Instruction manual

9
Hold
Hold is the length of time that you want the kiln to re
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main at the target temperature. Hold is also called soak or
dwell time. Hold maintains a steady temperature for the
length of time you specify. You can use Hold in both heat
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ing-up and cooling-down segments.
When Hold is set to 99.59 hours, the controller will re
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main at that temperature indefinitely, until you press
. To enter a 99.59 hour Hold, press the
once from 00.00 during programming.
Note: During firing, the display shows Hold tempera
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ture and time left in Hold.
Should a hold time be programmed as
total number of minutes, or hours and minutes?
Program a hold as hours and minutes
rather than the total number of minutes. (i.e., 90
minutes is programmed as 1:30.)
What is the maximum number of times
per minute that the Sentry Xpress controller can
turn on the relay during a hold?
The maximum number of relay cycles is 6
times a minute.
Temperature Over-Shoot
When a kiln is heated too fast, it may over-shoot the tar-
get temperature, especially in small kilns at lower tempera-
tures. To avoid this, add an extra segment in a Ramp-Hold
program to slow the firing. The segment with the slower
rate should begin approximately 40° - 60° below the target
temperature.
Programming a
Cooling Segment
For controlled cooling, program a segment to a lower
target temperature than that of the preceding segment.
Example: You fire at a rate of 500°F per hour to 1450°F
with your first segment. You want the kiln to cool at a rate
of 100°F per hour down to 700°F. Here is how you would
program the two segments:
Rate Temp.
Segment °F/°C °F/°C Hold
1 500 / 277 1450 / 788 00.00
2 100 / 55 700 / 371 00.00
The first segment is the heating segment. The second
one is the cooling segment. The controller does not use mi
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nus numbers for cooling. Just enter a lower target tempera
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ture than that of the previous segment.
If you prop the lid or door for a fast cooling, program a
fast cooling rate for that segment. If you lower the tempera
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ture quickly by propping the lid but program a slow cooling
rate, the controller will just raise the temperature again.
Example: Some glass artists flash-cool the glass just after
it fuses. They open the door a few inches to remove heat,
then close it again. This takes the glass down rapidly
through the devitrification range. To program a flash-cool,
use maximum rate. This shuts off the heating elements dur
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ing that segment, allowing the kiln to cool rapidly.
Note: During fast cooling, do not open the door all the
way. Do not force-cool the kiln with a fan.
A Ramp-Hold
Practice Program
To practice using the controller, we will enter a program
that includes three segments. The last segment is a cooling
segment.
Using the programming instructions on page 8, enter
this firing schedule. Then use Program Review (page 4) to
check for accuracy.
PrO1
rA1 = 250
°F1=750
HLd 1 = 00.00
rA2 = 900
°F 2 = 1425
HLd 2 = 00.30
rA3 = 150
°F3=750
HLd 3 = 00.00
rA4 = 0000 (zeroes cancel segments 4-8)
If you stop/abort a firing to change a
temperature and then resume firing, do you need to
skip segmentsto getbackto where you werebefore?
When you press Stop during a firing, re
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program the controller, and then press Start, the
controller will go to the first segment that matches
the temperature inside the kiln. For instance, if seg
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ment 3 starts at 1200 and ends at 1700, and the kiln
temperature is 1600 when you press Start, the con
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troller will go directly to segment 3.
Make a simple chart like the one above when planning a firing program.