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Heating, Ventilation and Conditioning
(HVAC) for Hospitals
Presented by Leach Wallace Associates
Presentation for:
September 8, 2011
Important Factors in the Selection of Hospital HVAC Systems
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First Cost
● Energy Efficiency / O&M Cost
● Maintainability
● Reliability
● Redundancy
● Flexibility:
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Change in Occupancy
● Partial Renovation
● Redundancy
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Controllability:
● Temperature
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Humidity
● Pressurization
● Air
Quality
● Infection Control
● Sound and Vibration
Traditional Hospital HVAC Systems
Decentralized Systems
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Packaged Air Handling Units
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Local Special Systems
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Direct Expansion
Chilled Water
Medical Equipment
Computer Rooms
Terminal Units
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Unitary or Served by a Central
Plant.
Fan Coil Units
Incremental Units
Heat Pumps
Induction
Packaged Terminal Air Conditioner
condenser fan
supply fan
compressor
air-cooled
condenser
filter
front grille
cooling coil
wall sleeve
Water-Source Heat Pump
refrigerant-to-air
heat exchanger
expansion
device
supply fan
refrigerant-to-water
heat exchanger
compressor
reversing
valve
Fan-Coil Unit
filter
supply-air outlet
cooling coil
supply fan
return-air inlet
Fan Coil Systems
• 4 pipe
• 2 pipe
• Central ventilation unit
Induction Units
• 4 pipe
• 2 pipe
• Central ventilation unit
Air-Cooled Chiller, Fan-Coil System
dedicated outdoor-air unit
fan-coil units
exhaust fan
air-cooled chiller
system-level controller
hot-water boiler
pumps
Small Chilled-Water System
water chiller
cooling coil
pump
control
valve
Rooftop VAV System
packaged rooftop
air conditioner
system-level
controller
VAV terminals
Traditional Hospital HVAC Systems
Central Systems
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Could Still Utilize Unitary
Equipment with All Air
All Air Systems:
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Central Heating:
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Constant Volume Terminal
Reheat
Variable Air Volume
Double Duct
Boilers
Central Cooling:
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Chillers
Single Zone, Constant Volume
EA
OA
RA
cooling
coil
supply
fan
SA
thermostat
zone
Multiple Zones, Constant Volume
EA
OA
RA
cooling
coil
supply
fan
SA
reheat coil
thermostat
zone
zone
Multiple Zones, Variable Volume
EA
OA
RA
cooling
coil
supply
fan
SA
VAV box
thermostat
zone
zone
multiple zones, variable volume
VAV Terminal Units
parallel
fan-powered
cooling only
cooling
with reheat
series
fan-powered
multiple zones, variable volume
Two-Fan, Dual-Duct VAV System
cooling air handler
OA
PA
dual-duct
VAV terminal
units
heating air handler
EA
RA
PA
multiple zones, variable volume
Dual-Duct VAV Terminal Unit
warm primary air
cool primary air
supply air
HVAC Filtration
HEPA or tertiary filter
Primary panel filter
Secondary filter
Pro’s and Con’s of Decentral and Central HVAC Systems
Decentralized
Centralized
Installed Capacity
Greater
Lower
First Cost
Lower
Higher
O&M Cost
Higher
Lower
Reliability
Lower
Higher
Redundancy
Little
More
Flexibility to Change
Little
More
Controllability
Poor to Good
Good to Excellent
Temperature
Limited
Excellent
Humidity
Limited
Excellent
Pressurization
Limited
Better
Sound/Vibration
Can be an Issue
Better
Infection Control
Equipment Can be in
Occupied Areas
Much Better
Sources of Chilled Water
• Chilled water from a central plant
• Chilled water from a single building chiller
• Dedicated chiller for equipment or application
Cooling Sources
• Chiller Plant
Constant or Variable Flow-Primary-Flow Systems
variable-flow
pumps
check
valves
control
valve
two-way
valve
optional bypass
with three-way valve
Primary-Secondary Configuration
production
pumps
distribution
pump
production
loop
distribution
loop
two-way valve
Variable-Speed Drives
variablespeed
drive
Boiler Plant
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Steam vs. Hot Water
Fire tube vs. water tube
Full size vs. Modular
Hot Water Only
What’s Changing Going Forward?
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LEED Requirements by the USGBC
(Adoption by local authorities having jurisdiction)
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LEED for HealthCare
What’s Changing Going Forward?
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Energy Conservation a significant part.
Establishes ASHRAE 90.1 for base performance.
LEED forces early consideration of all measures,
considers tradeoffs, evaluates the building in total.
Energy modeling required.
ASHRAE Standard 189.2P
● High Performance Healthcare Facilities
● Issued for public review March 1, 2011.
● Goal for Publication, June 2012.
FGI – Guidelines for Construction of Hospitals.
ASHRAE Standard 90.1 - 2007
Energy standard for Buildings except low-rise Residential Buildings
Purpose: To provide minimum requirements for the energy efficient design of building
What does it apply to:
● New Building
● New portion of Buildings – Additions
● New Systems and Equipment in existing Buildings.
ASHRAE Standard 90.1 – 2007
Continued…
Compliance with Standard
Option 1: Prescriptive Method – Comply with the specific provisions of each section.
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Building envelope requirements based on climate zones
● Ex. U-Values (Insulation)
Heating ventilation and air conditioning – Equipment efficiency and sizing.
Service water heating – Equipment efficiency recovery requirements.
Power – limitations and efficiency in usages.
Lighting – limitations and efficiency in usages.
Other equipment.
Option 2: Energy Cost Budget Method
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Energy Modeling
Evaluate proposed system operation using simulation software versus base building system
type.
Energy use and costs comparison.
Strategies to Reduce Energy Consumption
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Building Envelope Improvements
Reduce Building Volume (Height)
Reduce Fan Horsepower's.
● BIM as a resource.
● Requires less external static pressure.
● Larger ducts.
● Shorter horizontal duct runs.
Moving away from traditional all air systems
Dedicated ventilation air systems with exhaust heat recovery.
Chiller
● Heat recovery
Solar
● Hydronic
● PV
Strategies to Reduce Energy Consumption
Continued…
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Heat Recovery Chillers
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Using the rejected condenser heat
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Heat Pumps
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Heat Recovery
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Laundry
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Data Centers
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Ground Source Heat Pumps
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Cogeneration
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Trigeneration
Ground-Source Heat-Pump System
heat pump
geothermal
heat exchanger
pumps
Cogeneration
Trigeneration
Reduce Building Volume/Reduce Fan HP’s for All Systems
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Reducing building height and horizontal duct lengths.
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Requires more vertical duct risers.
Careful design can accomplish this but the duct shifts are
restricted to layout.
Code requirements to limit fan HP’s are forcing non all air
solutions.
In spite of the advantages there are limits as to what can be
accomplished without signification costs.
Non All Air Systems
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Separate ventilation and dehumidification air systems to
provide ventilation only.
Local unitary equipment to accomplish sensible heating
and cooling.
All of these alternatives have drawbacks and risks.
All provide less air delivery to control local pressurization.
Ventilation- Energy Recovery
Non All Air Alternatives
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Fan Coil Units
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Chilled Beams
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Positive Displacement Ventilation
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Hybrid VAV Systems
Active Chilled Beams In Cooling and Heating Mode
Passive Chilled Beams
Active Chilled Beams
Displacement Ventilation
What To Do Today
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Optimize Central Plant Performance
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Boilers
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Chillers
Controls, Maintenance, Calibration
and Monitoring
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Commissioning
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Retro Commissioning
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LEED for Existing Buildings