Commercial Tower – ROSC20 Commercial Gas System

Job History/ Description:

The needs of the client were for an upgraded domestic hot water plant that met their expectations of sustainability, energy reduction combined with durability and performance in a 40-story commercial tower in CBD Melbourne that was to be retrofitted within a suitable timeframe minimising DHW building shutdown.

Requirements of the Application:

To provide an energy efficient, durable water heating system with an off-grid renewal energy solar PV component providing 4,400 L at a 50°C rise in the first hour and 4,000 L each hour there after to meet the building domestic water heating duty load.

System Solution:

  • 2 x Rotex 500 litre tanks model SC544/43/0 comprising dual stainless-steel coils providing clean hygienic hot water with high flow rate capabilities to the 40-story commercial tower.

  • 2 x Noritz commercial condensing gas units delivering a 50 litre per minute flow rate – 330 mj/hr each – 95% thermal efficiency providing the main energy source.
  • 1 x Grundfos primary pump set for the system primary loop function.
  • 2 x ESW ROSC20 elements providing a total of 4 Kw of solar yield via 12 solar PV panels.

This system replaced the original buildings DHW plant that was approximately 12 years old and in poor condition with the domestic gas units of a mixed range and capacity and with original damaged solar thermal panels.

The initial gas system comprised of 8 x 199 mj/hr continuous flow 24, 26 & 27 litre models and was replaced with 2 x 330 mj/hr commercial condensing gas units that were fit for purpose for the application as the main energy source.

Facts and Figures: New Rotex plant

  • First hour delivery – 4,400 litres @ 65 degrees.
  • Recovery rate per hour – 4,000 litres @ 65 degrees.
  • Building occupation – 3500 people using 163 basins, 80 sinks and 41 showers throughout the facility.


In a retrofit example this project application being a large commercial tower is one of many that demonstrates how a ROTEX water heating solution can meet any existing commercial facility demand from design to commissioning and job completion using latest technology of renewal energy and solar yield performance combined with leading efficiency fit for purpose gas commercial units.