Solar Cable Junction Box 2x (4 to 1) with WAGO 221-615 connectors

Motivation

I want to use solar panels of an old solar system (Conergy C175M) in combination with a Microinverter for a balcony power plant.

[A: Panel groups connected in parallel]
As the panels have low power values (compared to current panels) and the microinverter has a limited input voltage that does not allow to set up module strings, I decided to connect the solar panels in parallel connected groups of 3 panels.

[B: MC3 to MC4 adapter]
The old modules have MC3-connectors and current wiring and microinverters use MC4-connectors.
Y-connectors 3-1 are not common on the market today.

[C: Compact and protected solution with clear wiring structure desired]
Connecting 3 solar panels in parallel with regular Y-connectors involves quite some cable management.
A compact junction box for Plus and Minus combined in one housing can reduce the wiring effort.
 

Solution

[A] Junction Box
A Junction box using two WAGO 221-615 elements (5 chambers each) allows to connect up to 5 wires with up to 6mm² cross section.
The PG7 wire gauges limit the wire diameter to 6.5mm but allow a slim and compact design.
The Y-connector variants 2-1, 3-1, 4-1 are possible.
Unused openings of the housing can be closed with the Blind Stuffing provided. 

[B: MC3 to MC4 adapter]
The input wires are crimped with corresponding MC3 connectors, so they can be directly be connected to the solar modules.
The output wires are crimped with MC4-connectors, so the junction box acts as connection box and MC3-MC4-adapter.
As the wires are connected via the WAGO 221-615 blocks, the open ends can be connected only by removing the insulation.

[C: Compact and protected solution with clear wiring structure]
The wires are organised in separate levels, so minimum bending radius is not violated and still a quite compact solution is possible.
The lid can be sealed with a 1mm silicone foam string.
Just insert the silicone foam string into the groove in the lid.
The lid is secured with 4 hexagon socket head screws M3x16.
 

Links
   https://wago-creators.com/de/design/674
 

Printing
Material:   Prusament PETG → also using a flame resistant V0 variant could be considered.
Brim:         none
Support:   not required
Slicing:     0.2mm layer height
                  5 perimeters for solid walls
                  7 massive layers top + bottom for stable housing
→ the PG7-wire-gauges can put quite some stress on the housing, so you should print a stable solution
 

Assembly

[Material list]
   1x   housing bottom (4to1_Y-JunctionBox_body_v00.stl)
   2x WAGO 221-615 connectors
   1x   housing lid (4to1_Y-JunctionBox_lid_v00.stl)
   1x   460mm silicone foam string with 1mm diameter
   4x   M3 x 16 Hexagon Socket Head Screw
   10x PG7 wire gauge (with sealing)
   2x  PG7 BlindStuffing + Nut (PG7_BlindStuffing_threaded_v01.stl + PG7_Nut_v01.stl)
   2x   PG7 Sealing (can be optionally printed with TPU from PG7_TPU-Sealing_v01.stl)
   [individual demand] solar cable red 4mm²/6mm² (max. 6.5mm diameter)
   [individual demand] solar cable black 4mm²/6mm² (max. 6.5mm diameter)
   2-4x   MC3-connector male
   2-4x   MC3-connector female
   1x        MC4-connector male
   1x        MC4-connector female

[Wiring]
a) Prepare the housing parts
    Cut M3 threads into the holes for the M3 fixation screws in the bottom housing
    Assemble the WAGO 221-615 connector blocks in their positions (snap in)
    Open the llevers of the WAGO connectors.
    Push the silicone foam sealing string into the groove of the lid.
b) Prepare the wires. 
    Crimp connector on one end, remove insulation 12-14mm for WAGO
c) Assemble the PG7 wire gauges as needed and close the unused openings with blind stuffings.
d) The junction has a lower and a higher level for wiring (see WAGO connector position)
     Finish the lower level completely before proceeding with the higher level.
     For each wire do: 
     Push open end through PG7, bend, remove insulation, push into WAGO connector and lock.     
     Firmly fix cable with PG7 wire gauges
e) Check the electrical connections
f) Assemble the housing lid.
    Properly align the sealing rib of the bottom part with the sealing groove of the lid.
    Fix the lid wit four M3x16 screws. 


Use
   Use at your own risk.


Feedback
    is very much appreciated.
    This helps me to further improve the design.



Have fun building & using the device.