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Self-Regulating Heating Cable Construction
Raychem XL-Trace self-regulating heating cables are comprised of two parallel nickel-coated
bus wires in a cross-linked polymer core, a tinned copper braid, and a fluoropolymer or
polyolefin outer jacket . These cables are cut to length, simplifying the application design and
installation .
Fig. 1 XL-Trace heating cable construction
With self-regulating technology, the number of electrical paths between bus wires changes in
response to temperature fluctuations . As the temperature surrounding the heater decreases,
the conductive core contracts microscopically . This contraction decreases electrical resis-
tance and creates numerous electrical paths between the bus wires . Current flows across
these paths to warm the core .
As the temperature rises, the core expands microscopically . This expansion increases
electrical resistance and the number of electrical paths decreases . The heating cable
automatically reduces its output .
At low temperature,
there are many
conducting paths,
resulting in high output
and rapid heat-up. Heat
is generated only when it
is needed and precisely
where it is needed.
At high temperature,
there are few conducting
paths and output is
correspondingly lower,
conserving energy
during operation.
At moderate temperature,
there are fewer conducting
paths because the heating
cable efficiently adjusts by
decreasing output, eliminating
any possibility of overheating.
The following graphs illustrate the response of self-regulating heating cables to
changes in temperature. As the temperature rises, electrical resistance increases,
and our heaters reduce their power output.
Temperature
Resistance
Power
Temperature
Constant wattage
Constant wattage
Self-regulating
Self-regulating
Fig. 2 Self-regulating heating cable technology
Nickel-plated copper bus wire
Self-regulating conductive core
Modified polyolefin inner jacket
Tinned-copper braid
Polyolefin or
fluoropolymer outer jacket