Heat Pumps, Fan Coils or VAV Terminals in Zones Check Valve On/Off Circulation Pump U-Tube Bores Close Header Purge Valves Optional Central Chiller(s) Central Pump(s) Heat Pump Sub-Header Isolation Valves Common Loop, Individual Pumps for Each Unit Central Multicircuit Ground Loop To/From Other Loops Three-Way Valves On/Off Pump Fluid Returns to Supply Line Heat Pumps or Coils for All Circuit Types Can Be Located in Closets, Mezzanines Above Halls, or in Classrooms. (Above Ceilings Not Recommended.) Multistory Building Central Loop, Central Pump From Other Heat Pumps To Other Heat Pumps U-Tubes On/Off Pumps Supply Duct Return Central Pumps Each Sized to Meet 50% Design Flow One-Pipe Loop, Central Pump + Individual Pumps Unitary Loop, Individual Pumps for Each Unit Figure 3: GSHP building and ground loop circuit types. ENERGY STAR designation with 100 two exceeding a rating of 90. There 90 appears to be little difference in the Variable Speed Drive Pumps Constant performance of those with variable 80 Speed speed drive pumps (six of 16 achievPumps 70 ing ENERGY STAR) and those with 60 constant speed motors (two of four achieving ENERGY STAR). 50 While most of the central sysChilled Water 40 VAV/GSHP tems were connected to unitary heat 30 pumps in the building, two were connected to central chilled water 20 loops with VAV air-distribution sys10 tems. As shown in Figure 4, these 0 systems received a below average ENERGY STAR rating. Four of the central loops had constant speed ES – Elementary School MS – Middle School HS – High School OFF – Office Mfa – Multifamily pumps that operated continuously. One of these systems had a variable speed drive but it was operated at Figure 4: ENERGY STAR ratings of central loop GSHPs with central pumps. full speed continuously by design. Two buildings in the survey were served by a central loop Six systems in the survey were central one-pipe loops that in the common areas while the classrooms and offices were were retrofits of existing schools. Five were built in the 1950s conditioned by unitary loops with individual units and and one in 1938. As shown in Figure 5 all of these GSHP ground loops. buildings achieved the ENERGY STAR designation with four ENERGY STAR Rating FL – Mfa GA – MS MW – MS MW – ES1 MW – ES2 TN – MS KY – ES1 GA – ES1 MW – HS1 MW – HS2 TN – HS1 TN – HS2 TN – ES1 KY – ES2 KY – Off MS – Off TN – Off FL – Off 52 ASHRAE Journal ashrae.org June 2012 TN – ES2 Hotel