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Kiln Pointers
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A Simple Thermocouple Error |
CONTENTS A Simple Thermocouple Error More On Getting To Know Your Kiln Recent Q&As: Replacing relays and elements; dark discoloration inside a kiln A SIMPLE THERMOCOUPLE ERROR Sometimes the most worrisome problems are the easiest to solve. If something goes wrong with your kiln, look first for the simplest solutions. Before assuming that you need new elements, for instance, check for a disconnected wire. Here is another example: If the display window on your kiln shows a temperature in the 100 – 150 degree F range (37 – 65 C) even though the firing chamber is much hotter, the problem is most likely due to bare thermocouple wires that are touching inside the switch box. Disconnect the power, open the control panel (switch box), and check the thermocouple wires, especially at the back of the controller circuit board. (The thermocouple is the rod that extends into the firing chamber. It senses the temperature.) You will find two wires that run from the controller to the thermocouple. Color coding for thermocouple wires: Type-K thermocouple: yellow wire (+ terminal) and red wire (- terminal) with brown or yellow outer wire insulation Type-S & R thermocouples: black wire (+ terminal) and red wire (- terminal) with green outer wire insulation Look for bare areas of the wire where the insulation has been stripped too far. The first place to check is the wire ends that attach to the back of the controller. If the bare ends cross over and touch, the thermocouple will register the temperature of the switch box instead of the firing chamber. This problem takes only a moment to fix. Remove the wires, cut them a little shorter, and reattach the wires to the controller. ------------- MORE ON GETTING TO KNOW YOUR KILN The last Kiln Pointer was “Getting to Know Your Kiln.” Here is another thought on that topic: One of the best backup systems is to know the temperature of the light around the lid. Here is a quick way to develop that ability: Check on your digital kiln from time to time as it fires. Each time you look at the kiln, guess at the temperature of the light. Do this without looking at the controller display. Then check the display to see how close you came. You can also use this same technique on a manual kiln with pyrometer. ---------- RECENT Q&As Q. When you replace relays in a glass kiln, should you also replace the heating elements? A. No. The lid or roof elements in a glass kiln last many years, because glass temperatures are so low especially compared to pottery temperatures. As long as the elements still fire, do not replace them. Q. I fired my SC-2 kiln for the first time and turned it off because of a strong smell. I also found dark discoloration inside the kiln. A. During the first firing, you may smell a strong odor from your kiln. This is normal and is caused by the burning of binders in the ceramic fiber firing chamber. The odor is accompanied by a discoloration, which disappears after the kiln reaches about 1000F (537C). It is nothing to worry about. ------------- Here is another example of a seemingly serious problem that had a simple solution. When I first started working at Paragon, I saw a 1965 VW Bug for sale parked outside a mechanic’s shop. The price was only $250, so I stopped, talked to the owner, and checked the car out. As I crouched at the back of the car with the hood open, I revved the engine and heard what sounded like a rod knock. That’s why the car is only $250, I thought. A rod knock meant the engine needed to be rebuilt. I bought the car anyway. After I drove it home, I checked the engine and noticed that the fan belt was too tight. I loosened it, and the knocking sound went away. The engine sounded perfect. The car was a joy to drive, and the engine ran beautifully the entire time that I owned it. Thank you, With best wishes, Arnold Howard Paragon Industries, L.P. – Better Designed Kilns 2011 South Town East Blvd. Mesquite, TX 75149-1122 Voice: 972-288-7557 & 800-876-4328 / Fax: 972-222-0646 ahoward@paragonweb.com / www.paragonweb.com -------------- PRIVACY NOTICE: Under no circumstance do we share or sell your email address. Copyright 2008, by Paragon Industries, L.P. |
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