Types Of Electrical Heat Tracing Systems

Electric trace heating cable can be divided into four distinct product classifications:

1.Self-regulating heating cables (variable watt output)

Self-regulating heat type uses a conductive core. This core becomes more conductive in colder weather, increasing the wattage used in response to dropping temperatures. This is ideal for homeowners and/or businesses that have annual problems with icicles or ice dam formations on the roof or gutters. Self-regulating heat tracing tapes are cable whose resistance varies with temperature - low resistance for temperatures below the cable set point and high resistance for temperatures above the cable set point. When the cable temperature reaches the set point the resistance reaches a high point and resulting in no more heat being supplied.

2.Parallel circuit heating cables (constant watt output)

These shortcomings necessitated the invention of parallel resistance heaters. They are also known as Constant Wattage or Constant Electric Power “Zone” cables. A constant wattage cable is composed of multiple constant electric power zones and is made by wrapping a fine heating element around two insulated parallel bus wires, then on alternating sides of the conductors a notch is made in the insulation. The heating element is then normally soldered to the exposed conductor wire which creates a small heating circuit; this is then repeated along the length of the cable. There is then an inner jacket which separates the bus wires from the grounding braid.

3. Series circuit, Mineral insulated (MI) cables (constant watt output)

A series heating cable is made of a run of high-resistance wire, insulated and often enclosed in a protective jacket. It is powered at a specific voltage and the resistance heat of the wire creates heat. The downside of these types of heaters is that if they are crossed over themselves, they can overheat and burn out, they are provided in specific lengths and cannot be shortened in the field, also, a break anywhere along the line will result in a failure of the entire cable. The upside is that they are typically inexpensive (if plastic style heaters) or, as is true with mineral insulated heating cables, they can be exposed to very high temperatures. Mineral insulated heating cables are good for maintaining high temperatures on process lines or maintaining lower temperatures on lines which can get extremely hot such as high temperature steam lines.

4. Skin effect heating

Skin effect is the tendency of an alternating electric current (AC) to become distributed within a conductor such that the current density is largest near the surface of the conductor, and decreases with greater depths in the conductor. The electric current flows mainly at the "skin" of the conductor, between the outer surface and a level called the skin depth. The skin effect causes the effective resistance of the conductor to increase at higher frequencies where the skin depth is smaller, thus reducing the effective cross-section of the conductor.

dpstar is the manufacturer and supplier of electrical heat tracing in Malaysia. Please send your inquiry to marketing@dpstar.com.my. Visit www.dpstar.com.my for more information.