Published on October 29, 2018
1. 1 Chapter: 1 Fundamentals of Refrigeration And Introduction to Thermodynamic 1 Fundamentals of Refrigeration And Introduction to Thermodynamic Fundamentals of Thermodynamic Understand the General Refrigeration Safety Tools and Procedures and Rules in Trade Areas Types of Strength of Metals Definition of Refrigeration The term “Refrigeration” may be defined as the process of removing heat from a substance under controlled conditions. It also includes the process of reducing and maintaining temperature of a body under below the general temperature of its surroundings. In other words, the refrigeration means a continued extraction of heat from a body whose temperature is already below the temperature of its surroundings. SI Units (International System of Units) In this system of units, there are seven fundamentals units and two supplementary units, which cover entire field of science and engineering. There are some derived units which will be commonly used.
2. 2 Photo- Refrigeration and Air conditioning- RS Khurmi Thermodynamic System The thermodynamic system (or simply known as “system”) may be broadly defined as a “definite area” or “space” where some thermodynamic process takes place. A thermodynamic system has its boundaries and anything outside the boundaries is called its surrounding (Fig. 1.1).
3. 3 Thermodynamic system may be classified into three groups- 1. Closed System; 2. Open System; 3. Isolated System. 1. Closed system- This is a system of fixed mass and identity whose boundaries are determined by space of matter (working substance) occupied in it (Fig. 1.2). 2. Open system- In the open system, the mass of working substance crosses the boundary of system (Fig. 1.3).
4. 4 3. Isolated system- A system is completely uninfluenced by surrounding called is an isolated system. Temperature The temperature of a body is measured with the help of an instrument known as thermometer which is in a form of glass tube containing mercury in its stem. Following are the two commonly used scales to measure the temperature- 1. Celsius or Centigrade scale Freezing point of water on scale is marked as zero and boiling point of water is marked as 100. The space between these two points has 100 equal divisions and each division represents one degree Celsius (1°C).
5. 5 2. Fahrenheit scale In this scale, freezing point of water on scale is marked as 32 and boiling point of water is marked as 212. The space between these two points has 180 equal divisions and each division represents one-degree Fahrenheit (1°F). Note. - Relation between Celsius scale and Fahrenheit scale. C = F – 32 100 180
6. 6 Kelvin The Kelvin, commonly called the degree Kelvin (o K). One kelvin is formally defined as 1/273.16 of the thermodynamic temperature of the triple point of pure water (H2O). A temperature of 0 K represents absolute zero, the absence of all heat. Rankine Rankine scale same works as Fahrenheit scale on which the freezing point of water 491.67 ° and the boiling point is 671.67°. Temperature Conversion Formula Degree Celsius (°C) (°F - 32) x 5/9 (K - 273.15) Degree Fahrenheit (°F) (°C x 9/5) + 32 (1.8 x K) - 459.67 Kelvin (K) (°C + 273.15) (°F + 459.67) ÷ 1.8 Some Useful Engineering Definitions and Units Pressure: Force exerted per unit area is called pressure. Pressure is defined as: P = F/A Where P = Pressure in Pascals (Pa) 1 Pascal = 1N/ m2 F = Force in N A = Area in m2 1 Bar = 105 Pa = 1.02 kgf/cm2 = 14.5 lbf/sq. in. 1 psig = 6894 Pa = 0.068 Bar At sea level, atmosphere exerts a force of 101325 N on one square meter area. 1 Atm. pressure = 101325 N/m = 1.01325 Bar = 1.033 kg f/m2 = 14.896 lbf/sq. in.
7. 7 Work or Energy: Force applied to a body to move it to a distance is called work. Work = Force × Distance Unit of work or energy in S.I. units is Nm or Joule (J). i.e. 1 Nm = 1 J If a force of 1N moves a body by 1m, it is called work of 1J or 1 Nm is done. In M.K.S. Work/energy = kgf m In case of heat energy in MKS, it is called k cal. Conversion of heat energy into work is by mech equivalent of heat (J). 1 k cal = 427 Kgf m In F.P.S., unit of heat is British Thermal Unit (BTU)) 1 k cal = 4.19 kJ = 3.968 BTU Power: Rate of doing work is called power. Unit of power in S.I. is Watts (W). 1 Watt = 1 J/s Electrical unit of work is also Watt i.e. 1 Watt = 1 amp × 1 volt = 1J/sec. In F.P.S. System, unit of power is Horse Power (H.P. imperial). 1 H.P. (Imperial) = 550 Ft lb/s = 746 J/s = 746 W In M.K.S. System, unit of power is H.P. (metric) 1 H.P. (metric) = 75 Kgf m/s = 736 J/s = 736 W 5.Unit of energy or work can also be derived from power W = J/sec ∴ J = W × sec Now, kWh is the unit of work 1 kWh = 3600 kJ. Common Conversion Factors: 1 k cal = 3.968 BTU = 4.187 kJ 1 kJ = 0.239 k cal 1 kJ = 0.948 BTU
8. 8 1 BTU = 0.252 k cal 1 BTU = 1.055 kJ 1 k cal/h = 1.163 W 1 kW/h = 3.968 BTU/h 1 H.P. (imperial) = 642 k cal/h (H.P. normally refers to H.P. imperial. Unless specified as H.P. metric). 1 H.P. = 2546.4 BTU/h Heat Flux 1 k cal/hm2 = 1.163 W/m2 = 0.3687 BTU/h ft2. Gauge pressure and Absolute Pressure All the pressure gauges read the difference between the actual pressure in system and atmospheric pressure(P0). The reading of pressure gauge is known as gauge pressure(Pg), while the actual pressure is called absolute pressure(P). Mathematically, P= P0 + Pg The negative gauge pressure is known as Vacuum Pressure. Photo- Refrigeration and Air conditioning- RS Khurmi Absolute Pressure = Gauge Pressure + Atmospheric Pressure Vacuum Pressure = Atmospheric Pressure- Absolute Pressure
9. 9 Gauge pressure is measured as PSIG (Pound/square inch gauge). Note: Atmospheric Pressure = 14.7 psi (The absolute air pressure at sea level is about 14.7 psi.) The unit of pressure in the SI system is the pascal (Pa), defined as a force of one Newton per square meter Heat The heat is defined as the transfer of energy without transfer of mass across the boundary of system because of the temperature difference between the system and surrounding. It is represented by Q and unit is Joule. They can be transferred in three distinct ways i.e., conduction, convection and radiation. The heat transferred through solid called conduction, while the heat transferred through fluid called convection. The radiation is an electromagnetic wave phenomenon in which energy can be transported through the electromagnetic waves. Gauge Pressure = Absolute Pressure - Atmospheric Pressure PSIG (Gauge Pressure) = PSI (Absolute Pressure) - Atmospheric Pressure (14.7 PSI)
10. 10 Sensible heat When a substance is heated and temperature rises as the heat is added, the increase in heat is called sensible heat. Similarly, when the heat is removed and temperature falls, the heat removed (subtracted) is called sensible heat. Latent Heat All pure substances are able to change their states. Solid become liquids and liquids become gas. These changes of state occur at same temperature and pressure combination for any given substance. It takes the addition of heat or removal of heat to produce these changes. The heat which brings about a change of state with no changes in temperature is called is called Latent (hidden) heat. Specific heat The specific heat of a substance may be broadly defined as the amount of heat required to raise the temperature of a unit mass of any substance through one degree. Photo- Refrigeration and Air conditioning- RS Khurmi
11. 11 Law of Perfect Gases A perfect gas (or an ideal gas) may be defined as a state of substance whose evaporation from its liquid state is complete and strictly obey the all the gas law under all condition of temperature and pressure. Boyle’s law This law was formulated by Robert Boyles in 1662. It states “The absolute pressure of a given mass of a perfect gas varies inversely as its volume, when the temperature remains constant.” Mathematically, P ∝ 1 or v Charles’ Law This law was formulated by Frenchman Jacques AC Charles in 1787. It states (1) “The volume of a given mass of a perfect gas varies directly as its absolute temperature, when the absolute pressure remains constant.” v ∝ T or v = constant T So, (2) “All the perfect gases change in volume by 1/273th of its original volume at 0° C for every 1° change in temperature, when the pressure remains constant.” pv1 = pv2= pv3 = constant v1 = v2 = constant T1 T2 pv = constant
12. 12 Pressure Temperature chart During the repairing of refrigerators, air conditioners and other machines that contain refrigerant gas, we use pressure temperature chart (PT chart). PT chart show the relationship between pressure and temperature for the given refrigerant. By changing the pressure of refrigerant, we can set its temperature to a given level. How to read a PT chart 1. Turn unit on; monitor system running approx. 15 to 30 minutes. Take a reading of your refrigerant system pressure at suction line (psig). 2. Find the corresponding saturated pressure for your refrigerant. Saturation Saturated liquid- When the temperature of a fluid is raised to the saturated temperature, that is, any additional heat applies to the liquid will cause a part of the liquid to vaporize, the liquid is said to be saturated. That liquid is called saturated liquid while the process is called Saturation. Saturated vapor- When the temperature of a vapor is decreased to the saturation temperature, that is any further cooling of the vapor will cause a portion of vapor to the condense, the vapor said to be saturated. Such a vapor called a “saturated vapor”. A saturated vapor may be described also as a vapor ensuring from the vaporizing liquid as long as temperature and pressure of the vapor are the same as those of saturated liquid from which it comes. Superheat Superheated vapor- When the temperature of a vapor is so increased above the saturation temperature, the vapor is said to be superheated and is called a “superheated vapor”. In order to superheat it is necessary to separate the vapor from vaporizing liquid. As long as the vapor remains in contact with liquid it will be saturated. This is because any heat added to liquid-vapor mixture will merely vaporize more liquid and no superheating will occur. Sub cooling Sub-Cooled liquid -If after condensation, a liquid is cooled so that its temperature is reduced below the saturation temperature the liquid is said to be “sub-cooled”. A liquid at any temperature and above the melting temperature is a sub-cooled liquid.
13. 13 Heat Load The rate at which the heat must be removed from the refrigerated space or material in order to produce and maintain desired temperature condition is called the heat load. In most refrigerating applications, the total heat load on the refrigerating equipment is the sum of the heat that leaks into the refrigerated space through the insulated walls, the heat that enters the space through door opening and the heat that must be removed from the refrigerated product in order to reduce the temperature of product to the space or storage conditions. Heat given off by the people working in the refrigerated space and by motors, light and other electrical equipment’s also contributes the load on the refrigerated equipment.
14. 14 Four factor Affecting Comfort Air Temperature When you talk about the weather, what’s the first factor you define? temperature. “It’s hot out.” “It’s cool and cloudy.” But temperature isn’t inherently stable. A room with the perfect temperature is in a constant struggle with external factors. Sunlight coming through a window adds heat. A draft coming in under the door lets heat escape. Even your own body can affect the temperature in a room. (The average human generates as much heat as a 100-watt light bulb). So, a comfortable temperature isn’t just about getting there, it’s about maintaining. It’s by far the most influential to your comfort. And it’s the only factor that most conventional thermostats let you control.
15. 15 Humidity It’s not the heat, it's… yes, and it’s the humidity, which can have a huge impact on how your room feels. Second only to temperature in its ability to affect comfort, humidity does more than most people realize. Humidity is made up of tiny water droplets in the air. And while these droplets are incredibly small, they can still prevent your body’s natural cooling response – sweating – from being nearly as effective. After all, moisture from your skin can’t evaporate (taking heat with it) if it has no place to go. Humid air also feels heavier and stickier, both of which add to the discomfort you feel on a hot day. In fact, humidity can affect the “felt temperature” by as much as 8 degrees, even if the actual temperature doesn’t change at all. Air quality A room with dirty air doesn’t feel as good. Airborne impurities can irritate eyes, noses and lungs, and create odors that make any space uncomfortable. There are three main offenders when it comes to air quality: Particles - made up of dust, dirt, pet dander and allergens, such as pollen Mold, Mildew and Germs - the tiny organisms floating in your air that thrive in damp environments and greatly exacerbate allergies and asthma. Chemical Vapors and Odors - generated by cleaning products, paint, adhesives and other chemicals found in nearly every home Filtration can take care of some of these pollutants, however, a UV germicidal light can add an extra layer of protection for the cleanliness, and comfort, of your air.
16. 16 Control Obviously, if humidity, temperature and air quality can change the way your environment feels, the ability to control those three factors is pretty important. Having the right home heating and air-conditioning system, controlled by the proper thermostat, will let you create and preserve your perfect indoor space. Conventional thermostats let you control the temperature, and that’s a good start.
17. 17 A. Refrigeration Tools 1. Tube Cutter- A tube cutter is a type of tool used by technician to cut copper pipe. Besides producing a clean cut, the tool is often a faster, cleaner, and more convenient way of cutting pipe than using a hacksaw, although this depends on the metal of the pipe. 2. Flaring Tool- Flaring tool is to make flares at end of copper tube as could be easily fit in the flare nut without any leakage of refrigerant. 3. Swaging Tool Swaging is the process to increase the diameter of any copper pipe with the help of swaging tool. Swaging tool is often called punching tool also. 4. Bending Tool- Bending tool is used for make different types of bend in copper pipes as the requirement of side position. We can use bending machine as well as spring to make bend in copper pipes.
18. 18 5. Pinch off Tool Pinch off tool is used to pinch off service line or any other copper line in order to make the sealed system. 6. Gauge Manifold Manifold gauge is often used to measure the gas vapor or liquid pressure or vacuum pressure inside the system.
19. 19 7. Vacuum Pump The purpose of a vacuum pump is to remove the undesirable materials that create pressure in a refrigeration system such as moisture, dust and dirt inside the coil. These include: • Moisture • Air (oxygen) • Hydrochloric acid
20. 20 8. Refrigerant Recycling Station Laws governing the release of chlorofluorocarbon refrigerants (CFCs) into the atmosphere have resulted in the development of procedures to recover, recycle, and reuse these refrigerants. Removing refrigerant from a system in any condition and storing it in an external container is called "recovery." The process of cleaning refrigerant for reuse by oil separation and single or multiple passes through filter-driers which reduce moisture, acidity, and matter is called "recycling." 9. Electronic leak detector Electronic leak detector equipment’s are the equipment which detects the leakage of gas by halogen leak detector method in halogen leak detector is work on the concept of halogen gas (Inert Gas) method.
21. 21 10. Thermometer A thermometer is a device that measures temperature or a temperature gradient. A thermometer has two important elements: (1) A temperature sensor (e.g. the bulb of a mercury-in-glass thermometer or the digital sensor in an infrared thermometer) in which some change occurs with a change in temperature, and (2) Some means of converting this change into a numerical value (e.g. the visible scale that is marked on a mercury-in-glass thermometer or the digital readout on an infrared model). Thermometers are widely used in industry to monitor processes, in meteorology, in medicine, and in scientific research. 11. Fin Comb Fin comb or fin straightener are used to straight the fins as it can make the proper rotation of cooling air through the fins. 12. Hermetic Tubing Piercing Valve Hermetic tubing Piercing Valve is often used for a non-soldier piercing valve that works very well. Simply follow the enclosed instructions. The only tip I would give would be to tighten the screws until they are very firm to prevent leaks.
22. 22 13. Compressor Oil Charging Pump Whenever it is impossible to drain oil in the conventional manner, it becomes necessary to hook up a pump. Removing oil from refrigeration compressors before dehydrating with a vacuum is a necessity. The pump shown in Fig. has the ability to remove one quart of oil with about 10 strokes. It is designed for use in pumping oil from refrigeration compressors, marine engines, and other equipment. 15. Air velocity meter Air Velocity Meters measure air velocity and temperature, calculate flow rate and perform statistical calculations. Some models also measure humidity and perform dew point and wet bulb temperature calculations. 16. Volt-ohm meter A VOM (volt-ohm-millimeter), is also known as a multi-meter or a multi-tester, it is an electronic measuring instrument that combines several measurement functions in one unit. A typical VOM can measure voltage, current, and resistance. Analog VOM use a micro- ammeter with a moving pointer to display readings. Digital VOM (DMM, DVOM) have a numeric display, and may also show a graphical bar representing the measured value.
23. 23 17. AC Clamp on meter AC clamp meter are widely used to measure the ampere, voltage and resistance and also to check diode and continuity on different sets. 18. U-Tube manometer It is one of the earliest pressure measuring instruments is still in wide use today because of its inherent accuracy and simplicity of operation. U-tube manometer, which is a U-shaped glass tube partially filled with liquid. This manometer has no moving parts and requires no calibration. Manometry measurements are functions of gravity and the liquid's density, both physical properties and it is used to measure absolute pressure. The fundamental relationship for pressure expressed by a liquid column is: Δp = P2-P1 = ρgh
24. 24 where: Δp = differential pressure P1= pressure at the low-pressure connection P2= pressure at the high-pressure connection ρ = density of the indicating fluid (at a specific temperature) g = acceleration of gravity (at a specific latitude and elevation) h = difference in column heights 20. Refrigerant Charging Hose Refrigerant charging hose are used when the system needs gas charging, vacuuming and nitrogen pressure holding. These refrigerant charging hoses are designed with a special material for bearing high pressure.
25. 25 21. Ratchet Wrench Ratchet wrench are used to general operation of machine, these are reversible type wrench. 22. Pin Valve Pin valve or service valve is used for gas charging or vacuuming of refrigeration system. Pin valve allows the refrigerant to enter in the system and make it enclosed within the system.
26. 26 Chapter: 2 Introduction to Strength of Material STRENGTH Strength is the ability of the structure to resist the influence of the external forces acting upon it. 1. TENSILE STRENGTH The tensile strength of a material is the maximum amount of tensile stress that it can take before failure, such as breaking or permanent deformation. Tensile strength specifies the point when a material goes from elastic to plastic deformation. 2. COMPRESSIVE STRENGTH Compressive strength is the maximum compressive stress that, under a gradually applied load, a given solid material can sustain without fracture. 3. SHEAR STRENGTH Shear strength is a material's ability to resist forces that can cause the internal structure of the material to slide against it. Adhesives tend to have high shear strength.
27. 27 4. BENDING STRENGTH Flexural strength is a measure of the tensile strength of concrete beams or slabs. Flexural strength identifies the amount of stress and force an unreinforced concrete slab, beam or other structure can withstand such that it resists any bending failures. Flexural strength is also known as bend strength or modulus of rupture or fracture strength. Elastic and Plastic behavior All materials deform when subjected to an external load. Up to a certain load the material will recover its original. Dimensions when the load is released. This is known as elastic behavior. The load up to which the material remains elastic is the elastic limit. The deformation or strain produced within the elastic limit is proportional to the load or stress. This is known as Hook’s Law Stress Strain or Stress = E*Strain. E is known as the Elastic Modulus. When the load exceeds the elastic limit, the deformation produced is permanent. This is called plastic deformation. Hook’s law is no longer valid in the plastic region.
28. 28 Chapter: 3 Basic Refrigeration System and Applications 2 Basic Refrigeration Systems & Practice Refrigeration Processes and Components of Domestic Freezers, Water Coolers and Ice Cream Machines Refrigeration A refrigeration system moves heat from a space, fluid or material for the purpose of lowering its temperature. In the past, this was done by collecting ice in the winter and using its specific heat to cool as the ice melted. When 1 pound of ice melts, it absorbs 144 Btu, as latent energy. When 1-ton (2000 lbs) melts over a 24-hour period: Q = 2000 lbs × 144 Btu/lb/24 hrs = 12,000 Btu/h This is the definition of 1 ton of refrigeration.
30. 30 Components of Refrigeration System There are four main parts of refrigerating and air-conditioning systems, these are: compressor, condenser, throttling or expansion valve and the evaporator. The refrigerant leaving the compressor is in the gaseous state and at a high pressure and temperature. This refrigerant then enters the condenser where it loses the heat to the coolant, which can be air or water. Evaporator An evaporator coils inside the refrigerator allow the refrigerant to absorb heat, making the refrigerator cabinet cold. Types of Evaporators The evaporators can be classified in various ways depending on the construction of the evaporator, the method of feeding the refrigerant, the direction of circulation of the air around the evaporator, etc. Here we have classified the evaporators based on their construction. 1) Bare Tube Evaporators The bare tube evaporators are made up of copper tubing or steel pipes. The copper tubing is used for small evaporators, while the steel pipes are used with the large evaporators where ammonia is used as the refrigerant. The bare tube evaporator comprises of several turns of the tubing, though most commonly flat zigzag and oval trombone are the most common shapes. The bare tube evaporators are usually used for liquid chilling. 2) Plate Type of Evaporators In the plate type of evaporators, the coil usually made up of copper or aluminum is embedded in the plate so as so to form a flat looking surface. Externally the plate type of evaporator looks like a single plate, but inside it there are several turns of the metal tubing through which the refrigerant flows. 3) Finned Evaporators The finned evaporators are the bare tube type of evaporators covered with the fins. When the fluid (air or water) to be chilled flows over the bare tube evaporator lots of cooling effect from
31. 31 the refrigerant goes wasted since there is less contact of surface for the transfer of heat from the fluid to the refrigerant. 4) Shell and Tube types of Evaporators The shell and tube types of evaporators are used in the large refrigeration and central air conditioning systems. The evaporators in these systems are commonly known as the chillers. The chillers comprise of large number of the tubes that are inserted inside the drum or the shell. Depending on the direction of the flow of the refrigerant in the shell and tube type of chillers, they are classified into two types: dry expansion type and flooded type of chillers. In dry expansion chillers the refrigerant flows along the tube side and the fluid to be chilled flows along the shell side. The flow of the refrigerant to these chillers is controlled by the expansion valve. In case of the flooded type of evaporators the refrigerant flows along the shell side and fluid to be chilled flows along the tube. In these chillers the level of the refrigerant is kept constant by the float valve that acts as the expansion valve also. 5) Natural Draught Evaporator Natural draught or ribbed-tube evaporator are used because cold air is denser than warm air, he falls without the help of a blower. Warm air rises up to take his place. Thus, this type of coil is mounted vertically on a high wall, or horizontally just below the ceiling space, it cools. Since the flow of air through natural draught, coils easily interfered with, the fins are far from each other and the number of coil line, as a rule, is limited to three or less. Evaporators are set such that they cover most of the length of the space cooling. This type of evaporator is typically used in refrigerated display cases, florist boxes.
32. 32 Compressor Compressors are mechanical devices that compress gases. It is widely used in industries and has various applications. Compressors have many everyday uses, such as in: Air conditioners (car, home) Home and industrial refrigeration Hydraulic compressors for industrial machines Air compressors for industrial manufacturing Condenser The condenser helps in rejection of heat to the surroundings. In the condenser, the refrigerant cools down and is condensed to liquid. There are three main types of condensers: 1) Air cooled condensers: Air cooled condensers are used in small units like household refrigerators, deep freezers, water coolers, window air-conditioners, split air-conditioners, small packaged air-conditioners etc. These are used in plants where the cooling load is small and the total quantity of the refrigerant in the refrigeration cycle is small. Air cooled condensers are also called coil condensers as they are usually made of copper or aluminum coil. Air cooled condensers occupy a comparatively larger space than water cooled condensers. Air cooled condensers are of two types: natural convection and forced convection. In the natural convection type, the air flows over it in natural a way depending upon the temperature of the condenser coil. In the forced air type, a fan operated by a motor blows air over the condenser coil. 2) Water cooled condensers: Water cooled condensers are used for large refrigerating plants, big packaged air-conditioners, central air-conditioning plants, etc. These are used in plants where cooling loads are excessively high and a large quantity of refrigerant flows through the condenser. There are three types of water cooled condensers: tube-in-tube or double pipe type, shell and coil type and shell and tube type. In all these condensers the refrigerant flows through one side of the piping while the water flows through the other piping, cooling the refrigerant and condensing it. 3) Evaporative condensers: Evaporative condensers are usually used in ice plants. They are a combination of water cooled and air-cooled condensers. In these 0condensers the hot refrigerant flows through the coils. Water is sprayed over these coils. At the same time the fan draws air from the bottom side of the condenser and discharges it from the top side of the condenser. The spray water that comes in contact with the condenser coil gets evaporated in the air and it absorbs the heat from the condenser, cools the refrigerant and condenses it. Evaporative condensers have the benefits of water cooled as well as air cooled condenser, hence it occupies less space. However, keeping the evaporative condenser clean and free of scale is very difficult and requires lots of maintenance.
33. 33 Metering Device As the liquid refrigerant enters the metering device it changes temperature, pressure and its phase. A partial amount of the liquid refrigerant flashes into a refrigerant gas or vapor. The refrigerant does this as it leaves the metering device and enters the evaporator coil. Metering devices are further classified as in two groups 1. Copper Capillary Tube Copper capillary tube is often considered as a metering device. A capillary is a very small aperture tube (small opening) which allows the liquid refrigerant under high pressure to expand by entering into the low-pressure zone (evaporator); it is generally used in air conditioner, refrigerator and freezer. 2. Thermal Expansion Valve A thermal expansion valve is a component in refrigeration and air conditioning systems that controls the amount of refrigerant released into the evaporator thereby controlling superheat. Thermal expansion valves are often referred to generically as "metering devices" and generally used in cold room, refrigerated van and marine refrigeration. Copper Accumulators Copper Accumulators hold unused system charge to prevent liquid slugging of the compressor and excessive refrigerant dilution of the compressor oil. “Copper accumulators are widely used for liquid storage, liquid/gas separation, impurity filtration, noise reduction and refrigerant cushion.” It is always installed at evaporator side.
34. 34 Filter/Drier- It is always installed at condenser side & it absorbs and retain residual moisture in system.
35. 35 Defrost & Automatic Defrost When the air flow is too slow either has completely halted across the cooling coil or the refrigerant is not being metered properly into the cooling coil, (too little is being released) then there is an ice formation on the evaporator coils which affects the cooling performance of the system. Defrost is a process to remove ice from evaporator coil through the defrost heater. Automatic Defrost is a process in a refrigerator heats the cooling element (evaporator coil) for a short period of time and melts the frost that has formed on it. Wiring and Control Please refer some electrical wiring diagram for Split air conditioner Fig. Panasonic Split AC electrical wiring Diagram
36. 36 Fig. Manufacturer’s Electrical Wiring Diagram
37. 37 Compressor Controls- Capacitor Single-phase compressors require a technician to have a proficient understanding of capacitors. The run capacitor is one of two types of capacitors that could be found on single-phase compressors. Run Capacitor The run capacitor is used to improve the running efficiency of a compressor’s motor. The run capacitor is placed in series with the start winding of the compressor and will remain in the circuit as the motor operates. As current flows through the run capacitor and the start winding, it causes a phase shift of the motor’s current, thus improving the power factor of the motor. Since the run capacitor remains in the circuit.
38. 38 Start Capacitor The start cap provides that electrical "push" to get the motor rotation started. It does this by creating a current to voltage lag in the separate start windings of the motor. Since this current build up slower, the armature has time to react to the rotating field as it builds up, and to begin rotating with the field. Once the motor is very close to its rated speed, a centrifugal switch disconnects the start cap and start windings from the circuit. Watching a single-phase motor starting you can see that this all happens very quickly. Starting Relay Potential or “voltage” relays are used with single-phase capacitor-start/capacitor-run motors, which need relatively high starting torque. Their main function is to assist in starting the motor. Potential starting relays consist of a high resistance coil and a set of normally closed contacts. The coil is wired between terminals 2 and 5, with the contacts between terminals 1 and 2. Terminals 4 and 6 is used for capacitors and/or condenser fan connections and has no electrical significance to the starting relay itself. In fact, terminals 4 and 6 are sometimes referred to as “dummy” terminals and are simply used for wire connections.
39. 39 Overload Protector An overload protector is an electrical device which we use for compressors protection, whenever the compressor temperature high from his range the compressor overload cut off the electric supply from compressor motor that's why we called him thermal overload. Contacts Compressor contactors are simply heavy-duty switches that allow it to carry extra amperage that is used by the compressor while it is running. The contactor is made up of a coil and typically two contacts for a double contactor and 1 for a single pole contactor.
40. 40 Compressor Start Circuit Compressor start circuits consist of a potential relay with normally closed contacts and start capacitor. When there is a malfunction of the start circuit, the start capacitor is usually destroyed. (Relief plug opens on top of capacitor.) The capacitor fails because it is an intermittent duty capacitor that should only be in the electrical circuit for a very brief moment. Causes of start circuit failure include low line voltage where the compressor pick up voltage is too low to energize the potential relay so the capacitor remains in the circuit for too long of a period of time.
41. 41 Function of accessories: Accessory Function Relay To disconnect start winding and / or start capacitor from circuit PTCR Same as relay but cost effective Start Capacitor To increase starting torque of motor Run Capacitor To increase running torque of motor and to improve power factor Overload Protector Protects compressor from over current and high temperature Procedure to checking Common, Run & Start terminals in motor circuit: - If in doubt, please follow the simple guides given below 1. Identify the correct compressor motor Terminals— 2. Run – Common (R– C) – Lowest resistance 3. Run – Start (R- S) – Highest resistance 4. Common – Start (C – S) – Intermediate resistance 5. Also, R S = C S + R C & C S is normally 3-4 times resistance of R C. 6. Show diagram of test result- 7.
42. 42 1. Effect of the wrong Capacitor on the compressor Higher MFD capacitor (THAN SPECIFIED) High current, high winding temperature, relay malfunction, Wiring burn out, Starting problem Higher MFD capacitor (THAN SPECIFIED) Low torque, relay malfunction, Wiring burn out, Starting problem Low voltage rating Capacitor Bursting 2. Effect of the wrong OLP on the compressor Oversized overload protector will not protect compressor. Undersized overload protector trips unnecessarily. 3. Effect of the wrong Relay on the compressor Start winding may stay in circuit for longer time leading to burn out Start capacitor may burst Relay contracts may get welded causing motor burn out 4. Effect of the wrong Relay on the compressor S-R Interchange condition There will not be any abnormality seen apparently at 230 V or above. Relay will chatter at 190 V or below. OLP will trip and cycle Star capacitor remains circuit for long time, it may burst Motor will burn 5. Electrical accessories Location in Motor circuit- MOTOR TYPE OVERLOAD PROTECTOR PTC STARTER CURRENT RELAY STRATING CAP. RUNNING CAP. RSIR YES YES RSCR YES YES YES CSIR YES YES YES YES CSCR YES YES YES YES 6. MOTOR TYPE RSIR Resistance Start Inductive Run This type is applied to compressors whose power is small and has low starting Torque. This type of motor is suitable for capillary systems where equilibrium pressure is achieved during starting. RSCR Resistance Start Capacitive Run This is similar to RSIR, but a Run Capacitor is connected to the PTC for higher efficiency. CSIR Capacitive Start Inductive Run
43. 43 This type of motor is suitable for capillary systems where equilibrium pressure is not achieved during starting. Medium and high range refrigerators & freezers where starting torque required is more use this type of motors. CSCR Capacitive Start Capacitive Run This is similar to CSIR model, but a run capacitor is connected for higher efficiency. Defrost Cycle, Light The defrost cycle in refrigeration is divided into medium- temperature and low-temperature ranges; the components that serve the defrost cycle are different. 1. Medium-Temperature Refrigeration The medium-temperature refrigeration coil normally operates below freezing and rises above freezing during the off cycle. The air temperature inside the box will always rise above the freezing point during the off cycle and can be used for the defrost. This is called off-cycle defrost and can be either random or planned. 2. Random or Off Cycle Defrost Random defrost will occur when the refrigeration system has enough reserve capacity to cool more than the load requirement. When the system has reserve capacity, it will be shut down from time to time by the thermostat, and the air in the cooler can defrost the ice from the coil. When the compressor is off, the evaporator fans will continue to run, and the air in the cooler will defrost the ice from the coil. When the refrigeration system does not have enough capacity or the refrigerated box has a constant load, there may not be enough off time to accomplish defrost. This is when it has to be planned. 3. Planned Defrost Planned defrost is accomplished by forcing the compressor to shut down for short periods of time so that the air in the cooler can defrost the ice from the coil. This is accomplished with a timer that can be programmed. Normally the timer stops the compressor during times that the refrigerated box is under the least amount of load. 4. Hot Gas Defrost The internal heat method of defrost normally uses the hot gas from the compressor. This hot gas can be introduced into the evaporator from the compressor discharge line to the inlet of the evaporator and allowed to flow until the evaporator is defrosted. Apportion of the energy used for hot gas defrost is available in the system. This makes it attractive from an energy- saving standpoint.
44. 44 Refrigerator Fan Motor This conversion is usually obtained through the generation of a magnetic field by means of a current flowing into one or more coils.
45. 45 Types of Electric Motor Further it can be categorized on the basis of propulsion of fan blades (size of Fan Blade): 1. Sirocco Fans Air is sucked in from one side and discharge in the rotating direction. The fans are completely enclosed in the fan housing. 2. Turbo Fans It is used for ceiling recessed cassette type of multi flow units. It sucks air from bottom and discharge to periphery. 3. Cross Flow Fans These are dedicated to wall-wall mounted type indoor units and have a long narrow structure. Air is sucked from one side a higher side resistance and discharged to other side lower resistance. 4. Propeller Fans The propeller fans are in most common use of outdoor units and called axial flow fans as well. Air is sucked in and discharge in the direction of rotary shaft. These types of fan provide a small static pressure, while enables the connection of simple ducts when outdoor units are installed in balcony.
46. 46 Refrigerator Servicing Refrigerator service mainly comprises the following steps- 1. Cleaning of Condensing coil. 2. Checking of door gasket. 3. Checking of voltage and current. 4. Checking of electrical wiring and components.
47. 47 5. Checking of cooling inside the cabinet. 6. Checking of thermostat. 7. Refrigerant charging if it is less.
48. 48 Chapter: 4 Copper Tube Handling and Evacuation Theory 3 Basic Refrigeration Systems & Practice Knowledge of refrigeration signs and symbols, diagrams and using them appropriately Know how to do the tubing, piping, system evacuation Refrigeration Signs and Symbols
50. 50 Purpose of Tubing The purpose behind the copper tubing is to provide smooth flow of refrigerant from indoor unit to outdoor unit. Copper tube is used widely as a means of conveyance of refrigerant in air conditioning and refrigeration. Copper is mostly used because of the following properties: Resistant to corrosion High level of heat transfer Easy Machinability and Consumption of less refrigerant Copper can handle bigger pressure differences Types of Copper Tube Types K, L, M, DWV and Medical Gas tube are designated by standard sizes, with the actual outside diameter always 1/8-inch larger than the standard size designation. Each type represents a series of sizes with different wall thicknesses. Type K tube has thicker walls than Type L tube, and Type L walls are thicker than Type M, for any given diameter. All inside diameters depend on tube size and wall thickness. Copper tube for refrigeration and air- conditioning field service (RAC) is designated by actual outside diameter. "Temper" describes the strength and hardness of the tube. Tube in the soft temper can be joined by the same techniques and is also commonly joined by the use of flare-type and compression fittings. It is also possible to expand the end of one tube so that it can be joined to another by soldering or brazing without a capillary fitting—a procedure that can be efficient. Tube in both the hard and soft tempers can also be joined by a variety of "mechanical" joints that can be assembled without the use of the heat source required for soldering and brazing. Tube Properties The dimensions and other physical characteristics of Types K, L, M and DWV tube are given in Tables. Advantages of Copper Tube Strong, long lasting, copper tube is the leading choice of modern contractors for plumbing, heating and cooling installations in all kinds of residential and commercial buildings. The primary reasons for this are: 1. Copper is economical. 2. Copper is lightweight. 3. Copper is formable. 4. Copper is easy to join. 5. Copper is safe. 6. Copper is dependable. 7. Copper is long-lasting. 8. Copper is 100% recyclable.
51. 51 Pressure System Sizing Designing a copper tube water supply system is a matter of determining the minimum tube size for each part of the total system by balancing the interrelationships of six primary design considerations: 1. Available main pressure; 2. Pressure required at individual fixtures; 3. Static pressure losses due to height; 4. Water demand (gallons per minute) in the total system and in each of its parts; 5. Pressure losses due to the friction of water flow in the system; 6. Velocity limitations based on noise and erosion. Types & Sizes of Copper Tube Nominal Pipe Size inches O.D. I.D. Wall Thickness Type K* L** M*** DWV**** K L M DWV ¼ 0.375 0.305 0.315 - - 0.035 0.030 - - 3/8 0.500 0.402 0.430 0.450 - 0.049 0.035 0.025 - ½ 0.625 0.527 0.545 0.569 - 0.049 0.040 0.028 - 5/8 0.750 0.652 0.666 - - 0.049 0.042 - -
52. 52 ¾ 0.875 0.745 0.785 0.811 - 0.065 0.045 0.032 - 1 1.125 0.995 1.025 1.055 - 0.065 0.050 0.035 - 1-1/4 1.375 1.245 1.265 1.291 1.295 0.065 0.055 0.042 0.040 1-1/2 1.625 1.481 1.505 1.527 1.541 0.072 0.060 0.049 0.042 2 2.125 1.959 1.985 2.009 2.041 0.083 0.070 0.058 0.042 2-1/2 2.625 2.435 2.465 2.495 - 0.095 0.080 0.065 - 3 3.125 2.907 2.945 2.981 3.030 0.109 0.090 0.072 0.045 3.5 3.625 3.385 3.425 3.459 - .120 .100 .083 - 4 4.125 3.857 3.897 3.935 4.009 .134 .114 .095 .058 5 5.125 4.805 4.875 4.907 4.981 .160 .125 .109 .072
53. 53 6 6.125 5.741 5.845 5.881 5.959 .192 .140 .122 .083 8 8.125 7.583 7.725 7.785 - .271 .200 .170 - *K, thick walled, underground residential, commercial and industrial uses. **L, medium walled, residential and commercial uses ***M, thin walled, above ground residential and light commercial uses. ****DWV, Drain/Waste/Vent, non-pressurized Copper Tube Insulation Copper tube insulation is a type of isothermal material which prevents loss of cooling or gain of heating to copper tube and external tear and wear of copper tube. ProcedureofPipeCuttingUsingCutter A pipe / tube cutter is best option to make a straight cut for copper pipes. It comes in single blade and an adjustable lever to provide the proper force while cutting. Prior to the work, wear safety shoes, gloves and goggles. Prepare copper tube, tube cutter, reamer, sand cloth, brush and hacksaw. Make measurements to the desired length of the pipe. Mark the pipe where cutting is to be done.
54. 54 Insert the copper pipe inside the cutting tool. Hold the pipe properly to produce a good result. Adjust the lever until the blade touches the pipe. Using a counter clockwise direction, move the pipe cutter by one whole turn until you feel that the blade is starting to cut the pipe. After that, reverse it by clockwise rotation. While on clockwise turning, adjust the lever from time to time until the pipe is completely cut By using a reamer, remove the burrs from the inside of the tube. The burrs must be removed because they restrict the flow of the gas. Clean the tube by sand cloth and by brush. PIPECUTTINGUSINGAHACKSAW Priortothework,makesurethatallPPE’sareavailableandisbeingused.PPE’slikesafetyshoesandgogglesshouldbe used. Make measurements to the desired length of the pipe. Mark the pipe where cutting is to be done. Make the cut at a 90 Degree angle to the tubing. A fixture may be used to ensure an accurate cut. After cutting, ream the tubing and file the end. Remove all the chips and fillings, making sure that no debris or metal particles get into the tubing.
55. 55 Tube Bending Several types of tubing benders are available for making accurate bends in tubing without causing flats, kinks, or dents. Procedure to Make Bends Using Spring benders Spring benders provide an efficient, low-cost method to bend soft copper tubing. Spring benders are available in a variety of sizes to fit tubing from 1/4″ OD to 3/4″ OD. Mark the area of bend with the help of measuring tape. First slip the spring over the tubing to completely cover the area of the bend. Make the desire bend. After each bend is made, let spring to slid along the tubing to the next section to be bent.
56. 56 Push the spring; do not pull, on the spring to remove it from the tubing. Pulling can permanently separate the spring coils, making the bender unfit for further use. Very little practice is needed to accomplish proper bends in smaller tubing with a spring bender. Procedure to Make Bends Using Bending Machine Always read the instructions for the bending machine before using it. Make sure that the correctly sized former and bending roller are fitted to the machine; one size of former/roller will only bend one size of pipe. Place the pipe in the machine, remember that the pipe is secured at one end, so carefully measure from the center of the former so that the bend is formed in the required position of the pipe. Use the lever handle of the machine to apply roller pressure to the pipe and form the pipe around the former. Move the lever smoothly until the required bend is achieved.
57. 57 The pipe will tend to spring back a certain amount when the pressure is released but be carefully of over bending as this is not always easy to recover it. Release the pipe from the machine. Swaging Techniques Swaging involves enlarging the diameter of one end of a length of soft copper tubing so the end of another length can be slipped into it. The connection is then soldered or brazed to make a strong, leak proof joint. Swaging is the preferred method of joining soft tubing since the process requires little time, and only one brazed joint is needed to complete the connection (compared to two joints for a fitting). Swaging method Swaged connections can be made using either the punch-type joint method or the screw-type joint method. Both punch- and screw-type joints require the use of special hand tools. Procedure to Enlarge the Diameter Using Punch-type swage Clamp the tube into a special tool called a flaring block. Accomplish the enlarging process by pressing swaging tool. Ensure that the depth of the finished swage is equal to the original tubing diameter. For example, 1/4″ tubing is swaged 1/4″ deep, and 1/2″ tubing is swaged 1/2″ deep.
58. 58 Swaging punches are available in diameters ranging from 3/16″ to 7/8″. Making Flare Joint Flaring copper tubing is a process of expanding or spreading the end of the tube into a funnel shape with a 45° angle. All refrigeration flare fittings are made with a 45° angle so the tubing will fit snugly against the fitting. A flare nut is used to compress the flare against the fitting to obtain a tight, leak proof, metal-to-metal contact. Refrigeration tubing connections must withstand at least 300 psi (pounds per square inch) of pressure without leaking. Because the flare connection is a mechanical, metal-to-metal contact without gaskets, it is vital that proper attention and care be given to making the flares. Procedure to Enlarge the Diameter Using Punch-type swage First of all, ream the tubing end properly with help of file and sand. Because burrs or rough edges will interfere with the smooth metal-to-metal contact and permit leakage.
59. 59 Don’t forget to insert a flare nut before flaring the cooper tube. Clamp the tube in a flaring block with its end protruding slightly above the chamfer (beveled edge) on the block’s top side.
60. 60 Now, a screw-type yoke with a special flaring adapter is then clamped onto the block and automatically centered above the tube. Turning the screw will force the cone-shaped adapter into the tubing end, spreading it until it is formed to a 45° angle against the chamfer.
61. 61 Connect to the fitting. Hold the flared end on the fitting and tighten the nut. Make it snug, but don’t over-tighten. Flare Defects Extending the tubing too high above the chamfer will result in a flare that is too wide. This prevents the nut from sliding over the flare. If the tubing is too low in the chamfer, the result is a small flare that can pull free from the flare nut. A properly made flare will almost fill the bottom of the flare nut without binding or rubbing the threads.
62. 62 Making a Double Thickness Flare A double thickness flare provides more strength at the flare end of tube. This is a two-step operation. Either a punch or block or combination of flaring tool is used with Adapter. Adapter tends to make double flare. The Oxy-Acetylene Process The oxyacetylene process produces a high temperature flame, over 3000 degrees C, by the combustion of pure oxygen and acetylene. Safe Storage
63. 63 Safe practice and accident avoidance Store the cylinders in a well-ventilated area, preferably in the open air The storage area should be well away from sources of heat, sparks and fire risk Safe practice and accident avoidance Cylinders are very heavy and must be securely fastened at all times Cylinder valves or valve guards should never be loosened Backfire or flashback Procedure After an un-sustained backfire in which the flame is extinguished: Close the blowpipe control valves (fuel gas first) Check the nozzle is tight Check the pressures on regulators Re-light the torch using the recommended procedure If the flame continues to burn: Close the oxygen valve at the torch (to prevent internal burning) Close the acetylene valve at the torch close cylinder valves or gas supply point isolation valves for both oxygen and acetylene Open both torch valves to vent the pressure in the equipment Close torch valves Check nozzle tightness and pressures on regulators Re-light the torch using the recommended procedure If a flashback occurs in the hose and equipment, or fire in the hose, regulator connections or gas supply outlet points: Isolate oxygen and fuel gas supplies at the cylinder valves or gas supply outlet points (only if this can be done safely) If no risk of personal injury, control fire using first aid fire-fighting equipment If the fire cannot be put out at once, call emergency fire services After the equipment has cooled, examine the equipment and replace defective components Set up Oxy-Acetylene Welding Equipment for Soldering and Brazing Process Step-by-Step Instructions: 1. Equipment assembly: Ensure that the equipment is assembled correctly as in figure. 2. Check equipment: First, make sure that the gas flow from both the oxygen and the acetylene cylinders is turned off tightly. The two cylinders are secured in an upright position. This is usually on a wheeled trolley. Look at the hose pressure and cylinder pressure gauges on top of each cylinder. Both gauges on each cylinder should read zero. If both gauges do not read zero, turn the main cylinder valve on the top of the cylinder clockwise, to close it completely. Then you must purge the system of any gas. 3. Purge the system: To purge the system, make sure the main cylinder valve is closed tightly. Pick up the torch handle and note that it has two hoses attached. One hose supplies acetylene, the
64. 64 other oxygen. Turn the oxygen regulator under the gauges clockwise and open the oxygen valve on the handle. This will purge any gas that may still be in the system and the gauges should both drop back to zero. Repeat this procedure with the acetylene cylinder. 4. Install the torch handle: The torch handle is the connection between the hoses and the working tips. It consists of a body and two taps. It’s used for both welding, Brazing and heating. Different attachments are connected to the handle to enable cutting. Examine the connections. One connection is marked “OX” and is for the oxygen hose. The other is marked “AC” and is for the acetylene hose. 5. Connect the hoses: As a further safety precaution, you’ll find the oxygen connector is right hand thread and the acetylene connector is a left hand threads. 6. Install the correct tip: Welding tips come in sizes that are stamped with a number. Number one is the smallest tip. The larger the number, the larger the tip and the greater the heat that it will provide. Select the tip size suitable for the task and screw it onto the end of the torch handle. Hold the torch handle in your hand, so that you can comfortably adjust the oxygen and acetylene taps. Position the tip so that it faces away from you. Gently tighten the tip-securing fitting. 7. Adjust the pressure of the gas flow: You are now ready to adjust the gas pressure for heating. Look at the two valves on the torch handle. The valve next to the oxygen hose controls the flow of oxygen to the tip. Close it tightly clockwise. The valve next to the acetylene hose controls the flow of acetylene to the tip. Also, close it tightly clockwise. 8. Turn on the gases: Now that you’re ready to use the torch, turn the main valve on the top of each cylinder counter-clockwise half a turn to open the valve. The needle on the cylinder pressure gauge will rise to show you the pressure in the cylinder. Turn the oxygen regulator handle clockwise until the needle in the gauge registers 2-5 PSI. Turn the acetylene regulator handle clockwise until the needle in the gauge registers 2-5 PSI. This is your working pressure for welding light plate. 9. Check the area: Before you light the torch, check the area you’re working in to make sure there are no flammable materials or fluids nearby. Workmates should also be clear of the area. The welding flame is not only extremely hot; it also produces dangerous ultra violet rays, which will damage your eyes. It is absolutely vital that you are wearing the right safety gear: gloves and tinted goggles or face mask. So, put them on and adjust them comfortably. 10. Ignite the torch: Now you are ready to ignite the torch with the striker. The tip of the torch must be pointing downwards away from your body and away from the gas cylinders. Turn the acetylene valve on the torch handle slightly towards the ‘ON’ position. You should hear the gas hissing. Hold the striker against the tip of the torch with the lighter cup between the torch and you. Flick the striker to create the spark that will ignite the gas at the tip of the torch. Open the
65. 65 acetylene valve slowly until the sooty smoke produced by the torch disappears. Then slowly open the oxygen valve on the torch handle. 11. Adjust the flame: As you open the oxygen valve, you will see the color of the flame change. The pure acetylene flame is yellow, and it will change to blue as you add the oxygen. Continue to open the oxygen valve until you can observe a small, sharp blue cone in the center of the torch flame. This is the “neutral”, you can now adjust to the desired flame, for the task you are doing. (Welding, brazing)
67. 67 Soldering Techniques Cut it tight and square. Use a tubing cutter, rather than a hacksaw, to make a perfectly square cut. Ream the end of the pipe to remove the burr left by the pipe cutter. Clean both surfaces until they shine like a brand-new. Now we need to a powerful safe torch, burn it up to blue flame not come. Direct the flame to the middle of the fitting (The hottest part of the flame). Continue to apply heat until the flux begins to melt and the copper takes on a shiny. Then touch the tip of the solder to the joint; if it’s hot enough, the solder will pour in and encircle the fitting before it begins to overflow.
68. 68 Work from lowest to highest. Solder the low end of a fitting first because the high side will stay hotter longer. Clean the joints after the cooling.
69. 69 Difference between Brazing and Soldering Process One of the main differences between brazing and soldering is working temperature. Soldering takes place below 449 ° C (840 ° F) while the brazing above 644° C (1190° F). Apart from this the all other techniques are same. Brazing Techniques Mark the tube for the proper length with help of measuring tape. Cut the tube using a hacksaw or tube cutter. Ream the ends of the cut tube to remove any metal spurs by sand cloth or file. Insert the tube onto the fitting to ensure a snug fit, but that also leaves enough room for the capillary action of the solder. Firmly support the tube.
70. 70 Hold the flame perpendicular to the tube and preheat both the tube and the fitting cup. Do not overheat since this could cause the flux to burn. Preferably use an oxy fuel torch with a neutral flame. Keep the flame in motion and to not linger on any one part of the tube. Touch the filler metal to the joint which should start to melt. Apply at the point where the tube enters the socket of the fitting. When the filler metal melts, apply the heat source to the base of the cup. Touch the filler metal to the joint which should start to melt. Apply at the point where the tube enters the socket of the fitting. When the filler metal melts, apply the heat source to the base of the cup. Leave the joints to cool without using water. After cooling clean the flux. Purpose of Evacuation When a typical system is installed and/or serviced, air and moisture enter the system. Oxygen, nitrogen and moisture are all detrimental to system operation. Removal of the air and other
71. 71 non-condensable is called “degassing,” and removal of the moisture is called “dehydration.” Removal of both is typically referred to as evacuation. It causes – Pressure in the system rises Operating current rises Cooling (or heating) efficiency drops Moisture in the air may freeze and block capillary tubing Water may lead to corrosion of parts in the refrigerant system. Theory Involved with Evacuation A suitable vacuum pump, one capable of blank-off to at least 300 microns or lower, must be connected to both the high and low sides of the refrigeration system. The size of the connecting hoses should be such that they will not restrict the flow from the system to the vacuum pump. A vacuum gauge that reads in microns should be connected to the furthest point in the system away from the vacuum pump. A triple evacuation process is strongly recommended. For triple evacuation, pump down the refrigeration system to 1,500 microns, and then break the vacuum using dry nitrogen. At 1,500 microns any moisture or ice trapped in the system will outgas. After backfilling with dry nitrogen to atmospheric pressure, operate the vacuum pump a second time to 1,500 microns and again backfill with dry nitrogen. Finally, operate the vacuum pump the third time to 300 microns, but no lower. Close all valves and isolate the vacuum pump, then turn the vacuum pump off.
72. 72 Caution: At a pressure below 300 microns (µT) the POE oil in the compressors will start to degrade and begin losing its lubricating ability. Watch the vacuum gauge to ensure vacuum is holding. If after five minutes there is a slight loss of vacuum, there could possibly be some residual out gassing in the system. Below 1,500 microns any remaining moisture is present as ice which will sublime. In this case the vacuum pump should be operated one more time to further dry the system. After a hold time of ten to fifteen minutes at 300 microns the system is considered successfully evacuated. An inability to pump down to 1,500 microns indicates a system leak or a pump problem. A loss of vacuum to above 1,500 microns during the hold test indicates a system leak. System leaks must be repaired before the refrigeration system can be safely operated. Any system leak requires you go through the necessary steps to insure there has been no contamination of the refrigerant. Something to remember: After you have finished using the vacuum pump, a good procedure is to change the oil. Any contamination in the refrigeration system is now in the vacuum pump oil. If you do not change the oil and the vacuum pump sits idle for any period of time, the contamination will start attacking its internal components. Deep Vacuum (Evacuation of system) Equipment, Tools and Supplies: 1. 4 port manifold gauge set 2. High Capacity dual stage Vacuum pump (4 cf. or greater) 3. 134A Charging Cylinder and Charging Hose 4. Refrigerant Charging Scale 5. Temporary access Valves 6. Brazing Equipment 7. Fire Extinguisher 8. PPE - Personal Protection Equipment - Approved Eye Protection 9. Tubing Cutters 10. 1/2” wrench, 7/16” wrench, Pliers, Triangle File and Assorted hand Tools 11. Extension Tube with Pin Valve (For insertion into process tube) 12. 90 Degree shut off valves 13. VOM /AMP Probe 14. Dye Drier Phase 1: Evacuation of System 1. Unplug or disconnect power to refrigerator, this will lock both sides of the 3-way valve in the open position in order to service sealed system.
73. 73 2. Remove the machine compartment cover. 3. Connect high and low side manifold hoses to the drier and process tube (Service Line) shut off valves. 4. Connect a hose from evacuation manifold gauge valve to the inlet of the vacuum pump. 5. (Charging Cylinder) Connect a hose from the charging cylinder to the Refrigerant port on the manifold. 5a. (Electronic scale) Connect a hose from the shut off valve attached to the refrigerant cylinder to the Refrigerant port on the manifold. 6. Close all valves. 7. Open vacuum pump vent and start the vacuum pump. 8. Open the inlet valve on the vacuum pump. 9. Open the VAC valve on the manifold. 10. Open the REF valve on the manifold. 11. Open the high side manifold valve. 12. Open the high side shut off valve. 13. Open the low side manifold valve. 14. Open the low side shut off valve – Close vacuum pump vent.
75. 75 15. E