Can I convert a 3 phase kiln to single phase?

It may be feasible to convert the kiln from 3 phase to a single phase; it depends on the model. You may have to upgrade the wires in your kiln’s switch box to handle the higher amperage of a single phase. In converting your kiln, you might not have to change the heating elements. If your 3-phase system is Delta, which means there is no neutral, you can probably use the same elements. If your system is Y, which means there is a neutral, you will need new elements.