Insulated Wall Electrical Box (KOPOS compatible)

Special electrical installation boxes and mounting plates designed for insulated building facades. They allow you to mount sockets, switches, cameras, lights, and motion sensors onto or into insulated exterior walls.

The system is inspired by, and compatible with, the KOPOS KEZ system from the Czech manufacturer KOPOS KOLÍN a.s.

Installation is similar to the method shown in this video: https://www.youtube.com/watch?v=IvAsyg0Cbl0.
 

The only difference is that the KEZ-2 double box and the MDZ mounting plate are installed into a milled recess in the polystyrene insulation. Both KEZ-2 and MDZ are screwed onto the tube, but before tightening the screws, you need to apply cement adhesive onto the polystyrene and press the KEZ-2 or MDZ into it using the exposed infill.
After that, the exposed infill is covered with mesh fabric and adhesive.

Print using a flame-retardant material — either Bambulab PC FR (note: a heated chamber is required; on a P1S the edges tend to warp even with 3D Lac or Dimafix, but this does not matter because the warped area will be hidden under the façade finish), or PETG FRjet by Filament PM: https://www.filament-pm.cz/petg-frjet-samozhasivy-bila-1-75-mm-0-5-kg/p166.
 

Auxiliary tools can be printed from regular PETG, but keep in mind that standard PETG is not fire-resistant — it burns and drips flaming droplets.

Warning:
The milling cutters for creating the KEZ-2 recess in polystyrene have not been tested yet. I designed them as accurately as possible and created a three-stage milling system for the cleanest results. However, it may be sufficient to use only Cutter #1 and then break or trim the remaining polystyrene with a knife.

Before installing the KEZ-2, apply a small amount of low-expansion PU foam around the recess and cement adhesive under the flange with exposed infill.

The MDZ mounting plate is designed with 20% honeycomb infill, which is ideal for 3.5–4.0 mm screws. A small test cylinder for checking infill density with other screw sizes is included.
 

The KEZ base tube has a height of 150 mm and 200mm. It can be shortened by cutting, but a better method is to use a negative part in Bambu Studio and print only the required height. Height markers are printed on the tube in 10 mm increments.

edit: 2026-04-03 added tube 200mm