Zehnder ComfoTube Inline Coupler Set

A set of couplers to make inline connection/repair of Zehnder ComfoTubes.

Normally when connecting lengths of ComfoTube together, you thread one inside the other, wrap it with tape and put a cable tie on it. That works fine, but it requires that you can rotate/twist one of the tubes around 3 times (to thread it in to the other tube). No problem when doing the initial installation (and the tubes are not anchored at both ends yet). However, if you need to repair or replace a section that is already installed in the wall, you do have a problem. You can't twist an installed tube 3 times to couple it. And Zehnder does not make a solution for this... so I designed one.

With this design, you thread one of each printed part into a ComfoTube, and tape it in place. Then you couple the printed pieces together with a small angle twist. To make sure it stays coupled, put another wrap of tape at the connection joint. (I only did 2 threads of rotation between the tube and the printed part. Since the tube is connecting to a rigid part, I think that's plenty and will not pull off.)

THESE ARE PROTOTYPES, and have not been thoroughly tested. I do not know their long term performance. Use at your own risk. I'm looking forward to feedback, so if you try them, let me know what you think. These are printed in PLA with 2 walls and 35% infil. They seem pretty strong. I might suggest ABS instead, for more durability in a real-world application.

Note: When I printed these, I put some supports on the coupling feature. After removing the supports, I had to file the surface just a bit to get the coupling to work. I think that was just leftover material, and the part dimensions are OK. For now, I'm leaving it like that, since it had a nice fit in the end. I only design-in 0.2mm of gap between those mating surfaces, so depending on your printer accuracy, that may not work for you. I included the Fusion files if you want to remix.