February 25, 2025
Description
This is a replacement cap / front piece / bracket for a broken eQ-3 Homematic IP Evo (HmIP-eTRV-E) Thermostat. The front cap has broken off on two of my thermostats, which happens quite easily by accidentally bumping into the thermostat, what then breaks the front pegs as seen in the picture. I first tried to call Homematic IP / eQ-3 to get a replacement part, but they insisted that they don't repair / sell replacements and for me the only option is to buy a new thermostat. These thermostats go for around 90-100€ in Germany, meaning for two thermostats becomes expensive quite quick, for a single piece broken and the thermostat otherwise (electronically) working perfectly fine. I then decided to design a 1:1 replacement for the bracket, by fully reverse engineering / 3D modeling the existing / broken piece.
Btw. I first tried reprinting / replacing just the front piece of the part (only the holding pegs), but gluing them on wasn't strong enough and the pegs broke again shortly after. The model is build up from scratch in Fusion 360 and it took me around 2 weeks to design / test fit etc. I successfully repaired both my broken thermostats with the print.
| V1 | Initial release of the Homematic IP Thermostat, good fit / easier to print, but might need some rework to ensure propper / free turning |
| V2 | Updated model, tighter tolerances optimized for ABS printing. This one is harder to print, but essentially should turn freely without further rework required |
Recommendation: Try with V2 first, before using V1!
To print I used eSUN ABS+HS or FormFutura TitanX ABS. V1 I tried priting with PLA+ and PETG, but both turned out to becoming too week, as the part is directly exposed to the heat of the heating pipe. Expecially the PLA+ part became soft and broke. So PETG is the absolute minimum, eSUN ABS+HS has a high melting point, that provided me with the best results.
I used OrcaSlicer with the 0.16mm print height setting and supports on the bottom side of the model. The model must be purposefully oriented horizontally instead of vertically, in order to provide the upmost tensile strength to the front pegs. Printing it vertically / upright results in a nicer surface finish, but the retaining pins will easily break when you try to push in the aluminum ring, or mount the part on your heating system. And as the part is not visible from the outside of the thermostat, the surface finish doesn't matter.
The hole for retaining the servo as well as the through-hole to the front don't need support, as otherwise the print might get unclean and the servo doesn't fit well. Here is a picture of the supports that worked out best in my test / final prints:
0. In preparation the only thing required is the replacement print and a T6 Torx screwdriver:
1. Start by removing the aluminum ring from the broken original piece, if it is not fully disconnected yet. Then lay it on the newly printed piece and while gently prying the pegs inwards pushing it through by force:
2. To start the repair remove the side panels of the thermostat on both sides and the batteries:
3. Remove the four screws at the side of the case, then carefully pull the case straight up. Note that there is a connector at the rear side of the case, which you will feel the resistance when pulling up. However it is important to not twist the case, there is no "notch" or anything holding it so pulling up straight is important:
4. Disconnect the little wire inside, connecting the top and the bottom half. Afterwards you can carefully tilt the inner piece up in the body and remove it from the case:
5. Remove the broken piece which is connected with three additional screws. It can be replaced with your printed piece and the instructions can be followed in reverse, in order to reassemble the thermostat:
Congratulations, you have repaired a 90€ piece of tech. for a couple of cents! ;)
You can print the model for yourself, friends and anyone in small quantities. I don't mind if you charge them for your material and efforts. Please don't try to sell the physical model / provide repairs of the part commercially (Etsy etc.). I have no affiliation with eQ-3 / Homematic IP, or any other associated company. The 3D model was created from scratch, by measuring the original / broken piece, so no original 3D models from Homeatic IP have been used in the process.
Digital files have a strict non-commercial, personal use only license.
You shall not share, sub-license, sell, transfer, or distribute in any way the digital file of this object. You can not host this files on other digital platforms, web stores or cloud repositories.
License:
Creative Commons — Attribution — Noncommercial
8
Kristian
