Signs Your Kiln Relay is Getting Old

What is a kiln relay?

A kiln relay is a component of electric kilns that acts as a switch, turning power to the heating elements off and on. Mechanical relays need to be replaced before they start to cause issues with your firings. Issues with your mechanical relay often show up before the relay completely fails. Pay attention to a few telltale signs that can either show up suddenly, or develop over time.

Missing clicking sounds

Mechanical kiln relays use moving parts to create a physical connection inside the relay and open and close the electrical circuit. Because of this, you can hear when the parts move inside the relay and they create a clicking sound. If you don’t hear the usual sound that accompanies your kiln firing there may be an issue with your relay.

Electrical buzzing

Your electric kiln typically makes a gentle buzzing sound while firing. This is because the electric current flows through the elements to heat the kiln. However, a louder, chattering, atypical, buzzing sound warrants some investigation.

Uneven heating across the kiln

Cones, along with your controller will be able to let you know when your firings are not going as planned. Temperature is measured by the thermocouple and displayed on the kiln’s controller. If the temperature readings during your firings are off more than 50°F from your program this should alert you to a problem. 

You can also measure the temperature evenness in your kiln by using pyrometric cones. If you place pyrometric cones in different areas of the kiln and different shelves, based on how they bend throughout the firing, you will be able to compare the heat work received in the areas you placed the cones. Using cones consistently and in different locations can also help you identify changes between firings. 

Differing glaze results across pieces

If you suspect your relay is getting old, you will also want to examine the results of your glazed pieces. If pieces with the same glaze come out looking very different, this may be an indication of some areas not reaching their desired temperature. Don’t rely on glaze results alone to evaluate your relays, since normal temperature differences between areas of the kiln can also affect how glazes turn out. If you notice differences in a glaze you use often, and it’s coupled with other signs, you’ll want to check your relay. 

Dark areas inside the kiln

You should also look out for darkness in your heating elements. When the elements heat up they produce a bright orange glow however, if one part of your kiln is darker than the other this could indicate an old relay. To find out if your elements are heating properly, you might want to perform a full power test. Refer to your owner’s manual on how to perform this test since it varies between kilns. If your kiln fails the test, and you have noticed other issues pointing you to your relay it may be time for a replacement.

Sudden kiln stoppage

If your kiln suddenly stops during a firing this can be an indication that your relay failed. A sudden stoppage can also be accompanied by error codes which should be able to give you more information on what caused the stoppage. However, you might not always receive a code.

Error codes depend on the controller that you have, so be sure to consult your manual to determine what the error code means for your specific controller.

Overheating and underheating

If you're noticing the kiln is underfiring or overfiring, there could be an issue with your relay(s).

The physical contacts on mechanical relays can wear out over time and fail to open or close properly. If the relay is not closing, the elements it controls won’t heat. If the relay is getting stuck in the on position, it causes uncontrolled heating or overheating.

Other Factors

Many of these signs can mean other issues within your kiln such as worn or broken elements, low voltage and other component issues. Check your kiln manufacturer’s troubleshooting guide to determine whether the relay or another component is causing the problem.