How can my kiln section stay on all the time on my manual kiln even when the kiln-sitter is off?

Usually this means a relay is stuck on and needs to be replaced.

  1. On 3-phase kilns, and on any kilns that pull more than 48 amps, only the power needed to turn on the relays passes through the kiln-sitter. The power to turn the elements on passes through the relays, but not through the kiln-sitter in these kilns.  This is why the kiln-sitter can be tripped off and you can still have one kiln section staying on.
  2. If a relay is on when there is power coming to the kiln, even when that kiln section's switch or the kiln sitter is off, usually it means that the contacts have welded themselves shut and even when everything else (except the breaker) is off, the relay will not turn it off.
  3. Contacts weld themselves shut for a number of reasons like misalignment, age, corrosion, cycling too fast etc. Really though, it is because they get too hot.
  4. Whenever any contacts open and shut, there is a little spark of electricity right before/ after they shut/ open.  This arc is very, very hot.
  5. If there is a lot of arcing, like in a chattering relay, you can melt the contacts together pretty quickly.