This week I had a rather salutary lesson with my burnout kiln. All
is well but it could have been much worse. My kiln is in a shed that
I share with my partner and her pottery kiln. Her kiln draws 19 amps
from a 240 volt circuit, We have a 40 amp sub main from the main
switchboard to the shed and both kilns are connected to a sub board
in the shed with a 20 amp combined ELCB and overload protector. The
pottery kiln is directly wired into the board while the burnout kiln
was connected through a 15 amp power outlet.
Obviously if we ever tried to run both kilns the circuit breaker
would immediately trip.
Last week Ii did a burnout and when I shut down everything I noticed
that the power plug had overheated and started to melt despite
running within specification for the plug and socket. It seems that
it is an entirely different matter using one of these 15 amp outlets
intermittently to say operate a welder than to run an 8 hour burnout
cycle.
The solution to the problem was obvious. The power point has now
been replaced with a 40 amp switch and both kilns are now directly
wired to the board. All the connections kept nicely cool for the nest
burnout. The lesson is we really need to keep a close eye on our
electrical connections.
What surpises me is that your circuit breakers are detached on a
wooden panel (!?) You’re lucky that this setup didn’t start to burn.
Secondly, what about the wiring between the main frame and the
subframe.
Are they heavy enough to handle all that current? If the circuit
breaker are chosen to heavy, the wiring starts to burn (using full
capacity) before the breaker(s) trip.
I picked up a kiln a few years ago that had been made in a
engineering lab.
I was told that it would accumulate moisture over time and hence was
likely to trip an earth leakage when first run after a break.
too true. It’s hard to find an un-earthed powerpoint these days. It
has done (with in 15 minutes) every time I’ve fired it up.
Stubbornness and stupidity I got it to the point where it had driven
off enough moisture to work without tripping the switch.
That was some time ago. Haven’t used it in some time. Might be
thinking about using it again. Or taking it apart and building it
better. Or landfill. Haven’t decided yet, but I suspect it’s more
trouble than it’s worth…
What surpises me is that your circuit breakers are detached on a
wooden panel (!?) You're lucky that this setup didn't start to
burn. Secondly, what about the wiring between the main frame and
the subframe. Are they heavy enough to handle all that current? If
the circuit breaker are chosen to heavy, the wiring starts to burn
(using full capacity) before the breaker(s) trip.
The modular circuit breakers on the sub board are all contained
within an approved DIN enclosure The line from the main switchboard
is rated at 40 amps and is connected through a 40 amp breaker on the
main board. The kiln wiring from the sub board breakers to the
switches is rated at 20 amps and is connected through 20 amp ELCB
breakers. The power leads to the kilns are also rated at 20 amps. The
only weak link in the system was the plug and socket which seemed
appropriately rated but obviously could not carry its rated current
for sustained periods. Things only overheated at the plug.
Once I removed that weak link everything ran cool (except the kiln)
on the next burnout.
Last week Ii did a burnout and when I shut down everything I
noticed that the power plug had overheated and started to melt
despite running within specification for the plug and socket.
It is a good idea to occasionally check the plug and receptacle of
your electric kiln. While the kiln operates, place your hand on the
power cord to check the temperature. The cord should never feel hot.
Heat is an indication that the plug and/or receptacle should be
replaced.
