High Performing Buildings - Fall 2009 - (Page 30)

K e y s u s ta i n a B l e F e at u r e s geothermal HVAC: dual compressor units with distributive water pumping geothermal domestic water heating occupancy controls district energy management program Approximately 435 students attend Plano Elementary School. Warren County is one of Kentucky’s fastest growing counties. WCpS and Cmta Consulting engineers chose dual compressor heat pump units to increase system efficiency. During part-load operating conditions, a dual-compressor unit will operate more efficiently than a single-compressor unit. Full load operating efficiencies occur infrequently. Cmta trended the first and second stage operating hours for one year after the building was occupied using plano’s direct digital controls system. Cmta determined that 87% of all operating hours were in the first stage. a 3.5 ton unit was field tested to determine the efficiency improvements. the heat pump unit consisted of a 1.5 ton and 2.0 ton compressor connected to a single 3.5 ton refrigerant circuit. Stage one efficiency is significantly higher than full load condition because the 1.5 ton compressor has 3.5 tons of evaporator and condenser coil surface area for heat exchange. a field test measured the condenser and evaporator pressures/ The mezzanine location of the heat pumps allows the units to be serviced without disrupting classes. Photo courtesy of Warren County Public schools temperatures and found that when both compressors operate, the 1.5 ton compressor has an energy efficiency ratio rating of 11. the compressor efficiency increases to 18 when running solely in the first stage (Figure 2). this results in a 64% efficiency boost when the dual compressor heat pump unit operates in stage one. distributed Water Pumping the next significant system change in the plano design was distributed water pumping. One of the significant benefits of geothermal HvaC for a school district is the figure 1 tyPical classroom section HigH Performing Buildings fa l l 2 0 0 9 Photo © CmTA Consulting engineers

Table of Contents for the Digital Edition of High Performing Buildings - Fall 2009

High Performing Buildings - Fall 2009
Contents
Commentary
Kitsap County Administration Building
McDonald's Corporation
Plano Elementary School
California Department of Education
Burns & McDonnell
Advertisers Index

High Performing Buildings - Fall 2009