I am switching my computerized L&L kiln from 208 volts to 240 volts. What do I need to do to the kiln?

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I am switching my computerized L&L kiln from 208 volts to 240 volts. What do I need to do to the kiln?
  1. All the elements will need to be replaced.  Why?  For example, the ohms on the JD2927 208 volt element circuits should be around 10.4. If you put 240 volts to each circuit it will pull around 23 amps per circuit- which is too much. There should not be more than 20 amps per circuit for the JD2927 208v kiln.

  2. Computerized controls will run fine on 208 or 240 volts.
  3. Changing voltage sometimes means pulling more amperage. Be sure to check the electrical specs for your kiln as it will be after the change.  For example, if you are changing to 240 volts look for the electrical specs your kiln as a 240 volt kiln. Be sure your breaker and wire size are large enough. Breaker size is determined by the new amp rating of the kiln, multiplied by 1.25 (125%) and then rounded up to the nearest breaker size. Wire size is tied to the breaker size:
20 amps
12 gauge copper
30 amps 10 gauge copper
40 amps 8 gauge copper
50 amps 6 gauge copper
60 amps 6 gauge copper
70 amps 4 gauge copper
80 amps 3 gauge copper
90 amps 2 gauge copper
100 amps 1 gauge copper
125 amps 1/0 gauge copper (pronounced "one aught")

150 amps 2/0 gauge copper (pronounced "two aught")

175 amps 4/0 gauge copper (pronounced "three aught")

200 amps 250 MCM copper wire (MCM = Thousand Circular Mils)
225 amps   
350 MCM copper wire

Additional Actions to Take

  1. Make sure the circuit breaker or fused disconnect switch is turned on.
  2. If you have a circuit breaker flip it back and forth to make sure that it is really on. Some circuit breakers, if they have tripped, will not be obviously in a tripped position. By flipping it back and forth you will reset the circuit breaker.
  3. Check voltage of your power supply at the receptacle using your multi-meter set to the next highest AC voltage above 240 (typically this will be 600 volts but may be 250)
  4. Check fuses for voltage continuity. You can do this with your multi-meter.
  5. Make sure fuses or circuit breaker are/is the proper amperage and type. See your wiring diagram for the required fuse type.

CAUTION: This test should only be done by an experienced person familiar with electricity.

  1. Check your voltage at the receptacle or at your fused disconnect box. 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.
  2. Make sure no other large electrical appliances such as a clothes dryer or electric oven are on when you are operating your kiln.
  3. Find out from your local utility company when the end of the peak period of electrical use is.
  4. Check to see what the wire size of your circuit is. If it is very far (more than 50 feet) from your main circuit box then the wire size might need to be higher.
  • Unplug kiln.
  • Open the outer control box. See the Assembly Instructions if necessary.
  • Using your Multimeter set on Resistance or Ohms, 200, check resistance on the wires numbered 1 and 2 and then again between 3 and 4.  These wires are thick black wires that attach to the terminal strip that carry power from the relays to the elements.
  • If you check the resistance at this point, the values you should get are as follows: 240 Volt Elements: 20.8 ohms, 220 Volt Elements: 17.6 ohms, 208 Volt Elements: 15.6 ohms.
  • The values should be within 6-12% of the listed values. Typically the resistance increases over time and use, and this makes the power generated by the elements decrease. Depending on the temperature one is firing at, wider variation may not be problematic.
  • In addition, here are the values for the individual elements: 240 Volt Elements: 10.4 ohms, 220 Volt Elements: 8.8 ohms, 208 Volt Elements: 7.8 ohms. Individual element resistance values are important as a way to provide a means of checking specific element resistance before you put elements in the kiln.

See this tutorial on how to use a multimeter.


  1. Unplug the kiln.
  2. Follow the instructions in the Assembly Instructions for removing the Control Box. (Click here for a list of all assembly instructions).
  3. Pack the control panel with cushioning material such as bubble wrap, balled-up newspaper or foam in a cardboard box and follow instructions from the factory or you local distributor about where to send it.

CAUTION: Do not send a control panel without calling first.

CAUTION: The controller contains electronic components which are sensitive to static electricity. Before handling the controller dissipate any static charge you may have by touching metal or a screw on the controller panel, the electrical box, the kiln lid, or some other grounded object.

 

This video shows how to remove a control panel on an Easy-Fire, School-Master or eQuadPro kiln for service.

  1. Unplug kiln.
  2. Remove the Control Box.
  3. Using a 3/8" nut driver or ratchet wrench or adjustable wrench, remove the nuts that hold the element end onto the Element Terminal Bolt. Note that the terminal bolt head is held in place by an inset shape on the underside of the ceramic terminal block and it will not turn much.
  4. Untwist the element end from around the Element Terminal Bolt. Straighten it out as much as possible.
  5. In most cases the element can be lifted out of the holder at this point. Sometimes, if the element has really disintegrated, you need to remove it in pieces with needle nose pliers.
  6. If element is hard to get out of the holders (because of growth of the element) you can try heating up the kiln slightly so as to heat up the element slightly to just the point where element is slightly pliable–don't let it get red. This will soften the wire. Then turn off the kiln and disconnect all power to the kiln. Using heat protecting gloves and a pair of needle nose pliers pull out the softened element.
  7. From the inside of the kiln, using needle nose pliers, grab the element as close to where it goes through the brick wall to Terminal Block. Pull the element end through the hole. Be careful not to enlarge the hole in firebrick. The brick is soft and will not take much abrasion.
  8. Be sure to check for failure points for evidence of contamination on the element and the element holder. If the element holder is contaminated it will cause rapid failure of the new element. Replace contaminated holders with the new ones.
  9. Using your multimeter check the resistance of the new element.
  10. Install the twisted ends of the elements through the holes in the wall of the kiln. Element ends should be straight at this point.
  11. Pull them up tight up to the wall of the kiln by pulling from outside the kiln.
  12. Lay the element into the groove. Note that the unfired element is going to have some springiness to it before it is fired for the first time. You may need to use a screwdriver to press the element into the holder. YOU DO NOT NEED PINS.
  13. FOR KILNS WITH NON-CERAMIC TERMINAL BLOCK OR ON RETROFITTED KILNS WHERE YOU HAVE ADDED A CERAMIC TERMINAL BLOCK BUT STILL NEED BUSHINGS: Be sure to replace the insulators and spacers over the element tails.
  14. Consulting your picture or labeling, wrap the appropriate element tails around the appropriate element connection bolt, clockwise, one around and cut off the excess tail.
  15. Install the elements and hardware: Place the wires from the jumper cord or connecting wires onto the appropriate bolts and tighten with stainless steel nuts.
  16. A washer goes under the first element.
  17. Twist the first element end CLOCKWISE around the Terminal Bolt.
  18. The next element gets twisted around the Terminal Bolt on top of the first element.
  19. Another washer goes over the Terminal Bolt.
  20. Place a nut on top and tighten it.
  21. Put another washer on.
  22. Put on the Ring Terminal of the Power Lead Wire.
  23. Put another washer on.
  24. Put another nut on and tighten it. How much the nut can be tightened is dependent on how tight the element connection bolt is on the element connection board. A tight connection is very important, but if you tighten too much and twist the element on the bolt too far you could break the element, the bolt, or the insulator.
  25. Reattach the ground wires and the element box if the kiln has them. DO NOT FORGET TO ATTACH GROUND WIRES. IF EACH KILN SECTION IS NOT GROUNDED THIS CAN BE VERY DANGEROUS.
  26. Test the resistance at the jumper cord's plug head or at the other end of the connecting wires.
  27. Reattach the control box, turn on the kiln and make sure all the elements come on.

See this tutorial on how to use a multimeter.

See this video: