ASHRAE Journal - September 2012 - 28

Long-Term

Commercial GSHP Performance
Part 3: Loop Temperatures

G

By Steve Kavanaugh, Ph.D., Fellow ASHRAE; and Josh Kavanaugh, Student Member ASHRAE

round loop temperatures have a significant impact on system performance. Systems with maximum average ground loop tem-

peratures below 90°F (32°C) had an average ENERGY STAR rating of 92 while those with temperatures above 95°F (35°C) had an average rating of 53. This article is the third in a series that summarizes a data collection and analysis project to identify common characteristics of successful ground source heat pump (GSHP) systems.1

In addition to ground loop temperatures, other data include differential loop temperatures, ground loop size, undisturbed ground temperature (tgrn), thermal conductivity (kgrn), pump sizes and variable speed drive (VSD) operation. Several ground loop temperature plots will be presented that will be sorted by temperature range: • Mild Loops: Maximum Leaving Water Temperature (LWT) < 85°F (29°C);
28 ASHRAE Journal

• Warm Loops: 85°F (29°C) > Maximum LWT < 95°F (35°C); and • Hot Loops: Maximum LWT > 95°F (35°C). Results of thermal property tests were rarely available, especially at the older sites. If no tests were performed, the undisturbed deep ground temperature (tgrn) values for tests performed at nearby sites or water well logs were used. Design loop calculations were not
ashrae.org

available at any of the sites and, in several cases no ground loop design details were included in the drawings. So, the comparison of loop performance results with design intent was not possible. A few of the newer sites had functioning energy management systems that could provide monitored ground loop temperature data. Ground loop and air temperature measurements at most sites were made with multichannel data loggers. They were installed at each site for three to five week periods during the site visits when building and GSHP system information was collected. Results indicate the primary reasons for elevated loop temperatures were insufficient heat exchanger bore length. About the Authors
Steve Kavanaugh, Ph.D., is a professor emeritus of mechanical engineering and Josh Kavanaugh is a post-graduate student in the mechanical engineering department at the University of Alabama, Tuscaloosa, Ala.

September 2012



ASHRAE Journal - September 2012

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

ASHRAE Journal - September 2012
Contents
Commentary
Industry News
Letters
Meetings and Shows
Feature Articles
Designing Air-Distribution Systems to Maximize Comfort
Long-Term Commercial GSHP Performance: Part 3: Loop Temperatures
Chilled Beams in Historic Building
Technology Award Case Studies:
GSHP for 1920s Building
Savings Funds Project
Solar Thermal Retrofit
Standing Columns
Engineer's Notebook
Guía Ferial AHR Expo-México
Indice
Mensajes de ASHRAE y AHRI
Listado alfabético de expositores
Plano de planta de la sala de exposiciones
La humedad en los edificios
Productos expuestos en AHR Expo-México
Lista de anunciantes
Emerging Technologies
Refrigeration Applications
Washington Report
Business & Management
Products
Classified Advertising
Advertisers Index
ASHRAE Journal - September 2012 - ASHRAE Journal - September 2012
ASHRAE Journal - September 2012 - Cover2
ASHRAE Journal - September 2012 - 1
ASHRAE Journal - September 2012 - 2
ASHRAE Journal - September 2012 - Contents
ASHRAE Journal - September 2012 - Commentary
ASHRAE Journal - September 2012 - 5
ASHRAE Journal - September 2012 - Industry News
ASHRAE Journal - September 2012 - 7
ASHRAE Journal - September 2012 - 8
ASHRAE Journal - September 2012 - 9
ASHRAE Journal - September 2012 - Letters
ASHRAE Journal - September 2012 - 11
ASHRAE Journal - September 2012 - 12
ASHRAE Journal - September 2012 - 13
ASHRAE Journal - September 2012 - 14
ASHRAE Journal - September 2012 - 15
ASHRAE Journal - September 2012 - 16
ASHRAE Journal - September 2012 - Meetings and Shows
ASHRAE Journal - September 2012 - 18
ASHRAE Journal - September 2012 - 19
ASHRAE Journal - September 2012 - Designing Air-Distribution Systems to Maximize Comfort
ASHRAE Journal - September 2012 - 21
ASHRAE Journal - September 2012 - 22
ASHRAE Journal - September 2012 - 23
ASHRAE Journal - September 2012 - 24
ASHRAE Journal - September 2012 - 25
ASHRAE Journal - September 2012 - 26
ASHRAE Journal - September 2012 - 27
ASHRAE Journal - September 2012 - Long-Term Commercial GSHP Performance: Part 3: Loop Temperatures
ASHRAE Journal - September 2012 - 29
ASHRAE Journal - September 2012 - 30
ASHRAE Journal - September 2012 - 31
ASHRAE Journal - September 2012 - 32
ASHRAE Journal - September 2012 - 33
ASHRAE Journal - September 2012 - 34
ASHRAE Journal - September 2012 - 35
ASHRAE Journal - September 2012 - 36
ASHRAE Journal - September 2012 - 37
ASHRAE Journal - September 2012 - 38
ASHRAE Journal - September 2012 - 39
ASHRAE Journal - September 2012 - 40
ASHRAE Journal - September 2012 - 41
ASHRAE Journal - September 2012 - 42
ASHRAE Journal - September 2012 - 43
ASHRAE Journal - September 2012 - 44
ASHRAE Journal - September 2012 - 45
ASHRAE Journal - September 2012 - Chilled Beams in Historic Building
ASHRAE Journal - September 2012 - 47
ASHRAE Journal - September 2012 - 48
ASHRAE Journal - September 2012 - 49
ASHRAE Journal - September 2012 - 50
ASHRAE Journal - September 2012 - 51
ASHRAE Journal - September 2012 - 52
ASHRAE Journal - September 2012 - 53
ASHRAE Journal - September 2012 - 54
ASHRAE Journal - September 2012 - 55
ASHRAE Journal - September 2012 - GSHP for 1920s Building
ASHRAE Journal - September 2012 - 57
ASHRAE Journal - September 2012 - 58
ASHRAE Journal - September 2012 - 59
ASHRAE Journal - September 2012 - 60
ASHRAE Journal - September 2012 - 61
ASHRAE Journal - September 2012 - 62
ASHRAE Journal - September 2012 - 63
ASHRAE Journal - September 2012 - Savings Funds Project
ASHRAE Journal - September 2012 - 65
ASHRAE Journal - September 2012 - 66
ASHRAE Journal - September 2012 - 67
ASHRAE Journal - September 2012 - 68
ASHRAE Journal - September 2012 - 69
ASHRAE Journal - September 2012 - 70
ASHRAE Journal - September 2012 - 71
ASHRAE Journal - September 2012 - Solar Thermal Retrofit
ASHRAE Journal - September 2012 - 73
ASHRAE Journal - September 2012 - 74
ASHRAE Journal - September 2012 - 75
ASHRAE Journal - September 2012 - 76
ASHRAE Journal - September 2012 - 77
ASHRAE Journal - September 2012 - Engineer's Notebook
ASHRAE Journal - September 2012 - 79
ASHRAE Journal - September 2012 - 80
ASHRAE Journal - September 2012 - Guía Ferial AHR Expo-México
ASHRAE Journal - September 2012 - S2
ASHRAE Journal - September 2012 - Indice
ASHRAE Journal - September 2012 - Mensajes de ASHRAE y AHRI
ASHRAE Journal - September 2012 - S5
ASHRAE Journal - September 2012 - Listado alfabético de expositores
ASHRAE Journal - September 2012 - S7
ASHRAE Journal - September 2012 - S8
ASHRAE Journal - September 2012 - S9
ASHRAE Journal - September 2012 - S10
ASHRAE Journal - September 2012 - S11
ASHRAE Journal - September 2012 - Plano de planta de la sala de exposiciones
ASHRAE Journal - September 2012 - S13
ASHRAE Journal - September 2012 - La humedad en los edificios
ASHRAE Journal - September 2012 - S15
ASHRAE Journal - September 2012 - S16
ASHRAE Journal - September 2012 - S17
ASHRAE Journal - September 2012 - S18
ASHRAE Journal - September 2012 - S19
ASHRAE Journal - September 2012 - Productos expuestos en AHR Expo-México
ASHRAE Journal - September 2012 - S21
ASHRAE Journal - September 2012 - S22
ASHRAE Journal - September 2012 - S23
ASHRAE Journal - September 2012 - S24
ASHRAE Journal - September 2012 - S25
ASHRAE Journal - September 2012 - S26
ASHRAE Journal - September 2012 - S27
ASHRAE Journal - September 2012 - S28
ASHRAE Journal - September 2012 - S29
ASHRAE Journal - September 2012 - Lista de anunciantes
ASHRAE Journal - September 2012 - S31
ASHRAE Journal - September 2012 - S32
ASHRAE Journal - September 2012 - Emerging Technologies
ASHRAE Journal - September 2012 - 82
ASHRAE Journal - September 2012 - 83
ASHRAE Journal - September 2012 - 84
ASHRAE Journal - September 2012 - 85
ASHRAE Journal - September 2012 - 86
ASHRAE Journal - September 2012 - 87
ASHRAE Journal - September 2012 - 88
ASHRAE Journal - September 2012 - 89
ASHRAE Journal - September 2012 - Refrigeration Applications
ASHRAE Journal - September 2012 - 91
ASHRAE Journal - September 2012 - 92
ASHRAE Journal - September 2012 - 93
ASHRAE Journal - September 2012 - Washington Report
ASHRAE Journal - September 2012 - 95
ASHRAE Journal - September 2012 - 96
ASHRAE Journal - September 2012 - 97
ASHRAE Journal - September 2012 - Business & Management
ASHRAE Journal - September 2012 - 99
ASHRAE Journal - September 2012 - Products
ASHRAE Journal - September 2012 - 101
ASHRAE Journal - September 2012 - 102
ASHRAE Journal - September 2012 - Classified Advertising
ASHRAE Journal - September 2012 - Advertisers Index
ASHRAE Journal - September 2012 - Cover3
ASHRAE Journal - September 2012 - Cover4
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