Electrical – Are WAGO lever splice connectors approved for use with solid aluminum #12 or #10 with WAGO joint compound

Yes, but a few points need to be observed to make sure it complies with BS7671 IET 17th Edition.

Firstly, the terminals must be installed in a Wagobox (when breaking into existing ring wiring). This needs to be UK sourced to ensure you get ones that are stamped with [MF], meaning that it's classed as BS 5733 Maintenance Free box.

To comply with the IET regulations, each Wagobox is limited to 50Amps in total. The compatible terminals, 773(solid) and 222 (lever), are also derated to 20Amps.

Therefore, for a regular 32Amp ring main, you will need to use two Wagoboxes - one at the start and one at the end of the extension. As the load from any socket is shared in both directions of the ring (albeit unevenly), the derated 20Amp terminals are sufficient.

Before:

                         +---------+
     L                   |         |
    +--------------------+  |   |  +-----------+
    |                    | - - - - |           |
    |                    |         |           |
+---+---------+          +---------+           |
|             |                                |
|  Consumer   |                                |
|  Unit       |                                |
|             |                                |
|             |                                |
+---+---------+          +---------+           |
    |                    |         |           |
    +--------------------+  |   |  +-----------+
     L                   | - - - - |
                         |         |
                         +---------+

After:

                         +---------+           +-----------+
     L                   |         |           |           |
    +--------------------+  |   |  +-----------+  Wagobox  +--------+
    |                    | - - - - |           +-----------+        |
    |                    |         |                           +----+----+
+---+---------+          +---------+                           |         |
|             |                                                |  |   |  |
|  Consumer   |                                                | - - - - |
|  Unit       |                                                |         |
|             |                                                +----+----+
|             |                                                     |
+---+---------+          +---------+           +-----------+        |
    |                    |         |           |           |        |
    +--------------------+  |   |  +-----------+  Wagobox  +--------+
     L                   | - - - - |           +-----------+
                         |         |
                         +---------+

The Wagobox capsule junction box for those connectors is IP68 rated - waterproof to 4m. Not sure if it is UL listed or allowed in US codes though.

However, those connectors should be ok in any junction box rated for exterior use..