University of Iowa Indoor Practice Facility
Outside-the-box HVAC
Lincoln Pearce, PE – KJWW Engineering
David Hahn – University of Iowa Chilled Water Plant
October 13, 2014
OUTLINE AND LEARNING OBJECTIVES:
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Project scope
Design criteria
Design concepts and solutions
Implementation lessons
Performance
PROJECT OVERVIEW
PROJECT SITE
BUILDING LAYOUT
DESIGN CRITERIA
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Project is being built in two phases
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Phase 1 (2012 practice field) is heating only. Phase 2
(2014 operations building) requires heating and cooling.
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Desire to use campus utilities - chilled water and
steam.
• Desire for quiet system operation.
DESIGN CRITERIA
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High bay space with a large volume to heat. Only
about 10% of the volume is occupied.
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Tight site – need to optimize site use to maximize
field area - reduce mechanical space.
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Chilled water was close and plentiful, but sufficient
reliable steam was about $1 million away.
HVAC SYSTEM OPTIONS CONSIDERED
1) Campus chilled water and steam HEX with radiant
floor heat for field.
2) Campus chilled water and water-to-water heat
pumps with radiant floor heat for field.
3) Campus chilled water and water-to-water heat
pumps with air rotation units for field.
4) Campus chilled water and natural gas boilers with
radiant floor heat for field.
HVAC SYSTEM SELECTION
Selected Design Solution – Option 2
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Route chilled water mains to facility under Phase 1.
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Use campus chilled water return as heat sink for water
to water heat pumps to create hot water for Phase 1
and Phase 2.
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Use in-floor radiant heat under turf field for practice
facility heating.
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Use natural/displacement ventilation as primary
means of summer conditioning. Supplement with an
ERV and exhaust fans.
HVAC SYSTEM SELECTION
Design Benefits
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Water to water heat pumps have a COP of 2.6 for
heating, 4.6 for simultaneous heating/cooling.
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System produces chilled water as a byproduct
which is sent back to campus mains or used in the
Phase 2 facility.
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Chilled water produced is approximately 180 tons.
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Utility company rebate of $343,394. Heat pump
system accounted for 57% of rebate. (Accounts for
Phase 1 & 2)
ENERGY ANALYSIS
Based on Phases 1 & 2 – Comparing to System 1
• Annual energy cost savings of $33,855 (11%).
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Annual EUI reduction of 24% (54.5 kBtu/SF vs.
71.5 kBtu/SF).
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$1 million lower life cycle cost over 25 years.
PRACTICE FIELD PIPING AND ZONING
SYSTEM EQUIPMENT
Water-to-Water Heat Pump Units
RADIANT FLOOR SYSTEM
Manifold Design Details
RADIANT FLOOR SYSTEM
Manifold Installation
RADIANT FLOOR SYSTEM
In-Floor Tubing
RADIANT FLOOR SYSTEM
Transition to Sub-Floor
RADIANT FLOOR SYSTEM
Floor Tubing Arrangement
RADIANT FLOOR SYSTEM
Sand Floor Base
NATURAL VENTILATION SYSTEM
Air Intake and Relief Path
NATURAL VENTILATION SYSTEM
Intake Louvers and Dampers
NATURAL VENTILATION SYSTEM
Relief Air Path
HEATING SYSTEM FLOW DIAGRAM
Heating with Chilled Water
HEATING SYSTEM DISCUSSION
Implementation Challenges
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First system of this type on campus.
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Campus plant does not want chilled water over 42°F
supplied. Heat pumps must control both chilled
and heating water.
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Campus chilled water PLC interface and building
DDC chilled water system needed to integrate to
operate reliably and seamlessly. Separate controls
though.
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What is the R-value of sport turf?
HEATING SYSTEM DISCUSSION
Getting it Running– Lesson Learned
• At start up there should only be one evaporator
valve open to allow flow proof for chiller start up.
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All other evaporator valves should be closed if their
associated compressor is not operating.
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The PID loops for the evaporator control valves on the
heat pump units needed to be sped up. They were
responding far too slowly causing wide control swings and
instability.
HEATING SYSTEM DISCUSSION
Getting it Running– Lesson Learned
• Required manufacturer design staff to physically
visit site to observe issues of chilled water control.
The slow responding evaporator valves were main
cause of instability.
• Chilled water system failures in other campus
buildings can affect the heat pumps.
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Differential pressure set point for the chilled water
pumps should be reset based on varying campus
system return temperature.
HEATING SYSTEM DISCUSSION
Getting it Running– Lesson Learned
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Chilled water pumps should be enabled to run for 60
seconds prior to enabling the heat pumps to stabilize
flow.
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Building heating water loop bypass valve needs to
be engaged to maintain system flow in the case of rapid
heating load reduction.
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The PLC for the U of Iowa chilled water interface
was limited in programming capability. Needed to
find rudimentary ways to control the bypass valve.
SYSTEM PERFORMANCE REVIEW
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The heating water system has operated in the Indoor
Practice Facility for two years.
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Specific knowledge of the system is needed to operate
and trouble shoot when required.
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Energy consumption over the past 24 months to heat,
ventilate, and light Phase 1 was ….
21 kBtu/SF/year
QUESTIONS?
THANK YOU!
Lincoln Pearce
KJWW Engineering
515.334.7937
pearceld@kjww.com
David Hahn
University of Iowa Chilled Water Plant
Thank You!
319.335.8625
david-c-hahn@uiowa.edu