Geothermal Heat Pump Association of New Zealand

GHANZ was established under the New Zealand Geothermal Association (NZGA) in 2012, forming this charter in 2017.

The following GHANZ members offer design, consulting and installation services for geothermal heat pump systems in New Zealand. As members of GHANZ, these companies are committed to quality and customer service:

- Central Heating NZ

- Collins Plumbing

- ENGEO

1. Ground Loop

The ground loop is formed by a network of pipes located underground and outside the building footprint. Depending on the energy load and particulars of the site the loops may be installed in either a vertical or horizontal configuration for closed loop systems, or may be installed in an open loop system to access groundwater or surface water directly. The primary function of the ground loops is to collect heat from or dispose heat to the ground, ground water or surface water. This is achieved by circulating a working fluid through buried or submerged pipes (closed loop systems) or taking ground water or surface water directly (open loop systems).

2. Heat Pump

In heating mode, the heat pump transfer heat collected in the ground loop into the building. In cooling mode, the process is reversed and heat from the building is transferred to the ground loop for disposal.

3. Distribution System

The distribution system delivers or removes heat to/from a building. One of the most efficient methods for space heating is to lay pipes in the buildings concrete floor through which warmed water from the heat pump is circulated. Alternative methods include radiators or forced air systems.

Heat pumps function in the same way as a standard household fridge. The following basic principles are used:
- A liquid absorbs heat as it vaporises (e.g. boiling water turning into steam)
- Compressing a gas increases its temperature
- Expanding a gas reduces its temperature
- As a gas loses heat, it will turn back into a liquid (e.g. steam condensing back to water)

A heat pump uses these principles, circulating a refrigerant through a loop with two heat exchangers – one exchanger to gain heat, one to lose it.

A refrigerant is a liquid with a very low boiling point, meaning that it can evaporate into a gas and condense back into a liquid at low temperature.

When circulated in a loop between two heat exchangers, the refrigerant gains heat from one exchanger so that it turns into a gas, the gas is compressed, and then passes through the second exchanger where it loses heat, before being expanded, returning to a liquid to begin the cycle again.

In a geothermal heat pump, the first heat exchanger is placed in the circuit with the ground loop, the second in the circuit with the building. The refrigerant can gain heat from the ground loop and lose it to the building, or can operate in reverse; heating or cooling the building respectively.

Always use an experienced installer for your Geothermal Heat Pump (GHP). Good design and installation practices are fundamental to the efficient and effective performance of a GHP as specialist knowledge and expertise are required. A firm’s reputation gained from earlier installations is your most reliable indicator as to the competency and likely quality of an installation at your site. Ask your designer and installer for clients that you can talk to directly about their experience. DIY installations are not recommended.

When looking for an installer, ask them about their qualifications and experience. Also ask about other installations they have carried out, and for contact details of owners from whom you can solicit information on the designer / installers abilities, and delivery quality.

Your installer should hold the appropriate license to carry out the required work (e.g. electricity, plumbing, drilling), and issue an electrical Certificate of Compliance if required. Ideally they should also hold a ‘no-loss certification’ for the handling of refrigerants.

A professional, experienced installer has the expertise and knowledge to:
- Calculate the buildings heat loss characteristics and associated heat demand.
- Size the system correctly (i.e., the ground loop, heat pump and building distribution system).
- Advise on environmental considerations for your GHP (e.g. ground conditions, take of groundwater, drilling).
- Advise on the best configuration of the ground loop suitable for the specific location.
- Advise on the best type of distribution system for the building.
- Install and commission the heat pump in compliance with the relevant regulations and standards.
- Advise on the service requirements.
- Provide you with a service checklist and contact names and numbers in case of problems.
- Provide a warranty for the heat pump with its installation.

- Geothermal Heat Pump Fact Sheet
- Introductory Technical Guide to Geothermal Heat Pumps
- Geothermal Fact Sheet
- New Zealand Geothermal Use Database