Amazon District Indirect Storage HIU

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Amazon District

The Amazon District range of cylinders are designed for the provision of domestic hot water on communal heating systems. The Indirect version also provides a plate heat exchanger interface for central heating.

The Amazon Unvented Cylinder is completely pre-fabricated with all the required controls, including both plumbing and wiring, and is supplied with an insulated casing and support frame that allows the system to be installed over a washing machine.

The system is aimed at installations that require the following:

  • High flow rates of DHW up to 50 litres/minute at 65C
  • Very low primary flow requirements
  • Allows primary supply temperatures to ramp down for significant periods, or off in Summer
  • Electric backup of DHW
  • Isolation of central heating circuit from heat network
  • Pressure independent flow control, independently settable for DHW and CH (up to 4 bar differential)
  • Fully pre-fabricated system for rapid installation
  • Standardised, documented, controls layouts
  • Compact use of space, with allowance for washing machine
  • Options for contract customisation



A number of additional options are provided on systems to cover system control, various types of central heating system, intelligent control, and billing services.

  • Specified central heating controllers (Danfoss as standard)
  • Secondary return pump
  • Hot water priority
  • Recovery initiated by primary temperature rise (patent pending)
  • Plate heat exchanger recovery of DHW, providing increased recovery rates, and return temperatures under 30C
  • Filling loop internal or external to casing
  • Underfloor heating manifolds
  • Various heat meter makes
  • Work in partnership with any of the major billing companies, including provision of security valve for pre-pay systems
  • Washing machine connections points
  • Discharge trap
  • IHIU Electronic controller, with Ethernet/Wifi connectivity to provide phone and tablet interface
  • Integral Managed Network Switches up to 16 port, for installation of Ethernet, Fibre or mixed networks
  • Network load management with group hot water priority (patent pending)
  • Staggered recovery
  • Communication of primary temp requirements to plant
  • Embed Database Connection, enabling system data to be saved to the Energy Saving Trust's protected servers

Schematic of Coil and PHE



DHW+CH Only, panels removed
  • 1 Unvented hot water cylinder 125 or 150 litres
  • 3 Plate heat exchanger, CH
  • 7 Thermostatic mixing valve for DHW feed
  • 8 DHW Expansion vessel
  • 9 Pressure reducing valve 3 bar
  • 10 Expansion relief valve
  • 11 Pressure and temperature relief valve
  • 12 ABQM valve with TWA-Z actuator, DHW
  • 13 ABQM valve with TWA-Z actuator, CH
  • 14 Heat meter
  • 15 Heat meter temperature sensors
  • 16 CH circulating pump
  • 17 Immersion heater 3kW
  • 18 Cylinder thermostat
  • 19 Overheat limit thermostat
  • 21 Primary strainer
  • 22 CH Expansion vessel 8 litre
  • 23 CH filling loop
  • 24 CH pressure gauge
  • 25 CH strainer
  • 26 CH tundish
  • 27 DHW tundish
  • 28 Lever isolating valves
  • 29 Pressure test points
  • 30 Frame enclosure, with steel cladding
  • 31 Internal moulded polyurethane insulation panels
  • 32 Lower support frame

Components for DHW Only

DHW Only, panels removed
  • 1 Unvented hot water cylinder 125 or 150 litres
  • 7 Thermostatic mixing valve for DHW feed
  • 8 DHW Expansion vessel
  • 9 Pressure reducing valve 3 bar
  • 10 Expansion relief valve
  • 11 Pressure and temperature relief valve
  • 12 ABQM valve with TWA-Z actuator, DHW
  • 14 Heat meter
  • 15 Heat meter temperature sensors
  • 17 Immersion heater 3kW
  • 18 Cylinder thermostat
  • 19 Overheat limit thermostat
  • 21 Primary strainer
  • 27 DHW tundish
  • 28 Lever isolating valves
  • 29 Pressure test points
  • 30 Frame enclosure, with steel cladding
  • 31 Internal moulded polyurethane insulation panels
  • 32 Lower support frame


The following dimensions are contract specific to create a space for a washing machine. Dimensions of the frame can be altered within limits to suit.

Minitec Aluminium Extrusions are used for the following frame option.

Dimensional Drawing.png



Primary Pipework Arrangements

The following schematics cover the most common primary layouts, using both coils and plate heat exchangers for reheat of stored water.

A plate heat exchanger can be used to reheat the unvented cylinder in place of a coil, with numerous benefits:

  • Return temperatures below 30C
  • Typically triple the heat transfer rate of a coil for any given primary flow
  • Control over the volumes of water heated
  • The ability to heat very small quantities of water very quickly
  • Primary temperatures can be as low as 3C above target store temperature
  • Overcomes pressure limits on coils, allowing connection to 16 bar primaries
  • Smaller storage requirements
  • The optional use of double wall plate heat exchangers


The unvented cylinder has 30mm insulation as standard, with an outer steel casing. In addition to this the void around the cylinder and Pipework is filled with moulded panels of polyurethane foam insulation, increasing the average insulation thickness to approximately 100mm. The panels are easily removed to access components for servicing.

This approach creates enough space to fit expansion vessels, controls and pipework within the overall dimensions, while reducing overal heat losses well below those of a cylinder with thicker base insulation but standard pipwork.

Support Frame

The standard frame is typically manufactured from 25mm box section, and power coated in white.

Alternative forms of frame are available on request, including stainless steel tubular support pillars.

Overall Assembly

70RD00011 Aluminium Upper Frame

70RD00012 Aluminium Lower Frame

AB-QM Control Valves

The AB-QM Pressure Independent Control Valve has been used by Thermal Integration for many years now as a reliable means to control flow rates.

AB-QM No Actuator
TWA-Z Actuator
Novocon Actuator
  • Exact and pressure independent flow limitation allows no overflows at partial conditions to keep temperature difference over terminal unit as high as designed
  • The AB-QM is able to control the temperature at low loads and is equally stable all through the range. All changes in the available differential pressure are corrected by the pressure controller. Therefore, less disturbances for temperature control and therefore less movements from actuator.
  • AB-QM offers full flexibility of flow adjustment - AB-QM valves can be set to a precise design value even when the system is up and running so no need for draining the system or use of flow charts or calculations - they allow full control over the real conditions in the system.
  • Due to the membrane design the valves are less susceptible to blockage.
  • Always the right flow, so no complaints from end-users
  • Exact flow limitation at any load condition prevents excessive energy consumption that occurs when static balancing method is used in variable flow system.
  • Covers two functions - Balancing & Control.
  • Measuring nipples allow optimisation of the system's performance.
  • 100% built in control valve authority allows lower pump head than traditional setup, thus minimizing energy consumption.
  • Easy adjustability allows late change of design flows without high costs.
  • Plug and Play even when installation is not yet completely finished. For example when some floors are already occupied while construction is still going on at other floors, the occupied floors are already fully functional and balanced.

AB-QM Valves

TWA-Z Actuator

The TWA-Z thermal actuator is used with the AB-QM valves to provide a cost effectibe means of control, where speed of response is not an issue. The actuator can be controlled with an on/off controller, pulse width modulation (PWM), or switch, or in conjunction with [/wiki/index.php?title=IHIU_Control_Systems IHIU Control Systems] fitted with a solid state relay for variable control.

  • 24 V AC/DC or 230 V AC supply
  • Position indicator
  • Normally opened (NO) or normally closed (NC) version
  • Max. medium temperature 120° C
  • Cable included


Novocon Actuator

The Novocon Actuator, combined with the AB-QM range of valves, provides vary fast linear control over water flow, independent of differential pressure of up to 4 bar. It can be controlled via a 5v signal, allowing direct control by [/wiki/index.php?title=IHIU_Control_Systems IHIU Control Systems], with the use of a 24vdc power supply.



Electrical Connections

The following wiring diagram covers basic mains control setup using standard programmer and room thermostat controls.

Alternative wiring diagrams available on request.

Standard supply required is 230vac via 3A fused spur.

Heat meter wiring not shown.


In addition to the controls supply, a 16A supply will be required for the immersion heater, via a locally switched spur.

Reheat Tests

The following test detail the reheat performance of a 150 litre Amazon unvented cylinder, with a standard coil.


IHIU Control Options

The IHIU controller represents the height of modern Linux control systems, providing a very powerful open-source software environment capable of connecting to virtually any device, while at the same time costing a fraction of the cost of traditional proprietary electronic controller. The miniature computer has built in Ethernet and WiFi, and runs the same software that runs on most internet routers, making it a powerful hub for secure communications to almost any web connected device or server.

Although the controller does have numerous inputs and outputs, its USB port, expandable by the use of a USB hub, allows one to also connect almost any peripheral designed for computers, from USB storage devices, through to GSM dongles, RS485 devices, or even cameras, making it more than just a controller for hot water systems.

Some of the things we can connect to the IHIU system include:

  • AB-QM valve actuators including TWA-Z and Novocon
  • PWM speed controlled pumps
  • Flow, temperature and pressure sensors
  • Heat meters (to be released 2016)
  • Z-Wave devices (to be released 2016)
  • Mesh networking modules
  • Other controllers via RS232 or RS485 cable
  • Other equipment via use of solid state relays
  • The Internet, via the on-board WiFi or Ethernet port
  • Smartphones, tablets, and PCs, via local network, or IHIU WiFi hotspot
  • Billing systems
  • The Embed database from the Energy Saving Trust
  • Email and SMS

The Linux system runs a number of software languages (including Python) and can host powerful PHP driven web sites for user interfaces. The core user-interface is indeed a PHP driven website running JQuery - the system that powers responsive websites that change their format depending on the device upon which they are viewed. Its power can be extended by the use of online APIs, allowing the system to interact with Dropbox or Twitter, or send emails and text messages.

What this delivers is a low cost solution that will provide:

  • Advanced control over both hot water and heating
  • Return temperature control and flow limitation
  • User and engineer interfaces
  • Heat network wide hot water priority (patent pending)
  • Link between heat meter and billing provider
  • Option for secure independent free data storage
  • Continuous remote optimisation of heat network flow rates to meet demand

The following tables demonstrate the advantages of properly managed load management, with a design peak load of 7 litres per hour per flat (<0.4 kW).


Related Articles

  • [/wiki/index.php?title=Communal_Heating_and_Hot_Water_Cylinders Communal Heating and Hot Water Cylinders]
  • [/wiki/index.php?title=Communal_Heating_and_Central_Heating Communal Heating and Central Heating]

Related Products

At Thermal Integration we have decades of experience in both storage and heat exchange systems, and can provide unbiased site specific advice to ensure the most suitable type of systems for each dwelling, and to help overcome flow rate limits in a network.



The DATA HIU is our latest twin plate HIU for instantaneous generation of hot water, and provision of indirect central heating. The Data represents the very cutting edge of HIU design, and has no equal. Just some of the features include:

  • DHW up to 80kW, and central heating up to 20kW
  • Very fast and accurate control over both hot water and central heating temperatures
  • Complete with full central heating sealed system control set, and pump
  • Very high levels of insulation using EPP casing
  • Compact dimensions
  • Economy and comfort stay-warm modes, to significantly reduce unwanted primary drain
  • Return temperature limitation
  • The latest asynchronous plate heat exchanger design to further reduce return temperatures
  • Options for integral security valve, differential pressure valve, secondary return pump, and hammer arrestor
  • Options for connection to billing systems and managed networks

Both Amazon Storage HIUs and Data HIUs can be supplied in a mix to suit varied demands across a network, both types fitted with a common metering and billing platform.

The UtilityMaster HIU


The UM2 UtilityMaster, shown here, provides an indirect primary interface to a heat network for up to 30kW load, and is designed to work in partnership with a hot water cylinder for DHW. The UM1 is fitted with two separately metered water supplies for drinking water and CWS. At only 590 x 390 x 165mm the unit is very compact, and lightweight, using a moulded EPP casing for insulation and structural strength, and voids within the casing are filled with further removable moulded insulation.

To manage utility supply the UM2 is fitted with:

  • 2 x cold water meters with pulsed output
  • Heat meter with M-Bus and 2 x pulse counters (for cold meters)
  • Pressure independent control valve for up to 1.7m3/h fitted with thermo-electric actuator
  • M-Bus relay for remote closure of control valve (prepay billing)
  • Steel outer cladding with security bolts to the wall and cutouts for heat meter and water meter displays