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, and 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 in 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 |