Hospital Boiler Replacement

Heat Pump Replacement of Diesel Boilers at Kaitaia, Dargaville and Bay of Islands Hospitals Northland.

The DHB was able to save hundreds of thousands in annual energy costs and maintenance costs along with significant reductions in carbon emissions through the replacement of diesel boilers using heat pump water heater technology.

Kaitaia, Dargaville and Bay of Islands Hospitals were heated with centralised diesel fuelled boilers. We applied newly developed heat-pump technology to replace the boilers which have high operating and maintenance costs.

The hospital heating systems were set up in a primary/secondary loop configuration, with both space and domestic hot water being supplied to various parts of the building.

The decision was made to use an air to water heat pump for the domestic hot water and a separate heat pump for space heating. This allows the targeting of the most appropriate heat-pump technology for the temperature range and seasonal demand of the water being heated. With the Hospitals located in Northland, the heating season is relatively short, allowing much of the system to be switched off during the summer months which was not possible with the boiler system with combined heating systems.

For space heating, with the distribution networks having been added to over the years it was not realistic to adopt a balanced flow distribution system, so we used a commercial variable speed (inverter) compressor. This approach allows the compressor to operate at a speed to maintain a unit outlet water temperature of 55 deg C. This system required 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 delivered 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.