Figure 5: A solution for lack of service access to problematic fan motor. Figure 6: Results of failure to maintain water chemistry in two steel pipe building loops. 1,200 1,000 Loop Flow Rate (gpm) 800 600 400 200 0 heat would be useful during emergency situations due to lack of personnel to repair multiple units in a large complex. He echoes many of Simmons’ sentiments including: • Minimum clearance specifications accommodate proper unit servicing is essential; • Water treatment is necessary to minimize blockage of heat exchangers and water lines; • Isolation valves are needed to clean strainers without draining the system; and • Custom air filters for some equipment is an unnecessary expense. He adds that the heat pumps have slow recovery time because the high school system does not preheat the outdoor air. “The high and low water temperatures in extreme hot or cold weather causes lost efficiency or failure of equipment.” Basinger realizes the extreme loop temperatures in the high school system are a result of a relatively small ground heat exchanger (113 ft/ton [10 m/kW]) and vertical bore spacing (15 ft [4.5 m]). He also recommends that the size and spacing “of the vertical piping be sufficient to allow proper dissipation of heat/cool into surrounding areas.” He encourages the use of high density polyethylene (HDPE) inside the building to minimize the problems with blocked strainers and mineral buildup. His final recommendation is to conduct “very close inspection of installation as it progresses.” Basinger’s perspective on BAS is upbeat. “In the everchanging world of technology, controls are becoming necessary. We have recently entered into a contract with an energy management company that requires the building to be shut down or placed at an energy demand temperature. Each time we receive a call from the contractor we have 20 to 40 minutes to prepare for this event. This is accomplished online with the assistance of our control companies without the need to visit every school. Understanding and being able to utilize control systems is becoming vital to increase energy savings as we continue to change with the times.” Results presented in a previous article4 indicate only one of the 14 variable speed pump drives (VSDs) observed during the project was functioning properly. Figure 6 includes pho28 ASHRAE Journal 0 4 8 12 16 20 24 Time of Day (Oct. 4, 2003) Figure 7: Flow rate with two-way valves interlocked with fans rather than compressors. tos that provide some insight into a possible reason for this result. The photo on the left was taken at a site in which the interior piping was a combination of PVC, steel, and copper. PVC tees regularly cracked at the mechanical copper connection and piping sections in which failure occurred could not be isolated. Maintenance personnel were preoccupied with keeping the system operating and were not able to keep up with the constant need for chemical treatment. The photo on the right demonstrates a plugged 0.5 in. (13 mm) hose connection at an office. The owners were not aware that water chemistry maintenance was required. At both sites it is likely that ports to differential pressure sensors for the VSDs were also plugged. Examples of Typical Operation Issues In one variable speed pump system with two-way valves on the individual heat pumps, very low differential temperatures and warm loops were experienced. Observation with an ultrasonic flow meter indicated continuous operation at full speed while the school was occupied and 70% flow at night as shown in Figure 7. It was discovered that the two-way valves opened with the continuously operating supply fans rather than with compresashrae.org January 2013