The challenge was to provide an environmentally friendly, ‘alternative fuelled’ district heating network, owned and operated by Stirling Council, with sustainable products in order to expand the network over the city and allow energy and cost savings for both public buildings and businesses.

The objective was to supply a cutting-edge combination of technologies, recovering heat from sewage waste water to generate low carbon heat and electricity in one single, highly efficient process.


Trane took up the challenge and provided two CITY RTSF 110 heat pump units, with a total capacity of 800kW using the low GWP HFO refrigerant R1234ze. The units were integrated in the Stirling heating network to extract heat from sewage and wastewater.

The selected products are perfect to satisfy Stirling Heat Network with their inverter-driven screw compressor technology and a large operating range. They can produce hot heating water at a temperature of 80°C and be used in cooling systems to produce water at temperatures of 6°C, or even lower. Another advantage to this Trane solution is that the City RTSF heat pump fits every kind of building – it is very versatile while using sustainable components.


The huge project was a success following up the Scottish Government’s Low Carbon Infrastructure Transition Program (LCITP). Thanks to this sustainable installation, the company has made impressive savings. "Harnessing heat from waste, the Stirling project has the potential to save hundreds of tonnes of carbon per year", said Donald MacBrayne, Business Development Manager at Scottish Water Horizons.

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Project highlights

Location: United Kingdom

Market application: District heating

Customer need:

Products installed: 2 x City RTSF Heat pumps

Social media: Read more

Featured products

Product name: City™ RTSF Water-to-Water Heat Pump

At a glance:

  • 99.5% reliability rate with screw compressor technology and Adaptive Frequency™ Drive as standard
  • Fully optimized for HFO R1234ze (<1 GWP). Available with R515B as an alternative
  • Minimized refrigerant charge with stainless steel plate heat exchangers

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