and even the color. Vent the lid. Set the alarm to
500°F/260°C. When the alarm sounds, close the lid from the
venting position and insert the peephole plugs.
Set the alarm again, this time to 1350°F/732°C. When it
sounds, check the glass through the peephole or kiln
window. When the glass fuses to your satisfaction, write
down the temperature and hold time for future firings, and
press
9
, then
ENTER
(Skip Segment).
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/565°C. Then close the
door / lid. The kiln will cool slowly through the annealing
range, then turn off.
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 pro-
grammed segments. For details about error mes-
sages, see pages 27 - 29.
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 29.
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 a hotter temperature. Then from
[IDLE]
, press
START
. The kiln will begin firing, taking up
where it left off.
Note:
By looking at the witness cones through a
peephole, 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 21 to check
the thermocouple type selected in Options.
Chapter 5
Multiple Zone Kilns
In this chapter you will learn to . . .
G
Understand multi-zone kilns
G
Know when one of the thermocouples fails
G
Understand which zone is turning on
G
Test the elements
Note:
See also Multiple Zone Options, page 26.
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 the tempera-
ture from one location. In the standard single-zone design,
when the controller turns on the heat, all the elements turn
on at the same time.
With two- and three-zone kilns, the Sentry measures the
temperature from each individual zone. It then adjusts the
heat separately for each zone to improve temperature uni-
formity.
To maintain even temperature, the Sentry calculates not
only the temperature difference between zones, but also
the length of time needed to adjust the temperature of the
zones. 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 instructions as sin-
gle-zone kilns.
Note:
Firing a Ramp-Hold program at FULL rate
(9999) shuts off multiple-zone control for that fir-
ing. The kiln then fires as a single-zone kiln.
Thermocouple Failure
In a Multiple-Zone Kiln
In a multiple-zone kiln, if a thermocouple fails, the firing
will continue as a single-zone kiln so long as one thermo-
couple still operates.
[TC 1] [TC 2]
or
[TC 3]
will appear,
indicating which thermocouple(s) failed. (See page 27 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.
I
Single-Zone Kiln
When the Sentry sends a signal to
the relays, these lights appear:
Kilns with 1 relay: middle light only
Kilns with 2 relays: top and bottom lights
Kilns with 3 relays: all 3 lights
18
Cone-Fire / Ramp-Hold
Do not leave your kiln unattended during operation.
