Radiance Thermal Interface Units (TIUs): ZEST  


A result of engineering excellence and years of in-depth knowledge of the heating industry, the Reliance Water Controls Radiance range of Thermal Interface Units (TIUs) are designed to be used as part of a community heating system (CHS). TIUs are highly efficient and eco-friendly. There is no requirement for a flue outlet resulting in an aesthetically pleasing exterior building design. Each unit is built in our state-of-the-art facilities in Evesham, to meet the exact specification requirements of the project. TIUs utilise components from our full range including TMVs, ball valves and strainers as well as our unique maintenance-free, long-life expansion vessels for enhanced durability.

Features and Benefits

Designed for High Efficiency Performance
• Designed and manufactured in the UK to be fully compatible with UK heating and hot water systems
• Highly energy efficient CHN systems are more eco-friendly and economical than alternative heating methods over system lifetime
• Radiance® TIUs are ‘Demand Controlled’ so there is only flow through the unit when there is a requirement for heat or DHW, which reduces unnecessary heat loss, lime-scale build-up and supports whole system longevity
• All internal pipe work is manufactured from high quality, flexible, fully insulated corrugated stainless steel pipes which reduce heat loss and permit bespoke configurations to be made with ease
• WRAS approved

Options to Suit Individual Projects
• Radiance TIUs can be configured with a number of optional extras to suit any individual projects requirements. Reliance Worldwide Corporation (UK) Ltd offer a system design support service to help Architects and Specifiers to ensure maximum energy efficiency is achieved for their projects
• Individual metering options include automatic meter reading or a prepayment type meters for minimal disruption to occupants. A meter reading service can also be provided via a partner organisation if required.

Easy to Install and Commission
• The absence of gas or flues increase safety for occupants and reduces whole system installation costs in terms of both materials and labour time
• Connections are made easy with SharkBite push-fit ball valves for an even faster installation. Ball valves with female BSP connections are also available if required
• Each unit is delivered fully factory assembled and is 100% pressure tested prior to despatch to ensure product performance and reduce commissioning time
• The absence of soldered or brazed joints minimises contamination and leak potential eliminating the requirement for flushing prior to commissioning

Reduced Maintenance
• All pipe connections are union connections sealed with washers for reliable connections and easy maintenance
• Radiance TIUs incorporate a patented spring loaded expansion vessel which delivers a high performance compact size unit with extended product lifetime which is entirely maintenance free
• Each unit is marked with a unique serial number, product code and production date to ensure individual product identifications/traceability for maintenance records

Zest Specifications

Indirect heating & DHW unit linked to a Pre-plumbed cylinder. 

  • Designed to work in conjunction with a pre-plumbed cylinder
  • A single plate heat exchanger allows the the pre-plumbed cylinder to be easily connected to a heat network
  • Hydraulic connections are made through SharkBite ball valves at the top of the unit (as standard) - BSP connections are also available if required
  • Pipes can be run behind the back plate to allow for bottom connection
  • The unit is delivered fully assembled and leak tested
  • Bespoke models available - A number of optional extras are available including a first fix rail for easy phased installation as well as a number of metering options


  • Weight 25kg (Approx)
  • Heating Capacity (kW) UK 20kW
  • DHW output (kW) max N/A
  • Dimensions (mm) Width x Depth x Height 505 x 265 x 840