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HOME --> MELT SHOP EQUIPMENT --> Kit Furnace Resistance Melting System

Foundry Products:
Kit Furnace Resistance Melting System

For Melting, Holding or Filtering
Aluminum or Zinc

This highly efficient furnace is the culmination of over nineteen years’ experience in the aluminum industry—listening in the field every day to what YOU, the customer, wants from a furnace. 
 

350#/Hour Melt Rate

This rating is based on the following typical test conditions:

We were pouring a 50 lbs part at a pouring temperature of 1,380°F. Our element chamber was being limited to 1,700°F to maximize the life of the heating elements. We were using a 1,200 lbs bowl and limiting our draw down to 2”. 
 

Efficiency

When the lid is in place, the ceramic fiber insulation gives us a “thermos bottle” effect, creating the ideal holding furnace. Our design uses slightly less than 3KW per hour when holding at 1,200°F and can melt for less than .24KW per hour per pound. 
 

The Numbers

The furnace diameter is 61”, and the height is 47”. It has a 4” ceramic fiber lining and can be configured for many standard silicon carbide bowls—ranging in size from 400 to 1,200 lbs. The standard installation will require a 3-phase, 480-volt, 100-amp electrical service. The furnace uses twelve separate heating element modules that can be replaced individually from the outside of the furnace—while the furnace is still at its melting temperature!! 
 

The Advantages 

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  • Promotes a cooler, quieter, cleaner working environment.
  • No furnace flue, avoiding the need to cut holes in your roof as well as some EPA requirements.
  • Round design allows you to locate the incoming power, drain hole, lid, or dip out station on any side.
  • Bowl size can be converted quickly and easily.
  • A bad heating element can be replaced in 15 minutes—while the furnace is still up to operating temperature!
  • A full proportional state-of-the-art SCR driven control panel with built in ON/OFF backup control.
  • A true 100% microprocessor based “CASCADED” temperature controller eliminates temperature overshoot.
  • Full voltage heating elements eliminate the need for a step down transformer and heavy gauge wires.
  • Built-in bowl leak detector circuit.
  • Reusable lightweight ceramic fiber upper ring.
  • Lightweight design allows you to move the furnace with most common forklifts—no need for riggers.
  • Heavy ¾” top plate can take a lot of abuse.
  • Ceramic fiber lining cannot be thermally shocked, so there is no need for yearly repairs.
  • Built-in alarm system with provisions for commercial alarm services.
  • The elements are individually fused with optional ELEMENT OUT indicators to identify an open element.
  • No need to remove the bowl while replacing or repairing the elements or insulation.
  • Simple, uncomplicated installation can be accomplished in days instead of weeks.
  • Furnace connections are only 10GA wire, connected through flexible conduit, allowing for some mobility.
  • Available in KIT form—We will provide the drawings, elements, and controls. Save money and build it yourself!! 
     

The Myth About Heating Elements
Why Smaller Gauge Elements Make Better Sense

The American Foundrymen have always stuck firmly to the belief that bigger is better. Why use a 12-oz. Hammer when you own a perfectly good 15-pound sledge? The truth is, it is best to use the correct tool for the job. Choosing the wrong tools (or elements) can cost you in the end. The first price you must pay is right up front, because larger diameter elements have lower electrical resistance and, as a result, you must use lower voltages to operate your furnace. This means that you must buy a step down transformer—typically a $2,000 purchase. If a furnace requires an SCR power control system—and most designs do—you are forced to buy a more expensive “phase angle fired” SCR drive in order to withstand the induction characteristics of the transformer.

On top of all of this, you are paying more for all of the hardware in your control panel, more for the conduit, wire, and hardware to install your furnace, and more for the labor to hook it all up! Why? Because any good electrician or electrical engineer will tell you that when you lower the voltage you must increase the amperage to maintain the kilowatts necessary for the job. In the electrical industry, the greater the amperage, the more expensive the hardware and its installation. Portable low voltage furnaces require very expensive (special order) plugs and sockets, while full voltage systems use cheap, off-the-shelf components. 

The Real Causes of Element Failure

The obvious and most common cause of heating element failure is contamination. It is extremely important to properly maintain the soft seal around the top of the crucible bowl. One drop of aluminum on any heating element—large or small—will burn through the element, usually in less than 48 hours. All heating element manufacturers void the warranty when contamination is discovered. This usually includes the chemicals (chlorine and sodium) commonly found in fluxes and metal modifiers. Most furnace manufacturers realize that you will eventually splash something on your element, which, to their advantage, voids any warranty claims.

The other major reason elements fail is due to overheating; not the overheating of the furnace, but the overheating of the element itself. This is usually the result of a poorly or cheaply designed control system. Never buy a furnace that doesn’t actually limit and control the element temperature! Many furnaces do not even have a thermocouple in the heating element section of the furnace! And, many of the furnaces that do have it only for “high limit” or NFPA fire protection requirements, which only require keeping the furnace from starting a fire and DO NOT protect the element. 

How do you know if the elements are being properly protected?

Ask questions and get it in writing! Ask for a letter from the manufacturer stating that this furnace has a fully proportional “cascaded” temperature control system. Watch out!—Some manufacturers use a proportional METAL temperature controller and then use an ON/OFF override to protect the elements. This does protect the element, but the intervention of the ON/OFF override can confuse the proportional metal temperature controller, resulting in metal temperatures that overshoot wildly. Another thing to watch for is contactor operated ON/OFF temperature control systems. There have been numerous studies that have shown that constantly expanding an element 100% and then contracting the element 100% with an ON/OFF temperature control system greatly reduces the life expectancy of any element. And, the money saved by building a cheap control panel isn’t passed on to the customer anyway. 

The Disadvantages of Low Voltage Elements 

Why put all your eggs in one basket?

That’s what happens with low voltage elements. The most common system uses three heating elements, installed from the inside of the furnace. What happens when you damage one? YOU ARE DOWN—Or limping at best…you have lost one-third of your power! Usually, only the most experienced SCR specialists can tell the difference between a shorted element, a shorted transformer, and a bad SCR drive. This is due to the induction characteristics of the transformer,

which masks the symptoms by throwing everything out of balance when the elements go out of balance. To make matters worse, many designers undersize the SCR system, which is fine when everything is balanced, but the SCR can be damaged by the surge from the transformer when the element fails.

To repair the low voltage element, you have to shut down the furnace, dip out the metal, remove the crucible, wait for it to cool down, then replace or weld the element and reverse the process. Welding the element can overheat or oxidize the alloy and lead to another failure in the near future. Replacing the element can cost thousands of dollars when it finally arrives, and you still might break the bowl when you heat it back up. The losses from all of this down time can really add up, and it is not uncommon for this to happen several times per year. 

The Advantage of Full Voltage Elements

The Kit Furnace’s full voltage systems use twelve separate heating elements, so, if one is damaged, only one-twelfth of the power is lost. You can continue to run until repairs are scheduled. Because there is no transformer involved, troubleshooting is as simple as looking for a blown fuse. Our modular heating elements can be replaced in less than 15 minutes—while the furnace is still full of molten metal! NO DOWN TIME! We carry replacement elements in stock, available for immediate shipment.

 
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