Advantages & Disadvantages to the Open Loop vs Closed Loop
New England seasons have large temperature variances. The winter temperatures consistently reach below zero so the heat pump needs to be sized according to the heat loss, not heat gain. We also have rocky and low soil conductivity to contend with which makes horizontal ground loops costly and difficult to install. However, there is a closed loop system that works very well here in New England, the vertical loop. This is a series of bore holes that have a glycol and water solution circulating between the ground loop and system to obtain temperature.
Several differences between the open loop (standing column well) and closed loop systems lead customers to choose one over the other. Water temperatures entering the system from an open loop range from typically 47 to 50 degrees in the Southern NH region. Entering glycol and water fluid temperatures on a closed loop system are between 36 and 40 degrees. In most cases, this temperature difference means that you are able to size the geothermal heat pump smaller for the open loop application, costing less up front. The installation cost of a closed loop is slightly higher than the standing column well since it requires drilling more holes. The other advantage to the open loop is you have the ability on new construction to use the ground source for your domestic water as well as for geothermal which can save money.
However, there are many advantages to the vertical closed loop. It does run more often since the temperatures on the incoming loop are lower but the loop is circulated by small, 0.7 amp circulators, which require much less electricity than the well pump that is submerged hundreds of feet in the ground. For this reason both the open and closed loop cost about the same when looking at operation costs. There is less maintenance to a closed loop since there is not any ground water sediment coming in to the system that needs to be cleaned. It is also much cheaper to replace a circulator pump at about $400 than a well pump at about $3500 and the pumps on a closed loop system are easily accessible in the mechanical room, not in the ground requiring a well rig to take it out. Both open and closed loop systems have their benefits and we look at everyone’s’ situation on an individual basis. For more information on this visit www.ultrageothermal.com
Open Loop Ground Source and Vertical Closed Loop System
