Wires Used for Heating Applications
We work mainly with three different groups of wires:
- Copper wire for control panels
- Nichrome (NiCr) wire for heaters
- Thermocouple wires
Resistance wires for open coil air heaters
Nichrome (NiCr) is a brand name for a nickel-chromium resistance wire, a non-magnetic alloy of nickel and chromium. A common alloy is 80% nickel and 20% chromium, but there are many others to accommodate various applications. The higher the Nickel content of the wire, the higher the cost. It is silvery-grey in color, it's corrosion resistant, and has a high melting point of about 2550degF. Due to its relatively high resistivity and resistance to oxidation at high temperatures, it is widely used in heating elements including open coil air heaters. Nichrome is wound in wire coils in all different gauges. To increase flexibility (required for flexible in silicone rubber heaters), it can be stranded meaning several smaller sizes wires are strung together).
Another popular resistance wire used for open coil air heaters is Kanthal.
Thermocouple wires are made out of two different materials. The combination of the wire materials depends on the wire calibration like J, K,T. Thermocouple wire can not be subsistuted with copper wire!! Thermocouple wire can be ordered with high temperature insulation, while for the thermocouple extension wire there is usually no need for the high temp protection. Thermocouple extension wire may not be used in the sensing point, because of this lower ambient temperature limit. A thermocouple extension wire has typically a brown outside insulation. The maximum length of an extension wire should not exceed 100ft with 20 AWG and avoid electromagnetic interferences.
Thermocouple wires are sold:
- with standard limits of error
- with special limits of error