Operating instructions

Glass Slumping Firing Schedule
Rate Temp.
Segment °F / °C °F / °C Hold
1 250 / 138 750 / 398 00.00
2 900 / 500 1250 / 676 00.30
3 9999 / 9999 1050 / 565 00.00
4 150 / 83 750 / 398 00.00
Stained glass,
1
8
", 2 fused layers, 12" circular pieces,
slumped into a bowl. Set the alarm to 500° F. When the
alarm sounds, close the lid from venting position and insert
peephole plugs.
Setthe alarm again,this time to1150° F.When it sounds,
check the glass through the peephole. When the glass
slumps into the bowl, write down the temperature and hold
time for future firings, and press , then (Skip Seg
-
ment).
This will advance the kiln to segment 3, a flash cooling
segment. Lift the kiln lid slightly or open the door ajar until
the temperature drops to 1050° F. Then close the door/lid.
The kiln will cool slowly through the annealing range. Then
it will turn off and cool to room temperature.
Note: A cooling rate of 9999 (FULL) shuts off the
warning alarm (error message) that sometimes
sounds during rapid cooling. This turns off the alarm
only for that particular ramp. The alarm codes still
work on the hold and the other programmed segments.
For details about error messages, see pages 26 - 28.
Starting a Firing in a Hot Kiln
Sometimes a firing begins in a hot kiln after a power fail-
ure or other interruption. In this case, the Sentry will begin
firing from the first segment that matches the current tem-
perature. See Power Failures, page 28.
When the Kiln Shuts Off Too Soon
Ceramic Firings
If the kiln fires to completion before the pyrometric wit
-
ness cone bends, you can turn the kiln back on and keep fir
-
ing. First, program ahotter temperature. Then from ,
press . The kiln will begin firing, taking up where it
left off.
Note: By looking at the witness cones through a peep
-
hole, you will know if the kiln shuts off too soon.
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.
Wrong Thermocouple Type
If a Type-K thermocouple is installed on your kiln, but
Type-S is selected in Options, the kiln will continually
underfire by a wide margin. (The kiln will overfire if Type-S
is installed and Type-K is selected.) See page 22 to check
the thermocouple type selected in Options.
Chapter 5
Multiple Zone
Kilns
Note: See also Multiple Zone Options, page 25.
An Overview of Multiple-Zone Firing
If you are not sure how many zones your kiln has, look
into the firing chamber. The number of thermocouple tips
indicates the number of
zones.
In single-zone kilns, the
Sentry measures tempera
-
ture from one location.
When the controller turns
on the heat, all the elements
turn on.
With two and three zone
kilns, the Sentry measures
temperature from each indi
-
vidual zone. It then adjusts
the heat separately for each zone to improve temperature
uniformity.
To maintain even temperature, the Sentry calculatesnot
only temperature differencebetween zones, but also length
of time needed to change temperature. By carefully timing
heat output, it maintains even temperature with a minimal
loss in firing speed.
Note: Multiple-zone
kilns use the same
Cone-Fire and Ramp-
Hold programming in
-
structions as single-zone
kilns.
Note: Firing a
Ramp-Hold program at
FULL rate (9999) shuts
off multiple-zone control
for that firing. The kiln
then fires as a single-zone
kiln.
Thermocouple Failure
In a Multiple-Zone Kiln
In amultiple-zone kiln, if a thermocouplefails, thefiring
will continue as a single-zone kiln so long as one thermo
-
couplestill operates. willappear,alternating with the
thermocouple that failed. (See page 26 for multiple-zone
thermocouple error messages.)
Power Output Lights
The three lights on the right of the temperature display
turn on when the controller sends a signal to the relays.
18 Cone-Fire / Ramp-Hold
Look into the
firing chamber.
The number of
thermocouple
tips indicates the
number of zones.
Keep a record of
your stored pro-
grams and all
your firings.
Write down the
results of each
firing. This may
become invalu
-
able later.