ASHRAE Journal - June 2012 - 23

letters
Handbook—HVAC Applications, Page 57.12, and in ASHRAE Standard 1302008, Methods of Testing Air Terminal Units, under Definitions. I agree that this adjustment can be very difficult sometimes on parallel units because of primary air leakage from the casing causing cold plenums, but that is the design. Second, in the next to the last paragraph they state, “Series fan-powered units are very inefficient; efficiency can be as low as 15%.” This statement is subjective and factually incorrect. Please refer to ASHRAE RP-1292 and additional research done by the Variable Air Volume Research Consortium at Texas A&M University, which has subsequently been donated to ASHRAE. I think both are available at ASHRAE and AHRI, a partner in the research. There have also been 11 ASHRAE papers written on this research to date with more to follow. Fan-powered VAV terminal units can be great assets in an all air system when selected and applied correctly, just like most other components. Thank you for a great article. Gus Faris, Member ASHRAE Houston, Texas overall energy input to large indoor air systems, but the power input to the fan/ blower adds to the cooling load, so, in effect, it is paid for twice. Along with minimizing over cooling and reheating, one of the main points of the variable air volume system, of which the terminal units are an essential part, is to save air moving energy by efficiently matching airflow to the cooling and heating that are required. John Dieckmann, Member ASHRAE, Lexington, Mass.

The Author Responds
We thank Mr. Faris for his general compliments on the column on terminal units. It is always good to hear that a topic we have covered is timely. The specif ic points he raises are useful information on the topic. Both cases illustrate the importance of implementing a particular design approach correctly to obtain the maximum benefit. The importance of fan efficiency to the performance of a series fan-powered terminal unit is one good example of the importance of fan and blower efficiency to the overall efficiency of the indoor air side of commercial air conditioning systems. Not only is air moving power a significant part of the
June 2012

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ASHRAE Journal - June 2012

Table of Contents for the Digital Edition of ASHRAE Journal - June 2012

Contents
Commentary
Industry News
Letters
Meetings and Shows
Feature Articles
Minimum Outdoor Airflow Using the IAQ Procedure
Basics of Atrium Smoke Control
 Long-Term Commercial GSHP Performance Part 1: Project Overview and Loop Circuit Types
Optimizing Design & Control of Chilled Water Plants Part 5: Optimized Control Sequences
Technology Award Case Studies:
Retail in Cold Climate
Rethinking Hospital Design
Standing Columns
Refrigeration Applications
Emerging Technologies
Engineering Applications
Washington Report
Products
IAQ Applications
Special Products
Classified Advertising
Advertisers Index
ASHRAE Journal - June 2012 - Intro
ASHRAE Journal - June 2012 - Cover1
ASHRAE Journal - June 2012 - Cover2
ASHRAE Journal - June 2012 - 1
ASHRAE Journal - June 2012 - 2
ASHRAE Journal - June 2012 - Contents
ASHRAE Journal - June 2012 - Commentary
ASHRAE Journal - June 2012 - 5
ASHRAE Journal - June 2012 - Industry News
ASHRAE Journal - June 2012 - 7
ASHRAE Journal - June 2012 - 8
ASHRAE Journal - June 2012 - 9
ASHRAE Journal - June 2012 - 10
ASHRAE Journal - June 2012 - 11
ASHRAE Journal - June 2012 - 12
ASHRAE Journal - June 2012 - 13
ASHRAE Journal - June 2012 - Letters
ASHRAE Journal - June 2012 - 15
ASHRAE Journal - June 2012 - 16
ASHRAE Journal - June 2012 - 17
ASHRAE Journal - June 2012 - 18
ASHRAE Journal - June 2012 - 19
ASHRAE Journal - June 2012 - 20
ASHRAE Journal - June 2012 - 21
ASHRAE Journal - June 2012 - 22
ASHRAE Journal - June 2012 - 23
ASHRAE Journal - June 2012 - Meetings and Shows
ASHRAE Journal - June 2012 - 25
ASHRAE Journal - June 2012 - Minimum Outdoor Airflow Using the IAQ Procedure
ASHRAE Journal - June 2012 - 27
ASHRAE Journal - June 2012 - 28
ASHRAE Journal - June 2012 - 29
ASHRAE Journal - June 2012 - 30
ASHRAE Journal - June 2012 - 31
ASHRAE Journal - June 2012 - 32
ASHRAE Journal - June 2012 - 33
ASHRAE Journal - June 2012 - 34
ASHRAE Journal - June 2012 - 35
ASHRAE Journal - June 2012 - Basics of Atrium Smoke Control
ASHRAE Journal - June 2012 - 37
ASHRAE Journal - June 2012 - 38
ASHRAE Journal - June 2012 - 39
ASHRAE Journal - June 2012 - 40
ASHRAE Journal - June 2012 - 41
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ASHRAE Journal - June 2012 - 44
ASHRAE Journal - June 2012 - 45
ASHRAE Journal - June 2012 - 46
ASHRAE Journal - June 2012 - 47
ASHRAE Journal - June 2012 -  Long-Term Commercial GSHP Performance Part 1: Project Overview and Loop Circuit Types
ASHRAE Journal - June 2012 - 49
ASHRAE Journal - June 2012 - 50
ASHRAE Journal - June 2012 - 51
ASHRAE Journal - June 2012 - 52
ASHRAE Journal - June 2012 - 53
ASHRAE Journal - June 2012 - 54
ASHRAE Journal - June 2012 - 55
ASHRAE Journal - June 2012 - Optimizing Design & Control of Chilled Water Plants Part 5: Optimized Control Sequences
ASHRAE Journal - June 2012 - 57
ASHRAE Journal - June 2012 - 58
ASHRAE Journal - June 2012 - 59
ASHRAE Journal - June 2012 - 60
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ASHRAE Journal - June 2012 - 73
ASHRAE Journal - June 2012 - 74
ASHRAE Journal - June 2012 - 75
ASHRAE Journal - June 2012 - Retail in Cold Climate
ASHRAE Journal - June 2012 - 77
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ASHRAE Journal - June 2012 - 79
ASHRAE Journal - June 2012 - 80
ASHRAE Journal - June 2012 - 81
ASHRAE Journal - June 2012 - 82
ASHRAE Journal - June 2012 - 83
ASHRAE Journal - June 2012 - Rethinking Hospital Design
ASHRAE Journal - June 2012 - 85
ASHRAE Journal - June 2012 - 86
ASHRAE Journal - June 2012 - 87
ASHRAE Journal - June 2012 - 88
ASHRAE Journal - June 2012 - 89
ASHRAE Journal - June 2012 - 90
ASHRAE Journal - June 2012 - 91
ASHRAE Journal - June 2012 - 92
ASHRAE Journal - June 2012 - 93
ASHRAE Journal - June 2012 - Refrigeration Applications
ASHRAE Journal - June 2012 - 95
ASHRAE Journal - June 2012 - Emerging Technologies
ASHRAE Journal - June 2012 - 97
ASHRAE Journal - June 2012 - 98
ASHRAE Journal - June 2012 - 99
ASHRAE Journal - June 2012 - Engineering Applications
ASHRAE Journal - June 2012 - 101
ASHRAE Journal - June 2012 - 102
ASHRAE Journal - June 2012 - Washington Report
ASHRAE Journal - June 2012 - Products
ASHRAE Journal - June 2012 - 105
ASHRAE Journal - June 2012 - IAQ Applications
ASHRAE Journal - June 2012 - 107
ASHRAE Journal - June 2012 - 108
ASHRAE Journal - June 2012 - Special Products
ASHRAE Journal - June 2012 - 110
ASHRAE Journal - June 2012 - Classified Advertising
ASHRAE Journal - June 2012 - Advertisers Index
ASHRAE Journal - June 2012 - Cover3
ASHRAE Journal - June 2012 - Cover4
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