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: Project scope Design criteria Design concepts and solutions Implementation lessons Performance

PROJECT OVERVIEW

PROJECT SITE

BUILDING LAYOUT

DESIGN CRITERIA Project is being built in two phases Phase 1 (2012 practice field) is heating only. Phase 2 (2014 operations building) requires heating and cooling. Desire to use campus utilities - chilled water and steam. Desire for quiet system operation.

DESIGN CRITERIA High bay space with a large volume to heat. Only about 10% of the volume is occupied. Tight site – need to optimize site use to maximize field area - reduce mechanical space. 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 Route chilled water mains to facility under Phase 1. Use campus chilled water return as heat sink for water to water heat pumps to create hot water for Phase 1 and Phase 2. Use in-floor radiant heat under turf field for practice facility heating. Use natural/displacement ventilation as primary means of summer conditioning. Supplement with an ERV and exhaust fans.

HVAC SYSTEM SELECTION Design Benefits Water to water heat pumps have a COP of 2.6 for heating, 4.6 for simultaneous heating/cooling. System produces chilled water as a byproduct which is sent back to campus mains or used in the Phase 2 facility. Chilled water produced is approximately 180 tons. 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%). Annual EUI reduction of 24% (54.5 kBtu/SF vs kBtu/SF). $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 First system of this type on campus. Campus plant does not want chilled water over 42°F supplied. Heat pumps must control both chilled and heating water. Campus chilled water PLC interface and building DDC chilled water system needed to integrate to operate reliably and seamlessly. Separate controls though. 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. All other evaporator valves should be closed if their associated compressor is not operating. 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. 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 Chilled water pumps should be enabled to run for 60 seconds prior to enabling the heat pumps to stabilize flow. Building heating water loop bypass valve needs to be engaged to maintain system flow in the case of rapid heating load reduction. 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 The heating water system has operated in the Indoor Practice Facility for two years. Specific knowledge of the system is needed to operate and trouble shoot when required. Energy consumption over the past 24 months to heat, ventilate, and light Phase 1 was …. 21 kBtu/SF/year

QUESTIONS? THANK YOU! Thank You! Lincoln Pearce KJWW Engineering David Hahn University of Iowa Chilled Water Plant