Heat Tracing Questions

Many modern types of heating tape do not use traditional resistance wire heating elements.

Instead they use Positive Temperature Coeficient materials as the heat source.

PTC elements have a lower resistance when cold and a higher resistance when hot, this change in resistance is very, very much greater than for metalic resistance wire.

A traditional resistance heating element might use 10 amps at freezing point and 9.5 amps at boiling point.

A PTC heater might use 10 amps at freezing point and almost nothing at boiling point. At sub zero temperatures it might use a lot more than 10 amps.

PTC heating tapes are much safer than the old resistance sort, since they cant overheat, any increase in temperature reduces the heat output. The operating temperature is fixed in manufacture, many types are available.


The MINIMUM size of circuit breaker is determined by the need to avoid tripping when first turned on in cold conditions. The actual operating current may exceed the MCB rating, but only briefly and should remain under the thermal trip curve.


The MAXIMUM circuit breaker size is determined by two factors. Firstly, if the heating tape suffers internal short circuit or external damage then an over-large circuit breaker makes "a bigger bang" with more risk of fire or other damage.

Also the PTC heating tape consists of two copper wires that run the length of the tape, with the PTC material between them. Like any other conductor, these copper wires have a finite current carrying capacity and that limits the size of OCPD that can be used. They are however pushed much harder than copper house wiring cables.


For a very large installation of PTC heat tape, circuits may need some form of sequential start to avoid overloading the DNO cut out fuses or any sub mains.


Operating temperatures vary from about 10 degrees to protect water pipes from freezing, up to about 70 degrees, to avoid domestic hot water cooling in the pipes.


Another advantage of PTC heaters in tape form or otherwise, is that they are not sensitive to voltage variations within reason. At a lower line voltage they will draw more current and maintain the same temperature.


ELV PTC heating mats are available to preserve the lives of premature infants, to warm pets, to warm fermentation vessels for home wine making, and for many other purposes. They are built into heated car seats.

Many modern types of heating tape do not use traditional resistance wire heating elements.

Instead they use Positive Temperature Coeficient materials as the heat source.

PTC elements have a lower resistance when cold and a higher resistance when hot, this change in resistance is very, very much greater than for metalic resistance wire.

A traditional resistance heating element might use 10 amps at freezing point and 9.5 amps at boiling point.

A PTC heater might use 10 amps at freezing point and almost nothing at boiling point. At sub zero temperatures it might use a lot more than 10 amps.

PTC heating tapes are much safer than the old resistance sort, since they cant overheat, any increase in temperature reduces the heat output. The operating temperature is fixed in manufacture, many types are available.


The MINIMUM size of circuit breaker is determined by the need to avoid tripping when first turned on in cold conditions. The actual operating current may exceed the MCB rating, but only briefly and should remain under the thermal trip curve.


The MAXIMUM circuit breaker size is determined by two factors. Firstly, if the heating tape suffers internal short circuit or external damage then an over-large circuit breaker makes "a bigger bang" with more risk of fire or other damage.

Also the PTC heating tape consists of two copper wires that run the length of the tape, with the PTC material between them. Like any other conductor, these copper wires have a finite current carrying capacity and that limits the size of OCPD that can be used. They are however pushed much harder than copper house wiring cables.


For a very large installation of PTC heat tape, circuits may need some form of sequential start to avoid overloading the DNO cut out fuses or any sub mains.


Operating temperatures vary from about 10 degrees to protect water pipes from freezing, up to about 70 degrees, to avoid domestic hot water cooling in the pipes.


Another advantage of PTC heaters in tape form or otherwise, is that they are not sensitive to voltage variations within reason. At a lower line voltage they will draw more current and maintain the same temperature.


ELV PTC heating mats are available to preserve the lives of premature infants, to warm pets, to warm fermentation vessels for home wine making, and for many other purposes. They are built into heated car seats.