2 Global Application Examples Benefits of VRF systems System Components CONTENTSWhat is VRFGlobal Application ExamplesBenefits of VRF systemsSystem ComponentsControlsBasic Design PracticesASHRAE Std 15 & 34I will begin this presentation by explaining the advantages of the 3 inverter compressor design and end with its easy installation and maintenance. There will be eight sections in total.
3 WHAT IS VRF“VRF” system is a short for Variable Refrigerant Flow system. Refrigerant flow is varied based on demand- System where multiple (up to 50 indoor units) can be connected to outdoor units.- Fan coils are controlled individually or by group controls.- Refrigerant flows to the unit that is calling for heating or cooling.
4 VRF Technology Overview Two VRF System TypesHeat RecoveryHeat PumpSingle Mode: Cooling or Heating OnlySimultaneous Cooling & Heating
5 VRF Technology Overview Primary Components of a Heat Pump SystemOutdoor UnitControls Compressor SpeedMaintains Operational ModeIndoor UnitTransfers Heating and Cooling to SpaceAllows for Optimal ZoningControllerControls Space Temp and IDU FanRemote or Central
6 Liquid line (fully liquid) Typical VRF Heat Pump SystemOutdoor unitCompressorLiquid line (fully liquid)Indoor unitRefrigeration Pipe(Liquid, Gas)Each indoor unit can be controlled individually.On/Off setting , Set point, Air volume, louver position can be set individually.（Operation mode priority : Cooling or Heating, not simultaneously in heat pump model）Cooling : Expansion=Indoor unit Liquid line=Condensed liquidHeating : Expansion=Outdoor unit Liquid line =Condensed liquid
7 VRF Technology Overview How does VRF work?Indoor UnitTransfers heating and cooling directly to the spaceMeasures Return Air TemperaturePulse Motor Valve (PMV) adjusts to meet setpointFilters and distributes the airUnit operates to match exact building loadFlow SelectorReceives superheated gas and subcooled liquid, adjusts flow direction to heat and coolAllows for indoor unit to be in either cooling or heating modeUnit operates to match exact building loadOutdoor UnitHouses multiple inverter driven compressorsCompressors change speed based on demand of indoor units, which varies the refrigerant flowSegmented ODU Coil for efficient heat transferUnit operates to match exact building loadControllerAllows for indoor unit control at zone levelTakes user desired space setpoint, fan speed, modeUnit operates to match exact building load
8 Typical VRF Heat Recovery System 3 - Pipe Simultaneous heating and cooling, uses cooling mode waste heat for heatingHeat Recovery Box
10 Varying Refrigerant Flow How does the outdoor unit respond to the varying demands and vary the flow of refrigerant?The compressor(s) in the outdoor units are inverter driven which means that their speed can be varied by changing the frequency of the power supply to the compressor.As the compressor speed changes, so does the amount of refrigerant delivered by the compressor.
11 SYSTEM ADVANTAGES High Efficiency High Stable Operation High ReliabilityHigh EfficiencyHighReliabilityI would now like to tell you about the high reliability which is offered by the 3 inverter compressor system.
12 Use Wherever Part Load Exists Application:In case of:Not all units are on.Example: office area is on, meeting room is off.OFFIn case of:Orientation of buildingExample: East/West exposureApartment,In case of:Decreased load.Example: office closedOffice building
13 ZONING OPERATION OF VRF (In case of cooling)OFFOFFOFFOFF: Piping: 4-way cassette type: Hi-wall type: Outdoor units
14 ADVANTAGES OF VRF - Comfort - Design flexibility - Energy savings (part load, heating)- Cost effective installation
16 COMPRESSOR COMPARISONS Rotary compressorScroll compressorWe can also divide compressors into two main categories, rotary compressors and scroll compressors. The construction of these two types differs significantly in that the compression part of a rotary compressor is positioned at the bottom of the main unit, while that of a scroll compressor is located at the top of the main unit.
17 COMPRESSOR COMPARISON Twin rotary compressorScroll compressorOutOutInInYou may be wondering why there is such a difference in characteristics. I will briefly explain, starting with the twin rotary compressor. The twin rotary compressor is constructed so that the compression ratio inside the cylinder and the refrigerant cycle are always balanced. The compression ratio inside the cylinder and the refrigerant cycle are the same, and there is minimal excess compression or insufficient pressure inside the cylinder. This means that even when the compression ratio inside the refrigerant cycle changes, the compressor still runs with high efficiency across the entire range.In17
18 ADVANTAGES OF VRF EASE OF DESIGN Multiple types of Fan Coils and Sizes provides designflexibility for many different applications
19 ADVANTAGES OF VRFModularity of equipment allows for Staging of installation, Redundancy in operation
23 Shengshi Qiantang Garden 1200 apartments in 7 buildingsRecognized by China’s Ministry of Construction as being among the most cost-effective air conditioning systems available.Shengshi Qiantang Garden3,840Tons
26 Burt Hill Architects Office Approx. 10,000 sq. ft7 floor multi-tenantoffice buildingBurt Hill Architects Office26
27 Installed in subway passages and administration offices Contracts extending to other linesChina Subway19,200Tons27
28 DESIGNING WITH VRF High Efficiency High Stable Operation High ReliabilityHigh EfficiencyHighReliabilityI would now like to tell you about the high reliability which is offered by the 3 inverter compressor system.
29 Designing for Energy efficiency Perimeter/CorePres. Office12 kBTUVP Office14 kBTUFoyer2.5kBTUWomen’s2.0kBTUMen’sCoffee/BrkOffice 1016.0kBTUOffice 102Office 103Office 1043.0kBTUOffice 105Office 106Office 107Office 108Office 109Office 1104.5kBTU7.5kBTUConf.28.0kBTUCorr613.5 kBTU112 kBTU7RejectedHeat5228 kBTU2.5 kBTU12 kBTUEach unit individually – list model numbers next to example3420 kBTU14 kBTUExample: 40oF Ambient
30 Ventilation Design Ventilation Strategies with VRF Room graphic w/Air into CornerDelivering OSA directly to the space:Best when it is Neutral temperature & Humidity (DOAS)An ERV-only is OK in the West & South, if low fraction and high ceilings (mixing time)Mild Climates can bring in small fraction untreatedBenefits are less ducting, more flexible application(close-up of a room in an office with an arrow showing air coming in at one end and leaving at the other. If time, include a grill & ductwork for Supply Air and Exhaust Air to go with.)
31 Ventilation Design Ventilation Strategies with VRF Delivering OSA ducted to the Fan Coil:Pre-Filtered, tempered air is best. (DOAS)Allows selecting to meet Envelope load for max comfortAir inlet point is before the filter on some ductless, so Filter is a must!An ERV-only is Good in the West & South, but may need additional heat in the NorthDOAS system or ERV+FC is best for Cold ClimatesMild Climates can bring in small fraction untreated (<30%)Benefits are better humidity control, no extra grillsShow a Ducted Fan Coil with air entering through the back, a 4-way cassette with air entering at the corner, (maybe even the extended casement with the extra air inlets?), and a Ceiling suspended with air coming from behind?
32 Ventilation Design DOAS using an ERV DOAS approach allows us to split the ventilation load away from the Mechanical system by tempering the air first.Can use an ERV only for most applicationsCan run OSA through a standard Fan Coil in Series for Neutral Air application, especially if not ducted to Fan CoilsCan apply Supplemental Heat for Cold Climate applications for Neutral Air, or even higherBy treating each separately, we can optimize for each, instead of a one-size fits all compromise. Add Graphic to show on Roof a DOAS w/ ducting down to conference room?, with each option, ie. DOAS, ERV, ERV+FC.(verify with Nick)
33 Heating Design Heating Design Strategies Heating with a VRF System: -VRF is a Heat Pump, but….But it is not your Grandpa’s Heat Pump!Capacity is better than traditional because of inverter compressors that can spin faster to compensateDe-rate due to ambient temperature is less, but must still be accounted for.Auxiliary Heat to cover the <averageVisual for a better heat Pump?? Make sure that it is clear how the system de-rates due to low ambient temperatures.
34 Heating Design Heating Design Strategies- Avg. vs. Design: The Design Heating in Billings is -20FBut the Average January Low is 16FDiscuss the difference between the design and the average, ie the bell curve, or the scatter-plots for annual temperatures. Maybe some red arrows pointing to the 3 key points on the heating capacity curve, at typical temperatures.“Avg. winter low in Billings, MT is 16F”
35 Ventilation Design Heating Design Strategies When to use Auxiliary Heat?Rule of Thumb is start considering it at 15F design temp.Simple Answer is when heating Design Day exceeds capacityERV & DOAS can provide significant contributions.“Avg. winter low in Seattle, WA is 36F”“Avg. winter low in Billings, MT is 16F”While it is necessary to design for the worst case load, it’s important to understand what the normal load on the system is. You can see the average low temperature, on the coldest day of the year for each of these cities is well within the normal operating range of the Toshiba-Carrier system. (Graphics: add the curves from weatherspark to show the difference between average & design.) Design for Seattle is 5F, Billings is -20F, Chicago -10F, and Nashville is 0F)“Avg. winter low in Chicago, IL is 17F”“Avg. winter low in Nashville, TN is 29F”
36 Heating Design Heating Design Strategies-Aux Heat Types of Aux. Heat: Electric Strip-Heater (Ducted Models only)Hydronic Coil (can feed from an upsized DHW source)Both of above can be placed in DOAS ducting for 90+F ventilation air if that meets the needed BTU’s!Baseboard Heating PanelsHydronic or Electric-All Fan CoilsRadiant PanelsWall HeatersTypically Electric-All Fan CoilsOr….Previously Existing Heating System!!Graphics:Swoop in with the different kinds of Heat System pictures? Or highlight A-G sequentially.
37 Heating Design Heating Design Strategies-Aux Heat There are 3 ways to activate the Aux. HeatIndividual Space Response:Zone temp drops, Aux heat activates at Temp. A, then deactivates at Temp B. Both must be less than heating setpointOutdoor Ambient Trigger. Aux heaters engage when FC is in Heating, Aux Heating system activated by separate Outdoor Ambient Thermostat.BMS Control system activation. Can use custom logic for zone by zone response, minimize setpoint drift.Graphics: A: Need graphic to show setpoint, Trigger point A, then release point B(use brent’s dwg). For B, show one of the weatherspark graphs with a line through it, showing below the line, the Aux. heat is always on if the FC is heating. Not sure if C needs one? Discuss custom respones like reducing setback below a certain ambient temperature, or if a zone tends to be colder, releasing setback earlier than with other zones?
38 Heating Strategies Heating Design Strategies-Aux Heat Heating Setback with VRF:A VRF system is different from a combustion heater because it’s efficiency gets better at part-load.When system is in recovery, system goes to full-load, which is less efficient than maintaining a constant temperature, but total heat loss is more.So, optimum use is probably minimal setback during weekdays, and more of a setback over weekends & Holidays, or just a 2F setback period.No setback during cold snaps to avoid using Aux Heat.
39 Heating Strategies Heating Design Strategies-Aux Heat Alternate to zone-level Aux. Heat-Put Outdoor Units in a Mechanical Room or “Doghouse”Graphics:show a simple shed, w/ Unit heater & discharge ducts, dampers
40 Heating Design Heating Design Strategies-Aux Heat Alternate to zone-level Aux Heat-Put Outdoor Units in a Mechanical Room or Doghouse:Simplifies controls of Aux. Heat by having one set of controls and heat source.Heater is typically a Gas unit heater, or other combustion unitBackup isolates from Outdoor air at preset ambient temp.Key Selection Criteria:Size the Unit heater for 70-80% of Heat LoadDucting system must be 0.2” esp max. in both modesActivation temp typically below freezing, but maintain interior temp around 45F to avoid frost buildup.Don’t forget to include a condensate drain, w/heat tracingGraphics:show a simple shed, w/ Unit heater & discharge ducts, dampers
41 Refrigerant system Design VRF and ASHRAE 15/34 In part, Standard 15, Safety Standard for Refrigeration Systems, strives to ensure a safe system by limiting the maximum quantity of refrigerant below that which is a danger to human occupants if a leak occurs.Because VRF uses the Refrigerant as the transport medium, it is inherently a more refrigerant intensive product than most traditional HVAC. Std. 15 is the application guideline that ensures a safe design every time.
42 VRF and ASHRAE 15/34 Refrigerant Concentration Limit (RCL) R410A R410A is a commonly used refrigerant for commercial VRF systems. Per Standard 34, Table 2, the safety classification of R-410A is Group A1 (meaning non-flammable and non-toxic). Even though R-410A is Group A1, its ability to displace oxygen could pose a danger to occupants if released in large quantities into smaller-volume spaces. Therefore, Standard 34, Table 2 has established an RCL for R-410A at 26 lbs of refrigerant per 1,000 cuft of room volume.For Institutional Occupancies such as patient care areas of hospitals and senior homes, the RCL is cut in half, changing the RCL for R-410A to 13 lbs/1,000 cuft.
43 VRF and ASHRAE 15/34 Smaller Capacity Systems Design for “Connected Spaces”Combine multiple smaller zones on a single ducted fan coil unitOne to-One SystemsDiversityRefrigerant Piping LayoutY-branching versus manifoldIsolate refrigerant circuit for Smaller RoomsR410A sensor and alarm, or isolation valvesStephen W. Duda’s article published in ASHRAE Journal, July Posted at Applying VRF? Don’t Overlook Standard 15