My Sierra burnout kiln died last year. The heating elements in the
walls died on two sides.
Apparently this was a common problem with this kiln. I tried to get
it repaired.
The company that made the Sierra sold the design to another company
that changed the design.
They won’t fix the old models. The elements are cast into the kiln
brick walls, so you have to change the whole interior muffle.
I found another company that said they could build a new muffle for
this kiln. I ended up getting a 220 line installed in my shop to run a
220v kiln instead. If you’re interested in pursuing repairs, I can
try to find the I gathered up while trying to get my old
Sierra fixed. In the meantime, I have this used not-quite-working
Sierra that I’d love to get out of my basement. available for parts,
cheap. 
Kathy Johnson