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Heat exchange drilling (geothermal systems)

Heat exchange drilling in Wisconsin requires a license.

geothermal temperatures

Geothermal works on the principal of using the earth's natural underground temperature and a geothermal heat pump unit to provide heating in the late fall, winter and early spring and cooling in the late spring, summer and early fall. In Wisconsin, the average underground temperatures range from about 52 degrees in the south to 42 degrees in the north. Below about 20 feet in depth, the influence of surface temperature variations begins to dissipate rapidly and becomes the average of all surface temperature values.

Four basic types of geothermal systems are allowed in Wisconsin:

  • A closed loop vertical system has the loops installed in a vertical or angled drillhole.
  • A closed loop horizontal systems has the loops installed in a shallow trench or angled drillhole.
  • A pass-through system or "pump and dump" draws water from a well and discharges it back to a surface source.
  • A direct exchange (DX) system has loops typically made of copper and are installed in a vertical or angled drillhole.
geothermal systems

Constructing heat exchange drillholes

Any geothermal system that involves construction of one or more drillholes extending more than 25 feet below the ground surface must meet construction standards and notification or approval requirements in NR 812, Wis. Adm. Code. In addition, heat exchange drillholes may only be constructed by a licensed Heat Exchange Driller or a Registered Heat Exchange Drill Rig Operator working for a licensed driller.

Heat exchange drilling projects require a prior DNR approval if any of the following conditions apply to the project:

  • Ten or more drillholes
  • Drillholes greater than 400 feet deep
  • Project within 400 feet of a municipal well
  • Project in Outagamie County
  • Project in Winnebago County

Use the Closed Loop Heat Exchange Well Application (Form 3300-255) [PDF] to apply for DNR approval. If none of the above conditions apply to the project, a Heat Exchange Notification number is required prior to construction.

Apply for a heat exchange driller license

geothermal temperatures

All applicants must submit:

Drillers seeking reciprocity for licensing in another state must also complete the Out-of-State Individual Heat Exchange Driller License Application (Form 3300-302) [PDF].

All applicants must take the written exam. You will be notified of your eligibility to take the exam along with further instructions regarding study materials, fees, exam and other logistics. Learn more about the heat exchange driller licensing process.

Study materials

Other resources

Last revised: Thursday October 24 2019