What to do when you see "FAIL"?

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  • Although we write this for our own kilns many of these articles apply to other makes - although L&L takes no responsibility for that.
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  • Actions are specific actions for you to take during the troubleshooting or repair process.
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What to do when you see "FAIL"?

BASICS

  1. FAIL usually just means a thermocouple is broken. It will read FAIL, TC3 or TC2 or TC1- telling you which thermocouple is out.
  2. When you inspect the thermocouples often, you can see that they can look old, corroded and even cracked at the tip.
  3. If all thermocouples are the same age, or close to it, replace them all.  The kiln will fire best when all the thermocouples are the same age and style.
  4. FAIL actually means that one of the thermocouple circuits is open- or not connected somewhere.
  5. A complete thermocouple circuit is the DynaTrol or other control, the thermocouple wires, and the thermocouple itself.
  6. The thermocouple could be fine and just the wires got pinched in the control box cover. Or the connection between the thermocouple wire and it's wire terminal could be loose. Or it could just be the thermocouple itself, just worn out from old age.  Though it is rare, the electronic controller could also be the problem.

THERMOCOUPLE BURNOUT PROTECTION

What happens when a thermocouple fails?

  1. The kiln will shut down automatically if all thermocouples burn out.
  2. The kiln continues to fire if only one or two thermocouples burn out.
  3. This protects your firing in the event of failed thermocouples. Of course, if all three thermocouples fail then the control stops firing.

TESTING

  1. To test if there is a bad thermocouple or thermocouple extension wire circuit, remove the offending thermocouple connection wires from the terminal on the thermocouple and bind the two colored wires (for Type K thermocouples they are red and yellow) together with electrical tape. The control should read room temperature for that thermocouple (typically 130°F because of the thermocouple offsets).
  2. If it does read room temperature, then the thermocouple is probably bad and needs to be replaced. If the control does not read room temperature, then there is either a bad thermocouple extension wire or the control is bad.
  3. If that test does NOT read room temperature then redo the test by putting a small jumper like a paperclip across the thermocouple terminals directly on the DynaTrol board. If the control now reads room temperature then you have a bad thermocouple extension wire or break in the thermocouple extension wire circuit. If it does not read room temperature then the DynaTrol board needs to be replaced.

CONTROL DISPLAYS CPLt

  1. Sometimes the code CPLt will be displayed.
  2. This code is always displayed after a successful firing to mean “complete”. If it appears after you attempt to restart the kiln after a FAIL message, or at any other time except for the end of the firing to mean “complete”, then it will have a different meaning.
  3. If CPLt appears randomly it means either your thermocouple wires are burning against the kiln case or your thermocouples are so close to failing that they are giving a reading that is so high that the DynaTrol thinks the firing is over.

WHY WOULD YOU GET A FAIL MESSAGE WITH NEW THERMOCOUPLES?

  1. FAIL with new thermocouples almost always means a poor connection somewhere in the thermocouple circuit.
  2. Usually it is one of the two center screws on the thermocouple connection block (terminal). If you can get half a turn on these two screws you will probably fix the problem.
  3. Be careful to not tighten the two outer screws as much as you tighten the two inner screws. The outer screws tighten down onto very thin thermocouple wires which can be crushed and will break if tightened too much. The inner screws tighten down onto much thicker wires of the thermocouple itself.
  4. Sometimes a thermocouple wire will be loose in the wire terminal. Look for this by wiggling the thermocouple wire while looking at the back end of the wire terminal.
  5. Sometimes there is a broken thermocouple wire somewhere in the length of wire between the thermocouple and the control. Jupiter and DaVinci kilns have long hanging thermocouple wires. Sometimes these can come up against the kiln and overheat.  Look for any sign of overheating on the thermocouple extension wires. If you find tape on the wires the thermocouple extension wires must be replaced. Thermocouple extension wire is inexpensive - if there are any doubts replace it.

NOTES

  1. You should not mix exposed thermocouples with sheathed thermocouples because their response rates are slightly different.
  2. It is a good idea to keep a spare set of thermocouples on hand.
  3. You can replace just the thermocouple element instead of the whole thermocouple if you want to save money.
  4. A failing thermocouple or thermocouple circuit can also lead to a condition the control display reads 2400 or CPLt when the control starts up.
  5. See this for how to check the thermocouple tip.
  6. See this for information on thermocouple offset.
  7. See this for information on how to know what thermocouples to get for your kiln.

Additional Actions to Take

Adjusting and Calibrating the DynaTrol for More Accurate Firing

WHY DOES A KILN NEED TO BE CALIBRATED OR ADJUSTED?

  1. Most people will be satisfied with the operation of their kiln right out of the box. 
  2. However for the most precise or accurate work a kiln needs to be calibrated or adjusted to match the type of load, the temperature that you typically fire to, the unique characteristics of the kiln such as size and insulation thickness, and the thermocouples. 
  3. It is important to remember that thermocouples do not measure heat-work (which is all that matters in ceramics). You must calibrate your kiln control to match the performance of a cone to get the most accurate representation of the process.
  4. The thermocouples, for instance, can read +/- 10°F from actual temperature even when when they are brand new. This is function of the variation in materials in the thermocouple. Even though L&L uses "Special Limit of Error" wire, there are still all kinds of variation in the thermocouples, the thermocouple circuit and the cold compensation on the control. (See this on Wikipedia for more information on thermocouples).
  5. On top of that there are variations in the accuracy of the control.
  6. Another factor is that the thermocouple protection tube introduces an offset from actual temperature of about 18°F. Although L&L programs this 18°F temperature offset into the control there are variations in the materials and thickness of the protection tubes that can affect the accuracy.
  7. The good news is that the kiln will be relatively stable once you have calibrated the kiln. 
  8. However, thermocouples will drift over time and kilns will change somewhat so you should at least use witness cones to check on your calibration occasionally if not every firing.

FIRING A KILN WITH WITNESS CONES

Click here is the video above about using witness cones does not display.

SOMETIMES AN EMPTY KILN WILL NOT GET TO TEMPERATURE

  1. Sometimes a new kiln does not get to temperature during the test firing. This is generally because of an empty kiln. It is generally a good idea to fire with your kiln furniture to put some mass in the kiln even during the test firing.

DIFFERENCES IN AN EMPTY KILN VS. FULL KILN

  1. One difference between an empty and full kiln is that an empty kiln cools a lot quicker which will freeze the cone very quickly. In a full kiln there is a lot of mass in the kiln that is just as hot as the kiln around it. It is this mass (the load in the kiln), which is radiating it’s heat as well, that will continue to melt the cone for a little longer after the kiln has been shut down.
  2. Once the kiln is fine-tuned, it is the variable of how you have loaded the kiln that will account for many of the variations you will see from firing to firing. 
  3. Loading will affect the speed of firing - an empty kiln will fire differently than a full one. Although the control does compensate for this that compensation is not totally perfect.

ADJUSTING / CALIBRATING  THE KILN WITH THE THERMOCOUPLE OFFSET

  1. The kiln cannot be calibrated until it has reached temperature and affected a witness cone. The reaction of the witness cone to the firing is how you begin the calibration process. (Kilns are not fired before they ship).
  2. You can fine-tune how the kiln reads temperature by adjusting the Thermocouple Offset.
  3. Fire the kiln with witness cones. Use the most typical or critical cone you fire to. Typically the most important cone you will fire to is your glaze temperature. Generally, bisque temperatures are less critical. 
  4. Thermocouple offset will change the reading of the thermocouples the same amount from room temperature to the maximum temperature of the kiln. (Cone Offset, which will be covered later on, will adjust how the kiln reacts to a particular cone/temperature).

WHAT IS THERMOCOUPLE OFFSET?

  1. Adding thermocouple offset lowers the temperature in the kiln (relative to the temperature reading on the control. For instance lets say the control reads 2000°F and you add 10°F of thermocouple offset. Now the control thinks there is 10°F more in the kiln and, for a setpoint of 2000°F, it will actually control to 1990°F in the kiln. 
  2. Subtracting thermocouple offset raises the temperature in the kiln. For instance lets say the control reads 2000°F and you subtract 10°F of thermocouple offset. Now the control thinks there is 10°F less in the kiln and, for a setpoint of 2000°F, it will actually control to 2010°F in the kiln. 
  3. Thermocouple Offset affects both Easy-Fire programs and Vary-Fire programs (Cone Offset, on the other hand, only affects Easy-Fire programs).

EXAMPLE AND PROCESS

  1. If the witness cone bent slightly during the first firing, but no more than a little bit, then start by reducing the thermocouple offset setting by 5°F to make the kiln fire slightly hotter.
  2. If the witness cone did not bend at all, then you can start by reducing the thermocouple offset setting by 10°F to make the kiln fire hotter.
  3. If the witness cone bent a little too much, you might wait and see how it does with a full load, or you could start by increasing the thermocouple offset by 5°F to make the kiln fire a little cooler.
  4. If the witness cone bent more than a little bit start by reducing the thermocouple offset settings 10°F which will make the kiln fire cooler.
  5. If the witness cone collapsed start by reducing the thermocouple offset settings 15°F.
  6. There are beginning suggestions - feel free to experiment outside of this.

HOW TO CHANGE THERMOCOUPLE OFFSET IN A DYNATROL: STEP BY STEP

  1. Turn kiln on with toggle switch. Wait 5 seconds.
  2. Press 1, wait 5 seconds. The kiln display will say STOP and then go into IdLE mode.
  3. Press OTHER about eight times until you see TCOS
  4. Press ENTER. See TC 1
  5. Press ENTER again
  6. It will flash between °FOS (which stands for Deg F Offset) and 0018 (The 0018 stands for a thermocouple offset of 18°F - which comes preprogrammed into the control to compensate for the ceramic protection tubes. By changing the offset to 0010 we are REDUCING the offset by 8°F- making it fire 8 deg hotter). (NOTE: On older kilns with a slightly different composition thermocouple protection tube the preprogrammed value is 0050).
  7. Press 0008 to reduce thermocouple offset by 10°F.
  8. Press 0013 to reduce thermocouple offset by 5°F.
  9. Press ENTER to accept your input.
  10. Do the same for all your thermocouples. The prompts will scroll past in the order of TC1, TC2 and TC3.

ADJUSTING FOR TEMPERATURE VARIATION TOP TO BOTTOM IN THE KILN

  1. Note that you can use different Thermocouple Offsets for the three (or two) different thermocouples. This allows you to make the top or bottom hotter or cooler to even out the temperatures in a kiln.

CONE OFFSETS

  1. Tune your kiln using the Thermocouple Offset for your most critical firing (typically glaze firings). Typically bisque firings are not very critical. 
  2. CNOS (Cone Offset) - is used to fine tune what the Dynatrol thinks the final cone temperature should be in EASY-FIRE programs. The final cone temperature can be raised or lowered a maximum of 99°F (or 55°C). When entering the offset temperature the following code is used: the left two digits designate whether to raise (00) or lower (90) the cone temperature, that is, “00” means plus (+) and “90” means minus (-). The right two digits are the number of degrees the cone temperature will be raised or lowered. This offset will remain programmed only for the specific cone number until you reprogram the cone offset differently

Examples:

Number

Meaning

0020

Raise the final cone temperature by 20°F

0040

Raise the final cone temperature by 40°F

0015

Raise the final cone temperature by 15°F

9030

Lower the final cone temperature by 30°F

9005

Lower the final cone temperature by 5°F

9045

Lower the final cone temperature by 45°F

NOTE: This option does not affect the VARY-FIRE (Ramp-Hold) mode but it will show up on the menu.

NOTE ABOUT PREPROGRAMMED CONE OFFSETS: The Cone Offsets come preprogramed. From cone 022 to cone 017 the cone offsets
are set at 9020. All other cones are preset at 0000. (Note on Blue DynaTrols made before Oct 1 2004 the cone offset was 9030 for cones 022 to 017 and 9020 for other cones. The offsets were changed when we switched to a more responsive thermocouple protection tube). You can always change this. The RESET option in Other menu will NOT reset these settings. This is part of the compensation necessary for the mullite thermocouple protection tubes.

Cone Offset Example: Adjust cone 07 to shut off the kiln at 20°F below Orton’s prescribed cone temperature.

Press

Display

Comment

OTHER
OTHER

CNOS

If CNOS does not show on the display, press the Other key until CNOS displays.

ENTER

Alternately flashing:
CONE & #

Cone Offset has been selected; the word CONE and the last entered cone number will alternately flash on the display. Now enter the cone
number which you want to adjust (in this example cone 07)

07

Alternately flashing:
CONE & 07

The word CONE and the entered cone number (07) will alternately flash on the display. If you type a wrong number, press 0 three times, press ENTER, then type the correct number.

ENTER

Alternately flashing:
°F0S & 0

°F0S and the previous offset setting alternately flash. Enter the new offset temperature using the rules above, in this example, 9020

9020

9020

The selected offset temperature is displayed. If you type a wrong number, press 0 four times, then type the correct number.

ENTER

IdLE flashes then the current temperature

IdLE appears indicating the offset temperature adjustment has been accepted. The current temperature then flashes in the display.

TROUBLESHOOTING WITH CONES

See our various instruction sheets about cones, specifically troubleshoot-cones.pdf.

Check Polarity of Thermocouples and Lead Wires

Standard Practice at L&L

The following is the standard practice describing thermocouple polarity for Type K and Type S thermocouples that is used on L&L kilns.

Testing polarity of a Type K thermocouple

You can easily test the polarity of a Type K thermocouples. The negative wire is MORE magnetic than the positive wire. Just put a magnet up to each wire. One will be more magnetic than the other. (This does not work for Type S thermocouples.)

TYPE K (USA)

  • Type K Thermocouple lead wire (Yellow on the outside)
  • Yellow Wire = PLUS (+)
  • Red Wire = MINUS (-)
  • The thermocouples are marked with a (+) and (-). Also the negative (-) is marked with a red marker. The negative wire is MORE magnetic than the positive wire.
  • NOTE: Ground the outside metal foil wrapper to the negative terminal of the control.

TYPE S (USA)

TYPE K (EUROPE)

  • Thermocouple wire (Yellow on the outside)
  • Green Wire = PLUS (+)
  • White Wire = MINUS (-)
  • The thermocouples are marked with a (+) and (-). Also the negative (-) is marked with a red marker. The negative wire is MORE magnetic than the positive wire.

TYPE S (EUROPE)

  • Type S Thermocouple wire (Green on the outside)
  • Orange Wire = PLUS (+)
  • White Wire = MINUS (-)
  • The thermocouples are marked with a (+) and (-). Also the negative (-) is marked with a black marker.

NOTES

  1. See this for information on how thermocouples work.
Check thermocouple tip
  1. Carefully examine thermocouple tip. This is the exposed welded joint at the end of the thermocouple that is not covered up by the ceramic tube.
  2. To do this you will have to remove the thermocouple from its protection tube (if it is a kiln that has one of our protection tubes). You can do this with the kiln disconnected from power.
  3. Look for corrosion - especially if it severe. These thermocouple tips will oxidize and otherwise corrode over time. That is normal. There is some point, however, at which the corrosion affects the ability of the tip to work (thermocouples work by generating a small voltage at the tip caused by two different metals reacting to each other).
  4. Make sure the two wires are securely joined. One of the things that can cause an intermittent problem is a bad weld. If the two wires touch each other (even if they are not welded) they may work temporarily. However, if the weld is not secure then the wires could separate when the kiln heats up and cause an intermittent failure.
  5. If the thermocouple tip looks healthy then test the control board.
Examine all wiring for short circuits, bad connections, and burned areas.
  1. Check the tightness of all connections. Do this by wiggling the connector to make sure it is not loose.
  2. Examine all connections for any sign of oxidation or discoloration.
  3. Examine all wires for signs that the wire may have burned.
  4. Make sure all wires are connected to their proper connection point. You may have to compare the kiln to the wiring diagram to be sure of this. This step would be particularly important if a wire has come loose.
  5. Look for any place where a wire may have shorted against the metal case or a component.

CAUTION: Turn power off to kiln form the circuit breaker or unplug the kiln.

Replace Control Board

The control board needs to be replaced if:

  1. The transformer is OK.
  2. You know you have voltage going to the control board but the control still shows no display.
  3. You know you have voltage going to the control board but there is no output form the control to the power relays (even if you have display). In this case the little transistors inside the control that regulate output are not functioning).
Replacing Thermocouples
  1. Unplug kiln.
  2. Remove or hinge open the control box.
  3. Remove the Thermocouple Lead Wire from the Thermocouple.
  4. Unscrew the Thermocouple from the kiln.
  5. Remove Thermocouple.
  6. Install a new Thermocouple and screw in place.
  7. Replace Thermocouple Lead Wire and tighten. Be sure to get red matched to the Plus sign and the Yellow matched to the minus sign.

See this video:

Applies to these Kiln Series