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Thermal Integration Ltd

Heat Interface Units

MASTER & MAJOR Heat Interface Units (HIUs)

An extremely versatile self-contained, pre-plumbed and pre-wired Heat Interface Unit ideally suited to district heating or central boiler applications.

  • Instantaneous hot water up to 75kW
  • Indirect central heating up to 124kW
  • Suitable for heating up to 25 modern individual properties
  • Designed to offer many options within one standard casing

The MASTER and MAJOR range of HIU’s (Heat Interface Units) provide central heating with optional domestic hot water in properties connected to a single boiler or a district heating system using a central boiler plant.

For many years, there has been an increasing use of centralised boiler plants in property developments. The advantages of removing gas boilers from properties and making use of high efficiency centralised boiler plants are numerous.

Advancing technologies such as combined heat and power (CHP), biomass, extract air heat pumps, waste incineration and solar are mostly uneconomical to employ in individual properties but can be utilised and combined to generate heat to numerous properties. HIU’s are fitted into each property and take the heat from the central plant; using this to provide central heating and hot water to taps.

It is easiest to think of an HIU as a boiler, running off heat from large pipes throughout the development, rather than a gas supply in each individual property. Occupants are charged for units of heat, rather than units of gas. The charge is calculated by a heat meter which measures energy use.

Higher outputs are suitable for larger properties, existing boiler replacements, connection to existing heating controls or cluster installations.

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Features and Benefits

  • Instantaneous hot water up to 75kW
  • Indirect central heating up to 124kW
  • Compact design, no need for clearance either side for servicing
  • Copper brazed plate heat exchangers
  • Insulated removable casing for ease of servicing
  • Insulation box for primary plate heat exchanger
  • Latest generation of pressure independent controls
  • Accurate domestic hot water temperature control
  • High efficiency ‘A’ rated heating pump
  • Range rated outputs from one unit
  • Standard connections:-primary flow & return top / central heating flow & return bottom
  • Automatic air vent on secondary circuit
  • WRAS approved (components)


  • Anti-tamper security fixings on casing and heat meter
  • Various heat meter and billing options
  • Optional wireless heat metering compatible with aftermarket billing systems
  • Built-in 10 litre expansion vessel
  • Built-in filling loop
  • Built-in security valve for instant landlord isolation
  • Customisable mains cold water and domestic hot water pipe work positions
  • Primary circuit trickle flow to maintain heat within the unit
  • External cold water meter

  • Dual Zone CH + Unvented Kit & Instant DHW

  • Dual Zone CH & Instant DHW

  • Single Zone CH + Instant DHW

  • Dual Zone CH + Indirect Cylinder Feed

  • Single Zone CH + Un-Valved Feed

  • Single Zone CH + Direct Primary Feed

  • Electronic CH Temperature Control

  • Mechanical Return Temperature Limitation

  • MAJOR and MASTER Case