FrogBlog
Hunting for a Dead Short in a Kiln
This post was written by Arnold Howard, a former employee at Paragon Industries who is now an independent kiln technician at Howard Kiln Services. The owner of a Paragon A-24B called to tell me he saw sparks flash inside the switch box on his kiln, and the circuit breaker tripped. He could see the flash through the ventilation louvers on the side of the box. “It made a loud noise that scared the hell out of me,” he said. “It happened when I turned the bottom switch to high.” “Your kiln has a dead short,” I told him. A dead short causes a large amount of electricity to flow suddenly through the wires. This shuts off the circuit breaker for your kiln because the surge of electricity is much greater than the amperage rating of the circuit breaker. A dead short usually happens when the protective insulation on a wire has been damaged, and the bare wire touches either another wire, an element connector, or the steel case of the kiln. After arriving at the customer's home, the first thing I did was open the switch box by removing hex-head screws with a 1/4” nut driver. The screws are on the sides of the switch box of most kilns. You can buy the 1/4” nut driver from a hardware store. Some brands of kilns require a different size nut driver. If the size you need is not available locally, you can order one online. This may be the case overseas as the 1/4” size is uncommon there. Remember, always BE SAFE! If you ever remove the switch box on your kiln, first unplug the kiln. This is essential because otherwise you will be exposed to live wires inside the opened box. In the first photo, you can see the element connectors, which are small brass barrels with a screw-on each end. Notice that a wire is attached to each connector. In the A-24B, those wires go to switches. In digital kilns, the wires go to relays, which turn the elements on and off. Lying on the garage floor, under the shadow of my lamplight, I hunted for the dead short. Since the sparks flashed when the bottom switch was turned to high, I started my search at the bottom of the switch box. In the second photo, you can see where the short occurred. Look at the element connector in the bottom center half of the photo. It is the blackened brass barrel that is against a white porcelain insulator. The element connectors are the hottest items in the switch box. If a wire touches an element connector, the insulation on the wire can eventually burn off and cause a dead short. In the bottom right corner of the photo is a red wire with a burned spot. That burned spot is where the wire touched the element connector. The spark blackened the connector. With any routine kiln maintenance, you or your kiln technician will need to open the switch box or protective cover panel on your kiln if you ever change a thermocouple, relay, switch, or repair a damaged wire. As you can see from the photos, it is important that as you reinstall the switch box or panel onto the kiln, check that the wires will not touch an element connector. To be sure that the wires would not touch element connectors or the kiln case, I looked at the wires from the side while closing the switch box, tucking some of the wires out of the way inside the box. Then I carefully positioned the switch box on the kiln and installed the screws. You might want to shine a flashlight into ventilation slots or louvers to check the position of the wires one last time after you have reinstalled the switch box. As you can see from this story, major kiln problems can be avoided by taking just a moment to check the small details whenever anyone works on your kiln. Thanks, Arnold!
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Troubleshooting Your Controller
From electrical power issues to temperature, display, and keypad problems, Paragon Kilns has designed a Troubleshooting Guide for the Sentry Controller. Even though it was created by Paragon for the Sentry 2.0, this guide can help with almost any digital controller as the basic principles are the same. With of all the great insight included in the guide, my favorite part is how it describes the six basic parts a digital kiln uses to control heat. And, understanding how your kiln works will simplify all of your troubleshooting efforts!
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How Low Voltage Affects Firing Time
Knowledge is POWER! Making sure you have the correct voltage is one of the most important factors of kiln efficiency! Plug the kiln into the correct circuit. Low voltage can double the firing time. If your kiln is firing too slowly, make sure the voltage listed on the kiln’s electrical data plate matches the voltage of the electric circuit. The electrical data plate is usually located on the side of the kiln or the switch box. Firing a 240-volt kiln on 208 volts reduces the kiln’s power by 25%. Even a small drop in voltage can affect the firing speed. Low voltage has the same effect as firing with worn out elements. Even a small drop in voltage can slow down your kiln. For example, we test-fired a 120-volt kiln that took 5 hours and 3 minutes to reach 2331°F (1277°C). On a separate electric circuit, the same test kiln took only 2 hours and 30 minutes to reach 2350°F (1287°C). The difference in voltage between the two circuits? Only 7 volts. Fire the kiln when the voltage is highest. Turn off other large appliances. If your kiln ever slows down temporarily, do not assume that it is due to worn elements. The voltage to your building may have dropped due to peak demand. Have an electrician check the voltage under load while the kiln is firing. Until you know the voltage, an amp reading of the kiln won’t tell you much, because low voltage also causes low amperage. If the voltage is low during a period of peak demand, fire your kiln when the electrical demand is lower and the voltage is higher. Fire at night or early morning. Also, turn off other large electrical appliances such as a clothes dryer while the kiln is firing. Program at a slower rate. A digital controller will show error messages when it has been programmed at a faster rate than the kiln is capable of firing. This can happen even when the voltage is normal and the kiln is new. You may be using a firing schedule that is designed for a faster kiln. In this case, program at a slower rate. Moist clay can slow down the kiln. Another reason your kiln may be firing slowly is that the firing chamber has too much moisture. Firing moist ceramic greenware or moist glass molds can slow down the kiln. Dry these materials before firing them. Reduce the load density. Overloading a kiln with a dense load of ceramics and kiln furniture can also slow down the firing. Have the power company check the transformer. If the kiln still fires too slowly after following the suggestions above, have the power company check your voltage and readjust the transformer for your area if necessary. You can also request that your power company put a voltage recording unit at your location to check the voltage over an extended period.
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Why we LOVE Quartz Tubing!
Paragon CS-26 Whether it's offered as standard or an upgrade, we always love kilns that have quart tubing! Quart tubing provides a cleaner kiln interior and magnifies the heat to the glass. They also support and protect the elements from contamination with foreign materials that could shorten the element life. In addition, quartz tubes protect the glass from any falling debris from exposed elements. If you fire enamels, the metal oxides can cake onto the elements causing them to sag, and drop colored debris... yuk! Gail has two kilns at her studio with quartz enclosed tubes and never has to worry that anything will drop on her, or her students' glass. Check out some more kilns with quartz tubes: Jen-Ken AFG ProFusion Fiber 38 Hot Shot Oven and Kiln - HS16 PRO Clamshell Olympic Champ XL (Available as upgrade)
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Little Wisp Bowls
Bullseye Glass Quick Tip: In this Quick Tip, you will learn to create your own streaky color palette! And, it's so easy! Start by layering Clear and White Streaky sheet glass over transparent tint glass styles. Then, slump in the Cone Bowl mold to upturn the edges and achieve luscious color at the rim. You might just find yourself making bowls for days! The Cone Bowl mold is a crowd pleaser and has always been a Bullseye Glass favorite! Glass fusers have dubbed it the original “the ice cream dish mold” and who doesn't love ice cream! The steep drop of this mold into a narrow space means this is one slumping project that requires special attention to preparation, firing schedules and placement in the kiln. Check out this additional tip from Bullseye... Cone Bowl Molds for additional best practices. Also, if this is your first time using clear, white streaky sheet glass, keep in mind that it may become more translucent upon firing. Remember to remove any needle pointed edges with a diamond pad prior to slumping to ensure you get a smooth, clean edge. Finally, for handy for minor adjustments of the flat, fused blank in the mold, as well as removing the slumped dish from the mold... just use this handy Small Suction Lifter.
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Is it time to change your mechanical relays?
It seems like every November we get the same phone calls and the same e-mails... "My kiln has stopped working and I have a show this weekend. Please HELP!" With that in mind, it's important to remember... owning a kiln is like being a Boy Scout, it's important to always BE PREPARED! Murphy's law says that whenever you need your kiln most and are firing the most, that's just when it's going to have a problem. So.... we all know that an ounce of prevention is worth a pound of I told you so. This is not directed to any one of our clients who've contacted us this month with an OMG moment! This is for all of us, who are just very busy and forget to take care of the basics. And yes... this has happened to me so, you're not alone. If you don’t already know, a relay is the part of the kiln that controls the power or current to the element, allowing the element to either receive current and get hot, or to interrupt the circuit thus not allowing the element to receive current and cool down. The mechanical relays, which come standard on most kilns, are what is responsible for the ubiquitous opening and closing clicking we hear while our kilns run. ALL MECHANICAL RELAYS in U.S. kilns are virtually the same... no matter the manufacturer. Mechanical kiln relays have a life of up to “X” amount of clicks and then they fail. This failure can either be in the closed position (Yikes, my kiln temperature keeps rising and it won’t turn off… everything is ruined!”) or they can fail in the open position. (Yikes, my kiln won’t heat up at all!) If they fail, it is not the manufacturer's fault, since they do not make the relays. They test them to make sure they work at the factory, but after that... it is your responsibility. We know that all failures stink and that is why we recommend changing your relays every 12-24 months. If you are a heavy kiln user, you should be smart and change your relays once a year. Think about it like an oil change or new tires... you wouldn't let your car drive on bald tires or your engine run on old oil. Pick a month and make it kiln maintenance month. Install new relays, paint the bottom with kiln wash, etc. and give your kiln a thorough inspection. Don't be the cautionary tale!! Finally, if this is something you don't want to hassle with... you can eliminate the problem by upgrading to mercury or solid state relays and almost never have to change a relay again. In our opinion, it's the best upgrade money can buy. With mercury relays it is important to make sure that regulations in your area don't prohibit them. The following states have prohibited the import of Mercury Displacement Relays within their jurisdictions: CA, CT, RI, IL, NH, MA, MN, ME, VT, NY, LA, MD, WI. If mercury relays are not for you, many kilns come with the option to add solid state relays for an additional charge. Hot Shot takes it one step further and makes all kilns with solid state relays by default.
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Creating Hollow Beads with Cork Clay
Cork clay is the perfect filler to create hollow shapes with Metal Clay. After creating the shape with cork clay, you must allow it to dry for at least 24 hours. Do not force-dry the cork clay with a heat gun. After it's dry, coat the cork clay with metal clay. Cork clay creations are usually fired in small jewelry kilns such as the Paragon SC-3 or Cress Kilns - C1006B It is important to fire cork clay in a well-ventilated area. Open windows and circulate the air with a fan. To prevent the cork from flaming out, always keep the kiln door closed between 500° - 800°F. Also, to give the cork enough time to burn out, fire no faster than 1500F per hour. Leave the kiln’s vent plug out from the beginning until around 800 °F. Hold at that temperature for 1 hour. After the hold, insert the vent plug and continue to fire the metal clay to the clay manufacturer’s recommended temperature. ⚠️Caution: When venting materials such as cork clay, remove the vent plug at the beginning of the firing. If you forgot to vent the kiln at the beginning of the firing, do not remove the plug later. Removing it later during the firing may cause the organic materials to flame up for a moment. If you ever remove the vent plug and the cork clay flames up, keep the kiln door closed so the flames can die out safely. Do not fire cork clay in a microwave kiln (the type that is placed inside a household microwave oven). The microwave kiln fires too fast to properly burn out the cork clay. Just for fun... cereal, pasta, and bread are other good core materials. Do not use wax or Styrofoam as a core as they emit harmful fumes.
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