We are running the 1.2.1 verision of the mod and it seem like we cannot change the temprature, when you over over the electric boiler, it doesnt show the option to change the temprature and pressing num+ doesnt do anything.

On my end, v1.2.1 switches modes fine – either with numpad + or upgrade planner. Two issues though: no downgrade from 165→100 for the boiler, and no downgrade from 500→350 for the heating tower. Also, switching the tower with num+ can break heat‑pipe connections occasionally; you'll have to rebuild the pipes. No fix found yet, sorry.
Maybe you're using it incorrectly – you don't need to open the building's GUI. Just hover your mouse cursor over the building and press num+ to cycle through the modes :)