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Operator's Manual |
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Installation Operation Maintenance |
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Operator's Manual |
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Installation Operation Maintenance |
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| Safety Furniture Ordering Parts Unpacking Bisque Firing Replacing Elements Location Glaze Firing Element Life Electrical Supply Caution Element Conditioning Controls Trouble Shooting Learning About Elements First Firing For Service Construction Notes |
| SAFETY Please read the following instructions and safety procedures before operating the kiln/furnace.
Electrical Make sure there is an adequate electrical supply available for the kiln/furnace chosen (see electrical supply). Install a disconnect or other shut-off device within 4 metres of the kiln/furnace. Always disconnect power while servicing. Shock Hazard Exposed elements are an electrical shock hazard while the kiln/furnace is firing. See note Burn Hazard Do not open the kiln/furnace while it is firing. The exterior surface may also become hot enough to cause burns - do not touch while firing. Ventilation It is recommended that all kilns/furnaces be vented outside to eliminate the risk of exposure to hazardous fumes. We recommend a system that vents directly from the firing chamber (Orton VentMaster, for example). Clearance The outside of the kiln/furnace will be hot while firing. Do not lean anything against the side of the kiln/furnace. Do not place flammable materials above the kiln/furnace. Ensure that the location allows adequate clearance (see page 2). For kilns/furnaces with top vents be sure to provide adequate ventilation for the hot air being vented. Temperature Never exceed the maximum recommended temperature for the particular model kiln/furnace. Please refer to the section Element Life, on page 8. Monitoring Always be present while firing to monitor the operation of kiln controls, and/or shut off devices, to make sure that a firing has been successfully completed. Lids Lids of top load kilns (R models) are designed to stay in the open position without the need of chains or supports. A secondary restraint (such as a hook over the handle, anchored to the wall or ceiling) is advised, as a precaution against the lid being bumped. Stands Top load kilns (R model) kilns should only be used with the stands provided. The floor under the kiln/furnace should be of a non-flammable material. Glass Firing When R model kilns are being used for glass work there should be a metal plate installed between the kiln bottom and the stand (it is possible that molten glass could melt through the brick, and it should not fall onto the floor below). This instruction manual is an important part of your kiln/furnace and should always be available to the operator and service personnel. Carefully remove any packing material from the outside and from within the firing chamber. Remember to check for items which may have been packed with the kiln/furnace - refer to the packing slip to account for all items shipped. When the firing chamber is empty it must be carefully cleaned to remove bits of packing material and dust. Use a vacuum cleaner with a crevice nozzle, being careful to clean out element grooves. The kiln/furnace was carefully packed at our factory, but it is possible that it has been damaged in transit. If so it is important that you:
There should be:
The kiln/furnace must be connected to the correct electrical supply - the design voltage and amps are printed on the specifications label. The kiln/furnace should have its own circuit, with a shut-off device (disconnect or plug/receptacle) within 4m/12'. This gives the ability to shut off the power in the event of a problem, or for servicing. The current (amp) draw must not exceed 80% of the capacity of the fuses, or circuit breaker, protecting the circuit. The supply cabling should be installed by an electrician, and must be of the correct gauge for the load. The supply cable should not touch the sides of, or pass underneath, the kiln/furnace. The most common cause of a new kiln/furnace firing to slowly, or failing to reach temperature, is low voltage. At time of ordering you will be asked to supply the actual voltage available (as checked by a reliable voltmeter). If an error has been made in ordering, and the available voltage is not suitable, we can supply a new set of elements for the correct voltage, at additional cost. It is usually possible to convert a single phase kiln/furnace to three phase, or a three phase to single phase, without changing elements. This will usually require changes to the cable, contactor (or other switch gear), and fuses or breaker. The kiln/furnace may have one of a wide variety of controls. Separate instruction manuals are provided for the control supplied. These should be read carefully. Notes on popular controls for hobby kilns: Switches - Three Heat (four position) LO, MED, HI, OFF This switch operates 2 elements on 220V (some types operate on 120/220V). On LO the two elements are connected in series for 25% power. On MED one element is on full for 50% power. - Infinite Heat (can be set to any position) LO-HI, OFF "Sunvic" Infinite Heat 0-100%, OFF Infinite heat switches may operate one or more elements. Sunvic switches may control the whole kiln by switching relays or a contactor. This type of switch turns the full power to the element(s) on and off at a rate determined by the setting. A pilot lamp may be connected so that it is on the whole time the switch is on, or so that it cycles on and off with the element(s). Pyrometer - A pyrometer indicates the temperature inside the kiln, but does not offer any control or shut off. The most common type is analog, with a needle that moves across a graduated scale. This type is not noted for its accuracy, but is still useful as a guide to the kiln temperature. This type is sensitive to the resistance of the thermo- couple - for maximum accuracy make sure that the thermocouple and leadwire are matched to the pyrometer.
Kiln Sitter - Shuts the kiln off as determined by the pyrometric cone. Before the first firing, check the alignment of the Release Claw to the Trigger Plate, using the Firing Gauge provided. Detailed instructions are provided in the Kiln Sitter manual. The Kiln Sitter manual recommends that a peephole be left open throughout the firing. This recommendation does not apply to kilns using direct venting systems (such as the Orton KilnVent). Automatic - AutoFire This control can be programmed to control rate(s) of heating and hold time(s) at temperature. Note that cone values set by the control may not be exactly as experienced by actual cones. It is recommended that test firing be done, with witness cones. Thermo- Automatic controllers and pyrometers measure the kiln temperature couples through a thermocouple, which passes through the wall of the kiln and should protrude into the chamber at least 25mm/1". The thermocouple will need to be replaced periodically. The leadwires connecting the thermocouple to the control are colour coded - yellow is positive, red is negative. It is very important that the leadwire be connected the correct way around at both ends. The negative leg of the thermocouple is magnetic, the positive leg isn't. Sunvic switches are supplied with Kiln Sitters, Automatic controls are supplied with circuit breakers. When a Sunvic or Automatic control is OFF, there may still exist a potential shock hazard from the kiln elements. THE BREAKER OR KILN SITTER MUST BE OFF BEFORE OPENING THE KILN. A label stating this warning should be located on the top front of the wiring cover, if this potential hazard exists. Before using the kiln/furnace for the first time it is important to make sure it is dry throughout. The insulation can absorb moisture during shipping/storage - if there is a noticeable amount this should be removed by heating to ±150oC/ 300oF and holding as long as necessary. The first firing will serve to test the control function. The firing need only be to a relatively low temperature - 020 cones should be supplied with a Kiln Sitter, or automatic controls can be set to 650oC/1200oF. The initial firing can also be used for the optional process of element conditioning, whereby a protective oxide coating is built up on the elements. This is particularly important if the kiln/furnace will be normally fired to in the range of 1200-1300 oC (2200-2400 oF), or under a reducing atmosphere. This is not recommended if normal use will not exceed 1050oC (1922oF), or for fibre lined kilns. Please refer to information on page 8 regarding life expectancy and element conditioning. The bottom kiln shelf should be supported at least 15 mm above the hearth, and each level of shelves above must be supported in at least three points with props of equal size and height. Make sure that props in successive levels are placed directly above each other. The shelves must allow 20 mm clearance from kiln walls, to allow for circulation and to reduce the risk of kiln damage. All shelves for glaze firings should be coated with kiln wash (on the top side only, do not use kiln wash on any part of the kiln itself). Greenware may be stacked two or three pieces high, provided they are well supported, to avoid warpage - this is best done by placing like sizes rim to rim and bottom to bottom. Smaller items can be placed inside of larger ones, but allow for shrinkage. Generally a bisque firing should rise slowly to 650oC/1200oF. Set switches to LO (infinite heat to 3, Sunvic to 25%), with the lid propped open, for about 1½ hr to ensure thorough drying. Then increase to MED (5, or 50%) for an hour, which should bring the kiln through 650oC/1200oF. Switch to HI (100%) to complete the firing. For automatic controllers use a single ramp of 140-200oC/250-350oF per hour, or use multiple ramps to simulate the above procedure (Orton AutoFires are preprogrammed for some firings - see the separate manual). These are general recommendations only - adjustments should be made to allow for thick walled ware, very heavy (or light) loading, and for personal experience. One peephole should be left open throughout the firing (unless a direct venting system is used). No two pieces should touch, and glaze should not contact kiln shelves. Stilts can be used for earthenware and other low temperature firings. For porcelain and stoneware the bottoms should be free of glaze, so that they can be placed directly on shelves. This minimizes the risk of distortion during firing. Glaze firings of pre-bisqued ware can be fired relatively quickly. Set switches at MED (5, or 50%) for one hour, to protect against thermal shock. Then set to HI (100%) to complete the firing. One peephole should be left open (unless a direct vent is used). It is always advised that test firings be done to determine correct firing rates for individual requirements. Always be present when the kiln is being fired, regardless of the automatic controls being used. Any mechanical equipment can malfunction. The operator is responsible for monitoring, adjusting and maintaining the kiln/furnace and controls. The kiln warranty does not cover the effects of overfiring, regardless of the cause. Make a habit of checking shut-off devices for proper operation, and turn all switches to OFF after each firing. A malfunction could result in the kiln/furnace overfiring, causing extensive damage. Our staff is always available for advice or assistance - don't hesitate to call, just to make sure.
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Problem
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Causes |
Solution |
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Kiln will not heat |
Not connected to power Fuses blown/breaker tripped Kiln Sitter reset button out Kiln Sitter timer off No control power Supply cable burned |
Check cord/plug and main supply switch Replace fuse(s)/reset breaker With weight set, push button in Set timer ½ hour more than firing Check control switch or fuses Call for service |
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Elements not heating |
Element connection burned (in series connection one element out will affect others) Element coil burned through Switch not working (check other elements on same switch) Control alarm/error |
Replace connector (element may also require replacement), tighten others Replace element Replace switch Refer to control manual |
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Uneven heating |
Element not heating Incorrect heat distribution |
See above Contact supplier |
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Fuse blows/breaker trips during firing |
Fuse/breaker rated too low Inadequate supply wiring Poor connection - at element, switch, cable or supply wiring |
Should be 25% more than amps on kiln nameplate Call electrician Check all connections (look for signs of overheating/burning) |
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Cable or plug becomes hot |
Inadequate supply wiring Loose connection in plug or receptacle |
Call electrician Clean and tighten connections - replace if noticeably overheated |
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Kiln not keeping up with automatic controller |
Control ramp rate set at more than kiln can keep up with |
Adjust control settings |
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Increase in firing time |
Aged elements Poor connection Change in supply voltage (check with Hydro) |
Replace elements See above May be necessary to change elements |
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Control or pyrometer reads negative |
Thermocouple connection reversed |
Correct thermocouple connections (be careful not to reverse thermocouple leadwire at both ends) |
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Pyrometer does not indicate |
Burned out thermocouple |
Replace thermocouple |
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Analogue control goes to top of scale |
Burned out thermocouple |
Replace thermocouple |
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For service Please call 1-800-296-5456 Before calling for service, please have kiln model and serial number, kiln voltage, and position of element (if applicable) on hand.
Please specify make, model, serial number and voltage. For elements, please specify location. For top load kilns start with number 1 at the top, and count down. For front load kilns count down the left side, across the bottom, and up the right side (elements across from each other will be the same). Elements will drop in power after the first couple of firings, and then be quite steady for a long time, until their age catches up with them. If a kiln's firing time is gradually getting slower and slower, it is probably old elements (an abrupt slowing in firing time, with all elements working, may be your supply voltage - check with your power company). Many people prefer to replace all elements at once. This is not necessary, as the new element will not affect the other elements in the kiln (unless the new element is connected in series with other elements - in this case the older elements will tend to be worked harder, which will shorten their life even more). That said, If all elements are old when one element fails, it is generally desirable to replace all of them, rather than face another element failure (and incomplete firing) in the future.
Element replacement is not difficult and most people do their own: Top Load Kilns 1. Disconnect the power supply to the kiln and remove wiring cover. 2. Make note of correct connection sequence. 3. Disconnect element from connector or terminal. 4. Straighten tail and pull out from inside kiln. 5. Pull coil from groove, being careful to minimize brick damage. Needle nose pliers may be helpful. 6. Carefully chip any foreign matter from groove, and vacuum. 7. Bend one element tail at 90o to the coil, and insert through kiln wall. 8. Feed element into groove. Be sure to push coil well into the groove. Open coil slightly and bend, to suit corners. 9. If element is not long enough, stretch out the last few feet of the coil as necessary. 10. Bend second tail at 90o and insert through wall. 11. Connect the two tails to the supply wires, and snip off excess wire. 12. Check condition of other element and switch connections, and tighten as required. Front Load Kilns 1. Disconnect the power supply to the kiln and remove wiring cover. 2. Make note of correct connection sequence. 3. Disconnect element from connector, being careful of other element connections. 4. Draw the element to be replaced from inside the kiln. 5. Carefully chip any foreign matter from groove, and vacuum. 6. Element legs must lie flat and parallel. Check that the hairpin dimension is correct, allowing both legs to lie flat in their grooves. 7. Slide new elements into the grooves, guiding the tails through the back wall. Push the tails all the way through, with the legs lying straight in the grooves. 8. Prepare jumper wires and/or supply wires for reconnection. 9. Place the connector over the tail, and pull the tail from the end to provide tension on the coil. Tighten the connector and cut off any excess tail length. 10. Check condition of other element and supply connections, and tighten as required.
There are too many variables for the wire manufacturer to be able to provide definite life expectancies for elements. In general, as operating temperatures go up, life expectancy goes down. Harmful atmospheres will also reduce element life. Element wire can be damaged by some foreign materials, such as glaze splashes. Debris in element grooves can shorten element life by reducing the element's ability to radiate heat. The following guide has been provided by one wire manufacturer (Kanthal) to illustrate the effect of operating temperature (the figures are for wire temperature; kiln temperature will be approx. 28oC/50oF lower):
Reducing atmospheres, caused by the introduction of gas, charcoal, wood, paper, or other, will strongly affect life expectancy, by impairing the oxidization of the element wire. Foreign materials will also affect oxidization. Steam from the kiln load will also affect element oxidization, as well as contributing to corrosion of the case. This is why ventilation during the early stages of bisque firing is important. Element Conditioning
From the Kanthal Handbook, referring to their FeCrAl alloys (i.e. A-1 alloy): "The durability of resistance alloys in air at high temperatures is greatly increased by an oxide surface layer formed by a reaction with the oxygen of the air. The protective nature of this oxide layer is proportional to its area and depth. Foreign matter usually interferes with the formation of the oxide layer, and this causes a reduced life. ... At high temperatures the protective layer of Kanthal materials consists almost entirely of aluminum oxide. This has a light grey colour and good chemical resistance. At temperatures below 1000oC (1832oF) the oxide layer has a dark colour since the aluminum oxide is impure." In order to protect elements from the effects of harsh environments, it is very desirable to condition the elements, by pre-oxidizing them. This is accomplished by firing them to a temperature of 1050oC/1922oF and soaking for several hors, 7-10 if possible. The process is enhanced by allowing good air flow into the kiln - leave the peepholes open, or the KilnVent on. If you are doing reduction firings in an electric kiln it is desirable to periodically re-oxidize the elements, for best life expectancy. The results of element conditioning can be quite dramatic. It may not have much affect for normal, low temperature firings, but can be significant for harsh operating conditions. If you are interested in learning more about element wire, or element design, contact us and we will be pleased to provide more information. Construction
Notes Brick thickness is more important for strength than overall wall thickness. On all R models we use 3" brick for the sides, lid and base. For the 10 and 16 cu. ft. models the 3" brick gives a significantly sturdier wall than 2.5" brick would. Why we don't use lid chains or supports: Chains can be dangerous - you could end up with the lid on your head! Supports can get in the way of loading, and can be awkward to manipulate (and they are one more mechanical part that can misbehave). Our hinges are designed to hold the lid in the full open position, without chains or supports, for maximum access and convenience. Why we don't offer double insulated lids: Kilns need to breathe, to allow moisture to escape. The problem of moisture collecting inside the case is a lot worse in a lid with a metal cover - we've heard of water running out when the lid is opened!, and have seen stainless steel cases rusted through. How we provide even heat distribution: Kilns will naturally tend to be cool in the bottom and in the top, due to heat loss through the floor and lid. Putting an element in the floor is one way of partially addressing the problem, but this weakens the floor, and the groove tends to get filled with debris - which reduces element life. We install hotter elements in the top and bottom of the sidewalls, specially designed (and proven by experience) to provide even distribution. In our small and medium size kilns (up to 7 cu. ft.) this allows us to do away with multiple switches to adjust heat distribution. In our larger kilns (10 and 16 cu. ft.) we do include switches, to allow fine adjustment for varying loads. Note: in our design the switches control relays; they do not switch the power themselves, as do standard infinite heat switches - this gives much longer switch life.
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