KNOWLEDGEBASE & FAQS

Once properly calibrated, your L&L digital kiln should fire reliably for many cycles. The controller ensures accuracy by constantly comparing the thermocouple (TC) readings to the programmed firing curve. Multiple TCs add redundancy. While slight over- or under-firing can happen, serious overfires are extremely rare.

However, there are a few scenarios where overfiring is possible—none of which the controller can fully prevent:

Stuck Relay

The relay controls power to the elements based on signals from the controller—it’s what makes the clicking sound inside the control box.

1. If a relay sticks closed (fails in the "on" position), it won't shut off even if the program ends or the controller shows an error. The kiln will continue heating. This is only a risk in small kilns with a single relay.
2. Larger kilns have multiple relays, one per heating zone. If one relay fails, only part of the kiln stays on, which is not enough to cause a full overfire.
3. While it's technically possible for multiple relays to stick simultaneously, it's extremely unlikely. Most relays fail in the open (off) position.

Thermocouple Issues

1. In a single thermocouple kiln, If the TC is not inserted far enough, it may read lower than the actual temperature, allowing the kiln to overfire.
2. Most L&L kilns use multiple, securely bolted TCs. If one reads too far off from the others, the controller will trigger an error and shut down.
3. Using the wrong type of TC (e.g., connecting a Type S TC when the controller is set for Type K) can cause inaccurate readings and overfiring.
   1. A small jumper on the control board must match the controller’s TC type setting (K or S).
   2. If the jumper and setting don’t match, the kiln will display an E-9 error.
   3. If they do match, but you still connect the wrong TC type, the kiln may overfire.

Incorrect Programming

1. You could mistakenly program Cone 6 instead of Cone 06, causing a major overfire.
2. Or you might enter a 10-hour hold at peak temperature instead of 10 minutes, especially dangerous at higher cones like Cone 10.
   1. Even a 1-hour hold at Cone 10 can cause severe damage.
   2. Long holds at lower temps may ruin clay or glass, even if they don’t damage the kiln itself.

While serious overfiring is possible, it’s highly unlikely with a properly functioning digital L&L kiln. Still, we strongly recommend being present when the kiln is scheduled to shut off to eliminate any risk.

Please note: overfiring is not covered by the 3-year factory warranty.