The challenge was the space heating systems. With the distribution networks having been added to over the years, it was not realistic to adopt a balanced flow distribution system, so the Temperzone R&D Department decided to trial commercial variable speed (inverter) compressor technology for this application. This approach would allow the compressor to operate at a speed to maintain a unit outlet water temperature of 55 deg C. Each heat-pump water heater contained at least two inverter compressors, allowing the compressor speeds to be maintained at the peak of the efficiency curve.
Such a system requires the heating distribution system to be converted from a fixed flow system to a variable flow system, with the building heating load controlled by the system flow rate. In practice, this is a straightforward design change, and is supported by high efficiency variable speed pumps.
The Bay of Islands Hospital was converted first, followed by the Dargaville Hospital. In early 2019 the Kaitaia Hospital upgrade was completed. The Dargaville site contains numerous separated buildings, so a distributed heat-pump water heating system approach was used, with the heat-pumps located around the site close to each area of heating demand. At Kaitaia, the buildings are more concentrated, so the heat-pumps were connected to a common flow / return manifold.
The upgrades were funded under the EECA Crown Loans scheme. Dargaville and Kaitaia Hospitals collectively saved over $200,000 on annual energy costs, over $100,000 on annual maintenance costs and a reduction of 794 tonnes of CO2 emissions each year. With numerous old boilers due for replacement around New Zealand, these projects have demonstrated the application and cost effectiveness of inverter heat-pump technology in commercial applications and are a key technology as we begin the transition to a low carbon future.
Variable outdoor fan