I
The safety lid switch is
broken, or a wire con-
nected to the safety switch
has come loose.
OTL / Over
Temperature Limit
The kiln has shut off be-
cause the temperature is hot-
ter than the one that was set in
the
[LIM]
option. See page 25.
PF1 / Power Failure
The power failed during a
controlled cooling segment.
The kiln temperature was be-
low the last active cooling segment temperature when the
power came back on. The kiln will not resume firing. See
“Power Failures,” next column.
PF 2 / Power Failure
The power failed, and the kiln temperature was below
212°F / 100°C when the power came back on. The kiln will
not resume firing. See “Power Failures,” next column.
PF 3 / Power Failure
The power failed, and the temperature dropped 72°F /
40°C while the power was off. The kiln will not resume fir-
ing. See “Power Failures,” next column.
Check for a loose wire between the transformer and the
controller.
TC 2 / Thermocouple Failure
The thermocouple of a single-zone kiln or the middle
thermocouple for a multi-zone kiln failed while the control-
ler was at
[IDLE]
.
TCDE / Uneven Multiple-Zone
Temperatures
The zones of a multiple-zone kiln are firing unevenly.
Causes:
I
A burned out relay or element.
I
The thermocouples and elements are improperly wired.
A thermocouple is turning on the elements to the wrong
zone. For instance, if the top thermocouple turns on the
bottom elements, the kiln will fire way out of balance.
When zones are out of balance by 180°F / 100°C,
[TCDE]
will appear in the display.
Visually compare the wiring of the thermocouples, re-
lays and elements in your kiln to the kiln’s wiring diagram.
Also, use the Element Test option shown on page 26.
TCR / Thermocouple Leads Reversed
Check that the thermocouple lead wires are connected
to the correct terminals.
Power Failures
The Sentry handles a power failure in two ways:
1
After a brief power failure, the controller continues
firing as before. It shows a normal temperature dis-
play alternating with
[PF]
.
2
After an extended power failure,
[PF 1] [PF 2]
] or
[PF3]
will appear. The kiln will NOT resume firing.
The kiln will remain turned off after a power failure if
the temperature is below 212°F / 100°C when the power co-
mes back on or if the temperature drops 72°F / 40°C or
more while the power is off.
When the Sentry aborts a firing after a power failure, the
display will show the following:
I
[PF 1] [PF 2]
or
[PF 3]
I
Total firing time before power failed
I
Temperature at the time of power failure
I
Current kiln temperature
To resume firing, select the program again and press
ENTER
. The kiln will begin firing again from its present
temperature. For example, the kiln reached 1000°F / 538°C
when the power failed. The temperature is 800°F / 426°C
when you turn the kiln back on. Firing will resume from
800°F / 426°C. You need not cool the kiln to room tempera-
ture before starting a ceramic firing over unless you decide
to use new witness cones.
When you resume firing by pressing
ENTER
, the con-
troller will begin firing in the first segment that has a higher
target temperature than the current kiln temperature.
However, if the power failed during a ramping down (cool-
ing) segment, the controller will resume firing from the
same cooling segment.
Using Ceramic Witness (Shelf) Cones
After an Extended Power Failure
I
The firing was interrupted more than 100°F/56°C
from the cone temperature:
Fire the ware again. It
is okay to use the same partially fired witness cones,
even if they cooled back down to room temperature. So
long as the cones did not heat to within 100°F/56°C of
maturity, they can be used again.
I
The firing was interrupted less than 100°F/56°C
from the cone temperature:
Fire the ware again. If
the kiln shuts off within 100°F / 55°C of maturity, and the
temperature drops 50°F / 28°C or more after the kiln
shuts off, do not depend on the witness cones. Once they
cool 50°F / 28°C after they have been heated to within
100°F / 55°C of maturity, they will not bend properly.
This is because they form a hard shell.
Keep the kiln lid or door closed when the kiln is not in use.
29
The lid switch two-pin terminal is
on the back of the circuit board in
the upper right corner.
