Idea Transcript
Efficiency Vermont is a Registered Provider with The American Institute of Architects Continuing Education Systems (AIA/CES). Credit(s) earned on completion of this program will be reported to AIA/CES for AIA members. Certificates of Completion for both AIA members and non-AIA members are available upon request. This program is registered with AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product. Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation. Joe Cefaly – Mitsubishi Electric
Learning Objectives
Basics of heat pump technology
How VRF systems are different than older technologies
Advantages of these systems for average buildings and high performers as well
How to properly apply VRF systems for cold climates
Course Evaluations In order to maintain high-quality learning experiences, please access the evaluation for this course by logging into CES Discovery and clicking on the Course Evaluation link on the left side of the page.
Basics of Heat Pump Technology
Basic Refrigeration Cycle
RED = Higher Temp/Pressure
BLUE = Lower Temp/Pressure
Basic Refrigeration Cycle Evaporator
High-Pressure Vapor
High-Pressure Liquid Low-Pressure Liquid Low-Pressure Vapor
Condenser
Basic Refrigeration Cycle RED = Higher Temp/Pressure Subcooled Liquid
Condensing
Gas
Expansion Cycle
Pressure
Liquid
Liquid and Gas
Evaporating
BLUE = Lower Temp/Pressure Enthalpy
Superheated Gas
Refrigeration Components
Scroll Compressor • Hermetic (refrigerant cooled) •Typically constant speed (on/off) • Improved technology provides variable speed/variable flow • Smaller sizes – Multiple scrolls used for larger capacities
Scroll Compressor Intake
Compression
Fixed Scroll
Orbiting Scroll
Assembled Scrolls
Discharge
Compressor Evaporator
High-Pressure Vapor
High-Pressure Liquid Low-Pressure Liquid Low-Pressure Vapor
Condenser
Condenser • Air or Water • Refrigerant changes from gas to liquid
Condenser Evaporator
High-Pressure Vapor
High-Pressure Liquid Low-Pressure Liquid Low-Pressure Vapor
Condenser
Thermal Expansion Valve (TXV) • Metering Device used in traditional DX systems • Controls superheat at outlet of coil Capillary Tubing
External Equalizer Line
TXV Evaporator
High-Pressure Vapor High-Pressure Liquid Low-Pressure Liquid Low-Pressure Vapor
Condenser
Evaporator Heat
and moisture is removed from the air stream Refrigerant evaporates
Suction Header
Fins
Feeder Tubes Refrigerant Distributor Evaporator Tubes
Evaporator Coils
Evaporator Evaporator
High-Pressure Vapor High-Pressure Liquid Low-Pressure Liquid Low-Pressure Vapor
Condenser
Reversing Valve • Used in Heat Pumps • Allows change in refrigerant flow direction to switch between heating or cooling mode
How VRF Systems are Different than Older Technologies
What is VRF?
Variable Refrigerant Flow
Brief Description VRF • Moving refrigerant rather than air for zoning • Inverter-driven compressor performs at the minimum energy level necessary to provide comfort in each zone (down to 6% capacity) • Each variable capacity indoor unit operates independently from the other indoor units for individual zone comfort control • Supply air conditioning and heating only to rooms that require it • Uses natural building diversity to reduce initial equipment investment
Worldwide Usage Window Unitary
Japan 90% 7.2M Systems
Chillers Moveble Ductless
China 86% 16.7M Systems
Europe 81% 7.6M Systems
USA 3% 0.2M Systems
Ductless is a small percent of the U.S. HVAC market but current building and energy usage trends indicate a large growth opportunity
Inverter-Driven Compressors • What is an Inverter? – A variable speed drive that changes the voltage and frequency being fed to the motor – Think of the inverter as a throttle control • Changes electrical frequency from 60 Hz to a varying range of 15 Hz to 125 Hz • Frequency is affected by: – Number of indoor units operating – Outdoor unit model – Outdoor unit target temps/pressures • Greatly reduces energy usage
Inverter-Driven Compressors Conventional ON/OFF Systems
Room Temperature
90°F
Very slow! Too warm
Uncomfortable! 79°F
Set Temp.
77°F 75°F Too cool
OFF 60Hz
Inefficient! ON
0Hz
High starting current = Energy loss
Inverter-Driven Compressors Inverter Compressor Advantage
Room Temperature
90°F
Very fast! Set Temp.
Comfortable!
Room temperature is steady 75°F High rotation speed up to 100‐125Hz generates accelerated performance!
150Hz
Adjust rotation speed precisely to keep steady room temperature
60Hz 30Hz
ON Compressor
0Hz
starting current at low level
Very efficient!
Keep rotation speed low after temperature is stabilized
VRF System Types VRF Heat Recovery Technology (Air-Source) – Simultaneous Heating and Cooling
Simultaneous Heating and Cooling
VRF System Types VRF Heat Recovery Technology (Water-Source) – Simultaneous Heating and Cooling
Heat is recovered between the condensing units within the water loop
(To cooling tower/boiler or geothermal field)
Heat is recovered between the indoor units within the refrigerant loop
VRF System Types VRF Heat Pump Technology (Air-Source)
HEATING
COOLING
VRF System Types • VRF Heat Pump Technology (Water-Source)
PQHY Unit “A”
COOLING Heat is recovered between the condensing units within the water loop
PQHY Unit “B”
HEATING Water Circuit (To cooling tower/boiler or geothermal field)
Refrigerant Circuit
Typical Heat Recovery System: Heat Recovery Systems with a connected capacity of 150%. Available up to 24 tons. Outdoor or Water Source Unit
+
BC Controller
+
Indoor Units
+
Control System
=
Simultaneous Cooling, Heating
Typical Heat Pump System: Heat Pump Systems with a connected capacity of 130%. Available up to 30 tons. Outdoor or Water Source Unit
+
Headers and/or Branch Joints
+
Indoor Units
+
Control System
=
Heat Pump
Product Lineup: Cassette Style Indoor Units
Ducted Style
Exposed Style
Product Lineup: Energy Recovery Ventilators • Cross-flow energy exchange core • ~ 70% recovery of sensible and latent energy • Integrates with control system
Product Lineup: Controls System • •
Easy to install and operate 2-wire direct digital control system – 16ga stranded and shielded, non-polar – Daisy-chain connection
• • • • • •
Customizable control scheme with web access Individual room controls Color touch screen centralized control Integration into building management system via BACnet® and Lonworks® Third-party equipment control Tenant billing capability
Advantages of these Systems for Average Buildings and High Performers as well
Zoned Comfort
• No more hot spot cold spot issues • Individual control means individual comfort • Quiet operation
Refrigerant Piping Flexibility PIPING LENGTH Water
Simultaneous
Total Piping Length
2460 ft.
Water Heat Pump 1650 ft.
PIPING HEIGHT
Air Cooled
Single Phase
3280 ft.
393 ft.
Air Cooled Water SSeries Series Series
Outdoor Unit HIGHER than Indoor Unit
164 ft.*
98 ft.
Outdoor Unit LOWER than Indoor Unit
131 ft.
65 ft.
Indoor Unit to Any BC Controller *Elevation differential up to 295’ available in 2009 . Additional limitations may apply
49 ft.
n/a
n/a
What Does QUIET Sound Like?
How QUIET is VRF? Mitsubishi Indoor Unit
As low as 19 dB(A)
Mitsubishi Ducted Unit
Mitsubishi Residential Outdoor Unit Mitsubishi Commercial Outdoor Unit
As low as As low as aAstraditional high as As low as How LOUD is HVAC unit? 23 dB(A) 46 dB(A) 57 dB(A) 61 dB(A)
25 dB(A) 33 dB(A) 40 dB(A) Recording Library Quiet Home Studio
50 dB(A) 60 dB(A) 70 dB(A) 78 dB(A) Refrigerator Conversation Busy Traffic Vacuum
90 dB(A) Motorcycle
50-60 dB(A)
65-75 dB(A)
75-85 dB(A)
PTAC Unit
Residential 3-ton HVAC Unit
Air-cooled Chiller
100 dB(A) Hand Drill
Energy Savings
• • • •
Inverter-driven compressors No waste heat with simultaneous heating and cooling Up to 130-150% indoor unit connected capacity Meets requirements for LEED points
EER
50%
VRF Unitary
0%
Power Consumption
100%
Full Load vs Partload Efficiency
0%
30%
50%
70%
Equipment Loading
100%
Space Savings Space Required to Deliver 20 tons of Cooling VRF 20 tons
Ducted 20 tons
30″ Round Supply Duct
11/8″ Liquid 11/8″ Gas
Chilled Water 20 tons
3″ CHW supply 3″ CHW return
Ducted 20 tons
40″ x 20″ Supply Duct
Ease of Installation
• • • •
Less intrusive to existing architecture Modular condensing unit design Smaller indoor unit electrical distribution Indoor unit flexibility and small size to meet the needs of any space
VRF Equipment Weight Savings • Average equipment weight per ton for VRF is 70 lbs per ton (outdoor unit only) • Average equipment weight per ton for water-cooled chiller is 101 lbs./ton
31% reduction in equipment weight 44
Weight Reduction = Structural Reduction
45
VRF Frees Up Building Space
46
Reduced Mechanical Space
• Traditional systems require space for pumps, boilers, chillers, ducts, piping, heat exchangers • VRF offers efficiency without requiring the space 47
VRF Installation Flexibility Ease of transportation
Easy installation
Roof top VRF Economy of Scale
Smaller Footprint = More Green Space
50
Where to use VRF? • Buildings where zoning is important
• Retrofits and renovations
• Sound-sensitive applications
Where to use VRF? • LEED and energy-efficiency projects
University of Washington: 25% Energy Savings
Hotel Terra: LEED Silver Mercy Corps: LEED Platinum
Case Studies • John Joseph Moakley United States Courthouse – Boston, MA – Replacement of fan-powered VAV system with VRF – Phase I was 9th and 10th floor renovations • 120 tons of CITY MULTI water-source VRF
– Phase II is an additional 100 tons – Future plans to replace all fan-powered VAV
Case Studies • T.C. Williams High School Minnie Howard Campus – – – – –
Alexandria, VA Replacement of chiller/boiler 4-pipe system Geothermal system with 60 wells 46 tons of CITY MULTI WR2 Building energy savings of $32,500 per year over the base case CHW/HW system
Superior High School – Superior, Nebraska 72,000 SF School 36,000 SF Heated and Cooled using VRF 36,000 Heated using Boilers
• School was served by two existing gas boilers and was heating only. • Replaced old boilers with VRF and new modulating boilers to function as back-up heat.
VRF Provided Cooling and Reduced Energy Use by 25%
Burlingham Hall LEED® Gold • Electrical usage reduction of 33.5% vs. ASHRAE 90.1 Baseline • Gas usage reduction of 67% vs. ASHRAE 90.1 Baseline • Awarded 7 LEED points for EAc1
$34,400 annual utility savings
How to Properly Apply VRF Systems for Cold Climates
Air-Cooled Heat Pumps
Extremely efficient, but what about heating in cold climates? Heating capacity rated at 47F db / 43F wb As outdoor temperature decreases, heating capacity decreases Up to 76% heating capacity at 5F wb Up to 68% heating capacity at -4F wb
How do we overcome this heating capacity de-rate?
Option 1: Hyper-Heat Unit PROS: Excellent low temperature heating performance 100% heating capacity at 5F wb 87% heating capacity at -5F wb 75% heating capacity at -13F wb
No auxiliary heat needed No need to oversize equipment
CONS:
Non-simultaneous system Requires changeover
208-230/3/60 only Higher cost of Hyper-Heat vs. Standard VRF Heat Pump
Option 1: Hyper-Heat Unit
Hyper-heating INVERTER Y-Series Outdoor Units Comfortable indoor air temperatures even at low outdoor ambient temperatures (P72 Model)
Indoor unit Discharge Temperature o
o
Discharge Temp F
PEFY-P24NMAU with 70 F Entering Air Temp High speed fan setting (671 cfm) High Heat Setting 120 115 110 105 100 95 90 85 80
112 107 103
104
-13
-10
-4
109
0
5
111
10
Outdoor Temperature
o
F
109
108
107
15
20
25
Hyper-heating INVERTER Y-Series Outdoor Units Component Diagram (Heating) Outdoor Unit Indoor Unit Reversing Valve
SV9
SV2
B
TH4
Indoor Coil
TH7
A
Comp.
Outdoor Coil
H LEV4 Accum. IDU LEV
J TH2
G
C HIC
LEV2a
TH3
F
D E
TH6
LEV1
High Pressure B - C Superheated Vapor Subcooled Liquid
Medium Pressure C - E/F Liquid Subcooled Liquid Liquid/Vapor Mix
Low Pressure G - H Saturated Liquid Superheated Vapor
Injection Circuit E - A Saturated Liquid Liquid/Vapor mixture
Hyper-heating INVERTER Y-Series Outdoor Units Pressure-Enthalpy Cycle (Heating) IDU LEV
Liquid is subcooled here before entering the outdoor coil
LEV1 F LEV2
E
D
B
C The heat that is normally wasted in the flash process at the outdoor coil is picked up here in the HIC (heat interchanger).
J
I
LEV4
HIC A Flash injection enters compressor here to cool compressor
Standard System G H Area of efficiency gained in the outdoor coil normally lost to flash gas
Option 2: Oversizing the System
Size the system for the heating load at the heating design day (low outdoor temperature) Ex: Use a nominal 14-ton system for a 10-ton heating load at 5F
Both outdoor units and indoor units must be oversized
Won’t over-cool because of inverter on compressor
Option 2: Oversizing the System PROS:
Can utilize simultaneous heat recovery system (R2) No auxiliary heat needed
CONS: Higher equipment cost / larger outdoor equipment Larger indoor units have more airflow Larger refrigerant piping / more refrigerant
Heating Comparisons PUHY/PURY Percent heating capacity @5F Current T/Y(S)HMU
NEW T/Y(S)JMU Standard Setting
NEW T/Y(S)JMU High Heat Setting
Approx. Increase High Heat vs Current Units
PUH/RY-P72
60%
60%
74.5%
24%
PUH/RY-P96
60%
60%
74.5%
24%
PUH/RY-P120
60%
60%
70%
31%
PUH/RY-P144
60%
60%
66%
10%
PUH/RY-P168
60%
60%
75.2%
25%
PUH/RY-P192
60%
60%
75.2%
25%
PUH/RY-P216
60%
60%
70%
24%
PUH/RY-P240
60%
60%
70%
31%
PUH/RY-P264
Y-Series only 60%
60%
66%
Y-Series only 16%
PUH/RY-P288
Y-Series only 60%
60%
66%
Y-Series only 14%
PUHY-P312
Y-Series only 60%
Y-Series only 60%
Y-Series only 70%
Y-Series only 28/%
PUHY-P336
Y-Series only 60%
Y-Series only 60%
Y-Series only 70%
Y-Series only 27%
PUHY-P360
Y-Series only 60%
Y-Series only 60%
Y-Series only 70%
Y-Series only 31%
Option 3: Auxiliary Heat Inside Building
Auxiliary control available with all indoor units by utilizing factory-provided contact
Two methods for energizing contact: Based on drop in space temperature Based on outdoor temperature
VRF is the first stage of heat, auxiliary source is the second stage of heat
Option 3: Auxiliary Heat Inside Building PROS:
Can utilize simultaneous heat-recovery system Take advantage of existing heating system if available Provide 100% heating capacity (no de-rate) No need to oversize equipment Auxiliary heat is usually small with low run hours
CONS: Higher system installed cost More complex installation for non-ducted indoor units
Option 4: Locate Outdoor Units Inside (Utilize a Penthouse)
By placing the outdoor units inside a penthouse, they are sheltered from the elements Can duct condenser air discharge (0.24” ESP capability) Must have heat source inside penthouse Must have heat trace if penthouse is kept below 32F Must carefully size and control louvers/dampers to ensure proper airflow and pressurization (condensers move a lot of air)
Option 4: Locate Outdoor Units Inside (Utilize a Penthouse) PROS: Can utilize simultaneous heat-recovery system Easier maintenance inside conditioned penthouse No need to oversize equipment Effective in extremely cold climates Aesthetics CONS: Penthouse design can be complicated Additional cost of penthouse Still need auxiliary heat (inside penthouse vs. inside building) Auxiliary heat runs on outdoor air temperature, not indoor space temperature Space required for penthouse
Questions?