ASHRAE Journal - May 2013 - 19

to a design/build approach, and Firm
A’s design became the bridging documents.
One of the design/build teams bidding on the project proposed a VAVR
system (designed by Firm B, the authors’ firm) and also carried the design through about the DD level in its
bid. Another bidder proposed a hybrid
chilled beam + VAV reheat system, designed by Firm C. The three designs
included equipment schedules, detailed
equipment layouts and zoning plans.
The team with the hybrid design was
awarded the job, but the project has
been placed on hold since.
After UC Davis selected a design/build
team, the ASHRAE Golden Gate chapter
decided to use this building for a competition between chilled beams and VAV reheat
since it had already been designed with
both systems and with a hybrid combination of the two. All three firms were eager to
participate. The results of the competition
were presented at a seminar sponsored by
the ASHRAE Golden Gate Chapter at the
Pacific Gas & Electric Energy Center in
San Francisco on Oct. 17, 2012.

Figure 1: Rendering of graduate studies building.

HW
Coil

VFD
CHW
Supply
Coil with
Fan
Bypass
Array

VFD
Exhaust

CH
Beam

CH
Beam

T

Active Chilled Beam Design
The ACB+DOAS design consists of
a 100% outside air, constant volume air
handler serving two supply risers. The
air handler has a chilled water coil with a Figure 2: Active chilled beam design.
bypass damper and a hot water coil. The
air handler has a variable speed drive primarily for reducing cludes one set of chilled water pipes supplying 45°F (7°C)
fan speed when the bypass damper is open. The air handler chilled water to the air handler and a separate chilled water
provides the primary air to the active chilled beams. The aver- heat exchanger and chilled water pump in the building to
age DOAS primary airflow rate is about 0.6 cfm/ft2 (0.28 L/ maintain the chilled water supply temperature to the chilled
[s·m2]), which is considerably higher than the minimum ven- beams at 57°F (14°C). The design engineer felt that a heat
tilation in low occupant density spaces, like offices, but close exchanger was needed, rather than just a blending valve, as an
to the minimum ventilation in higher density spaces such as added layer of protection against condensation.
conference rooms and classrooms. A DOAS flow rate higher
Each ACB has both heating and cooling coils. The primary
than the minimum ventilation in low density spaces is often air is maintained at 63°F (17°C), and the ACB heating and
needed to meet the space loads as the capacity of the chilled cooling coils are controlled by the thermostat to maintain
beams is a function of the primary airflow rates. In densely space conditions.
occupied spaces, it also ensures space dew point does not rise
The ACB design also includes a partially ducted exhaust
above the surface temperature of the chilled beams, possibly system—exhaust ducts extend from the air handler down the
causing condensation. It also improves the indoor air quality shafts and into the ceiling return plenum about two thirds of the
compared to code minimum ventilation.
way from the exhaust shafts to the building skin. This was in
Hot water and chilled water are provided by an existing response to perceived owner preference for ducted return. Howcampus central plant supplying 45°F (7°C) chilled water to ever, neither of the other two designs in the design/build compethe buildings on campus. However, 45°F (7°C) typically can- tition included ducted return and, therefore, the return ductwork
not be supplied to the chilled beams because of the likelihood was not included for any design in the cost model or energy
of condensation and dripping. Therefore, the ACB design in- model for the Golden Gate ASHRAE Chapter competition.
May 2013

ASHRAE Journal

19



ASHRAE Journal - May 2013

Table of Contents for the Digital Edition of ASHRAE Journal - May 2013

ASHRAE Journal - May 2013
Contents
Commentary
Industry News
Letters
Meetings and Shows
Feature Articles
VAV Reheat Versus Active Chilled Beams & DOAS
A Stable Whole Building Performance Method for Standard 90.1
Technology Award Case Studies:
PSU Design Build Project
Passive Cooling for School
Standing Columns
Building Sciences
InfoCenter
Refrigeration Applications
IAQ Applications
Engineer's Notebook
Products
Data Centers
Emerging Technologies
Classified Advertising
Advertisers Index
ASHRAE Journal - May 2013 - ASHRAE Journal - May 2013
ASHRAE Journal - May 2013 - Cover2
ASHRAE Journal - May 2013 - 1
ASHRAE Journal - May 2013 - 2
ASHRAE Journal - May 2013 - Contents
ASHRAE Journal - May 2013 - Commentary
ASHRAE Journal - May 2013 - 5
ASHRAE Journal - May 2013 - Industry News
ASHRAE Journal - May 2013 - 7
ASHRAE Journal - May 2013 - 8
ASHRAE Journal - May 2013 - 9
ASHRAE Journal - May 2013 - 10
ASHRAE Journal - May 2013 - 11
ASHRAE Journal - May 2013 - 12
ASHRAE Journal - May 2013 - 13
ASHRAE Journal - May 2013 - Letters
ASHRAE Journal - May 2013 - 15
ASHRAE Journal - May 2013 - Meetings and Shows
ASHRAE Journal - May 2013 - 17
ASHRAE Journal - May 2013 - VAV Reheat Versus Active Chilled Beams & DOAS
ASHRAE Journal - May 2013 - 19
ASHRAE Journal - May 2013 - 20
ASHRAE Journal - May 2013 - 21
ASHRAE Journal - May 2013 - 22
ASHRAE Journal - May 2013 - 23
ASHRAE Journal - May 2013 - 24
ASHRAE Journal - May 2013 - 25
ASHRAE Journal - May 2013 - 26
ASHRAE Journal - May 2013 - 27
ASHRAE Journal - May 2013 - 28
ASHRAE Journal - May 2013 - 29
ASHRAE Journal - May 2013 - 30
ASHRAE Journal - May 2013 - 31
ASHRAE Journal - May 2013 - 32
ASHRAE Journal - May 2013 - A Stable Whole Building Performance Method for Standard 90.1
ASHRAE Journal - May 2013 - 34
ASHRAE Journal - May 2013 - 35
ASHRAE Journal - May 2013 - 36
ASHRAE Journal - May 2013 - 37
ASHRAE Journal - May 2013 - 38
ASHRAE Journal - May 2013 - 39
ASHRAE Journal - May 2013 - 40
ASHRAE Journal - May 2013 - 41
ASHRAE Journal - May 2013 - 42
ASHRAE Journal - May 2013 - 43
ASHRAE Journal - May 2013 - 44
ASHRAE Journal - May 2013 - 45
ASHRAE Journal - May 2013 - PSU Design Build Project
ASHRAE Journal - May 2013 - 47
ASHRAE Journal - May 2013 - 48
ASHRAE Journal - May 2013 - 49
ASHRAE Journal - May 2013 - 50
ASHRAE Journal - May 2013 - 51
ASHRAE Journal - May 2013 - 52
ASHRAE Journal - May 2013 - 53
ASHRAE Journal - May 2013 - Passive Cooling for School
ASHRAE Journal - May 2013 - 55
ASHRAE Journal - May 2013 - 56
ASHRAE Journal - May 2013 - 57
ASHRAE Journal - May 2013 - 58
ASHRAE Journal - May 2013 - 59
ASHRAE Journal - May 2013 - 60
ASHRAE Journal - May 2013 - 61
ASHRAE Journal - May 2013 - Building Sciences
ASHRAE Journal - May 2013 - 63
ASHRAE Journal - May 2013 - 64
ASHRAE Journal - May 2013 - 65
ASHRAE Journal - May 2013 - 66
ASHRAE Journal - May 2013 - 67
ASHRAE Journal - May 2013 - 68
ASHRAE Journal - May 2013 - 69
ASHRAE Journal - May 2013 - InfoCenter
ASHRAE Journal - May 2013 - 71
ASHRAE Journal - May 2013 - 72
ASHRAE Journal - May 2013 - 73
ASHRAE Journal - May 2013 - 74
ASHRAE Journal - May 2013 - Refrigeration Applications
ASHRAE Journal - May 2013 - 76
ASHRAE Journal - May 2013 - 77
ASHRAE Journal - May 2013 - IAQ Applications
ASHRAE Journal - May 2013 - 79
ASHRAE Journal - May 2013 - 80
ASHRAE Journal - May 2013 - 81
ASHRAE Journal - May 2013 - 82
ASHRAE Journal - May 2013 - 83
ASHRAE Journal - May 2013 - Engineer's Notebook
ASHRAE Journal - May 2013 - 85
ASHRAE Journal - May 2013 - Products
ASHRAE Journal - May 2013 - 87
ASHRAE Journal - May 2013 - Data Centers
ASHRAE Journal - May 2013 - 89
ASHRAE Journal - May 2013 - 90
ASHRAE Journal - May 2013 - 91
ASHRAE Journal - May 2013 - Emerging Technologies
ASHRAE Journal - May 2013 - 93
ASHRAE Journal - May 2013 - 94
ASHRAE Journal - May 2013 - Classified Advertising
ASHRAE Journal - May 2013 - Advertisers Index
ASHRAE Journal - May 2013 - Cover3
ASHRAE Journal - May 2013 - Cover4
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