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Variable Refrigerant Flow - VRF


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The Comfort Conditioning Solution
Features and Benefits

Published in: Education

Variable Refrigerant Flow - VRF

  1. 1. Variable Refrigerant Flow - VRF The Comfort Conditioning Solution Features and Benefits
  2. 2. Air Conditioning System • The compressor is the highest power-consuming component in the air-conditioning system Expansion valves, •• Expansion valves, fans, bypass solenoid fans, bypass solenoid valves also affect valves also affect system performance system performance • Component optimization increases performance. 1
  3. 3. What is a VRF System? VRF • A system that provides ▪ Climate control & zoning comfort ▪ Effective energy consumption by means of optimized inverter driven scroll compressor & temperature controls, producing highly responsive cooling and/or heating 2
  4. 4. What makes a VRF? VRF • Outdoor units with single or multiple variable speed DC compressors • Single or multiple indoor units equipped with temperature sensing devices • A factory supplied zone temperature supervisory control, GUI and networking capabilities 3
  5. 5. VRF System & Inverter VRF • The inverter reacts to indoor and outdoor temperature fluctuation by varying the power consumption and adjusting the compressor speed to its optimum energy usage. • The refrigerant is compressed to the required high pressure level • Inverter provides superior energy efficiency performance 4
  6. 6. VRF Outdoor Fan Motor Control • Multi stage fan speed operation provides: • Input power savings, lower steps have lower power consumption compared to higher steps. • Optimizes condenser pressure control to achieve desired discharge pressure and ensure optimum mass flow through the system. • Cycle stabilization provides optimum efficiency as compared to fix fan speed. 5
  7. 7. VRF Piping VRF • Improves refrigerant cycle efficiency by connecting multiple indoor units to a common liquid and suction line through the use of STA Separation Tube Assemblies and/or Headers and EEV Electronic Expansion Valves 6
  8. 8. Reduces piping cost and work VRF • STA and or header diverts the common flow of refrigerant to an individual evaporator. The flow of refrigerant is further metered by an EEV or Electronic Expansion Valve. 7
  9. 9. Video VRF 8
  10. 10. VRF Benefits • • • • • • VRF Less copper versus multi-split Eliminates most ductwork Quicker installation OEM software simplifies layout Long piping lengths Compact ductless system 9
  11. 11. Flexible piping design VRF Suitable for apartment & office buildings too Total piping length 377 – 540 Ft.* Actual piping length 230 – 330 Ft.* Height difference 100 – 165 Ft.* * VARIES BY MANUFACTURER 100 to 165 ft. max. 10
  12. 12. Design freedom VRF This extra-long piping system can also cope with buildings of various shapes. Rectangular type Outdoor unit L type Square type Indoor units Refrigerant piping Actual max. piping length 230 ft, Total max. piping length 377 ft* *Varies by manufacturer 11
  13. 13. Design Software Piping Layout Remote Control Selection VRF Job Costing 12
  14. 14. Advanced Computer Controlled VRF • Low energy consumption • Inverter regulates compressor to its optimum energy usage • Higher refrigerant performance with less power 13
  15. 15. Central Air Inefficiency Central • VRF systems allows you to minimize inefficient ductwork. – Save money – Improve comfort – Protect health – Save Space – Reduce Noise 14
  16. 16. According to D.O.E. Central • “Typical duct systems lose 25 to 40 percent of the heating or cooling energy put out by the central furnace, heat pump, or air conditioner.” • “Homes with ducts in a protected area such as a basement may lose somewhat less than this, while some other types of systems (such as attic ducts in hot, humid climates) often lose more.” 15
  17. 17. Central Air Inefficiency VRF •• VRF systems systems minimize minimize inefficient inefficient ductwork. ductwork. Central 16
  18. 18. Multi-Split vs. VRF System • VRF systems allows you to minimize the refrigerant path compared to a multi-zone mini-split. Multi-Split VRF 17
  19. 19. The heart of a VRF system VRF • Inverter driven DC scroll compressor(s) provides highly responsive cooling and/or heating by quickly varying in speed from 1,000 up to 6,000 rpm. Scroll Compressor DC Inverter Control Signal line Temperature Sensor Temperature sensor Indoor unit Indoor unit Outdoor unit Senses the temperature of each room and optimizes operation. 18
  20. 20. What Zoning does for Efficiency VRF • Why cool spaces you do not occupy? • Individual zoning control of a VRF system minimizes electrical usage. 100% 90% 80% 70% 60% Central VRF 50% 40% 30% 20% 10% 0% Kitchen Living Bed-1 Bed-2 Dining 19
  21. 21. Effective comfort at lower cost VRF • Reacts to indoor and outdoor temperature fluctuation by varying power consumption and adjusting compressor speed to its optimum energy usage to achieve desired set point quickly and maintain it more closely. Set temperature 40 min. Inverter Room temperature (deg.) Room temperature (deg.) Conventional Model Time Revolution of COMPRESSOR Set temperature 20 min. Time Revolution of COMPRESSOR 20
  22. 22. Variable Refrigerant Flow VRF • Conventional: Room temperature drops rapidly when compressor turns OFF which result in an unstable room temperature Conventional Model Inverter Set temperature 3 deg. Revolution of COMPRESSOR ON ON OFF ON OFF Time Room temperature (deg.) Room temperature (deg.) Set temperature 1 deg. Revolution of COMPRESSOR Time • Inverter: Range of room temperature change is small. Because after set temp is reached, compressor will not shut off to control temp but will maintain temp by decreasing or increasing revolution. 21
  23. 23. Central Connectable Capacity • Central Air 100% Connectable Capacity VRF • VRF 50% to 150% Connectable Capacity 48,000 BTU 48,000 BTU 24,000 BTU 48,000 BTU 72,000 BTU 48,000 BTU 22
  24. 24. Connectable Capacity 24,000 BTU Apartment used only at night 150% Connectable VRF • Ability to connect up to 150% of name plate rated indoor units* * Varies by manufacturer • If all indoor units are operated simultaneously system will not produce more than 110% of system capacity 48,000 BTU Small Office used only during the day • Example A: – 2-Story Building Mixed Use. VRF stretches square footage covered by a single system when not all areas are occupied simultaneously 23
  25. 25. Lack of Connectable Capacity Multi-Split Load Calculation 48,000 BTU 10K 12K 7K 4K 5K 5K 5K Field Application 72,000 BTU 18K 9K 18K 9K 9K 9K • 6 tons applied where load only calls for 4 tons • Higher equipment cost by installing two systems in order to provide most rooms with individual control. 24
  26. 26. Example of Connectable Capacity Load calculation 48,000 BTU without party quests Actual 51,750 BTU with all indoor units calling 6.75K 10.5K 7K 10K 12K 4K 5K 9K 9K 9K 7K 7K 5.25K 5.25K 5K 5K Field application 69,000 BTU connectable capacity 14K VRF 7K 7K 6.75K 6.75K 5.25K 5.25K Actual 48,000 BTU available for party with bedroom units off 9K 14K 9K 9K 7K 25
  27. 27. Benefits of Connectable Capacity Multi-Split VRF 9K 14K 18K 9K 18K 7K 7K 9K 9K 9K 6-Tons when only 4-Tons required 9K 9K 7K 7K Indoor unit for every room yet 4-Tons • Reduced equipment cost by not installing additional equipment when a system can be shared instead. • The ability to flexible size for different loads. • Stretch square footage covered by over-sizing and reducing capacity at each indoor unit by design 26
  28. 28. VRF Benefits Benefit VRF Concept Central Air Multi-Split VRF System Cools off hot room Slowly Unresponsive compressor Quicker, Moderately responsive piping and compressor combination Quickest, Highly Greatest comfort responsive piping and Less temperature compressor fluctuation combination ½ the time of a conventional unit Refrigerant Cycle / Air Distribution Short piping run but great efficiency loss in ductwork Long piping but efficient air flow with evaporator in A/C space Shorter piping run with better refrigerant distribution Quicker cooling, greater comfort, more stable room temperature Energy Consumption Compressor runs at its maximum speed Variable speed compressor but refrigerant flow efficiency loss Variable speed compressor at optimum speed and maximizes refrigerant flow Least energy consumption with greatest comfort Zoning 1 or 2 zones without expensive zoning controls Up to 4 zones Wireless or wired remote Up to 16 zones. Wireless, wired, & group remotes Inverter provides more stable room temp. Flexible zoning. Cool the spaces you occupy not the spaces you don’t Connectible Capacity 100% connectible 100% connectible Up to 150% connectible Lower equipment 27 costs, more efficient
  29. 29. Flexible Remote Control Group Remote Controller Simple Wired Remote Full Featured Wired Remote Control Wireless Remote 28
  30. 30. Group Remote Controller Wiring A Power line/signal line + ground = 4 wires Power line + ground /signal line + ground = 6 wires Wiring B Power line + ground /signal line + ground = 6 wires 29
  31. 31. Wiring system Wiring is simplified by using a daisy chain approach. In this case wiring provides power as well as communication signal in a three wire harness. 30
  32. 32. Simplified Wiring • NEC compliant • Disconnect switch may be required • Outdoor units requires 208/230V 40A single phase or 3-phase, depends on BTU’s • Indoor units powered from the outdoor unit using 3 wires and ground. Usually 14AWG. • Indoor required two lines for power, typically 208/230 V single phase 15A. • 3rd line used for networking and data communication 31
  33. 33. Mix and Match Flexibility 1/4 Liquid 1/2 Gas Duct Type Coils from 18K to 45K BTU 1/4 Liquid 5/8 Gas 3/8 Liquid 3/4 Gas Compact Duct Coils from 7K to 18K BTU Large and Small Ceiling Cassettes From 7-42K BTU 1/4 Liquid 3/8 Gas Condensing Unit Combinations from 2Tons to 31.5 Tons 3/8 Liquid 3/4 Gas Wall Mount Coils from 7K to 36K BTU 1/4 Liquid 5/8 Gas 3/8 Liquid, 3/4 Gas 32
  34. 34. Piping system Refrigerant flow is accumulated by using STA separation tube assemblies in reverse and then dividing refrigerant flow to as many as 48 indoor units 33
  35. 35. VRF 1. Short Term Stop Gap Method • All manufacturers test up to five evaporators under an agreed upon test method to prove minimum EER efficiency (We estimate 1 year in development) 2. Interim Test Method • Develop test method for new ductless multi and VRF test standard based on 210/240.(Tentatively draft ARI1230) (We estimate 2 years in development) 3. Long Term Method • Computer simulation through OEM software approved by ARI to demonstrate efficiency regardless of combination (We estimate 3 years in development) 34
  36. 36. Two Temperature Controlled Zones Two Temperature Controlled Zones One Air Flow Settings per Zone One Air Flow Settings per Zone Central Equipment 1 - Outdoor unit 1 - Indoor unit 2 – Dampers 2 – Thermostats THERMOSTAT 2 HALL THERMOSTAT 1 Because room temperature sensor is housed in thermostat, the temp of only two rooms can be controlled. 35
  37. 37. VRF Individual Temperature Control Individual Temperature Control Individual Air Flow Settings Individual Air Flow Settings Equipment: Equipment: 1- Outdoor unit 1- Outdoor unit 8 Indoor units 8 --Indoor units 8 Remote controls 8 --Remote controls HALLWAY Each indoor Each indoor units has an units has an individual individual remote control remote control and a room and a room temperature temperature sensor sensor 36
  38. 38. Central No Individual temperature/air flow settings No Individual temperature/air flow settings Because set Because set temperature is temperature is matched to matched to living room, living room, the ideal the ideal temperature temperature cannot be cannot be selected for selected for other rooms. other rooms. 37
  39. 39. VRF Individual temperature/air flow setting Individual temperature/air flow setting HALL Individual units Individual units with temperature with temperature sensors in each sensors in each room provide room provide comfortable comfortable separate room separate room temperatures temperatures matched to the matched to the room’s use. room’s use. 38
  40. 40. No Individual temperature/air flow setting No Individual temperature/air flow setting Central Heat-sensitive adults present in living room Cold-sensitive infant Present in the bedroom Individual air flow cannot be selected because there is one set air flow for all rooms. Loud fan sound, rooms nearest indoor unit especially noisy, because large fan creates large air flow. When temperature and air flow are set to accommodate infant in bedroom, When temperature and air flow are set to accommodate infant in bedroom, people in other rooms are too hot because setting are same in all rooms. people in other rooms are too hot because setting are same in all rooms. 39
  41. 41. VRF Temperature and air flow can be individually set according to the room usage conditions. Quiet operation as low as 23db 40
  42. 42. Changing Sun Load Central When direct sunlight or other disturbances change room load, system response for individual rooms is impossible because set temperature matched to living room. A.M. P.M. 41
  43. 43. VRF Changing Sun Load When the heat load changes by direct sunlight or other disturbance, settings can be changed for each room. All the rooms can be kept comfortable. A.M. P.M. 42
  44. 44. Time to Reach Set Point Central Ex: When returning home in the summer Cool air also flows to unoccupied rooms so it takes time to reach set temperature. The farther the room is from the indoor unit, the poorer the cooling. Large amounts of cool air flow to the outlets nearest indoor unit. VRF Full capacity concentrated at operating indoor units located in the rooms in which people returning home congregate, other units turned off. Each room cooled quickly and 43 evenly.
  45. 45. Central Duct Maintenance After cooling stopped When cooling begins Mold is easily produced with the condensed water as the nutrient Mold spores sticking to dust are blown into room Since the area of the duct is large; a large amount of mold is produced. Inaccessible ducts are difficult to clean or remove mold. 44
  46. 46. VRF Duct Maintenance After cooling stopped When cooling begins Small amount of condensation form on each indoor unit (duct) Indoor units installed in each room with small duct area. Mold production and dust are suppressed. Since the area of the duct is small; mold production is minimized. Accessible ducts make periodic cleaning easy preventing mold production 45
  47. 47. VRF - Precise Modulation Variable Refrigerant Flow (VRF) technology provides effective comfort with low energy consumption. The operational savings come from the zoning because only occupied spaces are conditioned. The work of the refrigerant is adjusted with an inverter & and the flow further gauged with the EEV 46
  48. 48. Thermal Expansion Valve TXV • Susceptible to valve hunting: overfeeding and starving of refrigerant flow to the evaporator. • Hunting can be reduced by relocating the sensing bulb to a better location TXV Operation is TXV Operation is Totally Independent of Totally Independent of Compressor Operation Compressor Operation 47
  49. 49. Lack of TXV Integration • What standard TXVs do not do: – Control evaporator pressure – Cycle the compressor – Control running time – Control room temperature • Three main working forces on the TXV are: – Remote bulb or sensing bulb pressure (opening force) – Spring pressure (closing force) – Evaporator pressure (closing force) 48
  50. 50. Thermal Expansion Valve TXV Condenser Evaporator TXV Compressor • As evaporator load increases, available refrigerant will boil off more rapidly. If it is completely evaporated prior to exiting the vapor will continue to absorb heat (superheat). 49
  51. 51. TXV & Superheat • Super heat is heat added to a substance above its saturation temperature. The amount of super heat in a system is a concern. STOP • To little: liquid refrigerant entering compressor washes out the oil causing premature failure • To much: valuable evaporator space is wasted and possibly causing compressor overheating problems. 50
  52. 52. EEV – Positioning System • EEV function is to maintain the pressure differential and also to distribute the right amount of refrigerant to each indoor unit. • Fine control on the refrigerant flow provides a superior level of room temperature control & ensures no wastage of energy EEV is responding directly to room temperature and room load 51
  53. 53. EEV – Positioning System • EEV = Stepper Motor + Expansion Valve • Stepper motor is a brushless, synchronous electric motor that can divide a full rotation into a large number of steps, 500 steps/rev • Primary characteristic is its ability to rotate a prescribed small angle (step) in response to each control pulse applied to its windings 52
  54. 54. EEV – Positioning System • Expansion valve is the component that controls the rate at which liquid refrigerant can flow into an evaporator coil • Control algorithm is continuously providing signals to the EEV to open or close by small amounts to vary the amount of refrigerant being delivered to the evaporator meeting targeted superheat. 53
  55. 55. Thermistors • A type of resistor used to measure temperature changes, relying on the change in its resistance with changing temperature. 54
  56. 56. Control Loop Components • Measurement By a sensor (thermistor) connected to the refrigerant cycle or the “space" • Decision Made in Advanced Computer Controller • Action Taken through an output device ("actuator") such as the stepper motor in the EEV or Variable speed inverter compressor 55
  57. 57. Control Loop at Local Evaporator • The controller takes a measured value from the space (by means of a thermistor) and compares it with a reference SETPOINT value. • The difference (or "error" signal) is then used to adjust a system component in order to bring the spaces' measured value back to its desired SETPOINT. Setpoint + Σ error - Room temperature 56
  58. 58. Control loop at local evaporator • The digital controller can adjust space outputs based on the HISTORY and RATE OF CHANGE of the error signal, which gives more accurate and stable control. 57
  59. 59. Controller’s algorithm Controller uses 3 correcting calculations” • Proportional control to improve the rise time • Integral control to eliminate the steady-state error • Derivative control to improve the overshoot based on the rate of change of the error 58
  60. 60. PID Calculations P: Handles immediate error, the error is multiplied by a Proportional constant P, and added to controlled variable. I: Controller output is proportional to the amount of time the error is present. Integral action eliminates offset. It looks at the history of the error signal D: Controller output is proportional to the rate of change of the measurement or error. Controller output is calculated by the rate of change of the measurement with time. 59
  61. 61. So what’s an Inverter? • An inverter controls the operating speed of a DC motor by controlling the frequency and voltage of the power supplied to the motor. • An inverter provides the controlled power. In most cases, the inverter includes a rectifier so that DC power for the inverter can be provided from mains AC power. 60
  62. 62. Inverter Principle • Bridge Rectifier Provides the same polarity of output voltage for any polarity of the input voltage. In other words, converts alternating current (AC) input into direct current (DC) output. Diodes are used to rectify AC by blocking the negative or positive portion of the waveform 61
  63. 63. Diode Bridge Load • Alternating current (AC) whose magnitude and direction vary cyclically (60Hz) • Basic Operation: current flows to the right along the upper colored path to the output, and returns to the supply via the lower one. • If supplied current direction changes output current direction remains the same, DC • Result: Negative part of the waveform has been eliminated 62
  64. 64. Inverter Principle • Smoothing Condenser used to smooth the ripple voltage present in a pulsating DC voltage output of a power supply rectifier. • Most modern electronic devices require a steady DC supply 63
  65. 65. Inverter Block Diagram 64
  66. 66. Inverter Control Video VRF 65
  67. 67. Inverter Principle • IPM (Inverter Power Module) It is composed of 6 transistors and drives the motor by high speed signal switching. • The drive voltage signal is transferred to the drive circuit from a microcomputer, and varies the supply frequency to the motor (PWM system) to rotate the motor. • Currently, insulated gate bipolar transistors IGBT’s are used in most inverter circuits 66
  68. 68. PWM Pulse Width Modulation • Signal involves the modulation of its duty cycle, to control the amount of power sent to a load. • Many digital circuits can generate PWM signals outputs to control an electrical motor. • Usually use a counter that increments periodically and is reset at the end of every period of PWM. • If counter value is more than the reference value, the PWM output changes state from high to low. 67
  69. 69. PWM 68
  70. 70. DC Inverter Control Function Basic Circuit of 3-Phase Inverter 69
  71. 71. Why do I want an Inverter? • Benefits of an Inverter Air Conditioner: – Compared to the common On-Off controlled compressor; the inverter controlled compressor is able to run at the proper revolution to provide the best efficiency and reduce losses. – When the maximum capacity is not required, the compressor revolution is decreased. This means the input power decreases too, which results in increased system efficiency. 70
  72. 72. Low Electric Consumption Power balance control technology achieves high operational efficiencies by detecting low pressure and high pressure and precisely controls the optimum refrigerant condition via refrigerant flow rate. Efficient DC inverter scroll compressor varies capacity according to the load 71
  73. 73. Power Oil Return • Oil return is important to ensure that there is adequate lubrication for the compressor, especially during part load operation. • Reducing oil logging in the system improves heat exchange efficiency in the condenser and evaporators saving energy. 72
  74. 74. Effective use of heat exchanger The outdoor unit can achieve the most efficient operation by matching the heat exchanger of the outdoor unit to the systems requirements and the required load capacity of the conditioned space. Example 31.5 Tons of available heat exchangers 9 HP of compressors Max. 10.5 HP Max. 10.5 HP Max. 10.5 HP by using 3 outdoor units together 73
  75. 75. Operation / Comfort • Quiet operation (varies by manufacturer) Normal operation mode: 57dB(A) Night operation mode 54 dB(A) • Inverter compressor makes system even quieter when it is operating at slower RPMs 74
  76. 76. Central remote controller Up to 400 indoor units or 64 groups can be controlled. Central remote controller can control the system by selecting All Groups, User Defined Groups or Individual Remote Controller Groups 75
  77. 77. Central remote controller Central control by tenant Central remote controller Central remote controller Individual control 76
  78. 78. PC Control Rotating 3-D display Floor layout display List table display Calculating electricity charges Up to 400 indoor units or 400 groups can be controlled PC controller Operation control Schedule control Operating record 77
  79. 79. PC controller (Calculating electricity charges) Each tenant bill can be made by calculating function of PC controller Power supply Electricity company Meter Tenant bill Tenant-E Tenant bill Tenant-D Total Electricity bill Tenant bill Tenant-C Tenant bill Tenant-B Apportioned charges Tenant bill PC controller Tenant-A The accumulated refrigerant time and indoor unit capacity. 78
  80. 80. BMS compatibility BMS: Building Management System 79
  81. 81. Service tool (Software) Extensive monitoring and analyzing functions for maintenance Simple connection by transmission adaptor and RS-232C cable (RS-232C cable field supplied). 80
  82. 82. VRF - Summary • Climate control & zoning comfort • Effective energy consumption • Inverter driven scroll compressor & digital temperature controls, • Produces a highly responsive cooling and/or heating. • Cooling/Heating only on demand 81
  83. 83. Thank You for your time and attention. We hope you will consider VRF technology for your next project 82