Stafford Instruments ST312B Instruction Manual

ST312B User Handbook Page 1
ST312B
User Handbook
ST312B Temperature Programmer
TAFFOR
S
D
Issue: 3.00
Date: 05 Jan 2021
See separate handbook for Installation Instructions
© Copyright 2009 - 2021 Stafford Instruments Ltd.

Page ST312B User Handbook
2
MAIN DISPLAY
MIMIC
DISPLAY
DISPLAY
INDICATORS
CONTROL
KEYS
(5)
At A Glance
DELAYED
START LAMP
t1
SOAK TIME LAMP
SOAK TEMPERATURE LAMP
RAMP 1 LAMP
RAMP 2 LAMP
At A Glance
FIRING LAMP

ST312B User Handbook Page 3
Quick Start Guide
Quick Start Guide
Switch on & wait for kiln temperature display
To run a firing program set up previously press the
START/STOP key
To stop the firing at any time press the START/
STOP key again
To review firing data press the  key to enter the
programming menu
To change firing data press the  &  keys to
change the displayed value
Use the  key again as necessary to index to the
next firing value to be reviewed or changed
To exit the programming menu either wait 10 sec-
onds or press the ◼ key to start firing
If the keyboard is locked then press the  &  keys
together & hold down for 5 seconds to unlock

Page ST312B User Handbook
4
Contents
Contents
At A Glance.................................................. 2
Quick Start Guide......................................... 3
Contents........................................................ 4
Features ........................................................ 4
Turning On ................................................... 5
Programming................................................ 6
Firing ............................................................ 9
Cooling ....................................................... 13
Adjusting While Firing .............................. 14
Error Messages........................................... 16
Other Features ............................................ 18
Sample Programs........................................ 19
• Single program
• 2 controlled heating / cooling ramps + soak
• Soak time up to 99 hours 59 mins
• Ramp rates from 1 to 999°C/hour + full
• Suitable for ceramics and glass use
• Program can be altered while firing
• Program pause/un-pause + segment advance facilities
• Keyboard lockable
• Delayed start facility - up to 99 hours 59 mins
• Power failure recovery
• Energy used display
• Alarm buzzer & alarm output
Features
Features

ST312B User Handbook Page 5
Turning On
.
. .
. .
....
When turned on the ST312B performs a
display test by briefly illuminating all of
the display digits and all of the front panel
lamps.
The version number of the software embedded
within the ST312B is now displayed. If you ever
need technical support you will be asked for this
code together with the ST312B’s serial number.
Next displayed is the thermocouple type to which the ST312B is set. This
thermocouple type setting should match the type of thermocouple fitted to
the kiln and can be R, S, K or N type.
‘R’ type
thermo-
couple
‘S’ type
thermo-
couple
‘K’ type
thermo-
couple
‘N’ type
thermo-
couple

°C
°C/hr
hr.min
. 
°C
°C/hr
hr.min
.
°C
°C/hr
hr.min
The final display should show the
kiln temperature (20°C shown here)
with the ‘°C’ indicator on. All oth-
er lamps should be off.
If the left-hand decimal point is on
then the keyboard is locked. This is
an anti-tamper feature. Press the 
&  keys together & hold down for
5 seconds to unlock.
If any mimic panel lamps are on then
the ST312B is firing. Press the
START/STOP key to stop the firing.
During firing the right-hand decimal
point will light to show when the kiln
is heating.
Turning On

Page ST312B User Handbook
6
Programming
The firing segment
The ST312B firing segment comprises 2 ramps followed by a soak period.
This single segment can be used for simple firing (biscuit firing for exam-
ple).
The ST312B ramps the kiln temperature at ramp rate 1 until the kiln
reaches temperature t1. It then ramps the kiln temperature to the soak
temperature at ramp rate 2. It then soaks (dwells) at the soak temperature
for the soak time. It then allows the kiln to cool naturally.
The ST312B is capable of both positive (heating) ramps and negative
(cooling) ramps - as used in glassmaking for annealing.
Ramp rate 1 & ramp rate 2 are settable in the range 1°C/hour to 999°C/
hour or  (full power) or  (end of program).
t1 & the soak temperature are settable over the range 0 to 1400°C.
The soak time is settable over the range 00.00 (no soak) to 99 hours 59
mins.
Note: during soaking the ST312B display alternates every 5 seconds
between kiln temperature and soak time remaining.
Programming
t1
soak temperature
soak period

ST312B User Handbook Page 7
When the ST312B is not firing there are no lamps lit on the mimic panel,
the run lamp is off and the display shows the kiln temperature with the °C
indicator lit.
Altering the program
. 
°C
°C/hr
hr.min
If the left-hand decimal point is on
then the keyboard is locked. Press
the  &  keys together & hold
down for 5 seconds to unlock.
The controller settings can be reviewed by pressing the  key.
Note: holding down the  or  keys causes rapid change of the displayed
value.
.
°C
°C/hr
hr.min
The first push of the  key displays
the start delay time in the range 00.00
to 99.59 (99 hours 59 mins). This
can be altered with the  &  keys.
The DELAYED START lamp on the
mimic display will flash.

°C
°C/hr
hr.min
 then displays ramp rate 1 in the
range 1 to 999°C/hr or  or .
This can be altered with the  & 
keys. RAMP 1 lamp on the mimic
display will flash.

°C
°C/hr
hr.min
 then displays temperature t1 in the
range 0 to 1400°C. This can be
altered with the  &  keys. The t1
lamp on the mimic display will flash.

°C
°C/hr
hr.min
 then displays ramp rate 2 in the
range 1 to 999°C/hr or  or .
This can be altered with the  & 
keys. The RAMP 2 lamp on the
mimic display will flash.

°C
°C/hr
hr.min
 then displays the soak temperature
in the range 0 to 1400°C. This can be
altered with the  &  keys. The
SOAK TEMPERATURE lamp on the
mimic display will flash.
Programming

Page ST312B User Handbook
8
.
°C
°C/hr
hr.min
The next push of the  key displays the
soak time in the range 00.00 to 99.59 (99
hours 59 mins). This can be altered with
the  &  keys. The SOAK TIME lamp
on the mimic display will flash.
Note: to exit programming without cycling through all of the above steps wait 10
seconds without pressing any keys - the ST312B will revert to the idle display.
Alternatively press the START/STOP key to exit programming and to begin firing
immediately.
Programming
A further push of the  key completes data
entry and no lamps on the mimic display will
flash.

°C
°C/hr
hr.min
Data entry is also completed if  is selected
with the  key for either ramp rate 1 or ramp
rate 2.
Note: the  key can be used to reverse through the programming steps to correct
errors or to exit programming mode.
Note: available ramp rate displays are: ,  …  & . If  is
shown but another segment is required then push the  key to obtain the
required ramp rate (in the range 1°C/hr to 999°C/hr). If full power is required
then push the  key until  is diplayed.

ST312B User Handbook Page 9
Firing
To start a firing press the START/STOP key. The RUN lamp will light.
To stop the firing prematurely press the START/STOP key again.
. 
°C
°C/hr
hr.min
If the left-hand decimal point is on then
the keyboard is locked & the ST312B
will not respond to the START/STOP
key. Press the  &  keys together &
hold down for 5 seconds to unlock.
.
°C
°C/hr
hr.min
If a delayed start has been set then press-
ing the START/STOP key causes a time
delay to start. The time remaining is
shown on the display - this counts down
once per minute. The DELAYED
START lamp on the mimic panel will
light. The centre decimal point will flash
once per second.
.
°C
°C/hr
hr.min
If no delayed start has been set (00.00)
then pressing the START/STOP key
causes firing to commence immediately.
The RAMP 1 lamp on the mimic panel
will light. If kiln heating is required then
the right-hand decimal point on the dis-
play will light while heating power is
being applied to the kiln.
Information: The ST312B operates by calculating the amount of energy
required by the kiln every 30 seconds (installer selectable). If for example 40%
of full energy is required to maintain a particular ramp rate or a particular soak
temperature then the ST312B will apply heating power to the kiln for 12 seconds
every 30 seconds. The right-hand decimal point in the display will light for 12
seconds every 30 seconds. If the kiln has a contactor then a loud click will be
heard both when the decimal point lights up and when it goes out. If full
heating power is required then the decimal point will remain lit. If full cooling
is required then the decimal point will remain off.
Firing
Hint: it is good practice to check that the program is correct by pressing
the  key & checking the program contents before pressing the START/
STOP key to start a firing.

Page ST312B User Handbook
10
Program Record Sheet
Ramp 1
°C/hr
t1
°C
Ramp 2
°C/hr
Soak Temp
°C
Soak Time
hr.min
Please photocopy me!

ST312B User Handbook Page 11
Soak Time Program Description
Please photocopy me!

Page ST312B User Handbook
12
Operating Notes
If the ST312B is programmed to heat the kiln at a faster rate than the kiln
is capable of then the ST312B will turn on full power then wait until the
kiln temperature has risen to the correct temperature before proceeding to
the next ramp or soak segment.
Likewise if the ST312B is programmed to cool the kiln at a faster rate
than the kiln is capable of then the ST312B will apply zero power then
wait until the kiln has cooled to the correct temperature before proceeding
to the next ramp or soak segment.
Kiln too slow
Heating & Cooling Ramps
The ST312B is capable of controlled ramps for both heating and cooling.
If the soak temperature is set lower than t1 for example then ramp 2 will
automatically become a negative (cooling) ramp.
STOP key operation
If the START/STOP key is pressed during a firing then the firing will be
halted (not paused). Pressing the START/STOP key again will cause the
ST312 to restart the firing from the beginning. The ST312B will look at
the current kiln temperature and if this is greater than temperature t1 then
the ST312B will automatically cool from current temperature to t1 at ramp
rate 1. This may not be what is desired so the STOP key should only be
used to halt the firing in an emergency.
The program can be paused or program data can be changed while the
controller is firing (see page 14). This is a better option than using the
STOP key. The segment advance feature (see page 14) is however availa-
ble to recover quickly from STOP key operation if required.
Memory
All programs & necessary data are remembered when the ST312B is
turned off. In the event of power failure during firing the ST312B will
automatically resume firing when power is returned (this feature can be
disabled: see installation handbook).
Firing
Delayed Start
The delayed start time period is remembered while the ST312B is turned off.

ST312B User Handbook Page 13
Cooling
Upon completion of firing the ST312B lights all lamps on the mimic
display and the kiln is allowed to cool naturally.

°C
°C/hr
hr.min 
°C
°C/hr
hr.min

°C
°C/hr
hr.min 
°C
°C/hr
hr.min
While the kiln temperature is above 40°C the display alternates every 5
seconds between the kiln temperature and 
When the kiln has cooled to less than 40°C the display alternates every 5
seconds between the kiln temperature and 
To return the ST312B back to idle condition ready for the next firing press
the START/STOP key (or turn off the power to the instrument).
Cooling

Page ST312B User Handbook
14
Adjusting While Firing
Firing values can be adjusted while the ST312B is firing. Also there are
program pause/un-pause and segment advance features that are particular-
ly useful for glass work.
Adjusting Firing Values
While firing operate the  key to select the required parameter as shown by
a flashing lamp on the mimic display. The firing value is shown on the main
display and can now be adjusted with the  &  keys in the usual way.
Firing will still carry on as normal while these changes are being made. The
ST312B will return to its normal running display 10 seconds after key
presses cease (or immediately after  is displayed).
Changes made to the program in this way are stored and are used for
subsequent firings.
Segment Advance Facility
While firing press and hold down the  key for about 4 seconds. The
ST312B will sound a short beep and the executing program will immedi-
ately advance one step as indicated by lamps on the mimic panel. The
effect of this is as follows:-
If a start delay is currently executing then the ST312B will terminate this
and start firing immediately.
If ramp 1 segment is currently executing then the ST312B will switch to
ramp 2 using ramp rate 2 from the current kiln temperature.
If ramp 2 segment is currently executing then the ST312B will switch to
soak at the current kiln temperature.
If currently soaking then the ST312B will end the firing.
Changes made to the operation of the ST312B in this way are temporary
and are not stored.
Adjusting While Firing

ST312B User Handbook Page 15
Program Pause Facility
While firing press and hold down the  key for about 4 seconds. The
ST312B will pause the executing program. To un-pause the program
press and hold down the  key again for about 4 seconds. The effects of
pausing are as follows:-
If paused during a ramp the kiln temperature will be held (soaked) indefi-
nitely at the current kiln temperature. The ramp will continue when un-
pause is selected.
If paused during a soak then the soak time will be extended indefinitely.
The remainder of the soak period will be resumed when un-pause is se-
lected.
Segment advance ( key held down for about 4 seconds) can also be used
to terminate the pause. This will advance the segment and will immedi-
ately terminate a paused soak and end the firing program.
Changes made to the operation of the ST312B in this way are temporary
and are not stored.


°C
°C/hr
hr.min
As a warning during pause a double
beep is sounded every 10 seconds,
the display scrolls  for 5
seconds then shows the kiln temper-
ature for 5 seconds.
Adjusting While Firing
WARNING - PROGRAM PAUSE
The program pause facility should be used with care. Program execution is
suspended and the kiln will be held at its current temperature indefinitely.
If left too long at high temperatures kiln damage could result.

Page ST312B User Handbook
16
Error Messages
Error Messages
Error 1. The kiln temperature is not
increasing as required. The kiln has been
on full power for 1 hour but the kiln
temperature has not risen by at least 8°C.
Error 2. Thermocouple or thermocouple
wiring open circuit. Get thermocouple
and wiring checked. Have thermocouple
replaced if necessary.
Error 3. Thermocouple reversed (kiln
temperature apparently less than -40°C).
This is an installation fault. Get wiring
checked.
Error 4. Kiln temperature too high. The
kiln has been on zero power for 30
minutes but the kiln temperature has not
fallen by at least 1°C

°C
°C/hr
hr.min

°C
°C/hr
hr.min

°C
°C/hr
hr.min

°C
°C/hr
hr.min
Possible causes are: kiln door or lid not closed properly, heater element failure,
elements too old, power phase failure, contactor failure or thermocouple short-
circuit.
Error 5. Kiln temperature overshoot. The
kiln temperature exceeds the desired
temperature by at least 10°C / 20°C
(installer selectable).

°C
°C/hr
hr.min
Error 6. Maximum firing time exceeded.
The length of the current firing has
exceeded an installer selectable (10 - 999
hours) limit.

°C
°C/hr
hr.min
Possible causes are: contactor failure or thermocouple connection intermittent
or high resistance.

ST312B User Handbook Page 17
These error messages cause the ST312B to terminate the firing with all the
keys locked. An alarm buzzer sounds once per second.
SWITCH KILN OFF!
To reset the ST312B turn off the power to the instrument and have the
fault investigated by your installer or kiln service engineer to rectify the
fault.
Technical note: any error message will cause the auxiliary alarm relay
(if fitted) to open - see installation handbook for details.
Note: these error messages are provided to detect kiln faults and so offer
some protection to the kiln. For increased protection the use of a heat fuse
or other independent over-temperature trip is recommended - such as the
Stafford Instruments ST131.
Error 7. Maximum room temperature
exceeded. The internal temperature of the
ST312B has exceeded an installer
selectable (30 - 70°C) limit.

°C
°C/hr
hr.min
Possible causes are: room vent fan failure, ventilation grills blocked, kiln room
too small, damper or bung left open

Page ST312B User Handbook
18
Other Features
Energy Used Display
Pressing the  button at any time shows the amount of electrical energy used
in kW hours. If pressed during a firing it shows the energy used so far. After
a firing it shows the total energy used for that firing. This information is
stored while power is off and is only reset to zero when a new firing is start-
ed.
If the value displayed is always . then the kiln power rating has not been
configured into the ST312B - see installation handbook.
Keyboard Lock Facility
.
°C
°C/hr
hr.min
The keys on the ST312B can be locked so that pressing them has no effect.
This is an anti-tamper feature used to ensure that the operation of the
ST312B or the program data cannot be altered by un-authorised people.
The ST312B can be locked when it is idle (not firing) or while it is firing. It
cannot be locked while it is being programmed.
If the left-hand decimal point in the dis-
play is lit then the ST312B is locked.
Press and hold in both the  &  keys
for 5 seconds to unlock the ST312B.

°C
°C/hr
hr.min
If the left-hand decimal point in the display
is not lit then the ST312B is not locked.
Press and hold in both the  &  keys for
5 seconds to lock the ST312B.
Power Failure Recovery
If power fails during firing then the ST312B recovers as follows:-
For power failure during start delay the ST312B applies the remaining start
delay when power returns. For power failure during ramp 1 or ramp 2 the
ST312B goes back into the ramp it was previously executing. For power
failure during soaking the ST312B ramps back up to soak temperature at
ramp rate 2 then applies the remaining soak period. This recovery scheme
can be disabled if required (see installation handbook) - the ST312B will
then lock up with  displayed and kiln off in the event of power failure.
Other Features

ST312B User Handbook Page 19
Sample Programs
Name Ramp 1 t1 Soak timeRamp 2 Soak temp
Low Biscuit 70°C/hr 600°C 00:15FULL 960°C
Normal Biscuit 70°C/hr 600°C 00:15FULL 1000°C
High Biscuit 70°C/hr 600°C 00:15FULL 1160°C
Earthenware Low
Temperature Glaze
90°C/hr 600°C 00:30FULL 960°C
Earthenware Mid
Temperature Glaze
90°C/hr 600°C 00:30FULL 1040°C
Earthenware High
Temperature Glaze
90°C/hr 600°C 00:30FULL 1140°C
Stoneware Glaze 90°C/hr 600°C 00:30FULL 1250°C
On Glaze Enamel 90°C/hr 600°C 00:30FULL 780°C
Heavy Sculpture 50°C/hr 300°C 00:3070°C/hr 1000°C
Lustre 90°C/hr 600°C 00:00FULL 750°C
Sample Programs
Notes
Earthenware High Temperature Glaze is also suitable for Stoneware Low
Temperature Glaze.
Stoneware Glaze is also suitable for Porcelain.
On Glaze Enamel is also suitable for some enamelling work.
Heavy Sculpture is also suitable for Terracotta.

Page ST312B User Handbook
20
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