Presented By: John Dolan, P.E.

Variable Speed Compressor Technologies Presented By: John Dolan, P.E. President - Thermosystems, Inc. BS in Mechanical Engineering from UIUC 29 years HVAC Equipment Application Experience jdolan@thermohvac.com www.thermohvac.com March 14, 2017 Page 1

Variable Speed Compressor Technologies Why to Apply Energy Savings Capacity Control Available Technologies & Application Motors and Bearings Centrifugal Compressors Screw Compressor Positive Displacement Scroll Compressor Positive Displacement When to Apply When Not to Apply Questions 2

Positive Displacement Compressor 3

Basic Refrigeration Cycle LIFT (ΔP) 4

Water Cooled Flooded Chiller Refrigeration Cycle 5

Basic Direct Expansion (DX) Refrigeration Cycle 6

Refrigeration Cycle 4 3 1 2

Reducing Compressor Lift (P cond -P evap = ΔP) EXV EXV 8

Variable Speed Compressor Technologies Why to Apply? Energy Savings (Reduce Lift) Lower Compressor RPM = Less Work = Less Energy $ Fan/Pump Laws - RPM Energy³ Take Advantage of Lower than Design Condenser Temps How Often is Outside Ambient at Design Temp (DB or WB)? O'Hare Weather Bin Data 6 hours/yr 95 F Match Compressor Operation to Actual Condenser Conditions (Lower Temperatures Lower Pressures) Capacity Control How Often is Building or Space at Full Load? (<1%) Proportional Control with VFD vs. Staged Control (On/Off) Modulate Flow of Refrigerant to Match Load (Screw and Scroll) Chiller - More Stable Control of Leaving Water Temperature No Return Water Control or LWT Set Point Reset DX Air Handler - More Stable Control of Discharge Air Temperature (DB & WB) 9

Variable Speed Compressor Technologies Why to Apply? Higher Efficiency Motors with Variable Speed Operation AC Induction Motor with Variable Frequency Drive Permanent Magnet Synchronous Motor (PMSM) Motor Speed Operating Range with PMSM No longer limited to 1800 & 3600 RPM (AC Induction Motor Speeds) Direct Drive Operation Gears to Increase Impeller Speed no Longer Required No Transmission Losses (Gears) Magnetic Bearing Technology Eliminate Oil and Oil Components (Oil Sump, Oil Pump, Oil Heaters, Oil Separators, Safeties) Improve Heat Transfer & Reduce Compressor Wear Sustainable Efficiencies for Life of Chiller

Quick Electric Motor Review AC Induction Motor Most Common Motor in HVAC Fixed Speeds Based on 60Hz (1800 & 3600 RPM) Max Motor Speed 3600 RPM Slip Permanent Magnet Synchronous Motor (PMSM, ECM) More Efficient than AC Induction Motor - Especially at Part-Load Electronically Commutated (ECM) Synchronous Motor Zero Slip VFD for Starting Required (Even in Constant Speed Applications) VFD Integral to Motor in Some Sizes Smaller Size than Comparable Hp AC Induction Motor Higher Speeds Allow for Matching Speed to Application 11

Motor Efficiencies (AC Induction vs. PMSM) PMSM (ECM) NEMA Premium Eff AC Induction Motor

Oil Effects on Heat Transfer Conclusions and Recommendations: The heat transfer ratio drops steadily with oil concentration and reaches a value of 0.65 [from 1.0 normalized] at an oil concentration of 10%. From ASHRAE Research Project 751-RP, Experimental Determination of the Effect of Oil on Heat Transfer with Refrigerants HCFC-123 and HFC-134a, 35% heat transfer reduction with 10% oil concentration in refrigerant

Oil Effects on Chiller Efficiency Direct Drive PMSM Oil-Free Compressor Design Eliminates the Performance Degradation Due to Oil Contamination of the Refrigerant Source: The News, 04/15/04, by Jack Sine

Traditional Centrifugal Design (Oil Based) Impeller Gear Set (Oil) Thrust Bearings (Oil) 3600 RPM AC Induction Motor Radial Bearings (Oil)

Traditional Centrifugal Design (Oil Based) Traditional Centrifugal Compressor (Geared Impeller & Traditional Oiled Bearings)

Magnetic Bearing Centrifugal Compressor Impeller + Inlet Vanes Front Radial Bearing High Speed Permanent Magnet Synchronous Motor Rear Radial Bearing Axial Thrust Bearing

Magnetic Bearing Compressor Magnetic Bearings and Sensors VFD in External Panel Inlet Guide Vanes Suction Gas Single Stage Impeller Permanent Magnet Synchronous Motor Magnitude WME Compressor Rotating Group Discharge

kw / ton Water Cooled Centrifugal Chiller Efficiencies 1.2 1 0.8 0.6 30% energy reduction Fixed Speed Motor 0.4 0.2 10% energy reduction AC Induction w/ VFD High Speed VFD w/ Magnetic Bearings 0 0 10 20 30 40 50 60 70 80 90 100 110 Chiller percent load Note: Based on 500 ton Chiller with Same Condenser and Evaporator

Operating Hours kw / ton Operating Cost Comparison Centrifugal Chillers 900 1.2 800 700 Fixed Speed ~ $243,287/year Cooling Load Profile 1 600 0.8 500 0.6 400 300 Traditional VFD ~ $164,934/year 0.4 200 10% energy reduction High Speed VFD w/ Mag Bearing ~ $131,709/year 0.2 100 0 0 0 10 20 30 40 50 60 70 80 90 100 Chiller Percent Load Note: Based on 500 ton Chiller with Same Condenser and Evaporator and $0.10/ per kwh

fixed CONSTANT SPEED & VOLUME SCREW COMPRESSOR Discharge to Condenser P cond Over Compression or Lost Work P A B Pd Pc Ps fixed V displacement 2016 Daikin Applied

variable VARIABLE SPEED SCREW COMPRESSOR Discharge to Condenser VFD on Compressor Motor Varies the Volume of Refrigerant and Discharge Pressure is Controlled by the Slide Valves Point B Point A Pc B A variable Vd 2016 Daikin Applied

Scroll Compressor Technologies Fixed Speed Scroll On/Off Staged Control Digital Scroll Constant Speed Variable Capacity Load/unload 20sec time step Variable Speed PMSM or AC Induction Motor w/vfd Variable Speed Compression and Capacity Control 23

Variable Speed vs. Variable Capacity % Compressor Power 25% 35% 45% 55% 65% 75% 85% 95% 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Digital scrolls are Off/On for Compression with Constant Speed AC Motor Digital Scroll Rebel Variable Speed % Cooling Capacity 24

Compressor Operation Scroll Compressor Staging (Variable and Constant Speed) 2 Condensing Units 4 Compressors Capacity Control 100% INV NON INV NON 7% System Capacity 25

Airside Compressor Cycling Effects 26

When to Apply Significant Hours with Lower than Design Condenser Temperatures Take Advantage of Lower ECWT or Ambients Reduce Lift Wherever Possible Lower Condenser Temps (Water) Higher Evaporator Temps (Chilled Water Temp or Discharge Air) Significant Hours with Lower than Design Load Watch Minimum Loading with Constant Speed Machines Excessive Cycling on Large Hp Compressors Generator Back-Up VFD Compressors will have Lower Inrush at Start-up Variable Chilled Water Flow Applications Better Control of LWT Less Cycling of Compressors (Air Cooled Chillers) 27

When to Apply 28 Meeting or Exceeding ASHRAE 90.1 & IECC Efficiencies Water Cooled Compliance (Full Load kw/ton and IPLV) Air Cooled Compliance (EER and IEER) Path A (Constant Speed) vs. Path B (Variable Speed) Must Meet Both Full Load kw/ton and IPLV Utility Rebates for Higher Efficiency Equipment More Rebate $ for Better IPLV or IEER Rebate May Offset or Pay for VFD Humid Areas Stable Leaving Water Control or Leaving Air Control More Latent Cooling & Stable Coil Discharge Temperatures Minimize or Eliminate Condensate Re-Evaporation when Compressor Shuts Off Sound Sensitive Applications Variable Speed Equipment is Quieter than Constant Speed

When Not to Apply Centrifugal Chiller Applications with Minimal Condenser Relief Humid Areas with Constant Loads (High WB) Very Large Tonnage Plants 60,000 ton Plant with 20+ Chillers Large Airside Applications with Multiple Scroll Compressors 100+ tons with 6 or 8 stages Compressor that is Off is Always More Efficient than Operating Compressor Airside DX Applications in Dry Climates (Low Latent Loads) Sensible Load Applications Discharge Air Reset or Leaving Water Reset Heat Recovery Chiller Applications Fixed Lift Any Others? Page 29

Questions Page 30