Types of Loop Fields

Closed Loops System

Closed loops are the most common type of loop field. They are called “closed loops” because the solution is totally contained within the loop field; it never leaves the loop. The loop field brings the liquid into a heat exchanger inside a ground source heat pump where the heat is either removed or added. This allows the heat to be exchanged between the building and the ground without the solution every leaving the loop field.


Vertical Loop Field

Vertical Geothermal Loop SystemA vertical loop field consists of closed loops that are installed in holes drilled down to between 75 and 300 feet. After the hole is drilled, the loop is placed into the hole, and the holes is filled with grout. As the grout fills the holes, spacers are released that spread and hold the pipes apart to increase performance.

Advantages
  1. Vertical loops take up relatively little space. This makes them ideal for situations with limited space such as suburban homes and businesses on small lots. In these situations, the loop can even be installed under the driveway.
  2. The vertical system can go down into local water tables to reach soil that is higher in thermal conductivity soil than soil that is closer to the surface.
  3. They can be installed in almost any type soil conditions.
Disadvantages
  1. Vertical loop fields are they are most expensive to install.
  2. The large installation equipment may do considerable damage to the yard and landscaping, adding on additional costs to the project.

Horizontal Loop Field

Geothermal Horizontal Loopfield SystemA horizontal loop field consists of closed loops that are installed horizontally under the ground between 6 and 20 feet deep. Loops can range in length from 100 to 800 feet long depending on the situation.

Horizontal loops were traditionally installed by digging long trenches and laying the pipe in the bottom of the trench. The advent of horizontal boring equipment allows these fields to be installed quickly and easily without disturbing or damaging the ground above them. Horizontal boring also allows the loop field to be installed deeper – 15 to 20 feet – than the 6′ to 10’ feet that can be reached with trenching equipment

Advantages
  1. Horizontal fields are less expensive than vertical loop fields.
  2. When installed with horizontal boring equipment, minimal damage is done to yards and landscaping.
  3. They are installed deep enough that you can farm or build on top of them.
Disadvantages
  1. They require a large amount of space to install – at least a 300’ long.
  2. They can be difficult or impossible to install in dry sand/gravel or in areas with large rocks or boulders.

Pond Loop Field

Geothermal Pond Loop SystemA pond loop system taps into the high thermal conductivity of water to make a very efficient and less expensive system. Slinky style loops, special balls, or a flat plate heat exchanger is sunk into the water to allow for the heat exchange. A single supply and return loop is installed via trenching or boring to connect the pond loop to the ground source heat pump n the building.

Pond loop fields require a minimum of 1/3 acre of water that is at least 12 feet deep. Most public waters will not allow a pond system, so most systems are installed in private ponds.

Advantages
  1. Excavation costs are just about eliminated making these systems much less expensive to install.
  2. The high thermal conductivity of water makes these systems very efficient.
Disadvantages
  1. Requires a pond at least 1/3 of an acre and 12’ deep.
  2. Not allowed in most public water.
  3. If pond dries up or freezes out, the loop field will lose it’s efficiency.

Open Loop System

Geothermal Open Loop SystemIn an open loop system the water is not contained within the system. Instead the system uses the water from a well as the source of heat. Once the well water is pumped through the heat pump it is discarded into the ground or into a nearby body of water.

These systems are often referred to as “pump and dump” because the water is not reused as it is in the closed loop systems.

Advantages
  1. Less expensive, especially if there is an existing well that can be used.
  2. Use of ground water provides excellent thermal conductivity and performance.
Disadvantages
  1. State, local and non-profit agencies all discourage the use of these systems because of high water usage.
  2. Water usage permits are required from the governing State, Local and Private agencies.
  3. Permits are usually not granted when water is being taken from a “closed water table” that is located deep in the ground.
  4. Water usage is monitored by the DNR and a small yearly fee is charged.

Effective January 1, 2015 Minnesota has placed new regulations on open loop systems that effectively eliminate them in almost all retrofit or new construction situations.

UMR GeothermalUMR Best Practice

 

UMR recommends the loop field type that provides the best performance and the best value for the customer.