With Geothermal, it's good to be boring

Shown is one of the two 5-ton geothermal heat pumps from Florida Heat Pump installed in the mechanical room.
When the U.S. Postal Service’s bulk mail center in Allen Park, MI, decided to bury its heating and cooling system, it wasn’t because management was unhappy. They just decided to take the geothermal route to comfort control.

“The government is committed to taking a look at geothermal on its projects,” stated Bruce Kunkle, special project sales with mechanical contractor R.W. Mead & Sons, Fraser, MI, a member of the Geothermal Heat Pump Consortium (GHPC) and the Michigan Geothermal Energy Association. Due to a memorandum of understanding which the GHPC negotiated with the Postal Service, as well as other government entities, geothermal systems are now automatically considered for all new and retrofit hvac projects.

Tim Mahoney, co-owner of Michigan Energy Services, does the excavating for the piping connections at the building.
Bidding on the bulk mail center job in Allen Park started in September 1999, and Kunkle prepared a price on a geothermal system. To put together his bid, Kunkle talked to area subcontractors. However, the initial companies he talked to didn’t have a lot of experience with geothermal and their prices were “outrageous,” said Kunkle, because they were trying to cover themselves.

He then found two subcontractors with quite a bit of experience in the field - loop contractor Michigan Energy Services of Brighton, MI and drilling contractor Earth Energy Loop Systems of Dewitt, MI - and he was able to get his price down to a reasonable level.

Kunkle remarked that if systems were selected just on upfront cost, “geothermal probably would never be put in.” Its benefit comes from long-term energy savings. Considering the long haul, the Postal Service selected the R.W. Mead bid.

The original design called for a vertical loop. As Rob Derksen, co-owner of Michigan Energy Services, noted, vertical loops are commonly used in commercial installations. But there was some concern about potentially explosive methane gas in that area since they would be going down 250 ft. Also, where the vertical loop was to be drilled, “yards and yards of concrete chunks had been buried to build a berm that goes around the perimeter of the property,” said Kunkle.

When the contractors saw the big hunks of concrete and the extensive excavation that it would require, they changed the design to a horizontal loop that would be located under the parking lot.

The crew from Earth Energy Loop Systems uses a Ditch Witch directional boring machine to drill the 10 horizontal bores that go out 267 ft under the parking lot.
The loop consists of 10 bores under the lot, at a depth of 10 ft, which go out 267 ft. At the end of each bore, the concrete is opened up and the line is run back to complete the loop. The bores are spaced approximately 15 ft apart.

Kunkle pointed out that “It’s unusual to be going under 12 inches of concrete.” A difficulty with this approach was that the rebar in the concrete threw off the sensing device used for tracking the drilling head. Driller Jerry Shooltz was able to maintain the spacing between bores, but “he was not able to run in a straight line,” said Kunkle. Although the bores curve a bit, it does not affect the performance of the system.

“This loop can be an energy source for a minimum of 60 years,” stated Kunkle, providing long-term value.

FHP Manufacturing Inc. (Flor-ida Heat Pump), Ft. Lauderdale, FL, supplied the heat pumps - two 5-ton models. The application required 480-V units and the company was able to meet this requirement. A desuperheater is installed on one of the heat pumps to provide partial hot water heating.

No backup heat was specified originally. But Kunkle said that backup heat is recommended for this area and he convinced the Postal Service to add less than 5 kW of supplemental heat at 0¿F design temperature. “Proper engineering is critical” for a successful geothermal system, he emphasized, as well as “close supervision of installation.”

The installation was started the second week of April and it was completed by the beginning of July. Kunkle related that this is the first geothermal heat pump system installed in this district by the Postal Service.

By working to provide a reasonable price and on-time installation, he and his subcontractors certainly hope there are more to come.

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