ASHRAE Presentation: VRF Overview
Mitsubishi Electric
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©2011 Mitsubishi Electric& Electronics USA, Inc.
Agenda
General overview of VRF Technology
Review of Design Considerations
Benefits of VRF
Variable Refrigerant Flow (VRF)
Heat Pump
versus
Heat Pump with Heat Recovery
Heat Pump
Heat Pump
Outdoor
Unit
Indoor
Units
Controls
System
Heat Pump
Outdoor
Unit
Indoor
Units
Controls
System
Heat Pump Applications
Restaurants
Lobbies
Others?
Churches
Heat Pump with Heat Recovery
Simultaneous Cooling & Heating
Heat Pump with Heat Recovery
Simultaneous Cooling & Heating
Outdoor
Unit
Branch
Circuit
Controller
Indoor
Units
Controls
System
Heat Pump with Heat Recovery
Simultaneous Cooling & Heating
Outdoor
Unit
Branch
Circuit
Controller
Indoor
Units
Controls
System
Heat Pump with Heat Recovery Applications
Simultaneous Cooling & Heating
Schools
Assisted Living Facility
Others?
Offices
What is the purpose of each component?
Outdoor Unit
• Controls compressor speed
• Controls condenser fan speed
• Controls pressure of refrigerant to maximize capacity and efficiency
Branch Circuit (BC) Controller
• Separates refrigerant into gas and liquid
• Ensures units in heating receive superheated gas
• Ensures units in cooling receive sub-cooled liquid
Indoor Units
• 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
Controls System
•
Integrated sequence of operation
•
Takes input from the user and provides feedback to the system
Recall
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?
VRF Design Considerations
Equipment Layout
Diversity
Ventilation
Heating
Efficiency
Equipment Layout
Equipment Layout
Diversity
Ventilation
Heating
Efficiency
Ceiling Space
20 Ton System
40” x 20”
Rectangular Ductwork (DX System)
30” Round
Round Ductwork (DX System)
3” CHWS&R, 3” HWS&R
Piping (4-Pipe System)
13/8” Gas 1 1/8” Liquid
Piping (VRF)
Equipment
Layout
Diversity
Ventilation
Heating
Efficiency
Rooftop Equipment Weight
80 Ton System
12,000
10,000
8,000
Equipment
Weight (lbs)
6,000
4,000
2,000
0
VAV
Equipment
Layout
RTU w/
SS
Diversity
VRF
Ventilation
4-Pipe
Fan Coil
Heating
WSHP
Efficiency
Vertical Stack WSHPs
Equipment
Layout
Diversity
Ventilation
Heating
Efficiency
Water-source VRF
Equipment
Layout
Diversity
Ventilation
Heating
Efficiency
Piping Lengths
• There are piping considerations for:
▫ Total System Piping Length
▫ Intermediate Lengths
▫ Elevation Differentials
Equipment
Layout
Diversity
Ventilation
Heating
Efficiency
Condensation
• 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
Equipment
Layout
Diversity
Ventilation
Heating
Efficiency
Diversity
Equipment Layout
Diversity
Ventilation
Heating
Efficiency
Solar Diversity
5 Tons
Morning
3 Tons
Afternoon
3 Tons
Morning
5 Tons
Afternoon
What is the
block load?
What is the sum of
the zone peak
loads?
Equipment
Layout
Diversity
Ventilation
Heating
Efficiency
Occupant Diversity
WORK ROOM 103
CONFERENCE
105
OPEN OFFICE 101
COFFEE
105A
Equipment
Layout
Diversity
Ventilation
Heating
Efficiency
Occupant Diversity
WORK ROOM 103
CONFERENCE
105
OPEN OFFICE 101
What is the
sum of the
peaks?
COFFEE
105A
What is the
block load?
Equipment
Layout
Diversity
Ventilation
Heating
Efficiency
Building Diversity
HEATING
Waste Heat
What
equipment is
running?
COOLING
Equipment
Layout
Diversity
Ventilation
Heating
Efficiency
Designing with Diversity
• 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.
Equipment
Layout
Diversity
Ventilation
Contact your local representative
when designing at greater than
110% connected capacity.
Heating
Efficiency
Designing with Diversity
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
Contact your local representative
when designing at greater than
110% connected capacity.
Equipment
Layout
Diversity
Ventilation
Heating
Efficiency
Ventilation
Equipment Layout
Diversity
Ventilation
Heating
Efficiency
Ventilation
• 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
Equipment
Layout
Diversity
Ventilation
Heating
Efficiency
Heating
Equipment Layout
Diversity
Ventilation
Heating
Efficiency
Special Considerations for Heating
• Utilize manufacturer’s design software
• Minimize connected capacity for colder
climates
• Outside Air
• Consider Building Warm-up
Equipment
Layout
Diversity
Ventilation
Heating
Efficiency
Efficiency
Equipment Layout
Diversity
Ventilation
Heating
Efficiency
Efficiency
• 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
Equipment
Layout
Diversity
Ventilation
Heating
Efficiency
Efficiency
20 Ton System
System Type
Roof Top
Units
Air-Cooled
Chiller
Air-source
VRF
Water-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
Equipment
Layout
Diversity
Ventilation
Heating
Efficiency
What are the benefits of VRF?
• Two-pipe System
• INVERTER Technology
• Multiple Indoor Units
• Variable Capacity System
• Zoning System
• Complete Control Offering