ASHRAE Journal - February 2013 - 50

relaxed the minimum duct velocity from 1,500 to 500 fpm (8 m/s
to 3 m/s) in 2001, opening the door to proportional control of
the exhaust ventilation rate during periods with lighter levels of
cooking. A 2003 ASHRAE Journal article stated that such code
changes should “open the floodgates” for DCV in commercial
kitchens.3 But the floodgates did not open very wide!
Recognition of DCV as a best practice for an energy-saving
design had its genesis in the kitchen ventilation chapter of
the 2011ASHRAE Handbook—HVAC Applications and in the
standing standards project committee that wrote the 2003 edition of ASHRAE Standard 154, Ventilation for Commercial
Cooking Operations. The Standard 154 committee recognized
the value of multispeed and variable speed ventilation systems as an energy-saving strategy. Standard 154 committee
members worked with the International Code Council to allow
multispeed kitchen exhaust systems in the 2003 edition of the
International Mechanical Code.
Since that time, ASHRAE/IES Standard 90.1 adopted a more
aggressive approach that included requirements for transfer air,
demand-controlled ventilation, energy recovery devices and
high performance hoods. The revisions to Standard 90.1 were
adopted as an addendum and were incorporated into the 2010
edition. Other code writing bodies began seeing the importance
of encouraging DCV The Standard 90.1-2010 version exists
.
in whole or in part in many other codes and standards such as
ASHRAE/USGBC/IES Standard 189.1-2011 and International Association of Plumbing and Mechanical Officials’ Green
Plumbing and Mechanical Code Supplement.
In January 2014, California’s Building Energy Efficiency
Standard (Title 24) will be adopting similar language. The
2012 edition of the International Green Construction Code
(IgCC) refers to the DCV language in Standards 90.1-2010
and 189.1-2011. The Uniform Mechanical Code has had provisions for multispeed systems since its 2004 edition.

DCV and the Designer
The cornerstone of a DCV system is the complement of
VFDs that allow the DCV microprocessor to modulate the
exhaust and makeup air fan speed in response to cooking appliance activity. It also provides speed adjustment necessary
if a direct-drive fan is to be used. Without a VFD, usually the
speed of a direct-drive fan cannot be field adjusted, and the
ability to balance airflow on a CKV system is virtually impossible. It has been the authors’ position for many years that
restaurant HVAC designers consider using direct-drive fans
with VFDs regardless of whether they plan to pursue DCV
technology. The benefits of eliminating broken belts and gaining an increase in fan efficiency are obvious, but again, the
food-service design community has been reluctant to adopt
this technology on a wide-scale basis. That said, a VFD could
be successfully applied to an existing belt-driven fan as the
foundation for a DCV system.
The designer needs quick and easy access to the DCV components to design and specify a DCV system that performs
well for the cooking application. The hood and fan sizes can
50

ASHRAE Journal

be easily designed and laid-out with online software. The exhaust airflow design rates can be determined by the appliance
line and guidance in the Handbook, Standard 154-2011 or
similar standards. The hood static pressure can be found from
hood filter and collar design calculations.
However, integrating hoods, fans, and speed controllers can
be difficult. It is not always easy to determine which components are necessary to build the variable speed package. Are
the fans supplied with a direct drive speed controller, or does
a separate VFD need to be specified? How will the fans, hoods
and appliances communicate? What are the lower speeds and
airflow rates of the variable speed system during off-peak conditions? How will the system be interlocked and maintain the
air balance and pressurization? How will hood performance be
verified at the various speeds? When the replacement air is not
supplied through a dedicated makeup air unit, some method
of reducing the outdoor air being supplied through the HVAC
system must be incorporated. A DCV system should be able to
effectively communicate/integrate with an EMS system if it is
specified within the facility design. An auto-shutdown feature
is another important attribute of an integrated DCV system.
Some manufacturers with online software are able to assemble a variable speed motor package that integrates with the
hoods without too much difficulty; some are more detailed than
others (including wiring diagrams, etc.). However, many manufacturers leave too many questions to be answered with too little
information available. The result could be a poorly designed and
improperly installed DCV system that lacks performance and
proves disastrous for the chef and owner and, as a result, gives
a bad name to a system that could revolutionize the industry.
It is critical to recognize that an exhaust hood needs to effectively capture and contain the heat and smoke generated by
the cooking equipment when the hood is at its full speed—
before installing or engaging the DCV system. Although energy-conscious system design dictates an exhaust ventilation
rate that is not excessively high, sometimes this leads to inadequate performance if erred on the low side. Fortunately, with
the specification of a DCV system and ability to “commission
out” a safety factor, there is no need to take chances with a
design exhaust ventilation rate that might not be adequate.

DCV System Field Monitoring Data
DCV system data was collected from field-monitoring case
studies (conducted in collaboration with the California Investor Owned Utilities) at a total of 11 sites that reflect the range
in commercial food-service operations and exhaust ventilation
system design. The data compiled in Table 1 was used to determine the fundamental parameters upon which the saving model
was based and to assign statewide utility rebates. All DCV systems included in this field study comprised a combination of
temperature- and optics-based sensors. Field monitoring protocol was generally in accordance with a consensus-based guideline developed by a consortium, whose members are efficiency
program administrators and energy efficiency non-profits from
the U.S. and Canada.4
ashrae.org

February 2013



ASHRAE Journal - February 2013

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

Contents
Commentary
Industry News
Letters
Meetings and Shows
Feature Articles
R-22 Hard Act to Follow: Ammonia Low-Pressure Receiver Systems
Long-Term Commercial GSHP Performance: Part 7: Achieving Quality
Thermally Active Floors: Part 2: Design
Future of DCV for Commercial Kitchens
Standing Columns and Special Sections
Building Sciences
Emerging Technologies
ACREX India 2013 Show Guide
Refrigeration Applications
InfoCenter
Data Centers
IAQ Applications
Special Products
Classified Advertising
Advertisers Index
ASHRAE Journal - February 2013 - Intro
ASHRAE Journal - February 2013 - Cover1
ASHRAE Journal - February 2013 - Cover2
ASHRAE Journal - February 2013 - 1
ASHRAE Journal - February 2013 - 2
ASHRAE Journal - February 2013 - Contents
ASHRAE Journal - February 2013 - Commentary
ASHRAE Journal - February 2013 - 5
ASHRAE Journal - February 2013 - Industry News
ASHRAE Journal - February 2013 - 7
ASHRAE Journal - February 2013 - 8
ASHRAE Journal - February 2013 - 9
ASHRAE Journal - February 2013 - 10
ASHRAE Journal - February 2013 - 11
ASHRAE Journal - February 2013 - Letters
ASHRAE Journal - February 2013 - 13
ASHRAE Journal - February 2013 - Meetings and Shows
ASHRAE Journal - February 2013 - 15
ASHRAE Journal - February 2013 - R-22 Hard Act to Follow: Ammonia Low-Pressure Receiver Systems
ASHRAE Journal - February 2013 - 17
ASHRAE Journal - February 2013 - 18
ASHRAE Journal - February 2013 - 19
ASHRAE Journal - February 2013 - 20
ASHRAE Journal - February 2013 - 21
ASHRAE Journal - February 2013 - 22
ASHRAE Journal - February 2013 - 23
ASHRAE Journal - February 2013 - 24
ASHRAE Journal - February 2013 - 25
ASHRAE Journal - February 2013 - Long-Term Commercial GSHP Performance: Part 7: Achieving Quality
ASHRAE Journal - February 2013 - 27
ASHRAE Journal - February 2013 - 28
ASHRAE Journal - February 2013 - 29
ASHRAE Journal - February 2013 - 30
ASHRAE Journal - February 2013 - 31
ASHRAE Journal - February 2013 - 32
ASHRAE Journal - February 2013 - 33
ASHRAE Journal - February 2013 - 34
ASHRAE Journal - February 2013 - 35
ASHRAE Journal - February 2013 - Thermally Active Floors: Part 2: Design
ASHRAE Journal - February 2013 - 37
ASHRAE Journal - February 2013 - 38
ASHRAE Journal - February 2013 - 39
ASHRAE Journal - February 2013 - 40
ASHRAE Journal - February 2013 - 41
ASHRAE Journal - February 2013 - 42
ASHRAE Journal - February 2013 - 43
ASHRAE Journal - February 2013 - 44
ASHRAE Journal - February 2013 - 45
ASHRAE Journal - February 2013 - 46
ASHRAE Journal - February 2013 - 47
ASHRAE Journal - February 2013 - Future of DCV for Commercial Kitchens
ASHRAE Journal - February 2013 - 49
ASHRAE Journal - February 2013 - 50
ASHRAE Journal - February 2013 - 51
ASHRAE Journal - February 2013 - 52
ASHRAE Journal - February 2013 - 53
ASHRAE Journal - February 2013 - 54
ASHRAE Journal - February 2013 - 55
ASHRAE Journal - February 2013 - Building Sciences
ASHRAE Journal - February 2013 - 57
ASHRAE Journal - February 2013 - 58
ASHRAE Journal - February 2013 - 59
ASHRAE Journal - February 2013 - 60
ASHRAE Journal - February 2013 - 61
ASHRAE Journal - February 2013 - 62
ASHRAE Journal - February 2013 - Emerging Technologies
ASHRAE Journal - February 2013 - 64
ASHRAE Journal - February 2013 - ACREX India 2013 Show Guide
ASHRAE Journal - February 2013 - 64b
ASHRAE Journal - February 2013 - S1
ASHRAE Journal - February 2013 - S2
ASHRAE Journal - February 2013 - S3
ASHRAE Journal - February 2013 - S4
ASHRAE Journal - February 2013 - S5
ASHRAE Journal - February 2013 - S6
ASHRAE Journal - February 2013 - S7
ASHRAE Journal - February 2013 - S8
ASHRAE Journal - February 2013 - S9
ASHRAE Journal - February 2013 - S10
ASHRAE Journal - February 2013 - S11
ASHRAE Journal - February 2013 - S12
ASHRAE Journal - February 2013 - S13
ASHRAE Journal - February 2013 - S14
ASHRAE Journal - February 2013 - S15
ASHRAE Journal - February 2013 - S16
ASHRAE Journal - February 2013 - S17
ASHRAE Journal - February 2013 - S18
ASHRAE Journal - February 2013 - S19
ASHRAE Journal - February 2013 - S20
ASHRAE Journal - February 2013 - S21
ASHRAE Journal - February 2013 - S22
ASHRAE Journal - February 2013 - Refrigeration Applications
ASHRAE Journal - February 2013 - InfoCenter
ASHRAE Journal - February 2013 - 67
ASHRAE Journal - February 2013 - 68
ASHRAE Journal - February 2013 - 69
ASHRAE Journal - February 2013 - 70
ASHRAE Journal - February 2013 - 71
ASHRAE Journal - February 2013 - Data Centers
ASHRAE Journal - February 2013 - 73
ASHRAE Journal - February 2013 - 74
ASHRAE Journal - February 2013 - IAQ Applications
ASHRAE Journal - February 2013 - 76
ASHRAE Journal - February 2013 - 77
ASHRAE Journal - February 2013 - Special Products
ASHRAE Journal - February 2013 - Classified Advertising
ASHRAE Journal - February 2013 - Advertisers Index
ASHRAE Journal - February 2013 - Cover3
ASHRAE Journal - February 2013 - Cover4
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