ASHRAE Journal - January 2013 - 26

difficult with equipment that has many components inside small cabinets. His suggestions include: • Service technicians should be consulted when specifying equipment brands based on their experience. • Adequate valves are needed for isolating wings of buildings and individual units in the event of water leaks. • More space should be provided in equipment cabinets and rooms so that units can be serviced without removal of Figure 3: Service-friendly heat pump package (left). Classroom unit with room for unaffected components. service (right). • Standard filters should always be used since custom sizes are much more expensive. Although, the ground loop at the high school performed well the ENERGY STAR rating was only 59. Simmons’ insight provides clues to this result. “The VS drive on the loop pump has never operated below 95%. The control of the fresh air system has always been a source of problems. The system stays in alarm more often than not. The factory service technician worked on the system in the second year of operation, but it didn’t help much. Also, the dressing room area of the gym is poorly heated, Figure 4: Control circuits for “advanced” heat pump. Unit in difficult-to-service location. and there is no cooling other than the fresh air system. It is a glycol loop, which has never provided school has had higher than expected energy use, multiple the design heat transfer. Backup is provided by an electric re- service issues, and control problems since its installation in sistance duct heater. This was on ongoing issue between the 1995. The GSHP system replaced an R-11 chiller and elecengineer and others involved. Twelve years later it is still not tric heat. In the first full year of operation, the building total correct.” electrical usage was 2,298 MWh as opposed to an average of Mitchell Gravitt, energy coordinator for the Catoosa Coun- 3,481 MWh per year for the two years prior to the retrofit. This ty (GA) Schools sees the overall lower energy use in GSHP amounted to a 34% annual savings.3 Encouraged by these reschools as the primary advantage. He cautions that these sav- sults, water-to-air heat pumps replaced air-to-air units during ings “…can be reduced with the cost of water chemical con- a recent renovation and expansion but the ground loop was not trol, pump repair/replacement, VFD operational issues, and enlarged. The school system now has twelve GSHP systems piping leaks. One of our systems includes a cooling tower and that incorporated lessons learned from the first installation. this is a maintenance cost.” Figure 5 demonstrates one of the necessary solutions to The energy use and maintenance requirements of the GSHP problems that result when maintenance is not a primary desystems in the district have varied from good to poor. So sign consideration. A heat pump was installed in a confined Gravitt recommends, “Quality check the engineering calcu- space above a lighting fixture and sprinkler pipe. This prelations that determine the system thermal load to ensure the vented access to the side panel when the fan motor failed. Moground loop is sufficient. Cooling towers are an option but tor replacement necessitated removal of the entire unit. When maintenance cost should be considered up front. Continued the motor failed again a few years later, Basinger cut out the improvement in piping installation and material is needed to drywall blocking the panel access. “They could hang a picture reduce the chance of leaks.” over the hole if it bothers someone, but they were happy the Gary Basinger is one of five HVAC technicians serving 29 unit was repaired quickly.” buildings for the Washington County (TN) Board of EducaBasinger likes the fewer components in the self-contained tion. Twelve buildings have GSHPs and the oldest installation units and the absence of outdoor condenser units and fan moserved as a site for multiple “lessons learned” that helped im- tors. He feels no auxiliary heat is necessary when units are prove newer systems. This first GSHP system at a large high properly functioning. There are instances in which auxiliary
26 ASHRAE Journal ashrae.org January 2013

ASHRAE Journal - January 2013

Table of Contents for the Digital Edition of ASHRAE Journal - January 2013