Content:
Element types
Overview: Appliance element types
Element types
The embedded element type
The wire in the embedded element type is surrounded by solid or granular insulating material.
The supported element type
The wire, usually in coil form, is placed on the surface, in a groove, or a hole of the electrically insulating material. Kanthal® AF and Nikrothal® 80 are generally the most suitable materials. To avoid deformations in horizontal coils, the wire temperature should not exceed the values given in the diagram on this page.
The suspended element type
The wire is suspended freely between insulated points and is exposed to mechanical stress caused by its weight, spring force, and, in some cases, external spring forces. Nikrothal® 80 and Nikrothal® 60 are the most suitable materials.
Comparison of embedded, supported, and suspended elements for electric appliances
| Element type | |||
| Embedded | Supported | Suspended | |
| Mounting of wire | Embedded in electrical insulation | Fully supported by electrical insulation |
Supported at points only |
| Heat dissipation from wire | Conduction | Radiation Convection Conduction |
Convection Radiation |
| Shape of wire | Round wire (Ribbon) | Round wire | Round wire (Ribbon) |
| Wire surface load, W/cm² | <=25 | 1-10 | 3-15* |
| Wire surface load, W/in² | 6-160 | 6-65 | 20-100* |
| Hot strength of wire | Normally unimportant | Sometimes important | Often important |
| Access to ambient air | Limited | Rarely limited | No limitation |
| Electrical insulation requirements |
Important for life and safety | Rarely a problem | Problem only when wire sags |
* If immersed in water, even higher surface load is possible depending of water velocity. 20-60 W/cm2, 130-390 W/in2
Permissible D/d ratios as a function of wire temperature
Overview: Appliance element types
Embedded elements
Element type: Cartridge elements, powder filled
Characteristics: 
Straight wire or coil is wound on a threaded ceramic body and insulated by granular insulating material (MgO) from an enveloping metal tube. Terminals are at one end of the element. Elements are compressed when high-loaded.
Recommended alloys: Nikrothal® 80 in straight wire elements. Kanthal® D in coiled wire elements.
Surface load: On tube: 10–25 W/cm2 (65–161 W/in2) for elements with straight wire. Other types: about 5 W/cm2 (32 W/in2).
Typical applications: Metal dies, plates, refrigerators.
Element type: Heating cables and rope heaters
Characteristics: 
Wire is wound on a fiberglass core and insulated by PVC or silicone rubber (higher temperatures). Fiberglass insulation permits even higher temperatures. Heating cables with straight or stranded wires, sometimes enclosed in aluminum tube, also occur.
Recommended alloys: Kanthal® D, Nikrothal® 40 and Nikrothal® 80.
Surface load: Wire: <1 W/cm2 (<6 W/in2) on wire for PVC and silicone rubber, 2–5 W/cm2 (13–32 W/in2) for fiberglass insulation.
Typical applications: Defrosting and deicing elements, electric blankets and pads, car seat heaters, baseboard heaters, floor heating.
Element type: Metal sheathed tubular element
Characteristics: 
The heating coil is insulated from the encasing metallic tube by granular material (MgO). The tube is compressed to a round oval or triangular shape. Terminals may be at either end or at one end of the element.
Recommended alloys: Kanthal® D in elements with sheath temperature >700°C (1,290°F). Nikrothal® 80 in elements with sheath temperature >700°C (1,290°F).
Surface load: Wire: Normally 2-4 times the element surface load. Element: 2-25 W/cm2 (13-161 W/inch2).
Typical applications: Hot plates, domestic ovens, grills, deep fryers, immersion heaters, dishwashers, washing machines, radiators, storage heaters, air heaters, oil heaters.
Supported elements
Element type: Ceramic cartridge elements
Characteristics: 
Most common design consists of round ceramic bodies with longitudinal holes or grooves for heating coil. Elements are often in metallic tube with terminals at one end. Often provisions are made to avoid excessive sagging of the coil when the element is operating vertically.
Recommended alloys: Kanthal® A-1 or Kanthal® D for horizontally operating coils. Nikrothal® 80 (usually) for long vertically situated coils when sagging is a problem.
Surface load: Wire: 3–6 W/cm2 (20–40 W/in2). Element: 2–5 W/cm2 (19–39 W/in2).
Typical applications: Liquid heating, storage heaters.
Element type: Other ceramic elements
Characteristics: Coiled and straight wire is located on smooth ceramic tube or in grooves or holes of ceramic bodies of various shapes (plates, tubes, rods, cylinders, etc.).
Recommended alloys: Kanthal® A-1, Kanthal® AF and Kanthal® D. Nikrothal® 80 (for pencil bars).
Surface load: Wire: 3–9 W/cm2 (19–58 W/in2).
Typical applications: Boiling plates, air guns, hobby kilns, radiators.
Element type: Quartz tube heaters
Characteristics: Heating coil or porcupine shaped wire is placed inside quartz tube (or tube of glass ceramic). When the element is operating vertically or at an angle, the coil should be tightwound and pre-oxidized. For horizontal use, the relative pitch is 1.2–2.0.
Recommended alloys: Kanthal® AF.
Surface load: Wire: 2–8 W/cm2 (13–52 W/in2). Element: 4–8 W/cm2 (26–52 W/in2).
Typical applications: Space heating, infrared heaters, industrial infrared dryers etc.
Element type: 
Bead insulated coils or stranded wire
Characteristics: Heating coil, or stranded wire, is insulated by ceramic beads. With beads having two holes heating mats are made.
Recommended alloys: Kanthal® D. Nikrothal® 80 (for panel heaters).
Surface load: Wire: 1–8 W/cm2 (6–52 W/in2).
Typical applications: Mats for in-situ annealing of welded parts, panel heaters.
Suspended elements
Element type: 
Suspended coils
Characteristics: Wire coil is supported at intervals, e.g. by ceramic holders.
Recommended alloys: Nikrothal® 80, Nikrothal® 60 and Nikrothal® 40.
Surface load: Wire: 7–8 W/cm2 in forced air, 3–4 W/cm2 in natural convection.
Typical applications: Air heaters such as: laundry dryers, fanheaters, land dryers.
Element type: Porcupine elements
Characteristics: 
Heating conductor consists of hairpinshaped wire bends protruding in all directions, with hole in center. Element is supported by central insulated rod or insulating tube around its circumference.
Recommended alloys: Kanthal® AF and Nikrothal® 80.
Surface load: Wire: 4 W/cm2 (26 W/in2) in natural convection. For toasters: 12 W/cm2 (77 W/in2) in forced convection.
Typical applications: Hot air guns, radiators, convectors, tumble dryers, domestic ovens with forced convection.