Node-HIU Control Panel

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The node-HIU Control Panel is a pre-fabricated control system for use on heat networks and plant, providing a turn-key solution to monitoring and commissioning all the assets on a system.

The panel has been designed to interface with HIUs fitted in properties, a well as plant rooms running on commercial BMS systems, pulling all the available data together to a central point where it can be monitored and acted upon.


All customers want reliability, efficiency, and support when needed. So now we have put this into a box.

We call it the Node-HIU Control Panel, and its purpose is to fulfil our customers demands for reliability, efficiency, and support on heat networks, by keeping an eye on things, commissioning and tweaking control systems or HIUs, and connecting support with any problems identified.

The Node-HIU Panel is in essence a router, taking data and routing it to where it needs to go.

It adds the ability to decide what data goes where, and when, as well as performing any calculations or analysis needed en route. At the same time, it acts as a communications hub and firewall, bridging internet networks, with local networks, and pulling in the various local control circuits such as HIUs, M-Bus meters, BMS systems, and Modbus devices.

Many customers have shown a strong desire for systems they can fully own, and which are contract free, so the panel delivers on that request. The panel is built using open-source technologies including Linux, OpenVPN, MQTT and Node-RED.

The use of MQTT and encryption, along with simple wiring logic, allows data to be regulated on site, with communications filtered and protected as needed, and sent on a need to know basis. MQTT allows two way communication, and is a standard for M2M communications and home control systems.

The panel it is delivered fully working, pre-commissioned, and communicating with the outside world, requiring only wall space and power to get started.


  • Increase system efficiency by monitoring load and providing signals to plantroom equipment and HIUs
    • DP control of pumps
    • Boiler sequencing
    • Network supply temperature
    • Load shifting or shedding to reduce peak loads
  • Simplify the installation of systems by catching every snag as it appears
  • Detect problems with systems requiring human intervention
    • Low heating system pressure
    • Component failure or wear
    • Open bypasses
    • Blockages in pipes
  • Route alarms to the correct persons
  • Follow strict rules regarding data protection and transmission
    • No data storage unless a fault is detected
    • Data analysed at source, with defined alarm content sent to 3rd parties as programmed
    • Reduce traffic to alarms and messages only (for SIM limits as well as data protection)
  • Give users remote control over services
  • Option to run the whole lot contract free (other than internet provision) and without any ties to bespoke hardware or services
  • Ability to easily migrate new control logic from one system to another, and enable the collaborate evolution of heat networks.

See Also

Panel Types

All panels follow a standardised MQTT data structure, allowing data from distributed panels to be combined into a single heat network data flow. See Heat Network Protocol.

Type 5v Power 24v Power RPi Touch
AIn AOut DIn DOut Relay Other
PR Panel 1 2 2 1 GSM modem, WiFi, Ethernet switch, Node-RED, MQTT & VPN services
Substation Panel 16 4 8 4
Pump Panel 1 8 4 Modbus pump control
Boiler Panel 1 8 4
Storage Panel 1 8 8 2
User Panel 1 8 2 8 Red/Green Indicator lights, Off / Hand / Auto switches
RB Panel 1 1

PR Panel

Plantroom Control Panel - Cover Off.jpg

Plantroom Control Panel - Cover On.jpg

  • Touch screen display
  • GSM modem
  • 2 year SIM contract with 5GB/m and fixed public IP address
  • Power supplies for controls
  • 2x RPi3 Linux computers providing:
    • Node-RED control software
    • MQTT servers (primary & backup)
    • VPN servers (primary & backup)
  • Valid HTTPS certificate
  • Reverse proxy
  • Pre-commissioned before arriving on site
  • TCP I/O module(s) for:
    • Analogue (0-20mA / 0-10v / 0-0.5v) inputs and outputs
    • Digital inputs and outputs
    • Relay outputs
    • Modbus control
  • Optional M-Bus module(s) for meter reading
  • All network variables, inc. HIU data, plantroom data, meter data, and operational data presented over standardised MQTT data structure
  • Alarm detection and reporting via email, SMS, automated voice call or postal letter

RB Panel


  • Node-HIU RPi3 controller with touch screen monitor
  • Node-HIU RPi3 controller with 375GB hard disk storage
  • Node-HIU RPi3 controller with I/O
    • 2 x RS485 (Modbus or other protocols)
    • 0-24v analogue inputs
    • Cross over relay for fault circuit
    • Digital temperature sensors
    • 24v digital inputs/outputs
  • 5v and 24v power
  • GSM modem with twin SIM cards
  • Diversified protected aerials
  • 8 port managed Ethernet switch
  • Spare mains plug socket and USB power
  • DIN rail space for 3rd party metering equipment (e.g. M-Bus master)


  • 8 port managed Ethernet switch with PoE
  • 16 port managed Ethernet switch with Ethernet + Fibre
  • LoRaWAN radio network base station (up to 5km) (in development)
  • M-Bus Master


  • Full management of connected HIU network
  • GSM internet connection for commissioning and backup)
  • WiFi access point (for plantroom equipment and engineers)
  • MQTT server
  • Dynamic DNS (via NOIP)
  • Port forwarding
  • VPN server (x2)
  • Node-RED control system (x3)
  • Modbus master (RTU/TCP)
  • Commissioning dashboard (via LAN/VPN)
  • Heat network monitoring dashboard (via LAN/VPN/Display)
  • Fault diagnosis and reporting
  • Alarm routing to email, SMS, remote partner screens, or mobile push alerts

Control Software

  • Visual drag and drop programming environment
  • Javascript (Node.js) coding
  • Open-source

The software used to program the Node-HIU panel is Node-RED, an open source system driven by IBM. The platform allows one to easily program in logic by wiring together components, requiring no prior coding skills, and is similar to both the programming languages taught in schools, and those used on graphical PLCs. It also allows one to dive into a full coding environment based on JavaScript - possibly the most common software language there is.

Logic components or full systems can be easily copied and pasted, enabling collaborative development of standardised control functions. 3rd parties are able to develop their own components, with 'nodes' available to interact with a growing number of systems and online services.

Analysis Software

The following is a sample loading profile over 24 hours for hot water load on a network, taken from real world systems. The data is one second resolution, and enables the very brief (<10s) peak loads to be analysed.

Similar data on any system variables can be logged and analysed.



  • All communication made through MQTT
  • No ports open to the internet other than for MQTT and VPN
  • Traffic on a network to be restricted to known routes
  • Each service on each controller given random passwords

MQTT is a robust and extremely versatile protocol, used by many internet services, and can be opened up to the internet. The same is true of OpenVPN, the open-source standard package for providing secure remote network connections. No other incoming ports are required for operation of the system.

The Liberatum GSM Modem provided with the panel provides all firewall services, and enables port forwarding for MQTT and OpenVPN. Communications can be locked down to the known devices preventing access from unknown devices plugged into the network without authorisation.

Commissioning dashboards are only available within the local network, or over VPN connection.

Screen Examples


Remote DP & Temperature SensorPlantroom control systemM-BusData optionsHIU readings

Function Example 1: DP Control of Pumps

All plant-rooms need to be able to control the speed (power) of their main circulating pumps to match demand.


  • DP sensors on local heat network via Modbus RTU
  • DP sensors on remote heat network via MQTT
  • DP sensors in plant-room via 0-10v analogue
  • DP signals from HIUs running hot water outlets via MQTT/Modbus


  • Pump speed via Modbus RTU
  • Alarms via email


  • Minimum DP at an HIU
  • Minimum DP at a sensor on network


  • Run the pump to the minimum speed that keeps all minimum DP settings satisfied


Function Example 2: Load Balancing


  • Instantaneous HIU hot water loads
  • Network supply heat meter readings


  • Short term load request to HIUs
  • High resolution day-of-week load csv files
  • Alarms via email
  • Supply temperature valve control


  • Maximum network supply flow rate
  • Maximum/minimum network supply temperature
  • Maximum rate of change of network supply temperature


  • Meet short term peaks in demand by shutting down central heating temporarily (network wide hot water priority)
  • Match supply temperature to load patterns

I/O Controllers


We have searched far and wide for the best means to reliably connect Node-RED to control inputs and outputs, in order to enable the panel to fulfil the full range of plantroom functions expected of a typical BMS system. The Brainboxes range of control equipment provides us with Ethernet based modules that enable a device running Node-RED to communicate through:

  • Digital inputs and outputs, typically at 24v dc
  • 16 bit analogue inputs and outputs of types:
    • 0-10v or 2-10v (full range can go as low as 50mV)
    • 0-20mA or 4-20mA
    • +/- 20mA
  • Thermocouples
  • Relays
  • RS485 and Modbus

They take redundant power supplies, operate across a wide temperature range, and come with a lifetime guarantee and support.

Together with Node-RED running on a Raspberry Pi, we have a robust open-source controls architecture that is far more powerful than current BMS technology.

The open nature of the software allows collaborative development of system logic, and reliable implementation of this logic in practice.

Controls Wiring