Geothermal Heat Pump Systems

A geothermal heat pump system is a heating and cooling system that provides heat in winter and cooling in summer, at efficiencies that are far better than those for alternative systems. Like a conventional heat pump, it is essentially an air conditioner that can also run in reverse to provide heat in the winter. The primary difference is that it relies on the nearly constant temperature of the ground or groundwater for heat transfer instead of the widely fluctuating temperature of the outside air. As a result, a geothermal heat pump system saves energy, cuts electric bills, reduces greenhouse gas emissions, and offers lower maintenance and lower hot water costs than conventional heating and cooling.

Questions for consumers considering geothermal heat pump systems

Questions for professionals to ask geothermal heat pump drilling contractors

[Note: Click here for a link to state regulations on geothermal heat pumps.]

[Note: Some of the questions that follow have explanatory information while others do not. All the questions are designed to help you evaluate the qualifications of geothermal heat pump system drilling contractors to do the job properly.]

Mechanical engineers, architects, developers, HVAC contractors, and others involved in geothermal heat pump installations should evaluate the qualifications of geothermal drilling contractors to protect groundwater and optimize heat pump system operation.

Estimates by the HVAC industry suggest that as much as 50 percent of the total geothermal heat pump market involves the use of vertical borehole subsystems.

There are several different configurations of geothrmal heat pump system installations involving vertical Earth drilling:

  • Open loop: Single well for water withdrawal, water returned to a surface source
  • Open loop: Single well for water withdrawal, water returned to a second well
  • Standing column: Single well for water withdrawal and water return
  • Closed loop: Vertical boreholes
  • Direct exchange (DX): Vertical boreholes using concentric pipe systems.

Experienced geothermal heat pump installers confirm that it is critical these systems 1) be installed with a properly constructed borehole, 2) equipped with a properly placed loop tube assembly, and 3) have properly grouted boreholes, not only for optimal heat transfer but also for groundwater protection.

Licenses, Certifications, Accreditations

Is the loop well drilling firm (“the contractor”) appropriately licensed to do the firm’s work within the state where your job is being done? Does only the firm require a license, or will the drilling rig operator also need to have a license?

Ask for copies of all certifications, licenses, and training documentation the contractor has for geothermal heat pump work. Keep this information on file with insurance forms and other relevant documents.

Does the drilling contractor or the driller working for the drilling contractor have meaningful credentials from a relevant third party, such as the National Ground Water Association or the International Ground Source Heat Pump Association?

As a means of protecting the public, 48 states have instituted statewide programs to license individuals installing water wells, and in many states these regulations also apply to geothermal heat pump wells. Although specific requirements for these programs vary from state to state, generally some combination of testing, years of experience, and other criteria are used to measure the competence and knowledge of the contractor regarding well construction techniques. These laws also provide the states with an enforcement tool to assure compliance with applicable construction codes.

The NGWA Certified Vertical Closed Loop Driller (CVCLD) designation reflects an individual who has passed a written examination administered by NGWA that evaluates an individual’s knowledge of the skills and competencies associated with constructing a loop well. The candidate must pass one exam composed of 75 multiple-choice questions. An individual is eligible to apply for the CVCLD designation if he or she:

  • Is at least 20 years old
  • Has at least 24 consecutive months of full-time drilling experience
  • Submits references verifying experience from two professional contacts not with their employer.

To sustain the CVCLD designation requires 1) the completion and reporting of at least seven (7) hours of annual continuing education; 2) maintaining a high standard of work as agreed to in the “Certification Agreement” signed by the certification candidate when he or she took the exam; 3) signing an affidavit each year verifying that he or she has no pending legal action against them for failure to properly construct wells, and 4) that he or she has maintained the qualified licenses to operate in their state.

The International Ground Source Heat Pump Association offers to anyone, regardless of their drilling experience, accreditation as a geothermal driller following completion of an IGSHPA-sanctioned training program and successful scoring on an open-book exam.

Skills and Competencies of the Contracting Firm

How many loop wells has this drilling firm drilled as this firm?

Ask about the number of holes drilled and their depth, and ask about previous geothermal project profiles with a list of reference contacts.

When was the last time the lead personnel from the drilling firm that will be working on your project attended a formal program of continuing education that related to their roles in a quality geothermal heat pump installation?

  • Evidence
  • Provider name. When, where, what?

What drilling methods is the drilling contractor proficient in? Can he produce an acceptable work history with a specific method?

  • Will the contractor’s preferred method work in the formations expected?
  • Will the contractor’s preferred method work with the site features? Example: Air drilling near a water way may require enhanced site protection to contain drill spoils.

What diameter borehole does the drilling firm construct? Is the borehole diameter adequately specified so loop tubes fit appropriately in the borehole, along with a grout tremie?

Too large of borehole diameter could increase the borehole’s thermal resistance, reducing its ability to transmit energy.

Does this firm have experience drilling in the geology likely to be encountered at your job site?

What may seem like a bargain on drilling costs may be reflective of inexperience in the local geology and its drilling conditions. Consider the potential impacts to your project of substituting less expensive drilling rates for experience and capability.

Does the drilling firm have qualifications and experience to design the loop field? Is the drilling firm being assigned this responsibility?

If the drilling firm says it has the ability to design the loop field, then it should provide you evidence of its qualifications, including the use of appropriate system design tools.

Does the drilling firm have the ability to do thermal conductivity testing of the geologic setting of the proposed loop well field?

If not, then who will do this critical step?

Does the drilling firm have the proper equipment and trained workforce to complete your job?

The drilling firm should understand 1) that a borehole is constructed to exact specification and is not simply a hole in the ground; 2) how complications are handled; and 3) proper loop well grouting and its related procedures.

Does this firm have experience in mixing, pumping, and placing by pressure tremie method so-called thermally enhanced bentonite grout?

Construction of a geothermal heat pump loop well includes, in continuous order, 1) drilling of the vertical borehole into the Earth, 2) placement of the loop tube to the bottom of the vertical borehole with the grout tremie pipe, and 3) pressure grouting of the annulus space between the loop tube and the vertical borehole wall, from the bottom of the vertical borehole to the Earth’s surface. When these three steps are completed, the vertical borehole may now be considered a loop well. Loop emplacement and grouting should be performed in a timely manner to guarantee successful loop tube placement, grout installation, and environmental protection.

Requirements for the grouting of all water wells and geothermal boreholes are likely an intengral part of a state’s well construction code, and proper grouting contributes  to proper system performance.

Thermally enhanced grout has silica sand added to increase its thermal conductivity. It is more difficult to mix and pump than plain bentonite grout, so be certain your prospective drilling contractor has not only experience with these materials but has the equipment to put these materials properly into place.

How does the drilling firm control the diameter of the borehole?

How does the drilling firm control the plumbness of the borehole?

What are the drilling firm’s procedures if the borehole is to be drilled in a different formation from the test loop well?

How does the drilling firm prepare the borehole for inserting the loop tubing?

What does the drilling firm do if the loop tube does not reach the bottom of the borehole?

How will the drilling firm grout the borehole with the loop tubing in place to the bottom of the borehole?

How is the grout tremie attached to the loop tubing?

Does the contractor know and understand the type of antifreeze agent, if any, being used, and is he aware of the local and/or state regulation of what may be used?

Does the drilling contractor employ personnel who have butt and socket fusion training?

If not, you, the HVAC contractor, may need to become qualified in this work, or subcontract with someone who is appropriately qualified.

Contract and Job Site Administration Issues

Who will be the person in charge of the loop well construction crew?

Who has the final authority for the resolution of situations that may arise relating to the construction of the loop well field?

Does the well drilling firm have workers’ compensation insurance (if required by state)?

Does the well drilling firm have contractor’s general liability insurance for the job requirement?

Can the well drilling firm furnish certified wage payroll for any federally financed or assisted-construction contracts?

Will you or will the drilling firm get the appropriate permits required both by local and state government?

Does the drilling firm’s response to your contract list the drilling equipment and grouting equipment the drilling firm will use on your project?

How does the drilling firm handle a borehole that cannot be completed to the required depth? If a borehole has to be abandoned, is there a charge to the project or to you? How will they decommission the abandoned borehole?

Do your contractor’s specifications identify the type and amount of loop tubes and grouting materials, and who is responsible for acquiring the adequate amounts to match the design of the loop field?

How will the drilling firm control, treat, and then discharge the muddy groundwater produced during air rotary drilling in accordiance with state and local erosin and sedimentation requirements?

If required, how will the drilling firm dispose of the drilling mud if the boreholes are drilled by the mud rotary method?

What is the drilling contractor’s safety policy (not the insurance policy) for this job?

Does the drilling contractor have the appropriate MSDS for the materials being used on this job?