Friday, 1 March 2013
What about Geothermal HVAC in Commercial Applications

Roger Eldridge, Partner , and Jeff Stone, Technician, explain how geothermal systems  heat and cool commercial buildings.

Commercial applications tend to be schools, universities, and churches.  We have done projects as small as a bank and as large as a school. We are doing a project at Lipscomb University for the nursing building that is geothermal. They are taking a building that was recently a water source heat pump system and they are converting it to geothermal. The front end costs are high but overtime it will pay for itself and once it’s paid for the efficiencies will more than pay for itself in the future. We all know that energy costs are not going down they are going up. 

What kind of payback period is there?  It depends. It could be as short as five years or as much as twenty years.  Obviously the larger the facility, and there are a lot of factors that play into that, runtime, weather, large increases in utility costs. We can only calculate payback based on what we know today. 

One Nashville geothermal commercial installation needs capacity of 42 tons.  One ton equals 12,000 BTUs per hour of heating or cooling (more). A 500 ft deep well has 1,000 feet of continuous pipe and provides for 3.5 tons.  This installation has 12 wells spaced 25 feet apart.  Thus 12 times 3.5 equals 42 tons.

Jeff Stone, who was in charge of installation, explained the equipment room. There are 9 heat pump units of various capacities from 2 tons to 12 tons. The total capacity of all 9 units is 42 tons.  Each unit is ducted to a different zone in the building. By having separate units  one zone can be heating with another cooling.  Two large diameter paralleled pipes coming from the wells surround two sides of the room. One pipe is the supply line and the other the return line. A single electronically controlled variable speed pump adjusts the flow of water throughout the system.  Valves are provided to protect the water from draining out in the over 12,000 feet of piping in case the motor needs to be repaired.  An air separator lets any air in the pipe loop to bleed off without losing any water thus preventing an air lock.  The main supply and return pipes are tapped at each unit to supply water to the unit. Valves allow the water supply for the unit to be shut off permitting maintenance on that unit such as replacing a coil without shutting down the entire system. Each unit has one or two easily replaced air filters.

Posted on 03/01/2013 1:30 AM by Roger Eldridge
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