X472 HVAC System Design Considerations Class 3 Central Plants and Specialty Systems

X472 HVAC System Design
Considerations
Class 3 – Central Plants and
Specialty Systems
Todd Gottshall, PE
Western Allied
Redwood City, CA
Reinhard Seidl, PE
Taylor Engineering
Alameda, CA
Fall 2015
Mark Hydeman, PE
Continual
San Francisco, CA

2
General
 Contact Information
Reinhard: rseidl@taylor-engineering.com
Mark: mhydeman@continual.net
Todd: tgottshall@westernallied.com
 Text
• None
 Slides
• download from web before class
• Log in to Box at https://app.box.com/login
• Username: x472student@gmail.com
• Password: x472_student (case sensitive)

3
Course Outline
Date Class Topic Teacher
9/02/2015 1. Introduction / Systems Overview / walkthrough RS
9/09/2015 2. Generation Systems TG
9/16/2015 3. Distribution Systems RS
9/23/2015 4. Central Plants TG
9/30/2015 5. System Selection 1 - class exercises RS
10/07/2015 6. Specialty Building types (High rise, Lab, Hospital,
Data center)
TG
10/14/2015 7. System Selection 2 - class exercises RS
10/21/2015 8. Construction codes and Project delivery methods TG
10/28/2015 9. 2013 T24 and LEED v4 MH
11/04/2015 10. Life-Cycle Cost Analysis and exam hand-out TG
There are three instructors for this class. Todd Gottshall (TG), Reinhard Seidl (RS)
and Mark Hydeman (MH). The schedule below shows what topics will be covered by
who, and in what order.

4
Birds Eye View of Systems
 Single Story – tilt-up
• Single zone rooftop AC
• Split units, VRV
 Two-Story
• Multi-zone rooftop AC
 3-8 Story
• Centralized systems
• Dual Duct
• VAV RH
 High-rise
• Floor-by-floor
• Built-up Systems
• Condenser loops, tenant heat
pumps
 Campus Systems
• Central plant, airside/water
side economizers, thermal
energy storage
• Cogeneration
 Specialty Systems
• Hotel
• Library
• Laboratory
• Data Center
• Underfloor
• Natural Ventilation
• Direct/Indirect
• Cascading cooling towers
Covered
last lesson

5
 Two-Story
 3-8 Story
• Dual Duct
• VAV RH
 High-rise
• Floor-by-floor
pumps
 Campus Systems
energy storage
• Cogeneration
• Hotel
• Library
• Laboratory
• Data Center
• Underfloor
• Direct/Indirect
This lesson

6
Overview
 Central plant types and distribution
systems

7
Agenda
•Hydronic Circuiting
Primary only
Primary-secondary
Primary-secondary-tertiary

8
Central Plants
 Campus system
• Chilled water plant
• Basic chiller types
• Basic water circuiting types
• Cogeneration

9
Constant Volume
Central Plants
3-Way Mixing
Valve
Bypass Balance
Valve
Designs for constant volume assured system
balance and simple chiller control

10
Constant Flow Chiller
Single Chiller,
multiple coils

11
Constant Flow Chillers
Multiple Chillers,
multiple coils

12
Central Plants
 Old Paradigm
• Controls respond to changes in CHW temperature
• Variable flow causes low temperature trips, locks
out chiller, requires manual reset (may even
freeze)
• Maintain constant flow through chillers
 New Paradigm
• Modern controls are robust and very responsive to
both flow and temperature variations
• Variable flow OK within range and rate-of-change
spec’d by chiller manufacturer

13
Central Plants
 Vary Flow Through Coil Circuit
• Two-way valves
• Variable speed coil pump
 Configurations
• Primary-only
• Primary-secondary
• Primary-secondary variations

14
Variable Flow Plant –
Chilled Water
Primary only, variable flow
system
COILS are now controlled
with 2-way valves, not 3-way
valves
CHILLER pump can “ride the
pump curve” or be equipped
with a variable speed drive to
vary flow.

15
Chilled Water
Multiple chillers,
headered pumps,
primary only,
variable flow
system

16
Variable Flow Plant
Multiple chillers,
headered pumps,
primary only,
variable flow
system

17
Primary pump
Primary/Secondary Plant
Primary and
secondary pumps
de-couple the
chilled water flow
in the system
from the chilled
water flow in the
plant
Secondary
pump
Primary and
secondary pumps
de-couple the
chilled water flow
in the system
from the chilled
water flow in the
plant
Secondary
pump
Primary pump
Secondary
pump
ON
ON
100
gpm
100
gpm
100
gpm
ON
OFF
100
gpm
100
gpm
0 gpm

18
Chilled Water
Multiple chillers,
headered pumps,
primary/secondary,
variable flow
system
Primary pumps
Secondary
pumps

19
Variable Flow Plant
Multiple chillers,
headered pumps,
primary /
secondary,
variable flow
system

20
Chilled Water
Primary,
distributed
secondary
Primary,
secondary,
tertiary

21
Chilled Water
Dedicated Pumping Advantages:
• Less control complexity
• Custom pump heads w/ unmatched chillers
• Usually less expensive
Headered Pumping Advantages:
• Better redundancy
• Valves can “soft load” chillers with primary-only
systems
• Easier to incorporate stand-by pump

22
Condenser Water
Dedicated Pumping Advantages:
• Less control complexity
• Custom pump heads w/ unmatched chillers
• Usually less expensive
Headered Pumping Advantages:
• Better redundancy
• Valves can double as head pressure control
• Easier to incorporate stand-by pump
• Can operate fewer CW pumps than chillers
Isolation
valve for low
flow – avoid
by using low-
flow options
on towers

23
Low dT – primary only
system
Low load but excessively open valves – high flow,
low dT – problem originates on the use side, not on
the plant side
Becomes a problem on the plant side – have to run
multiple chillers to generate sufficient flow – now
running multiple chillers at low load, inefficiently

24
“Death spiral” –
primary/secondary
As before, problem with coils results in high
flow on building side and low dT, and high
secondary pump speed
Primary
pumps
Secondary
pumps
Unless the primary pumps are sped up, CHWR (warm) now goes
through the bypass backward, and gets into the CHWS, heating it
up, and thus forcing valves even more open / secondary pumps
to even higher speed
Indepth Article:
http://www.taylor-
engineering.com/downloads/articles/ASHRAE%20Symposium%2
0AC-02-6-1%20Degrading%20Delta-T-Taylor.pdf

25
 Lower First Costs
 Less Plant Space Required
 Reduced Pump HP
• Reduced pressure drop due to fewer pump
connections, less piping
• Higher efficiency pumps (unless more expensive
reduced speed pumps used on primary side)
 Lower Pump Energy
• Reduced connected HP
• “Cube Law” savings due to VFD and variable flow
through both primary and secondary circuit
Advantages of Primary-only Vs.
Primary/Secondary

26
 Use Primary-only Systems for:
• Plants with many chillers (more than three) and
with fairly high base loads where the need for
bypass is minimal or nil and flow fluctuations
during staging are small due to the large number of
chillers; and
• Plants where design engineers and future on-site
operators understand the complexity of the
controls and the need to maintain them.
 Otherwise Use Primary-secondary
Primary-only Vs.
Primary/secondary

27
UC Merced – Large Scale
Energy Efficiency
 500,000 sq.ft., growing
 LEED Gold Campus
 Comprehensive Controls and
Commissioning including Central
Plant
 Classroom Building, Health and
Wellness Center, Sierra Terraces
Housing, Dining Center

28
Thermal Energy Storage
(TES)

31
 Two-Story
 3-8 Story
• Dual Duct
• VAV RH
 High-rise
• Floor-by-floor
pumps
 Campus Systems
energy storage
• Cogeneration
• Hotel
• Library
• Laboratory
• Underfloor
• Direct/Indirect

36
 Two-Story
 3-8 Story
• Dual Duct
• VAV RH
 High-rise
• Floor-by-floor
pumps
 Campus Systems
energy storage
• Cogeneration
• Hotel
• Library (Bancroft)
• Laboratory
• Data Center
• Underfloor
• Direct/Indirect

37
The Bancroft Library, UCB
Archival Storage of Rare Books and Artifacts

38
Bancroft Library
Multiple systems serving different
portions of the building with
different environmental criteria
Full size duct diagram: See Bancroft Iso.pdf

40
Bancroft: Base HVAC
Systems
 Two water-cooled screw chillers – 120
tons each
 Design chilled water temperature = 39oF
 Class A System criteria: 60oF, 40% RH =
36oF DP
 Cannot adequately dehumidify with
Chilled Water

41
Desiccant Dehumidification
The outdoor air (OA) point on the chart is shown at the dehumidification design conditions described in
section 2.6.3 above. OA is cooled with the pre-cooling coil to a dry-bulb (DB) temperature of 45°F. With
39°F CHW this is an achievable temperature.
The resulting point is labeled OA-cooled on the chart.
The cooled OA is now run through the desiccant dehumidification wheel and dried/heated. The chart
shows this as an adiabatic process where the moisture level goes down and the DB temperature goes
up. Air leaving the desiccant wheel is at the point labeled OA-dry.
Some of the cooled OA is bypassed around the desiccant wheel and some goes through
the wheel. After the wheel, the bypassed air and dried air is mixed. Design ratio is 2400
cfm through the wheel and 2600 cfm bypassed. Resulting mixed air condition is at point
OA-mix.
This OA-mix air is then mixed with the return air from the Class A spaces. Design
quantities are 4000 cfm OA-mix and 19,500 cfm return air. Resulting condition is labeled
The mixed air would then be cooled with the
cooling coil to down to the required supply
air temperature (SAT) of 54.8°F. This is
point “SA” on the chart. The cooling process
is not shown. This would be sensible cooling
only.
“Mix” on the chart. This mixed air has a DP of 36°F, which is below the
37°F DP required to make the Class A spaces the required relative
humidity. Actual quantity of air that is bypassed around the desiccant
wheel will be modulated by the control system. to achieve the correct
supply air dew point, but this chart shows we have adequate capacity for
the design scenario.
Outdoor air
cooled to 45°F
With CHW
Outdoor dried
w desiccant
unit
Mixed w
return air
Cooled to final supply
temp with CHW
1
2
3
4

42
Desiccant Process
Complete control diagram: See Bancroft ctrl_a-system.pdf

43
The “B” systems serve the archive areas of the building where active research is occurring. The relative
humidity requirements of these areas are the same as the “A” areas, but the temperatures are warmer
to allow more comfortable conditions for researchers. The Class B air handling system consists of 2 air
handling units, AH-B1 and AH-B2.
AH-B1 delivers cold, dry air to the zones while AH-B2 delivers “neutral” (70 °F temperature) humid air
to the zones. AH-B2 is essentially a large humidifier for the entire building. The Class B spaces require
both temperature and humidity control. Cold dry air from AH-B1 is mixed with neutral humid air from
AH-B2 and then a reheat coil is provided in each zone to be able to achieve the required space
conditions.
COOLING: The cold deck with air coming from AH-B1 is shown at the
lower left, with some heat gain from fan and duct. The air is reheated for
temperature control and mixed with neutral deck air for humidity control.
This scheme allows zones to be individually controlled for
both temperature and humidity, without the more typical
approach of using individual humidifiers per zone.
Humidity/Temp control w. dual
duct
From cold deck AHU, reheated to
move the “Cold VAV Reheat”
point left or right on the chart, and
thus change the slope of the
mixing line.
1
Air warms up in room to go from
“VAV mix” at 58°F / 65%RH to
“Room mix” at 72°F / 43% RH
3
Air from neutral deck AHU is essentially
like laundry exhaust – warm and very
humid, at about 72°F / 50% RH
2

44
HEATING: The cold deck with air coming from AH-B1 is shown at the
lower left, with some heat gain from fan and duct. The air is now
significantly reheated for temperature control and mixed with neutral
deck air for humidity control.
This scheme allows zones to be individually controlled for
both temperature and humidity, without the more typical
approach of using individual humidifiers per zone.
Humidity/Temp control w. dual
duct
In addition to fan and duct heat
gain, reheat (HW) is added to get
to correct leaving air temp (much
like typical VAV RH)
1
Neutral deck air mixed
in to control humidity
2
The “B” systems serve the archive areas of the building where active research is occurring. The relative humidity requirements of these areas are the same as the
“A” areas, but the temperatures are warmer to allow more comfortable conditions for researchers. The Class B air handling system consists of 2 air handling units,
AH-B1 and AH-B2.
AH-B1 delivers cold, dry air to the zones while AH-B2 delivers “neutral” (70 °F temperature) humid air to the zones. AH-B2 is essentially a large humidifier for the
entire building. The Class B spaces require both temperature and humidity control. Cold dry air from AH-B1 is mixed with neutral humid air from AH-B2 and then a
reheat coil is provided in each zone to be able to achieve the required space conditions.
Room cools air w slight
addition of moisture
3

45
 Two-Story
 3-8 Story
• Dual Duct
• VAV RH
 High-rise
• Floor-by-floor
pumps
 Campus Systems
energy storage
• Cogeneration
• Hotel
• Library
• Laboratory
• Data Center
• Underfloor
• Direct/Indirect

46
Laboratory – Form Factor,
Livermore
 Final product
 Clean room
RAH

47
Livermore
 Final product
– clean aisle

48
Livermore
 Final product-
utility chase

49
Laboratory – Animal
Facility
 Fume
Exhaust

50
Hospitals and Laboratories
 Both need pressure control
• Hospital: infection control
• Lab: infection / toxic / flammable control
 Historically, constant volume systems
used to ensure pressure control
 Big reheat penalty for fluctuating loads
 T24-2013 Section 140.9c has prescriptive
requirement for VAV supply/exhaust

51
Low load Low Load High load Low load
A B C D
Constant volume system means easy pressure control (which is a plus)
But: the supply air temperature from the air handler has to be low
enough to handle the room with the highest load (room C). Since the
other rooms have low loads, they all have to reheat (their full design air
flow) to maintain temperature.
Some reheat ($$)Big reheat ($$$) Big reheat ($$$)

52
 Ways around this energy penalty
• VAV lab:
 Tracking VAV controls: one VAV zone makes up air, one exhausts air, CFM on
hood monitored by air valve position or fume hood face velocity monitor with
sash sensor, or exhaust duct airflow sensors
 Pressure control: hoods take what they need, supply maintains load and min
ACH, exhaust maintains room pressure
 Adaptive control: combination of the two above, where room pressure sensor
resets cfm differential between supply and exhaust
• Zone coils: install heating and cooling coils at the zone level, so there is
no reheat penalty
• Dual duct system with mixing operation: maintain constant airflow with
neutral air (from hot deck) mixed with cooling air
• Active chilled beams – is essentially little different than zone coils: means
installing zone level temperature controls with DOAS upgraded to
maintain pressurization minimums. In theory, this is more efficient than
zone coils because of reduced pressure drop.

54
 Zone coils:
• Expensive solution
• Requires lots of piping and adds pressure
drop to central system unless fan-powered
terminals are used, or terminal units such
as fancoils or induction units
• But: gets rid of potentially high reheat
energy cost which is driven by high air
volumes

55
 Dual Duct:
• Less expensive solution than zone coils
• Requires a good floor plate as interior with
spaces like offices or general purpose
rooms – this provides neutral (return) air
that can be used for mixing high-minimum
rooms such as labs.
• For buildings with lots of exterior spaces, or
buildings with mostly lab spaces, this
system offers little advantage because of
large outside air requirements.

56
 Chilled beams:
• Works for load driven rooms, if the actual loads are higher
than the minimum airflow requirements or hood
requirements already cover (for air-change or hood driven
rooms).
• Only difference to zone coils is that the chilled beam
operates without condensation, so that a wet surface
(prohibited in some hospital applications, for cleanliness)
is prevented.
• However, the same thing can be achieved with terminal
coils running warmer water, will have more Btu/h for same
coil because of higher airflow through coil (not just
induced)

57
Control methods
 Pressure tracking
• Cheapest. Hoods and terminals don’t need to communicate. Hood “does its
own thing” and exhaust simply trims room pressure.
• Disadvantage: when a door is opened, pressure cannot be maintained, and
terminals either go haywire or are limited to begin with in their range. Slowing
reaction of system helps combat doors opening and closing, but then makes
control less effective
 Volume or Flow tracking
• Always “keeps its cool” regardless of envelope / door changes, maintains a
steady offset
• Disadvantage: More expensive, does not actually check room pressure
which is the original driver for the whole mechanism
 Adaptive offset (both pressure and volume tracking)
• Most expensive
• Offset between supply and return is reset by pressure readings, giving the
best of both worlds – fast, steady operation AND actual pressure control

58
Laboratories
With hoods, typically 3 elements involved: Hood, Supply, and general exhaust. In
VAV hood application, all three have controllers. For critical applications, all three
will be fast acting.

60
1. Pressure tracking
Hood just looks at its own exhaust
(typ. with face velocity monitor).
Only hood velocity matters, the
exhaust volume “is what it is”
1
Supply valve satisfies 2 conditions:
A. Heat load (with thermostat)
B. Airflow minimum, either
1. Air change minimum (set by
designer or owner, code)
2. or CFM/sqft
2
3 Exhaust valve
modulates to maintain
room pressure

61
2. Flow tracking
Now calculates airflow (either with
hood velocity and sash position,
or with flow sensor in exhaust)
1
2. or CFM/sqft
2
3 Exhaust valve
airflow offset by
subtracting hood
exhaust from makeup,
and then exhausting a
little bit more than the
result to get a
negative room

62
3. Adaptive offset
2. or CFM/sqft
2
3 Exhaust valve
airflow offset by
subtracting hood
exhaust from makeup,
and then exhausting a
little bit more than
the result to get a
negative room
PLUS: the “little bit
more” differential
keeps getting reset to
new values to ensure
that the room pressure
is actually doing what
we want

63
 Pressure-based VAV Tracking
• Pressure control: hoods take what they need, supply VAV
maintains load and min ACH, exhaust VAV maintains room
pressure
 No hood cfm monitoring required, although hood volume still
modulates (sash position or face velocity monitor)
• Low pressures (0.03”-0.05”). Can be done with “through the wall”
hot-wire sensors or pressure transducers without flow across
wall.
• Disadvantage: hard to tune correctly to ignore doors opening
(no reaction wanted even though pressures will swing wildly).
Typically more expensive
• Advantage: better feedback on actual operation.

64
 Airflow Tracking VAV
• Tracking VAV controls: Hoods take what they need, one VAV terminal
makes up air for loads and min. ACH, one terminal exhausts air to
maintain overall CFM differential. CFM on hood monitored by
 Air valve position or
 Fume hood face velocity monitor and sash sensor or
 Exhaust duct airflow sensor
• Either differential (i.e. maintain 100 cfm negative per door)
• Or ratio (i.e. maintain exhaust at 110% of supply)
• Disadvantage: no real feedback on how well system works to maintain
room pressure (typ. = lab negative with respect to corridor). No check
on whether balance is maintained over time
• Advantage: (less) expensive and stable

65
 Adaptive offset control
• Basic control loop uses airflow tracking
• The airflow differential may not be correct after some time (think 1-2
years) because of changes in leakage rate in the envelope (door
frames warp, holes drilled for wiring, conduit) or in the short term
because a door opens
• Pressure sensor then used to update the airflow differential at slower
loop speed than airflow tracking, to reset differential for what is
required to maintain room pressure
• The reset mechanism can be slow to avoid unstable controls, but
airflow control can be fast
• Disadvantage: Most expensive option (combines all sensors from
both underlying control methods)
• Advantage: best stability and performance.

66
Hospitals
Tracking exhaust: One supply VAV zone and one
exhaust VAV zone.

67
Hood exhaust valves can be a venturi-type valves that are self-balancing (like griswold flow
controllers) to their setpoint, and can be actuated without a flow sensor (to prevent
corrosion of sensor)
Other air valves use vortex shedding sensors in lieu of pitot-style flow crosses and fast
actuators to maintain airflow. Benefits are that the airflow can be reset via the control
system.
Spring-loaded venturi
damper maintains a pre-
defined cfm flow rater over
wide pressure range when
actuator is set to a certain
setting. Example: 40%
open actuator means 840
cfm, regardless of duct and
room pressure
Used without actuator for
constant volume hood
systems. No flow cross.
Actuated Dampers and
Fast Control Algorithms
adjust the airflow to Airflow
Setpoint from the DDC.
Airflow can be set by
Space Load, ACH
Requirements, or Pressure
Offset. Can be used on
Supply and Exhaust
Butterfly Dampers without
flow sensing can be used
with hood face velocity
sensors.

68
 Two-Story
 3-8 Story
• Dual Duct
• VAV RH
 High-rise
• Floor-by-floor
pumps
 Campus Systems
energy storage
• Cogeneration
• Hotel
• Library
• Laboratory
• Data Center
• Underfloor
• Direct/Indirect

69
Data Centers
 History:
• Started off with all PC’s crammed into one room, then rack mounted
• As more racks were added, first more house air and then ceiling splits or
fancoils were added.
• When that failed to work, dedicated large splits or fancoils
(CRACs=computer room air conditioning unit or CRAHs=computer room
air handlers) were developed and added.
• With ongoing problems and hot spots, underfloor distribution gained
acceptance followed by hot-aisle/cold aisle configuration
• With larger densities still, additional fancoils on top of racks, in line with
racks or on the rear of racks (heat exchangers) are now coming onto the
market.
• In combination with these, capped aisles (hot or cold) are also being
added (This is now a Prescriptive requirement for rooms larger than
175KW.)

70
Data Centers
Slides from NREL Presentation, 2015
Data Center Efficiency Metric
Power Usage Effectiveness (PUE)

72
Data Centers
Step 1: small IT
room

73
Data Centers
Step 2: more load
Add more house air or
small fancoils/splits
Maintenance nightmare,
ongoing hotspots, hard to
fit

74
Data Centers
Step 3: more load
Dedicated up-flow
CRAC or CRAH

75
Data Centers
Step 4: more load
Dedicated downflow with raised floor (added cost!)

76
Data Centers
Step 5: more load
Large scale dedicated facilities with perimeter CRAC/CRAH
Underfloor distribution with hot aisle/cold aisle setup in racks

77
Data Centers
Step 6a: more load
Fewer CRACs/CRAHs (base load, dehum., filtration)
Overhead fancoils for added cooling density

78
Data Centers
Step 6a: more load
Overhead fancoils for added cooling density

79
Data Centers
Step 6b: more load
In-row fancoils for more direct cooling

80
Data Centers
Step 6b: more load
Capped cold aisles for better air flow management

81
Data Centers
Step 6b: more load
Capped hot aisles for better airflow mgmt – note return duct

82
Data Centers
Step 6c: more load
More CRACs/CRAHs (base load, dehum., filtration)
Rear door heat exchangers leave entire room neutral

83
Data Centers
Step 7: more load
• No CRACs/CRAHs
• Chimney racks with 100% flow-through

84
Data Centers
Step 7: more load
• No CRACs/CRAHs
• Chimney racks with 100% flow-through

85
Data Centers
Elimination of chiller plant
• Higher overall temperatures make cooling without chillers
a possibility,
• Typical arrangement with chilled water shown below
95°/66°
55°42° CHW
75° CW
85° CW
55° CHW

86
Data Centers
a possibility
• Alternate arrangement shown below, uses a coil with CW
in the AHU
85°
75° CW
85° CW
95°/66°

87
Data Centers
a possibility
• “Insert” cooling tower into AHU as it were (swamp cooler,
Indirect Evaporative Cooling)
68°
95°/66°

88
Data Centers
a possibility
• “Insert” cooling tower into AHU as it were (swamp cooler,
Indirect Evaporative Cooling)
• Slide from ASHRAE Journal March 2015 Article

89
Data Centers
a possibility
• Also possible: dry plate air-to-air HX in AHU, with swamp
cooler on scavenger air side
• Slide again from March 2015 ASHRAE Journal

90
Data Centers
• Also possible for rear doors when load density per rack not
too high (~ 10kW/rack or so)
70° CW possible in Bay Area
w 66°F design wet bulb
85° CW
78°78° 100°
Example: 600 gpm, 85°->70°F tower, 375 tons
30 Hp fan, 20’ L x 10’ W x 12’ H

91
 Two-Story
 3-8 Story
• Dual Duct
• VAV RH
 High-rise
• Floor-by-floor
pumps
 Campus Systems
energy storage
• Cogeneration
• Hotel
• Library
• Laboratory
• Underfloor
• Direct/Indirect

92
Multi-stage towers
 Not common, but in theory allow cooling tower system to
produce water at wetbulb of surrounding air (note – very
similar principle as used in the Coolerado cooler)
 Direct 2-stage
83F DB,
62F WB

93
Multi-stage towers
 Not common, but in theory allow cooling tower system to
produce “chilled” water at or lower than the wetbulb of
surrounding air
 Indirect 2-stage
83F DB,
63F WB

94
Data Centers
• Title-24 2013 Requires Economizers on Computer Rooms over
20 Watts / SF. Eliminates the “Process Load” Exception
• Can be incorporated with Direct Evaporative Cooling
• Additive Energy Conservation Measure: Use waste heat to heat
adjacent Office spaces
Hydeman, 2012

95
Data Centers
Step 8: more load
• On-Board liquid cooling
• See http://hightech.lbl.gov/training/modules/08-liquid-
cooling.pdf
• and
 http://datacenterpulse.org/The
ChillOff

96
 Two-Story
 3-8 Story
• Dual Duct
• VAV RH
 High-rise
• Floor-by-floor
pumps
 Campus Systems
energy storage
• Cogeneration
• Hotel
• Library
• Laboratory
• Underfloor
• Direct/Indirect

97
Orinda: Indirect Direct
Evaporative Cooler
Indirect Direct Fan

X472 HVAC System Design Considerations Class 3 Central Plants and Specialty Systems

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X472 HVAC System Design Considerations Class 3 Central Plants and Specialty Systems