Shelly Housing (1/1PM Gen3)

Disclaimer: Be aware that in many jurisdictions, mains voltage installations must only be executed by qualified or even only certified individuals! This model description as well as the attached pictures are only for demonstration purposes.  For installation instruction and wiring diagrams, consult Shelly's official documentation

Note: Some plug designs (such as the German Schuko plugs) don't have a keying mechanism to ensure the fixed orientation of the live (phase) and neutral conductors. As a result, it cannot be guaranteed whether the Shelly switches the live or the neutral line. This may lead to situations where a connected device appears "off" while still being electrically live.

Note: Pull-test every connection. 

The original design was developed to house a Shelly PM Mini for monitoring refrigerator energy consumption. Later, an adaptation was made for the Shelly 1 (Gen 1) to control printer power. Motivated by the ongoing Get Creative with WAGO contest, I’ve now extended the series with a version for the Shelly 1 (Gen 3).

Additionally Required Hardware

¹ Alternatively, an insulated butt connector can be used.

² I strongly suggest implementing some sort of strain relief. Use either zip ties or the provided strain relief ring. The latter can be fixed to the cable using super glue. You may have to scale the ring according to the cable you're using. The provided file is supposed to go on a 7mm outer diameter cable. The hole in the case is 7 mm as well.

Features

I designed this model to improve on a few areas I found less than ideal in similar designs—such as extra bulk and reliance on too many fasteners. The result focuses on streamlined functionality, a lower parts count, and easier assembly. Key features include a compact clamp-based closure that reduces both footprint and hardware, a simple wall-mounting clamp for straightforward installation, and built-in access for the LED and button. The model was designed with printability in mind, with careful attention to overhangs and bridges to ensure reliable results.

Operability

The design includes a thinned-out section to reveal the Shelly 1’s LED indicator, as well as a compliant lever that enables external actuation of the button.

Mounting Option

Protrusions on the bottom of the lower half engage with a flexible locking clamp. Compared to earlier versions, the clamp has been redesigned for greater stiffness and improved printability. The locking tabs have also been enlarged to provide a more secure hold.

Clamshell design

Compared to similar models, the closing mechanism in this design has been simplified to find a balance between security and minimal hardware. The top half is secured with just two screws and a latch on the opposite side. While some designs use heat-set inserts—which can look impressive on 3D-printed parts—this model uses plain 2.7 mm holes. This provides enough grip for an M3 screw to thread directly, eliminating the need for inserts or pre-processing. For those who prefer inserts, a compatible version is available in the download section.

Minimal Footprint

After several design iterations, the housing has been refined to an optimal, compact size. The width is determined by the space required for two WAGO clamps and the Shelly 1, along with the necessary internal walls. Height and depth have been minimized while ensuring all components fit securely. The raised center section compensates for the height difference between the connectors and the smart relay.

Designed for Printability

All walls are modelled with consistent thickness to minimize print artifacts and weak points. Overhangs—such as those around the counterbored screw holes—are designed to allow the slicer to generate clean, reliable bridging paths.

Print Instructions

The compliant mechanism on the base will work best printed in PETG, but ABS or ASA will be fine as well. I advise against using PLA due to the potential heat generated by the Shelly. PLA may soften, which is undesirable for a case containing mains voltage.

This model ist optimizes to be printed with a 0.4 mm nozzle. Use your favourite slicing profiles with 4 perimeters.

Assembly

Only attempt assembling this if you understand the risks involved with mains voltage!

For a detailed installation guide study Shelly's official documentation. My instructions here only cover the mechanical details. 

Preparation

Given the limited space within the housing, precise wire lengths are crucial for a successful assembly. To simplify the process, I’ve outlined the necessary wire lengths below. Don't forget cutting the lengths listed in the Extras column. If you're using strands from the same cable for these, you definitely want to get these first.

For a reliable connection, I recommend using ferrules on all wire ends. However, be sure to check WAGO’s technical documentation for specific guidance on using ferrules with the 221 connectors.

¹ Leave these long, so that in case of pulling on the cable, PE rips off last. 
² I’m using 8 mm ferrules. To ensure they seat fully on the Shelly side, I trimmed about 3 mm from the tip. The listed measurements include the extra length.

Customization

The Fusion 360 source files for all the parts can be found in the download section. 

Changelog

2025-11-02

This release serves as the baseline version for this remix. The updates below describe improvements made over previous publications:

• Enlarged mounting tabs: The original design featured smaller tabs, but they’ve been increased in size to improve alignment and stability.

• Relocated locking feature: The latch between the two halves has been moved to the outside. In earlier versions, its central position made it easier to unlatch before the screws were installed.

• Raised screw surfaces: The areas around the screw holes have been slightly elevated, making them the primary contact points and reducing the risk of stripping threads.