I am switching my less than 50 amps manual kiln from 208 volts to 240 volts. What do I need to do to the kiln?

strict warning: Only variables should be passed by reference in /home/hotkilns/public_html/sites/all/modules/captcha/captcha.inc on line 61.

Search Knowledgebase

Knowledgebase FAQ

  • See the Sales FAQs for Frequently Asked Sales and Preorder Questions
  • The Knowledgebase is organized into a series of questions and answers having to do mostly with technical troubleshooting and understanding of kilns.
  • Although we write this for our own kilns many of these articles apply to other makes - although L&L takes no responsibility for that.
  • Many Knowledgebase articles have Actions, PDFs and Videos associated with them.
  • Actions are specific actions for you to take during the troubleshooting or repair process.
  • Each Action may also have Videos and PDFs associated with it and, in addition, specific Cautions.
I am switching my less than 50 amps manual kiln from 208 volts to 240 volts. What do I need to do to the kiln?

All the elements will need to be replaced. For example, the ohms on the J230 208 volt element circuits should be around 14.2. If you put 240 volts to each circuit it will pull around 17 amps per circuit- which is too much. The infinite switch used in manual L&L kilns can only handle 15 amps.

Some older J models, DaVincis, Ovals, B, SQ, G models were made with 208 volt infinite switches. It has been proven that 240 volt infinite switches work fine at 208 volts, but it has never been determined if 208 volt switches work fine at 240 volts. L&L's official recommendation is to replace 208 volt infinite switches with 240 volt switches when switching to 240 volts. When switching to 208 volts from 240 volts a switch change is not necessary.

Changing voltage sometimes means pulling more amperage. Be sure to check the electrical specs for your kiln as it will be after the change- i.e. 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 is 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. 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: