ASHRAE Journal - February 2013 - 32

Characteristics of Successful GSHPs
•	 The ENERGY STAR rating of the building exceeds 90.
•	 Maximum loop temperatures returning from the ground
tend to be below 90°F (32°C) for systems in which the
cooling mode determines loop length.
•	 The systems surveyed during this project were primarily
10-month schools and 8 a.m. to 5 p.m. offices located in
areas where the measured ground thermal conductivity
was between 1.0 and 1.5 Btu/h·ft·°F (1.7 and 2.6 W/m·°C).
Under these circumstances, the successful vertical ground
loops tend to be in the range of 200 to 240 ft of vertical
bore per installed ton (17 to 21 m/kW) of cooling capacity for a ground temperature of 63°F (17°C). This corresponds to a range of 155 to 185 ft per ton (13 to 16 m/
kW) for 55°F (13°C) ground temperature and 270 to 320
ft per ton (23 to 28 m/kW) for 70°F (21°C) ground.
•	 The ground loop lengths of systems in this survey were
all dictated by the cooling mode requirements. This resulted in advantageous heating mode ground loop temperatures even at the coldest sites in Central Illinois.
At the one site that was monitored continuously, the
ground loop return temperature remained above 46°F
when the outdoor temperature was –6°F (–21°C).
•	 The primary equipment type tends to be water-to-air
heat pumps.

•	 Pump control tends to be on-off for these smaller loop
circuits rather than variable speed.
•	 Ground loop pump power tends to not exceed 10
hp/100 tons (kWPump/kWHeatPump). This value is
deemed to be average (Grade = C) using recommended guidelines.7
•	 Due to the selection of piping materials and pH level of
the fill water, piping systems tend to not require chemical treatment. However, caution is advised against using PVC pipe. It is not recommended for service when
contact with polyolester oil is possible8 if leaks occur in
the water coils of HFC-refrigerant systems.
•	 Control is provided by individual thermostats or a building automation system that is simple with a clear and
concise sequence of operation so program adjustments
(or retrocommissioning) can be performed by the
maintenance staff.
•	 When surveyed, occupants rate indoor comfort, indoor
air quality, acoustics, lighting, maintenance responsiveness, and system controllability as satisfactory.
•	 When surveyed, the maintenance staff rates system serviceability, quality of design, and quality of installation as
satisfactory.

•	 Installed outdoor ventilation air equipment capacity
tends to be 20 cfm/person (9.4 L/s per person) or less.

•	 Owners and designers are satisfied with utility cost and
they openly share results (and permit ENERGY STAR
rating).

•	 Systems with heat pumps circuited to individual ground
loops, small central, or multiple common loop circuits
out-performed systems with large central loop circuits
by a significant margin.

•	 Owners and designers are satisfied with the installation
costs, they will openly share itemized results, and they
are confident the project provides positive economic
value.

ergy use cannot be recommended with GSHPs. It is recommended that the Standard 90.1 mechanical section be revised
to allow the best performing GSHP systems to be compliant
and to disallow systems with excessive auxiliary power requirements (i.e., 2.3 hp/1,000 cfm).

Heat Pump Efficiencies
Manufacturers of water-to-air heat pumps are currently advertising products with cooling EERs in excess of 40 Btu/W·h
(11.7 W/W). These values are attained at part-load rating
points that do not reflect actual operating conditions.4
• External static pressure: 0 in. w.g. (0 Pa);
• External water pressure: 0 ft of water (0 kPa);
• Full load airflow used with part-load capacity (no cooling dehumidification in cooling and cool air delivery in
heating);
• Water temperature entering the condenser: 68°F (20°C); and
• Return air conditions: 80.6°F (27°C) db/66.2°F (19°C) wb.
32

ASHRAE Journal

(Car mileage per gallon is not rated going downhill with a
tailwind, so why is heat pump cooling efficiency rated with a
condenser fluid colder than the evaporator fluid?)
Figure 2 indicates cooling and heating efficiencies of constant speed heat pumps are higher than multi-capacity and
variable speed units at ground loop temperatures experienced
in commercial applications (cooling: >80°F [27°C], heating:
<50°F [10°C]). Trends indicate ratings at higher entering water temperatures are needed since almost all the systems in
this survey exceed 86°F (30°C). Furthermore, the efficiency
improvements of multi-capacity and variable speed machines
are minimal or non-existent when corrected to typical partload field conditions.5
This field study demonstrates it is possible to achieve ENERGY STAR ratings of 95 to 100 with simple equipment.
Higher cost heat pumps exacerbate the discrepancy in the
cost increases of HVAC components compared to the increases in ground loops costs. A standard that rates heat
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
http://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_ABEDGD
http://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201910
http://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201909
http://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2019septmeber_v2
http://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2019september
http://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201908
http://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201907
http://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201906
http://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201905
http://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201904
http://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_2019april
http://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201903
http://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_2019march
http://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201902
http://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201901
http://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_showguide2019
http://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_2018december
http://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_2018november
http://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2018fall_v2
http://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2018fall
http://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_2018october
http://www.nxtbook.com/nxtbooks/ashrae/ashraemexico_2018
http://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201810
http://www.nxtbook.com/nxtbooks/ashrae/ashraeinsights_201806
http://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201805
http://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201804
http://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201803
http://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201712
http://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201711
http://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201710
http://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2017fall_v2
http://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2017fall
http://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201709
http://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201705
http://www.nxtbook.com/nxtbooks/ashrae/ashrae_meetinginsert_201610
http://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2016fall_v2
http://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2016fall
http://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_acrexindia
http://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2015summer_v2
http://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2015summer
http://www.nxtbook.com/nxtbooks/amca/2014summer2
http://www.nxtbook.com/nxtbooks/amca/2014summer
http://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_acma_2014summer
http://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201311
http://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201309
http://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_acmasupp_2013fall
http://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201305
http://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201303
http://www.nxtbook.com/nxtbooks/ashrae/pubcatalog_2013winter
http://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201211
http://www.nxtbook.com/nxtbooks/ashrae/achr_expo_mexico2012
http://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201209
http://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201208_v3
http://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201208_v2
http://www.nxtbook.com/nxtbooks/ashrae/pubcatalog_2012summer
http://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201205
http://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201203
http://www.nxtbook.com/nxtbooks/ashrae/pubcatalog_2012winter
http://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201111_v2
http://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201109_v2
http://www.nxtbook.com/nxtbooks/ashrae/pubcatalog_2011summer
http://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201105
http://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201103
http://www.nxtbookMEDIA.com