Air Source Heat Pumps for High Performance, Cold Climate Buildings [PDF]

Window. Unitary. Chillers. Moveble. Ductless. Worldwide Usage. Japan. 90%. 7.2M Systems. China. 86%. 16.7M Systems. Euro

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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

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