Kilns, just like any machine, will need a little care from time to time. Maybe your controller has seen better days or it's time for a new heating element. Well, Olympic Kilns has got you covered with our comprehensive replacement parts price list. Kiln Sitters are the control boxes on electric (or manual) pottery kilns that utilize pyrometric cones to dictate a kiln’s firing. Prongs within the kiln sitter extend to support a pyrometric cone or rod. Once the kiln reaches a specific temperature, the cone will start to bend, causing a lever to drop, switching the kiln off.
by BeverlyHowardOriginally Published in Dec 1986
The Studio Potter Magazine
Electricity is LETHAL! The following informationis provided for those who are knowledgeable, experienced and comfortableworking with and around 240 volt ac electrical systems and high temperatureceramic kilns. If you are not, please do notattempt to implement any of the following suggestions without the helpand assistance of a licensed electrician.
In addition to the electrical dangers, electricaland firing problems can easily lead to accidental fires that can destroystructures not to mention the possibility of killing or injuring people. While the author has executed the following modifications and those modificationsare currently in use in a full time pottery studio at the time of thiswriting, the author does not accept any responsibility for any injury,damage or other losses that may result from attempting to implement anyof the suggestions and designs shown in the following page. The useand implementation of these suggestions are at your own risk.
I have spent my life working with electricity and electrical circuits.Some of my most vivid childhood memories are of being jolted by a fulldose of house current. Even so, the first time I looked at the wiring ona kiln I was intimidated. I can see how the idea of rewiring an electrickiln could be overwhelming to most potters, but, as I found out, it isnot as difficult as you might think. When you have been through it once,the lessons learned can reduce subsequent rewiring times to the point thatelement and switch replacement can be thought of more as regular maintenancethan as a major project.
In addition to replacing the worn-out elements, the kiln can also beupgraded with some of the improvements that you now find on the newer models.A Kaowool blanket can be placed between the switches and the kiln wallto increase switch and wire life. Old style element connector posts can,and should, be replaced with the newer screw clamp types. Ceramic guidestraws can be inserted through the kiln wall to make future wirings easierand protect the firebrick.
Before the disassembly begins, it is best to have the elements, andany other components that you know will have to be replaced, on hand. Alsohave information on where other replacement parts can be quickly obtained.In addition to having the ceramics suppliers and kiln manufacturers asa source for the elements and other replacement parts, knowing alternatesources for parts can save both time and money.
Specialty companies will supply standard and custom-wound elements,and the variable switches used on most kilns are standard items that areused on electric stoves and heaters, available at appliance supply houses.The push-on type connectors have been standard for two decades. The sameholds true for the supply wire and wall outlets, which are available atany wholesale electric supply.
When ordering the elements, have both the model number and the electricaldata available to assure getting the correct elements. The heating elementsfor any kiln design are available for either 110 volts or 220 volts. Themanufacturer may design a kiln using only 110-volt elements so that withsimple switch wiring changes, the kiln can be set up for either voltage.Crusader, for example, uses pairs of 110 volt elements wired in seriesto make one 220 volt heating unit. Wiring a 110 volt element directly to220 volts will produce spectacular but disastrous results.
For replacement switches and other components, it is best to take oneof the original components with you while you shop as the part number usedby the kiln manufacturer will be different from the component's part number.
The Right Tools
Good tools will make the job easier and safer. Here is the minimum youwill need;
Volt/Ohm Meter The Volt/Ohm Meter has two important uses forthe potter. The first is to detect and measure voltage and the second isto check resistance which will confirm a connection when testing a deadcircuit. The simplest (about $8) will work, but the resistance of a heatingelement will be on the order of 20 ohms (very little) so having adigital meter (about $30) set to the 2-k/ohm scale will help the troubleshootingprocess greatly.
Diagonal Wire Cutters These should be big enough to to allowyou to clip the twisted ends off the elements easily. Too small and theextra effort and movement required to cut the elements may cause damageto kiln walls or asbestos cover plates. End- or plier-type cutters willnot allow you to cut wire in confined spaces like firebrick slots.
Crimpers
These are necessary to make a good electrical connection between thepush-on connector and the high temperature wire. Crimping electrical connectionswith pliers will not make a good connection.
Others
Screwdrivers, pliers, and a Crescent wrench will be necessary.
Hardware
The screws that you remove will not be reusable, but replacements shouldbe available at any hardware store. If there is a marine supply nearby,replacement with stainless hardware will help the next time around. Thecontact blocks are the only electrical component that will be hard to findlocally, and the best source may be your kiln manufacturer.
Stripping The Kiln
The first step is to disconnect the kiln from the power supply. If thekiln is wired directly to the box, turn the breaker off and padlock thebreaker box closed. Electricity is a life and death matter and it is foolishto rely on verbal cautions or paper notes to others. First, inspect theplug. If it is discolored or burned, both the plug and wall receptacleshould be replaced. Cleaning the prongs will provide only a short termsolution because the spring tension in the wall receptacle has probablybeen lost due to the heat generated by the poor connection.
Next, remove the box covering the connections to the elements. Makeeither detailed photographs or a diagram of the connections. Ona kiln with infinitely variable switches, each switch will probably havefour connectors (Figure 1). Two of these will lead to the ends of an elementor element pair, and the other two will be connected to the power source,usually coming from the Kiln Sitter box. The wires from the power cordare connected to the posts marked L1 and L2, and the heating element(s)to H1 and H2. There may be another post (P) for a pilot light. If thereis no pilot light, it doesn't have to be connected.
If wires are broken or break as you remove the box, look carefully atthe location of the broken wires before you disturb them further. The heatnormally sets their shape and they will remain close to the location wherethey broke.
After you have a record of the wiring, use a pair of cutters and cutthe old element wire at each place where it exits the kiln. Use large enoughcutters and brace your hands on the kiln to avoid damage to the firebrickand asbestos cover panels. Keep the clamp-type connectors unless they arebadly corroded.
If the connections are made at the kiln wall with a nut and 28 boltarrangement, they will probably not be reusable and care must be takennot to break the asbestos mounting blocks. By trying to remove the nutswith a wrench, the bolts will probably shear flush with the bottom nutand can be left in place. Once the wires have been cut, you can place theswitch box to one side.
Next, take a pair of heavy diagonal cutters and, from inside the kiln,cut the element free at the last coil. Remove all the coils, but keep atleast one intact to use it as a length measurement for stretching the newcoils. Use caution as you work to keep from breaking the ledges cut inthe firebrick, particularly at the bottom of the kiln. The cut off leadsshould be easy to remove through the kiln wall.
Inspect the high-temperature connecting wires in the connection box.These are covered with a high-temperature insulation and cannot be replacedwith wire covered . with anything less. If the wire can be pulled out ofthe push-on connectors, the connectors should be replaced. The connectingwires will generally be much longer than necessary. If the connector needsto be replaced on either end, cut off about half an inch arid strip abouta quarter inch of insulation.
Replacement push-on connectors are available at appliance supply housesas well as at automotive, electronic, or hardware stores. Take an old connectorwith you to avoid lengthy descriptions. These connectors are 'crimped'onto the end of the wire. (Again, don't use pliers for crimping.)
Replace any switches, wires, and other parts as needed at this time.If you are new at wiring, replace one component at a time to reduce thechances of wiring mistakes. Replacement switches may have an extra postfor connection to a pilot light that can simply be ignored. Look for burnedor loose contact posts by comparing the old switches to a good one. Anyswitch that makes a 'sizzling' sound at any time during a firing shouldbe tossed out.
If you wind your own elements, be sure to twist two strands of heatingwire together at each end of the coil to connect the pigtails. By twistingtwo element wires together, the resistance is lowered and the heat producedin the pigtail will be halved, reducing the stress on the element-to-wireconnection.
Stretch the new coils slightly longer (1 to 3 inches) than the old coillength. This will take several tries as the coil will slowly shrink backa couple of inches after each stretch.
Using The Volt/Ohm Meter
The only tool used during the reassembly and checkout procedure thatis likely to be unfamiliar to most potters is the Volt/Ohm Meter. All ofthe checks described below are made with the meter set as an ohmmeter atthe most sensitive setting. At this setting with the test leads not touchinganything, the reading will show a high resistance, and when they are touchedto each other, the meter will show contact by registering 0 ohms.
To use the meter to check an element, for example, the leads are touchedto opposite ends of the element. If the element is good, the meter willshow a low reading. If the element is broken at any point, the readingwill be high, the same reading as with the leads touching nothing.
With this meter, it is then possible to check for the correct wiringbefore the power is connected. It is also possible to check for any shortcircuits before sparks have a chance to fly.
Putting It Back Together
First, insert the twisted leads through the ceramic straws or wall openings.Starting on one side, carefully replace the new coils in the brick slotsand move around the kiln. There will be a bulge of coil left, so startback in the other direction, gently compressing the coils to work the bulgeout by the time you get three quarters of the way back to the startingpoint.
Gently seat the coils into the grooves. Because the coils have beenstretched long, the tension will hold them in place until after the firstfiring, after which the seating should be checked again. Continue untilall the elements have been installed.
If the coils were wired in pairs, the next step is to connect the pairs.Check with your photos or Figure 2 to confirm the correct wiring. If youhave any tendency toward dyslexia, as I do, making mistakes here is easy.Hold the element lead with a pair of needlenose pliers where it exits fromthe kiln, and bend the element ends to be connected
together neatly so they lie as close to the kiln wall as possible.
Cress Lt 3k Kiln Manual
Make the connections with screw clamp contact blocks then clip off anyexcess element wire. The results of your wiring should be symmetrical withthe last coils connecting just like the first. With the ohmmeter, checkto make sure there is no connection (no change in the meter reading) betweeneach element and the metal parts of the kiln. If you have a digital meter,make a reading of the resistance of each coil or pair.
Cress B23h Electric Kiln
The readings should all be equal. If not, check the connections again.Place the old (or new) Kaowool blanket over the protruding element ends.With the switch enclosure supported on a box or stool to hold it closeto its mounted position, begin to connect the wires from the switches tothe element ends as close to the blanket as possible. Work slowly and methodically,starting at either the top or bottom and connect only one switch at a time.
Clip off any excess element wire after the connection is made. Aftereach switch is connected, use the photos or diagrams to confirm the wiring.Once all of the connections have been made and double checked, carefullymove the switch enclosure into place.
Cress Kilns Manual
Check up and down the entire height for connecting wires that may bepushed against a hot surface like the kiln wall or the ends of elements.Check also for contact blocks or bare wires that may be too close to orin contact with the connectors on the back of switches. Also check forcontact blocks touching the side of the enclosure or wires pinched betweenthe switch box and the kiln.
Mount the enclosure with new screws top and bottom.
Checkout Procedure
(Power disconnected!)
1. Turn all of the element switches to 'Off and the Kiln Sitter 'On.'
2. Using an ohmmeter or continuity checker, check first between thetwo supply lines or prongs on the plug, then between each supply line andthe ground line. The meter should show no connection between any of thewires or prongs.
3. Check to confirm that there is a connection between the ground lineand the kiln or switch enclosure casing. (Ground is the green or bare wire.)
4. Connect the ohmmeter to the two supply lines. Turn each switch onand off to confirm that each makes a connection. If you have a digitalmeter, the resistance should equal the reading you made before connectingthe switches.
5. Turn all switches on and confirm that there is no connection betweeneither supply line and ground.
6. Trip the Kiln-Sitter to 'Off and confirm that there is no connectionbetween the two supply lines. Check again that there is no connection betweeneither line and ground.
If any of the above tests fails, it's time to go back and check thewiring again. If the failure occurred in a specific switch test, it shouldbe easy to trace it by starting at that switch. By disconnecting the switch,you can determine on which side of the switch the problem is. Don't forgetthat the switch could be defective even if it is brand new.
The First Power Up
When the tests all pass, turn all switches off and reconnect the kilnto the power. Turn the Kiln Sitter on and turn each switch on 'High' individually.You should be able to first hear, then smell the element heating.
Turn the switch 'Off and test the next one.
Kiln Model Lt 3k Price
Replace the remainder of the switch-box mounting screws.
Assuming everything went well, be careful with your first firing usingthe new elements. The performance of the old elements degraded too slowlyto be noticed.
Cress Electric Kiln B 23 H Manual
The temperatures during the first firings will come up much more quicklythan you are used to and peak temperatures will be reached hours earlier.Failure to monitor the temperature and cut-off closely could result ina lost load or even the loss of the kiln in the event of a Kiln Sitterfailure.