Geothermal Think Tank Takes on an Extraordinary Job

Carl Orio spearheaded development of the standing-column geo-exchange well almost 35 years ago. Today the company he founded in 1981, Hampstead, NH-based Water Energy Distributors, Inc., is recognized as a global leader in geothermal design and distribution.
Three years after he incorporated Water Energy Systems, his daughter Christina joined the business as general manager. In 2000, she became president of the firm, changing the name to Water Energy Distributors, Inc.
In 2005, Water Energy Distributors was hired as a subcontractor by McFarland-Johnson, an engineering firm of Binghamton, NY, to design an all-geothermal mechanical system for the Merrimack County Nursing Home (MCNH), in Boscawen, NH. The system – installed in stages during the past several years – incorporates 16 standing column wells and 326 ClimateMaster water-to-air heat pumps for a total of 615 tons of capacity.
Many subcontractors came together to complete the county-owned 243,108sf, 296-bed facility.
“The first order of business was to closely study the area’s hydrogeologic properties to determine the best location for the well field. Water Energy was instrumental in determining optimum well spacing and number of wells within the identified area having the best hydrogeologic parameters,” said Fred Mock, McFarland-Johnson vice president.
“Based on the heat load, we recommended 16, 10-8-6 wells, each 1500 feet deep,” said Orio. The term “10-8-6” stands for a 10 inch casing sealed into the bedrock, an eight inch rock bore, and a six inch sleeve and pump. Each submersible pump has a 10 hp motor to push water to the building’s mechanical room, and from there to all the heat pumps
All 16 wells are located in the nursing home’s parking lot. Split up into two well fields, eight wells are located in the upper parking lot, and eight in the lower, with the farthest well being 850 feet from point of entry into the building. Each eight-well field is piped to its own supply and return manifold. The caps are protected by manhole covers, and can be found in the green spaces between parking areas. Amherst, NH based Skillings and Sons was the driller contracted for the MCNH job.
“Each well took us about six days to drill,” said President Roger Skillings. Drilling an eight inch hole through 1500 feet of solid granite is no small task; it was a blessing in disguise, though. According to Skillings, the number-one enemy of a healthy standing column well is soft rock that cracks, collapses and caves in.
“At this site, we found some of the best, mineral-free water we’ve ever seen, and the rock was also very stable,” he added.
“Each of the eight-well supply and return manifolds feed well water to a series of risers to the upper floors,” explained Orio. “There are two of the big manifolds; each field feeds half of the building. We generally prefer to have no more than 10 wells, or 300-400 tons, on a given field. At MCNH, there’s a nominal 310 tons on each field.”
As customary for all standing column well systems, no circulators are used; there aren’t even any flow centers on the ClimateMaster units.
Pressure at the mechanical room supply manifolds are maintained by the VFD-controlled submersible pumps which operate in parallel. Pressure in the manifold that serves the upper field is kept at 52 psi, and at 55 psi for the lower manifold, insuring 25 psi at the furthest, fourth floor heat pump. “You take the farthest well and the most distant heat pump, and that gives you the requirement for sizing the submersible pumps,” said Orio.
Suspended above drop-ceiling tiles are either three or four-ton ClimateMaster TS units with copper-nickel heat exchangers. The majority of the units serve two bedroom areas. With the smaller systems, air movement is limited to two rooms, greatly reducing the threat posed by airborne pathogens.
“I was skeptical at first,” said Sid McDonald, director of facilities at MCNH. “The bugs got worked out the first year the system was in, and ever since then, it’s has been phenomenal.”
Aquifer flow was much better than expected. The flow of water in the wells is so steady, easily maintaining design temp despite the influence of system geo-exchange, that there’s no need even for a five % bleed off of water.
So rich and steady is the supply of waterborne BTUs that, for eight or nine months of the year, only 10 of the 16 wells are used. So, just to keep things equal in the wells, BTUs are tapped from different wells on a rotating basis year-round.