IPLV Method to test HVAC equipment at part load conditions For water cooled chillers: 100% load ( % hrs) + 75% ( Hrs ) + 50% ( Hrs ) + 25% ( Hrs ) = IPLV value Manufacturer can favor this number by tweaking design Better to get data from 100% down to 10% from manufacturer
IPLV Do computer model to simulate actual building part load performance, then you have actual load in 10% increments with wet bulb data Insert manufacturer data with hours Much closer to actual usage vs one single IPLV number
Chilled Water Systems Two or more Chillers Three different Pumping methods
Single-Chiller System air-cooled chiller pump coil three-way valve
Chillers Piped in Parallel Single Pump off 54 F [12.2 C] 54 F [12.2 C] on 42 F [5.6 C] 48 F [8.9 C]
Chillers Piped in Parallel Dedicated Pumps off on 42 F [5.6 C] 54 F [12.2 C] 60% to 70% of system flow coil starved for flow
Chillers Piped in Parallel Dedicated Pumps 2 pumps head pressure 1 pump system curve 65% 100% percent flow
Chillers Piped in Series absorption chiller electric chiller three-way valve
Three-Way Valve Control airflow three-way modulating valve bypass pipe
Primary-Secondary Configuration production pumps production loop distribution pump distribution loop two-way valve
Primary-Secondary System Rules The bypass or de coupler pipe should be free of restrictions Sized for minimal pressure drop Avoid random mixing of supply- and return-water streams No check valve Sized for the flow of only one chiller Bi directional flow meter
Two-Way Valve Control airflow two-way modulating valve
Production Loop production pumps supply tee return tee
Manifolded Production Pumps production pumps isolation valves
Distribution Loop supply tee distribution pump return tee two-way valve
Multiple Distribution Pumps distribution pumps return from loads supply to loads
Tertiary Pumping distribution pump tertiary pump two-way valve bleed line
Distribution Loop Characteristics Reduced pump energy use Distribution loop sized for system diversity Higher returnwater temperatures
System Operation production loop supply tee return tee distribution loop
Deficit Flow 1,000 gpm at 42 F [63 L/s at 5.6 C] 1,000 gpm at 56 F [63 L/s at 13.3 C] 1,200 gpm at 44.3 F [76 L/s at 6.8 C] 1,200 gpm at 56 F [76 L/s at 13.3 C]
Excess Flow 2,000 gpm at 42 F [126 L/s at 5.6 C] 2,000 gpm at 54.6 F [126 L/s at 12.6 C] 1,800 gpm at 42 F [114 L/s at 5.6 C] 1,800 gpm at 56 F [114 L/s at 13.3 C]
Variable-Primary-Flow Systems variable-flow pumps check valves control valve two-way valve optional bypass with three-way valve
Critical VPF System Requirements Chillers must handle variable evaporator flow new chillers and panels System must include a bypass System-level controls must limit the rateof-flow change Adequate time to design and commission controls Operator must understand the system
Critical VPF System Requirements Must keep the evaporator flow between the manufacturers min and max flow. Staging is the critical time in chiller sequencing both adding and subtracting. Consider One Large CW Pump (with Standby) vs a pump for each chiller. Some of the modular chiller manufacturers actually remove evaporators as the stage down in variable flow applications.
Heat-Recovery Chiller heat-recovery condenser standard condenser evaporator
Chiller Heat Pump Any water cooled chiller is a heat pump within certain temperature limits Some can be designed and selected for high temperature hot water applications Screws and Scrolls are easiest for high lift duty Centrifugals are harder to get high lift, two compressors in series
Chiller Heat Pump Work with the manufacturer on product selection MUST have an evaporator load to make heat, so be very careful if this chiller is expected to run at part load
Application Outside Range of Chiller air-cooled chiller 240 gpm at 45 F [15 L/s at 7.2 C] 240 gpm at 56.7 F [15 L/s at 13.7 C] 80 gpm at 80 F [5 L/s at 26.7 C] 80 gpm at 45 F [5 L/s at 7.2 C] process load
Free Cooling Cool Chilled Water System with the Cooling tower water Outdoor WB dependent Chillers can be off or supplement the system Plate & Frame heat exchanger rated to AHRI 400-2015
Waterside Economizer Plate-and-Frame Heat Exchanger distribution pump plate-and-frame heat exchanger
Waterside Economizer Refrigerant Migration from compressor to compressor condenser liquid flow shutoff valve shutoff valve vapor migration evaporator
Chilled Water Plant Control Temperature Flow Load KW or Amps Critical Zone or CW Valve Position
Load Indicators Temperature supply-water temperature return-water temperature chiller-plant controller
Load Indicators Flow chiller-plant controller flow meter
Load Indicators Capacity return-water temperature flow meter supply-water temperature chiller-plant controller
Chiller Rotation equal-capacity chillers
Improving Chiller/System Efficiency Maintenance is the first place to start Leak Check, Brush Condenser Tubes, Clean Air Cooled Condensers Lower Cooling Tower Water temperature BUT not so low that Oil Pressure differential is lost Be careful on W/C screw chillers as so don t have an electric oil pump.
System Optimization Chiller Decrease condenser-water temperature Increase chilled-water temperature Chilled-water pump (variable-flow system) Increase chilled-water T Cooling tower Increase condenser-water temperature Condenser-water pump (variable-flow system) Increase condenser-water T
Chilled Water Reset Pros Reduces chiller energy Can work in constant-flow systems Cons Increases pump energy in variableflow systems Can cause loss of space humidity control Complicates chiller sequencing control
Trend Toward Lower Flow Rates electric-driven chiller evaporator flow rate leaving chilled-water temperature condenser flow rate entering condenser-water temperature yesterday 2.4 gpm/ton [0.043 L/s/kW] 44 F [6.7 C] 3.0 gpm/ton [0.054 L/s/kW] 85 F [29.4 C] today 1.5 gpm/ton [0.027 L/s/kW] 41 F [5 C] 2.0 gpm/ton [0.036 L/s/kW] 85 F [29.4 C]
Low-Flow Systems annual energy consumption, kwh 750,000 600,000 450,000 300,000 chiller 150,000 pumps 0 cooling tower fans base case low flow
Control of Condensing Pressure condenser evaporator control panel
Evaporative Condenser fan refrigerant vapor condenser coil liquid refrigerant sump subcooler pump
Cooling Tower propeller fan sprays fill outdoor air sump 85ºF [29ºC] to condenser from condenser 95ºF [35ºC]
Condensing Temperature Control flow-regulating valve condenser water pump condenser
Vary Condenser Water Flow Rate cooling tower cooling tower variable-speed drive condenser diverting valve bypass pipe condenser
Vary Entering Water Temperature variablespeed drive cooling tower cooling tower condenser bypass pipe condenser diverting valve
Cooling Tower Bypass 40ºF [4ºC] cooling tower 55ºF [13ºC] bypass pipe condenser diverting valve 65ºF [18ºC]
Condenser-Water Temperature annual energy consumption, kwh 300,000 200,000 100,000 85 F [29.4 C] 70 F [21.1 C] 55 F [12.8 C] optimal control condenser-water temperature set point cooling tower chiller
Chilled Water Plants Look at chilled water plant kw/ton, not just chiller kw/ton Add chiller, chilled water pumps, condenser water pumps and cooling tower fans together to get the plant kw/ton Need a good and accurate flow meter
Thermal Storage Cooling Can be designed or added to a chilled water system Chilled water tanks, 1 BTU is 1 lb of water changed 1 degree F, larger in size Ice storage, 144 BTU is 1 lb of water changed from liquid to water at 32 degree F, smaller in size
On-Peak and Off-Peak Periods 100 cooling load, % of design 75 50 25 off peak on peak off peak 0 midnight 6 a.m. noon 6 p.m. midnight
On-Peak Cooling with Ice 100 cooling load, % of design 75 50 25 make ice melt ice 0 midnight 6 a.m. noon 6 p.m. midnight
Ice Storage Tank
Ice Storage Tank water ice heat-transfer fluid inside tube near beginning of freezing process near end of freezing process
Positive-Displacement Compressors Impact on Chiller Capacity operating leaving-fluid refrigerant refrigerant mode temperature temperature density* cooling 40 F 36 F 0.972 lb/ft³ (4.4 C) (2.2 C) (15.6 kg/m³) ice-making 22 F 15 F 0.640 lb/ft³ (-5.6 C) (-9.4 C) (10.2 kg/m³) *HFC-134a
Small Air-Cooled System bypass valve pump cooling coil with three-way control valve ice valve air-cooled chiller ice storage tanks
Large Water-Cooled System cooling coil with two-way control valve ice pump bypass pipe VFD ice storage tanks load pump VFD water-cooled chiller chiller pump
Intermediate Heat Exchanger ice storage tanks cooling coil load pump VFD chiller pumps heat exchanger ice valve existing chillers ice-making chiller ice pump
Maintenance Suggested basic maintenance plan In all cases, refer to the manufacturer s data for their exact requirements Be aware of maintenance requirements for warranty Electric Chillers-Scroll, Recip, Screw and Centrifugal Absorption
Maintenance Considerations Mechanical Components Required maintenance Compressor and motor: no maintenance required Controls: no maintenance or calibration required Recommended maintenance Visually inspect overall unit Inspect safety controls and electrical components Tighten electrical connections Check for leaks Meg Electric Motors
Maintenance Considerations Mechanical Components Other design-specific requirements Change oil when oil analysis dictates Replace oil filter periodically Replace filter drier periodically Clean oil strainers annually Check shaft alignment annually Check coupling annually Replace shaft seal every 2 to 4 years Compressor teardown inspection every 5 to 10 years
Maintenance Considerations Heat Transfer Surfaces Recommended maintenance Use a qualified water treatment specialist Clean condenser tubes as needed Clean water-side strainers Test tubes every 3 years with Eddy Current
Heat Transfer Surfaces Log and track the approach temperature Approach temp is the difference between the refrigerant temperature in the heat exchanger to the leaving water temp i.e., evaporator refrigerant temp is 40 F and chilled leaving water temp is 42 F so the approach temp is 2 F
Fluid Analysis Oil analysis Conduct annual analysis to verify system integrity Measure oil pressure drop to determine if filter needs changing Measure charge Refrigerant charge Conduct analysis of refrigerant Inspect purge system
Oil Analysis Why perform regular oil analysis? Helps reduce maintenance costs Detects problems without compressor disassembly Extends service life of oil charge Reduces environmental problems related to oil disposal Helps maintain compressor efficiency and reliability Helps lower refrigerant emissions
Maintenance Water-Cooled Care must be taken on chillers with Brazed Plate Heat Exchangers to ensure long life with good filtration and water treatment as they are not mechanically cleanable. If they are fouled, reverse flow cleaning, acid cleaning OR replace!!
Absorption Chiller Types singleeffect doubleeffect directfired
Absorption Refrigeration Cycle reject heat heat energy in D C condenser generator expansion device pump A evaporator absorb heat B absorber reject heat
Absorption Refrigeration Cycle 1 psia [6.9 kpa] 1.5 psia [10.3 kpa] 5 psia [34.5 kpa] 15 psia [103.4 kpa] B C D concentration 0.1 psia [0.69 kpa] A F E 50 F [10 C] 100 F [37.8 C] 150 F [65.6 C] solution temperature 200 F [93.3 C] LiBr solution
Absorption Refrigeration Cycle steam or hot water generator evaporator heat exchanger absorber B D E C F A cooling water condenser chilled water expansion device
Single-Effect Chiller condenser generator evaporator absorber
Double-Effect Chiller low-temperature generator high-temperature generator condenser evaporator absorber
Direct-Fired Chiller condenser low-temperature generator evaporator absorber high-temperature generator
Direct-Fired Burner Daily maintenance Verify proper operation Seasonal maintenance Inspect burner firing rate, blower, linkage, and safety controls Test run with alternate fuel, if dual-fuel burner
Heat Transfer Surfaces Recommended maintenance Use a qualified water treatment specialist Clean absorber and condenser tubes as needed Clean waterside strainers Test tubes every 3 years with Eddy Current
Corrosion Inhibitors Absorbent solution analysis Conduct annually or semiannually Verifies corrosion inhibitor levels Verifies performance additive levels Refrigerant analysis Conduct annually
Mechanical Components Recommended maintenance Pump teardown and inspection every 5 to 10 years Controls: no maintenance or calibration required Visually inspect overall unit Inspect safety controls and electrical components Meg Electric Motors
Purge System Weekly maintenance Check level of liquid refrigerant in purge condensing unit Check vacuum pump oil Semiannual maintenance Inspect purge condensing coil and clean as necessary Change vacuum pump oil as needed
Credits for Seminar Trane Air Conditioning Clinic Series ASHRAE Handbooks, Standards and Guidelines AHRI Standards Climacool Corp Emerson Electric Calmac Ice Storage
Helpful Websites www.aps.com www.ashrae.org www.ahrinet.org www.carrier.com www.mcquay.com www.trane.com www.jci.com/york
Closing Comments Questions Future of HVAC Industry Future for Arizona Future for Electric Utility Industry Future of Energy Costs