KNOWLEDGEBASE

What to do if the kiln fires slowly?

Incorrect Loading

  1. If your kiln is loaded unevenly it can cause the 3-zone control to slow the kiln down to compensate.
  2. Try evening out the load. A common mistake is to put too much heavy work in the bottom of the kiln.
  3. Also try to space the bottom shelves so that there are two elements inbetween the shelves. This allows as much of the heat to be transmitted to the work.

Bad or Wrong Voltage

  1. Check your voltage. Do this at the kiln at the Power Terminal Block with the control panel open or check it at your fused disconnect box. CAUTION: This test should only be done by an experienced person familiar with electricity and its dangers. You need to see what the voltage is when the kiln is firing. Low voltage will make the kiln fire considerably slower. For instance a kiln designed for 240 volts will have 25% less power when operated on 208 volts. Check voltage at your panel and where the kiln is connected. Check the voltage when the kiln is firing and when it is not firing. Sometimes the high amperage draw of the kiln will cause a voltage drop at the kiln. A voltage drop of 5 to 10 volts is not uncommon and is to be expected. If your voltage drop is more than that then you may have a problem with your electrical supply.
  2. Make sure no other large electrical appliances such as a clothes dryer or electric oven are on when you are operating your kiln. This may cause a voltage drop which would slow the kiln down.
  3. Voltage may vary in your area depending on season and time of day. Frequently there are "brown outs" during the summer months in some areas. This is when the electric utility reduces the voltage. Try firing at night after peak electrical use hours. You can use your Delay feature to do this easily. Find out from your local utility company when the end of the peak period of electrical use is. Some utilities offer preferential rates for using electricity at night because it is cheaper for them.

Element Aging

  1. See troubleshoot-elements.pdf.
  2. See some of the factors that affect element life.
  3. See What makes elements melt and sag?

Power Relays

  1. Power Relays may cause poor transfer of power to elements when they have been used for a long period of time. It is not always a total failure - which is of course harder to troubleshoot. If these are suspected replace them. See this page for how to check your power relays.

Bad Wiring

  1. Have an electrician check your wiring. We have seen aluminum wire cause intermittent problems with allowing enough voltage through. We do not recommend aluminum wiring although some electricians will swear by it. The problem with it is that aluminum oxide, which is formed from heat, is a resistor while copper oxide is not a resistor. With kilns you will often develop some heat in the electrical lines. If all connections are perfect and the wire is oversized you probably will not have a problem - but why take that chance? Make sure your wires are of the proper size and that all connections are good.
  2. Check your circuit breaker for proper operation. These sometimes go bad over time.
  3. If all the elements are firing and the kiln is still firing too slow check the amperage draw of the kiln under a full load. CAUTION: This test should only be done by an experienced person familiar with electricity and its dangers. You need to see what the voltage is when the kiln is firing.
  4. On a kiln with a DynaTrol you can tell if all zones are firing by pressing the number 8 on the control numeric pad. You will see one little light per zone under the numbers on the control display. If you see two dots on an e23S or e28S, then you are firing at full load. If you see three dots on an e23T or e28T, then you are firing at full load. See if the amperage drawn is the same as what the kiln is rated for. See the product literature and/or data nameplate on the kiln for the rated amperage draw. There is also a complete table of this information in the Installation Instructions part of this manual. For instance, a model e23T rated for 240 volts, Single Phase should draw 48.0 amps. If it is substantially less than the rated amperage draw and your voltage is within 5% of the rated voltage (for instance 230 volts for a 240 volt unit), then chances are the elements have changed in resistance. This will require element replacement. Pressing the number ”8” will turn on 2 or 3 small LEDs that indicate whether the various zones are firing.
  5. The gauge of the hookup wire is not large enough which creates a voltage drop and reduces power to the kiln. See this link for more information.

Wiring in the Kiln

  1. Unplug kiln.
  2. Trace wiring for missing or bad connections.
  3. Check wiring against wiring diagram. Especially check parallel vs. series wiring of the elements.
  4. Check for corroded connectors or connectors that have frayed wires. Replace the damaged parts if you see this.
  5. Make sure all kiln sections are plugged in (if applicable to your model). Make sure ALL plug connections are good and not oxidized.

Element Connections

  1. The holes where the elements go through the firebrick walls are too large. This could cause too much heat to escape from the kiln thereby overheating the element terminals. This can be remedied by lightly stuffing non-RCF ceramic fiber in the element holes. (See the Parts List for non-RCF fiber). You can stuff this in from the inside of the kiln using a sharp tool like a very small screw driver.
  2. Check to see if the element ends are twisted properly. They should be twisted clockwise around the terminal screw. If the twist is too loose this could generate extra heat at the element ends. Check for corrosion on the terminal. If there is corrosion sometimes you can remove it with a wire brush. Photo of element terminal with element end twisted around it properly:
  3. The element connection hardware may not be tight enough. A loose connection can generate heat and cause oxidation of the hardware which in turn will cause a worse electrical connection (because of resistance) and more heat. Replace with new hardware.

Heat Leakage & Vents

  1. Make sure peephole plugs are in.
  2. Make sure hole for vent is proper. Check Vent-Sure instructions for proper hole sizes.
  3. If you are using a different brand of vent make sure it is the appropriate size for your kiln. Check with the vent manufacturer and tell them how many cubic feet are in your kiln.
  4. If your lid or bottom is cracked check to see if it seems to be leaking much heat at high temperatures. Patch or replace if extreme. Some cracking is OK.

Single vs Three Zone Control (DynaTrol Only)

  1. Three zone control will slow a kiln down. It helps even out the temperatures in a kiln by shutting off one or more zones while firing. In addition zone control introduces other issues like LAG (on older controls) that sometimes complicate a firing. The first thing to try if you are getting a slow firing is to switch the kiln to single zone operation. That may get you back into operation quickly. Then, if that makes the problem go away you can fine tune the specific issue within the zone system that is causing the problem.
  2. Normally Easy-Fire, Jupiter, DaVinci and most other L&L kilns with a DynaTrol are programmed to be either two or three zones. You can easily change this to be single zone operation.
    Press OTHER, 4, 4, 3
  3. The display says notC This stands for “number of thermocouples”.
  4. To run the kiln using only one thermocouple press ENTER at the notC prompt. You will then see 0003 or 0002 (depending on whether it is currently programmed for three zones or two zones). Then press 1, then ENTER. The display will then say StOP. All the zones of the kiln will turn on and off simultaneously when you program the DynaTrol to use only one thermocouple.
  5. To run the kiln using only two thermocouples press ENTER at the notC prompt. You will then see 0003 or 0001 (depending on whether it is currently programmed for one zone or three zones). Then press 2, then ENTER. The display will then say StOP. When you program the DynaTrol to run using only two thermocouples the bottom zone and the middle zone go on and off simultaneously. If you have a three section kiln the bottom section and the middle section will work off the middle (#2) thermocouple and they will fire together. This configuration can be an interesting option to help speed up the kiln but still get some advantage from the zone system.
  6. To run the kiln using three thermocouples press ENTER at the notC prompt. You will then see 0002 or 0001 (depending on whether it is currently programmed for one zone or two zones). Then press 3, then ENTER. The display will then say StOP. If you choose to do this thermocouple #1 must be in the top zone, thermocouple #2 in the middle, and #3 in the bottom. All three zones will operate independently, tied to their respective thermocouples.
  7. To exit the OTHER-4-4-3 series of menus without doing anything press OTHER until you come to PCt. Then press ENTER twice. You will then see CPL, and then IdLE, tC2, and the current temperature cycling in the display again.

ShtO (Shut-Off) Setting (DynaTrol Only)

  1. This option is used to shut off the automatic feature in the DynaTrol that holds the hottest part of the kiln at each segment's set point until the average of the three (or two) thermocouples reaches that set point. This can have a dramatic effect on speed of firing and is worth trying to see if it helps you if you are having a problem.
  2. When you press OTHER, 4, 4, 3.
  3. Press OTHER until ShtO is displayed.
  4. Pressing ENTER here allows you to toggle, using any number key, between On and OFF.
  5. On means that as soon as the hottest zone gets to the segment's set point the entire kiln switches to either the "hold time" or the next segment. This will result in a quicker firing.
  6. OFF means that the DynaTrol will not let the hottest zone's temperature rise until the average temperature of the three zones reaches that segment's set point. Then the kiln can begin the "hold time" or the next segment. This will result in more even firing.
  7. When you have the setting you want shown in the display (On or OFF) press ENTER. CPL will display for a few seconds and then IdLE , tC2 and current temperature.

PId Setting (DynaTrol Only)

  1. This setting generally should be left at its factory default because it is hard to predict the changes that it will create in your firing. However, a full explanation is given for more advanced users who want to experiment with this.
  2. This setting comes pre-programmed at the factory for 65%. Basically this setting determines how much help the middle zone of the kiln gives the bottom zone of the kiln when the bottom zone is lagging behind during heating. This comes into play when the bottom zone is on 100% of the time. With this feature, the middle zone of the kiln will come on the programmed percent (Pld) of the time that the TOP zone comes on, if the bottom zone is on all the time. Tests showed that if the bottom was on 100% of the time, the top zone was generally on 90% of the time, but the middle zone was on only about 40% of the time. By programming a higher percent you can greatly speed up your firings. (you will have to experiment, try the factory setting 65% then try maybe 100% and compare your results). Basically the higher the PId setting the faster the firing at the potential price of unevenness.
  3. As your elements age firing by firing, this setting will activate earlier and earlier in the firing because the bottom will be working at 100% earlier and earlier. This will allow the artificial inflation of the center's temperature sooner and sooner. Because this center is heating based on mathematics now and not it's own thermocouple's reading, it will have a longer and longer period of time to get hotter than the top and the bottom. In some cases this can lead to gross unevenness. You may find yourself dialing down the PId to something like 50% or 60%. Remember that if it is set around 40% (it's normal operating percentage) or below, the thermocouple's reading then will be the control for that section, not the mathematics of the PId feature.
  4. When display flashes IDLe, tC2 press OTHER see rSEt. Press 4, 4, 3. See notC
  5. Keep pressing OTHER to cycle through the menu options until you get to PId.
  6. Press ENTER. See PCt, 0085 cycling.
  7. Press any number from 0 to 150, see the number you have entered preceded by a zero like 0120 if you entered 120. Press ENTER, see CPL or StOP for a few seconds, then IDLE, etc.
  8. Pressing ENTER here allows you set another percent setting that can help a slow, heavily loaded kiln fire faster.

Adding More Insulation

  1. In L&L's top loading kilns an additional bottom may be placed under the original bottom. This will improve the insulation in the kiln, thereby slowing heat loss and speeding the firing time. You can also put a 2” layer of calcium silicate on top of the stand beneath the bottom of the kiln.
  2. Also try raising the height of the kiln from the floor or putting a reflective stainless steel or aluminum sheet under the kiln. All these things keep the floor from absorbing the radiant energy from the kiln and will improve heat up times (as well as bottom of the kiln uniformity).
  3. Put a 1” layer of non-RCF ceramic fiber on the lid. This is completely non-hazardous which is important in this application because you will be releasing fibers into the air when you move it while loading. While this is a somewhat extreme measure we have found that a disproportionate amount of the heat loss from a kiln is through the top. Non-RCF ceramic fiber is soluble in the body and is considered totally safe. (See the Parts List).
  4. Whatever you do be sure NOT to put the kiln directly on the floor. If the floor is cement or other hard non-flammable material it will absorb the heat from the kiln. If the floor is wood or other flammable material you will create a very DANGEROUS situation which could cause a serious fire.

LAG Setting (On Older DynaTrols Only)

  1. Note: This option does not show up on controls made after about 2005.
  2. LAG is the zone control setting that determines the temperature differential allowed between zones.
  3. The lower the LAG number the more even the firing. However, this can slow the kiln down considerably. It is somewhat like a convoy - the kiln can only move as fast as its slowest zone (although of course it is more complicated than this because the faster zones help heat the slower zones).
  4. The default LAG setting is 25. If you increase this to 50 or even 75 is allows the kiln to fire its zones with a greater differential which will speed the kiln up.
  5. Press OTHER until you see LAG.
  6. Hit ENTER.
  7. You will see LAG and a number such as 0025 flash.
  8. Input a new number (from 5 to 99) with the keypad and hit ENTER. We do not recommend less than 25 unless you have a very critical process and where speed is not an issue like on low fire. A very low number like 0005 could really slow the kiln down. If you want lower than 0025 try 0015 or 0010.
  9. AUL6 (Autolag) will now display, flashing with either On or OFF. See next section.

Autolag Setting  (On Older DynaTrols Only)

  1. Autolag automatically disables the LAG control until the end of the firing.
  2. Having Autolag turned On speeds up the firing considerably. Most ceramics applications do not require exceptional uniformity until the end of the firing. With Autolag On the LAG feature is disabled until the last 45°F of the firing when it comes back on to it's programmed setting. Basically this allows the faster sections to help pull the slower sections along.
  3. However, for glass and other industrial applications turning OFF Autolag is probably recommended.
  4. Press OTHER until LAG appears.
  5. Press ENTER.
  6. As soon as you press ENTER after entering the LAG setting (you can leave it as is - just press ENTER) you will see AUL6 for approximately two seconds, and then see either ON or OFF.
  7. Press 1 to toggle between ON and OFF.
  8. Then press ENTER

For Manual Kilns Only

  1. Check many of the same things as you would for an automatic kiln like element resistance, wiring, etc.
  2. Switches are sometimes defective.
  3. Relays or contactors may cause poor transfer of power to elements when they have been used for a long period of time. Examine contacts for wear. Replace contactors if contacts are worn or pitted.
  4. Make sure all elements are firing. You can do this by simply looking inside the kiln while the elements are on. They should all be glowing a similar color red. CAUTION: In most kilns the power does not turn off when you open the lid. Be careful not to put your hand inside the kiln while it is on. Dangerous electric shock could result.
  5. If all the elements are firing and the kiln is still firing too slowly, check the amperage draw of the kiln under a full load, i.e. with all Infinitely Variable Zone Input Switches on 100%. See if the amperage drawn is the same as what the kiln is rated for. See the product literature and/or data nameplate on the kiln for the rated amperage draw. For instance, a model J230 rated for 240 volts, Single Phase should draw 43.93 amps. If it is substantially less than the rated amperage draw and your voltage is within 5% of the rated voltage (for instance 230 volts for a 240 volt unit), then chances are the elements have changed in resistance. This will require element replacement. You can check element resistance by disconnecting the elements and checking the elements with an ohmmeter. See your instructions or check with factory for proper resistance.
  6. See more about how to diagnose a slow manual kiln.