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Imported from GitHub: energietransitie/needforheat-boiler-monitor-hardware · commit 1120404 · license CERN-OHL-P-2.0

Description

Open hardware design files for the NeedForHeat Boiler Monitor devices

README

NeedForHeat Boiler Monitor hardware

This repository contains the open hardware design files for the NeedForHeat Boiler Monitor hardware, which consists of PCB and 3D printable pipeclamps for:

  • Boiler-BASE module for the on the back of an M5Stack CoreInk device;
  • Thermostat Cable Splitter module, which is inserted by the subject in the signal path between boiler and thermostat;
  • Two pipe clamps with temperature sensors that can be clipped on the supply and return pipes that carry hot water from the boiler to the radiators and returning from the radiators.

This integrated device can:

  • monitor OpenTherm signals between boiler and thermostat, similar to the Twomes OpenTherm monitor;
  • monitor on/off signals between boiler and thermostat that do not adhere to the OpenTherm standard;
  • monitor with supply and return water temperatures, similar to the Twomes Temperature Monitor Hardware.

Table of contents

General info

This repository contains the open hardware designs files and production files for the NeedForHeat Boiler Monitor. It also includes a docs folder with recent printouts of:

The splitter features a 4 wire pluggable screw terminal on each side in which the cables can be connected to in almost any order.

The associated firmware that you need to run on this device was not yet implemented. I will be a combination of:

Producing

Printed Circuit Board

To manufacture the printed circuit board you can use various PCB services.

The folder pcb production includes all exported files needed to have the PCBs manufactured by JLCPCB. Upload a zipped gerber file to the JLCPCB quote page, select the amount of PCBs and a colour for the silkscreen. All other options can be left on default.

If you do not want to solder components on the PCB yourself, select PCB assembly and JLCPCB will do it for you (even for through-hole components if you so desire). This will take you to a page where the BOM and POS file can be uploaded. Use the files in BOM-CPL.

JLCPCB provides detailed steps on their website to select component assembly, including wave soldering. For wave soldering or through-hole component assembly, specify this requirement when uploading your BOM and POS files.

In the table below, you will find the files per PCB.

PCBzipped gerberBOMCPLComponents that do not need to be placed
BoilerBASEGERBER-BoilerBASE.zipBOM-BoilerBASE.csvBOM-BoilerBASE.csv
Thermostat Cable SplitterGERBER-ThermostatCableSplitter.zipBOM-ThermostatCableSplitter.csvCPL-ThermostatCableSplitter.csvR13, R14, R15
Pipe ClampsGERBER-PipeClamp.zipBOM-PipeClamp.csvCPL-PipeClamp.csv

Enclosures

To manufacure the pipe clamps you can use your own 3D printer or use a 3D printing service.

The folder enclosure contains exported STL files for:

The STL files can be imported into any slicer and turned into G-Code for a 3D printer.

We do not yet have designs for the Thermostata Cable Splitter.

Deploying

Cost

To deploy the NeedForHeat Boiler Module to a home, you need all hardware listed below. Prices indicate price per Boiler Monitor, based on ordering enough hardware for 10 Boiler Monitors, June 2024 including 21% VAT and shipping to an address in the Netherlands.

#ItemSupplierPrice per UnitSubtotalShippingTotal
1BoilerBASE PCB€2.38€2.38€2.38€4,79
1BoilerBASE EnclosureJLCPCB€1.23€1.23€2.38€3.60
1Thermostat Cable Splitter PCB1JLCPCB€5.02€5.02€3.23€8.25
1Thermostat Cable Splitter enclosure€2.38€2.38€2.38€4,79
2Pluggable Terminal Blocks (5.08 mm. 4 ways)€1.15€2.30€1.82€3.12
2Pipe Clamp PCBJLCPCB€3.41€6.81€2.30€9.11
1Pipe Clamp enclosureJLCPCB€1.00€2.00€2.38€4.38
4LEGO pen with frictionBlokjeskoning€0.03€0.12€0.30€0.42
1M5Stack CoreInkTinyTronics€43.00€43.00€0.00€43.00
2RJ12 cable (male-male; 6P6C; straight; 1 m)AlleKabels€3.08€6.16€0.13€6.29
1RJ45 cable (male-male; 8P8C; straight; 1 m)AlleKabels€1.29€1.29€0.13€1.42
1USB-A 230V charger + USB-A to USB-C cableAlleKabels€14.95€14.95€0.13€15.08
TOTAL€87.64€17.46€107.65

Connecting

Assuming that the PCBs are fully assembled, the devices have an enclosure, and the device has been programmed with the needforheat-p1-reader-firmware, you can proceed and connect the device as follows:

Tools needed;

  • Screwdriver (flat head, 3 mm)
  • Wire cutter
  • Wire stripper

Steps:

  1. Unplug the power

    • Unplug the boiler and thermostat from power outlets.

  2. Connect the Boiler Monitor

    1. Cut the signal cable between the boiler and thermostat within 1.5 meters of a power outlet.
    2. Strip 2 cm of the outer sheath and 0.5 cm of insulation from each wire.
    3. Insert wires into the green pluggable screw terminal connectors and tighten screws.
    4. Attach connectors to the Thermostat Cable Splitter (boiler side: connector J2 on the PCB and CV on the enclosure, thermostat side: connector J1 on the PCB and T on the enclosure).
    5. Connect the BoilerBASE to the M5Stack CoreInk MI-BUS using the 2x8 male pin header.
    6. Use an ethernet cable (RJ45) to connect the Thermostat Cable Splitter (connector J3 on the PCB) to the BoilerBASE (connector J3 on the PCB).
    7. Power the M5Coreink+BoilerBASE via USB-C.
    8. Insert PipeClamp PCBs into enclosures and secure with locking pins.
    9. Use cables (RJ12) to connect the BoilerBASE (connector J1 and J2 on the PCB; order does not matter) to the PipeClamps (connector J1 on the PCB).
    10. Attach the M5Coreink+BoilerBASE to the boiler with its magnetic back on a flat metal surface of the boiler.
    11. Check LEDs on the Thermostat Cable Splitter; if not blinking, switch wires 1 & 2 or 3 & 4 in the pluggable screw connector on the thermostat side.

  3. Plug the power back in

    • Reconnect the boiler and thermostat to power outlets.

Disconnecting

After the measurement period, the user only needs to unplug the RJ45 cable from the Thermostat Cable Splitter, which can remain connected with the thermostat cable in the user's home. The rest can be sent back and re-used in other homes.

Developing

Printed Circuit Board

To change the hardware design of the PCBs, you need:

The KiCad source files of the PCB can be found in subfolders of the folder pcb:

To convert the PCBs into a format suitable for fabrication, consult the webpage of your PCB manufacturer of choice. For example, see the JLCPCB guide on how to export Gerbers and the JLCPCB guide how to export the BOM and POS files. You may also use a KiCad plug-in for this purpose such as kicad-jlcpcb-tools.

Enclosures

To change the hardware design of an enclosure, you need either:

The source files of the enclosures can be found in subfolders of the folder enclosure:

  • BoilerBASE
  • ThermostatCableSplitter (We do not yet have a design for this enclosure)
  • PipeClamp

Features

The NeedForHeat Boiler Monitor features the follwoing main hardware components:

  • Thermostat Cable Splitter PCB with 4-wire pluggable screw terminals and circuit to monitor OpenTherm communication, including LEDs and optocouplers;
  • Circuit in the Thermostat Cable Splitter that allows (mostly) order agnostic connection of the 4 wires per pluggable screw connector (see also connecting the devices);
  • Pipe Clamp PCB to measure temperatures from the supply and return pipes below the boiler.
  • Pipe Clamp enclosures, which can be 3D printed as a clamp that presses the temperature sensors agains a water pipe below a heating boiler and provide a locking mechanism the prevent the PCB from falling out.

To-do:

  • Thermostat Cable Splitter
    • Reconsider the choice of pluggable screw connectors: reversible? lever-operated (e.g., WAGO PCB terminal block)?
    • Redesign the thermostat side such that the user can mount the wires truly in any order.
    • Design an enclosure.
  • BoilerBASE
    • Add an 868 MHz SMD transceiver chip to enable monitoring of wireless thermostats.
    • Add connectors to BOM and CPL files and repair rotation errors to enable through-hole soldering by JLCPC.
    • Evaluate relocating the 2x8 pin header from the bottom side to the top side of the PCB to reduce JLCPCB manufacturing costs.
    • Improve BOM and CPL for JLCPCB through hole assembly.
    • Design an enclosure that adds multiple mounting options
      • room to embed permanent magnets to make it stick to flat metallic surfaces of boilers;
      • a tie wrap hole.
  • Pipe Clamps
    • Redesign 3D printed enclosures to ensure strength and durability.

Status

Project is: in_progress

License

The hardware designs in this repository are available under the CERN-OHL-P v2 license, Copyright 2024 Research group Energy Transition, Windesheim University of Applied Sciences

Citation

If you use this repository in your research or work, please cite the following pre-print, which describes the overall NeedForHeat DataGear system of which this repository is a part:

Ter Hofte, H., & van Ravenzwaaij, N. (2025). NeedForHeat DataGear: An Open Monitoring System to Accelerate the Residential Heating Transition. arXiv preprint arXiv:2509.06927. https://doi.org/10.48550/arXiv.2509.06927

Note: This is a pre-print submitted on 8 Sep 2025 and has not yet been peer-reviewed. For the full paper, see https://arxiv.org/abs/2509.06927.

Credits

This hardware is a collaborative effort of:

Earlier versions of this open hardware were designed by:

  • Huub Buter · @h-buter
  • Mirjam van Wee
  • Kees Fokker

Product owners:

We use and gratefully acknowlegde the efforts of the makers of the following designs:

Footnotes

  1. Only the Thermostat Cable Splitter remains at the home of the user; the rest can be sent back after the measurement period. ↩

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