Temperzone Aquanex R32 Potable Heat Pump Water Heaters (NZ only)

Aquanex Single-Pass potable heat pump water heaters are commercial potable hot water systems (currently available in NZ only).

Aquanex Single-Pass systems heat water to over 62°C in a single pass. Single-Pass / single temperature rise technology is ideal for commercial markets where meeting the peak demand for hot water is the key driver of system specification. Functioning like an instantaneous heater, the products deliver a constant leaving water temperature to the top of storage tanks as it draws from the bottom of storage tanks. This provides a stratified / layered temperature from top to bottom of storage tank being heated. This thermal layering is surprisingly stable, and will maintain the separation of the hot and cold layers over several days. Single-Pass units contribute significantly to real-time hot water demand, and therefore can be used to reduce required storage capacity, which increases the cost effectiveness of the heat pump system.

Cost Effectiveness

Aquanex Single-Pass systems are designed to significantly reduce the installed system cost compared to other water heating alternatives. Single-Pass systems contribute to real-time hot water demand and therefore can be used to reduce required storage capacity, which substantially reduces the installed cost of the hot water system and greatly reduces system running cost.

Reduced Storage Capacity

This layering of the hot water has a distinct advantage when it comes to meeting high peak hot water demands. Every hour of operation results in up to 1000L of additional hot water capacity. A system with 2000L of storage can deliver 4000L of hot water over a 2 hour period in the morning. This feature saves both capital costs in extra storage capacity, and running costs in maintaining the storage losses of excess tank capacity - capacity only required to meet the largest load a few days a year.

Reduced Piping Costs

The Single-Pass design works off a large temperature rise between the cold water into the heat pump and the hot water out. A multi-pass system on the other hand has to circulate the water many times between the heat exchanger and the tank, with only a 4-6°C rise in temperature each time. The flow rates between the two designs are almost an order of magnitude different, which is reflected in the pipe sizes required.

Single-Pass system capital and running cost savings

As an example an Aquanex Single-Pass System delivering 35kW produces 600 L/hr of 62˚C water. A 1200 litre capacity tank with a 35kW Single Pass system allows the tank capacity to be extended to a maximum of 2400 litres over a 2 hour peak period with a recovery rate of 600 L/hr. This allows for savings in water heating costs in off-peak times and also enables the utilisation of a smaller tank to service peak periods.

Aquanex MWS vs Conventional Multi-Pass Potable Hot Water System with Plate Heat Exchanger

The Multi-Pass system slowly increases the water temperature of the tank on each pass, this system means you can only use the hot water currently in the tank. For example, a Multi-Pass system storage tank must contain sufficient volume to meet the entire peak usage period (in this example 2400 litres). Whilst the system will begin to reheat the water this hot water is not available until the entire tank reaches a usable temperature.


Aquanex Single-Pass systems are low maintenance, with low service requirements. Its ThermoShell® heat exchanger, unlike traditional heat exchangers, are fouling resistant. Our inhouse developed UC8 controller, controls the internal inline BLDC pump to produce the required leaving water temperature (62°C) with set speed compressors installed.

Aquanex heat pump water heaters utilise R32 refrigerant. Due to a smaller refrigerant charge and a reduced refrigerant GWP of 677, these R32 refrigerant systems represent a 75-80% reduction in overall GWP per kW of heating when compared to R410A systems (GWP 2088)*.

Capacity Range (heating):

MWS 250  27kW (single-fan chassis)
MWS 500  54kW  (twin-fan chassis)
MWS 1000  98kW  (quad-fan chassis)



Aquanex Single-Pass Design:

  • Reduction in required pump power - Internal BLDC pump
  • Liquid injection – for better performance in low ambient conditions
  • Greatly reduced piping costs
  • Reduced water storage required
  • Usable hot water in real time
  • Low service / maintenance requirements
  • Reliable long life system
  • Efficient system design
  • Compact Design


Potable water heating applications (eg residential, commercial kitchens, hostels, laundry, fitness centres, elderly care facilities)


The energy-saving potential of the Aquanex range application has been evident from the Dargaville Hospital Project, funded by EECA’s Crown loans programme, where a centralised diesel boiler system was replaced with a distributed heat-pump system with integrated controls. Aside from a seasonal heating signal, no further controls work was required for these units.

The space and domestic water heating loads were separately heated by dedicated Aquanex MWH and MWS heat pump water heaters suited for individual applications. An independent EECA report showed that after one year the hospital was set to save $111,000 on energy costs and $41,600 on maintenance.

* AR4 Standard

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