11/12/2012
1
ASHRAE Presentation: VRF Overview
Mitsubishi Electric
Eric Veit
©2011 Mitsubishi Electric& Electronics USA, Inc.
General overview of VRF Technology
Review of Design Considerations
Benefits of VRF
Agenda
11/12/2012
2
Variable Refrigerant Flow (VRF)
Heat Pump
versus
Heat Pump with Heat Recovery
11/12/2012
3
Heat Pump
Outdoor Unit
Indoor Units
Controls System
Heat Pump
11/12/2012
4
Heat Pump
Outdoor Unit
Indoor Units
Controls System
Heat Pump Applications
Restaurants Lobbies
Others?
Churches
11/12/2012
5
Heat Pump with Heat RecoverySimultaneous Cooling & Heating
Outdoor Unit
BranchCircuit
Controller
Indoor Units
ControlsSystem
Heat Pump with Heat RecoverySimultaneous Cooling & Heating
11/12/2012
6
Heat Pump with Heat Recovery
Outdoor Unit
Branch Circuit
Controller
Indoor Units
ControlsSystem
Simultaneous Cooling & Heating
Heat Pump with Heat Recovery Applications
Schools Assisted Living Facility Offices
Others?
Simultaneous Cooling & Heating
11/12/2012
7
What is the purpose of each component?
• Controls compressor speed
• Controls condenser fan speed
• Controls pressure of refrigerant to maximize capacity and efficiency
Outdoor Unit
11/12/2012
8
• Separates refrigerant into gas and liquid
• Ensures units in heating receive superheated gas
• Ensures units in cooling receive sub-cooled liquid
Branch Circuit (BC) Controller
• Sense the space temperature
• Contain a Linear Expansion Valve (LEV) that automatically modulates
• Allow the precise amount of refrigerant through the
heat exchanger
• Filter and distributes air
Indoor Units
11/12/2012
9
• Integrated sequence of operation
• Takes input from the user and provides feedback to the system
Controls System
What system type requires a Branch Circuit Controller?
Which system type cannot provide cooling and heating simultaneously to connected units?
Is there any difference between the controls offered for Heat Pump Systems versus those offered for Heat Pump with Heat Recovery?
Recall
11/12/2012
10
VRF Design Considerations
Equipment Layout Diversity Ventilation Heating Efficiency
Equipment Layout
Equipment Layout Diversity Ventilation Heating Efficiency
11/12/2012
11
20 Ton System
Ceiling Space
Rectangular Ductwork (DX System) 40” x 20”
Round Ductwork (DX System) 30” Round
-Piping (4 Pipe System) 3” CHWS&R, 3” HWS&R
3/ 1/8Piping (VRF) 1 8” Gas 1 ” Liquid
Equipment
LayoutDiversity Ventilation Heating Efficiency
Rooftop Equipment Weight
0
2,000
4,000
6,000
8,000
10,000
12,000
VAV RTU w/SS
VRF 4-PipeFan Coil
WSHP
Equipment Weight (lbs)
80 Ton System
Equipment
LayoutDiversity Ventilation Heating Efficiency
11/12/2012
12
Vertical Stack WSHPs
Equipment
LayoutDiversity Ventilation Heating Efficiency
Water-source VRF
Equipment
LayoutDiversity Ventilation Heating Efficiency
11/12/2012
13
• There are piping considerations for:
▫ Total System Piping Length
▫ Intermediate Lengths
▫ Elevation Differentials
Piping Lengths
Equipment
LayoutDiversity Ventilation Heating Efficiency
• Outdoor Units
▫ Consider location of unit
▫ Consider area drains and floor stands
• BC Controller
▫ Drain pipe connection
• Indoor Units
▫ Drain pipe connections
▫ Some styles include standard condensate lift mechanism
▫ All styles include contact for condensate alarm/safety switch
Condensation
Equipment
LayoutDiversity Ventilation Heating Efficiency
11/12/2012
14
Diversity
Equipment Layout Diversity Ventilation Heating Efficiency
Solar Diversity
5 Tons Morning
3 Tons Morning
What is the sum of
the zone peak
loads?
5 Tons Afternoon
3 TonsAfternoon
What is the
block load?
Equipment
LayoutDiversity Ventilation Heating Efficiency
11/12/2012
15
OPEN OFFICE 101WORK ROOM 103
CONFERENCE
105 COFFEE
105A
Occupant Diversity
Equipment
LayoutDiversity Ventilation Heating Efficiency
OPEN OFFICE 101WORK ROOM 103
CONFERENCE
105 COFFEE
105A
What is the
sum of the
peaks?
Occupant Diversity
What is the
block load?
Equipment
LayoutDiversity Ventilation Heating Efficiency
11/12/2012
16
COOLING
HEATING
What
equipment is
running?
Waste Heat
Building Diversity
Equipment
LayoutDiversity Ventilation Heating Efficiency
• Connected Capacity:
▫ Connect up to 150% of the outdoor unit capacity.
• Actual Capacity:
▫ The actual system capacity is the capacity of the associated outdoor unit.
• A system cannot provide more than 100% of the outdoor unit’s capacity.
Designing with Diversity
Contact your local representative when designing at greater than
110% connected capacity.
Equipment
LayoutDiversity Ventilation Heating Efficiency
11/12/2012
17
Example:
• Indoor units totaling 14 tons can be connected to a 12 ton outdoor unit
▫ Connected Capacity = 14 Tons, 117%
▫ Actual Capacity = 12 Tons, 100%
• The maximum amount of cooling that can ever be provided at a single instant is 12 tons
Designing with Diversity
Contact your local representative when designing at greater than
110% connected capacity.
Equipment
LayoutDiversity Ventilation Heating Efficiency
Ventilation
Equipment Layout Diversity Ventilation Heating Efficiency
11/12/2012
18
• Duct required Outside Air (OA) directly to space or indoor unit
▫ Always calculate entering coil temperatures
• Use Dedicated Outside Air System (DOAS),Energy Recovery Ventilator (ERV), or both to temper the air
• Adhere to local codes in designing ventilation
Ventilation
Equipment
LayoutDiversity Ventilation Heating Efficiency
Heating
Equipment Layout Diversity Ventilation Heating Efficiency
11/12/2012
19
• Utilize manufacturer’s design software
• Minimize connected capacity for colder climates
• Outside Air
• Consider Building Warm-up
Special Considerations for Heating
Equipment
LayoutDiversity Ventilation Heating Efficiency
Efficiency
Equipment Layout Diversity Ventilation Heating Efficiency
11/12/2012
20
• INVERTER-driven compressor matches compressor speed exactly to load
• Simultaneous cooling and heating allows heat recovery between zones
• All efficiency values now available via AHRI Directory
▫ http://www.ahridirectory.org
Efficiency
Equipment
LayoutDiversity Ventilation Heating Efficiency
Efficiency
System TypeRoof Top
UnitsAir-Cooled
ChillerAir-source
VRFWater-source
VRF
IEER 11.5 - 17.7 19.6
EER 9.7 10.3 10.9 10.5
IPLV - 14.2 - -
SCHE - - 18.6 N/A
20 Ton System
Equipment
LayoutDiversity Ventilation Heating Efficiency
11/12/2012
21
• Two-pipe System
• INVERTER Technology
• Multiple Indoor Units
• Variable Capacity System
• Zoning System
• Complete Control Offering
What are the benefits of VRF?