950 may have methyl formate, methyl chloride, or sulfur dioxide as refrigerants and require special recovery equipment What should be done before charging a new system with refrigerant? - The unit should first be pressurized with NITROGEN (inert gas) and leak checked What are the leak repair requirements for comfort cooling appliances and commercial appliances containing 50 pounds or more of refrigerant? - The leak rate exceeds 15% in comfort cooling appliances The leak rate exceeds 35% in all commercial and industrial process refrigeration Using large vacuum pumps can lead to freezing of water in the system. What are two ways the technician can help prevent freezing? - Increase pressure by introducing nitrogen to counteract freezing. Liquid charging of an R-12 refrigeration system should begin with vapor from a vacuum level to a pressure of approximately 33 psig followed by a liquid charge through the liquid-line service valve. Foaming at start-up may be found in what component? What does this mean? - Refrigerant in the oil will cause oil foaming in the compressor at start-up