VRF Applications ASHRAE (ASHRAE 15 & 34, ASHRAE TC 8.7)

Report
VRF Equipment & Applications
Ruben Willmarth
West Region Sales Manager
Toshiba Carrier Ductless & VRF
November 07, 2014 Billings, MT Joint
Engineering Conference
CONTENTS
What is VRF
Global Application Examples
Benefits of VRF systems
System Components
Controls
Basic Design Practices
ASHRAE Std 15 & 34
WHAT IS VRF
“VRF” system is a short for Variable
Refrigerant Flow system. Refrigerant
flow is varied based on demand
- System where multiple
(up to 50 indoor units) can be
connected to outdoor units.
- Fan coils are controlled
individually or by group controls.
- Refrigerant flows to the unit that is
calling for heating or cooling.
VRF Technology Overview
Two VRF System Types
HeatRecovery
Pump
Heat
Simultaneous
Cooling
& Heating
Single
Mode: Cooling
or Heating
Only
VRF Technology Overview
Primary Components of a Heat Pump System
Outdoor Unit
Indoor Unit
Controller
• Controls
Compressor Speed
• Maintains
Operational Mode
• Transfers Heating
and Cooling to
Space
• Allows for Optimal
Zoning
• Controls Space
Temp and IDU Fan
• Remote or Central
Typical VRF Heat Pump System
Outdoor unit
Compressor
Liquid line (fully liquid)
Indoor unit
Refrigeration Pipe
(Liquid, Gas)
Each indoor unit can be controlled individually.
On/Off setting , Set point, Air volume, louver position can be set individually.
(Operation mode priority : Cooling or Heating, not simultaneously in heat pump model)
Cooling : Expansion=Indoor unit
Liquid line=Condensed liquid
Heating : Expansion=Outdoor unit Liquid line =Condensed liquid
VRF Technology Overview
How does VRF work?
Indoor
Outdoor
Flow
Selector
Unit
Unit
Controller
• • Transfers
Houses multiple
Receives
heating
superheated
and
inverter
cooling
gasdriven
and
directly
subcooled
compressors
to theliquid,
spaceadjusts
Compressors
flow
direction
change
toAir
heat
Temperature
speed
and cool
based
onlevel
demand of indoor
• • Measures
Allows
for Return
indoor
unit
control
at zone
Pulse
units,
Allows
Motor
which
fordesired
indoor
Valve
varies
(PMV)
unit
theto
refrigerant
adjusts
be in either
tofan
flow
meet
cooling
setpoint
or heating
• • Takes
user
space
setpoint,
speed,
mode
• • Filters
Segmented
mode
and distributes
ODU Coilthe
for air
efficient heat transfer
Unit operates to match exact building load
Unit
Unitoperates
operatestotomatch
matchexact
exactbuilding
buildingload
load
Typical VRF Heat Recovery System
Simultaneous heating and cooling, uses 3 - Pipe
cooling mode waste heat for heating
Heat Recovery Box
Typical VRF Heat Recovery System
2 - Pipe
Varying Refrigerant Flow
How does the outdoor unit respond to the varying
demands and vary the flow of refrigerant?
The compressor(s) in the outdoor units are inverter
driven which means that their speed can be varied by
changing the frequency of the power supply to the
compressor.
As the compressor speed changes, so does the
amount of refrigerant delivered by the compressor.
SYSTEM ADVANTAGES
High
Efficiency
High
High
Reliability
Reliability
Stable
Operation
Use Wherever Part Load Exists
Application:
In case of:
Not all units are on.
Example: office area is on,
meeting room is off.
In case of:
Orientation of building
Example: East/West
exposure
In case of:
Decreased load.
Example: office closed
OFF
Apartment,
Office building
ZONING OPERATION OF VRF
(In case of cooling)
: Piping
: 4-way cassette type
: Hi-wall type
: Outdoor units
ADVANTAGES OF VRF
- Comfort
- Design flexibility
- Energy savings (part load, heating)
- Cost effective installation
ADVANTAGES OF VRF
COMPRESSOR COMPARISONS
Rotary compressor
Scroll compressor
COMPRESSOR COMPARISON
Twin rotary compressor
Scroll compressor
Out
Out
In
In
In
ADVANTAGES OF VRF
EASE OF DESIGN
Multiple types of Fan Coils and Sizes provides design
flexibility for many different applications
ADVANTAGES OF VRF
Modularity of equipment allows for Staging of
installation, Redundancy in operation
ADVANTAGES OF VRF
HX, and
ADVANTAGES OF VRF
TECHNICAL TRAINING
1200 apartments in 7 buildings
Recognized by China’s Ministry of
Construction as being among the
most cost-effective air
conditioning systems available.
Shengshi Qiantang Garden
3,840Tons
2
3
Jae Neung Education Building
2,400Tons
2
4
Portal Commercial Development
280Tons
2
5
Approx. 10,000 sq. ft
7 floor multi-tenant
office building
Burt Hill Architects Office
2
6
26
Installed in subway passages and
administration offices
Contracts extending to other lines
China Subway
19,200Tons
2
7
27
DESIGNING WITH VRF
High
Efficiency
High
High
Reliability
Reliability
Stable
Operation
Designing for Energy efficiency
Perimeter/Core
Office 107
3.0kBTU
Pres. Office
12 kBTU
Office 108
3.0kBTU
13.5 kBTU
6
1
12 kBTU
Foyer
2.5kBTU
Corr
2.0kBTU
Rejected
2
5
Women’s
2.0kBTU
Coffee/Brk
2.0kBTU
12 kBTU
2.5
kBTU
Heat
Office 104
3.0kBTU
Office 105
3.0kBTU
Men’s
2.0kBTU
VP Office
14 kBTU
4
Office 106
3.0kBTU
Conf.
28.0kBTU
Office 110
7.5kBTU
20 kBTU
Office 101
6.0kBTU
7
28 kBTU
Corr
2.0kBTU
3
14 kBTU
Office 110
4.5kBTU
Office 109
3.0kBTU
Office 102
6.0kBTU
Office 103
6.0kBTU
Example: 40oF Ambient
Ventilation Design
• Ventilation Strategies with VRF
Room graphic
w/Air into Corner
Delivering OSA directly to the space:
1. Best when it is Neutral temperature & Humidity
(DOAS)
2. An ERV-only is OK in the West & South, if low
fraction and high ceilings (mixing time)
3. Mild Climates can bring in small fraction
untreated
4. Benefits are less ducting, more flexible application
30
Ventilation Design
Ventilation Strategies with VRF
Delivering OSA ducted to the Fan Coil:
1. Pre-Filtered, tempered air is best. (DOAS)
1.
2.
Allows selecting to meet Envelope load for max comfort
Air inlet point is before the filter on some ductless, so Filter is a
must!
2. An ERV-only is Good in the West & South, but may need
additional heat in the North
3. DOAS system or ERV+FC is best for Cold Climates
4. Mild Climates can bring in small fraction untreated (<30%)
5. Benefits are better humidity control, no extra grills
31
Ventilation Design
DOAS using an ERV
1. DOAS approach allows us to split the ventilation
load away from the Mechanical system by
tempering the air first.
A. Can use an ERV only for most applications
B. Can run OSA through a standard Fan Coil in Series for Neutral
Air application, especially if not ducted to Fan Coils
C. Can apply Supplemental Heat for Cold Climate applications for
Neutral Air, or even higher
32
Heating Design
Heating Design Strategies
Heating with a VRF System:
-VRF is a Heat Pump, but….
A. But it is not your Grandpa’s Heat Pump!
B. Capacity is better than traditional because of inverter
compressors that can spin faster to compensate
C. De-rate due to ambient temperature is less, but must still be
accounted for.
D. Auxiliary Heat to cover the <average
33
Heating Design
Heating Design Strategies- Avg. vs. Design:
1. The Design Heating in Billings is -20F
2. But the Average January Low is 16F
“Avg. winter
low in Billings,
MT is 16F”
34
Ventilation Design
Heating Design Strategies
When to use Auxiliary Heat?
A. Rule of Thumb is start considering it at 15F design temp.
B. Simple Answer is when heating Design Day exceeds capacity
C. ERV & DOAS can provide significant contributions.
“Avg. winter low
in Seattle, WA is
36F”
“Avg. winter low
in Chicago, IL is
17F”
“Avg. winter low
in Billings, MT is
16F”
“Avg. winter low
in Nashville, TN is
29F”
35
Heating Design
Heating Design Strategies-Aux Heat
Types of Aux. Heat:
A. Electric Strip-Heater (Ducted Models only)
B. Hydronic Coil (can feed from an upsized DHW source)
C. Both of above can be placed in DOAS ducting for 90+F
ventilation air if that meets the needed BTU’s!
D. Baseboard Heating Panels
A. Hydronic or Electric-All Fan Coils
E. Radiant Panels
A. Hydronic or Electric-All Fan Coils
F. Wall Heaters
A. Typically Electric-All Fan Coils
G. Or….Previously Existing Heating System!!
36
Heating Design
Heating Design Strategies-Aux Heat
There are 3 ways to activate the Aux. Heat
1. Individual Space Response:
1. Zone temp drops, Aux heat activates at Temp. A, then
deactivates at Temp B. Both must be less than heating
setpoint
1. Outdoor Ambient Trigger. Aux heaters engage when FC
is in Heating, Aux Heating system activated by separate
Outdoor Ambient Thermostat.
2. BMS Control system activation. Can use custom logic
for zone by zone response, minimize setpoint drift.
37
Heating Strategies
•
Heating Design Strategies-Aux Heat
Heating Setback with VRF:
A. A VRF system is different from a combustion heater because
it’s efficiency gets better at part-load.
B. When system is in recovery, system goes to full-load, which is
less efficient than maintaining a constant temperature, but total
heat loss is more.
C. So, optimum use is probably minimal setback during
weekdays, and more of a setback over weekends & Holidays,
or just a 2F setback period.
D. No setback during cold snaps to avoid using Aux Heat.
38
Heating Strategies
• Heating Design Strategies-Aux Heat
Alternate to zone-level Aux. Heat-Put Outdoor
Units in a Mechanical Room or “Doghouse”
39
Heating Design
• Heating Design Strategies-Aux Heat
Alternate to zone-level Aux Heat-Put Outdoor Units
in a Mechanical Room or Doghouse:
A. Simplifies controls of Aux. Heat by having one set of controls
and heat source.
B. Heater is typically a Gas unit heater, or other combustion unit
C. Backup isolates from Outdoor air at preset ambient temp.
D. Key Selection Criteria:
A. Size the Unit heater for 70-80% of Heat Load
B. Ducting system must be 0.2” esp max. in both modes
C. Activation temp typically below freezing, but maintain
interior temp around 45F to avoid frost buildup.
D. Don’t forget to include a condensate drain, w/heat tracing
40
Refrigerant system Design
VRF and ASHRAE 15/34
In part, Standard 15, Safety Standard for Refrigeration
Systems, strives to ensure a safe system by limiting the
maximum quantity of refrigerant below that which is a
danger to human occupants if a leak occurs.
Because VRF uses the Refrigerant as the transport
medium, it is inherently a more refrigerant intensive product
than most traditional HVAC. Std. 15 is the application
guideline that ensures a safe design every time.
VRF and ASHRAE 15/34
Refrigerant Concentration Limit (RCL) R410A
R410A is a commonly used refrigerant for commercial VRF
systems. Per Standard 34, Table 2, the safety classification
of R-410A is Group A1 (meaning non-flammable and nontoxic). Even though R-410A is Group A1, its ability to
displace oxygen could pose a danger to occupants if
released in large quantities into smaller-volume spaces.
Therefore, Standard 34, Table 2 has established an RCL for
R-410A at 26 lbs of refrigerant per 1,000 cuft of room
volume.
For Institutional Occupancies such as patient care areas of
hospitals and senior homes, the RCL is cut in half, changing
the RCL for R-410A to 13 lbs/1,000 cuft.
VRF and ASHRAE 15/34
 Smaller Capacity Systems
 Design for “Connected Spaces”
 Combine multiple smaller zones on a single ducted
fan coil unit
 One to-One Systems
 Diversity
 Refrigerant Piping Layout
 Y-branching versus manifold
 Isolate refrigerant circuit for Smaller Rooms
 R410A sensor and alarm, or isolation valves
Stephen W. Duda’s article published in ASHRAE Journal, July 2012. Posted
at www.ashrae.org. Applying VRF? Don’t Overlook Standard 15
Questions
?
Thank
You

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