What temperature can a cable withstand? It almost always depends on the insulation material it is made of, not just on the conductor. In the Caviterm range, silicone cables reach 180°C, PTFE cables 260°C, impregnated glass fibre cables between 320°C and 400°C, and mica cables up to 500°C. Special constructions in special glass fibre and mica go up to 600°C. You will find all the details below.
When a cable short-circuits and discharges near a furnace or a heating element, the conductor is usually still intact. What fails, in most cases, is the insulation: it has hardened, cracked or carbonised, and the cable, no longer insulated, discharges the voltage. That is why choosing a high-temperature cable means, first of all, identifying the right insulation material for the actual temperature of the installation.
In this guide we cover:
In an electrical cable, the first component to degrade with heat is the insulation. The conductor melts above 1,000°C, while standard insulation loses its properties just a few tens of degrees above room temperature. In practice, the maximum temperature of a cable therefore coincides with that of its insulation.
What happens when insulation operates beyond its limit:
The conductor, however, is not irrelevant. As the temperature rises, bare copper oxidises faster, and oxidation impairs contact and conductivity. This is why high-temperature cables use nickel-plated copper and pure nickel alongside plain and tinned copper. The MVV 500°C, the highest-performing standard cable in the Caviterm catalogue, uses a nickel conductor.
The practical rule: insulation and conductor must offer the same performance, so they should be chosen according to the temperature resistance required by the operating temperature of the application.
The operating temperature is the range, minimum and maximum, within which the cable can work while maintaining its characteristics. On Caviterm datasheets it is expressed like this: for example “-40°C +260°C” for the PP.
Three things to check carefully.
The thermal class indicates the maximum temperature at which an insulating material can operate continuously. The international reference is the IEC 60085 standard. The classes, from A (105°C) to H (180°C) and above, are explained in our guide to the insulation class of electrical cables.
When choosing a cable, the thermal class is mainly a common language between designer and supplier. The reference value remains the operating temperature stated on the cable datasheet.
Each insulation material has its own threshold: the higher the temperature, the more you move from polymer materials to mineral materials such as glass fibre and mica. Here is the overview, with some examples from the Caviterm range. For an overview of the functions and standards of insulation, see also the guide to electrical cable insulation.
| Insulation | Maximum temperature | Examples |
| PVC and HEPR rubber | 70°C (PVC), 90°C (HEPR rubber) in general-purpose cables | standard installation cables: not suitable for high temperatures |
| Silicone rubber | up to 180°C | GS 180°C |
| PTFE | up to 260°C | PP 260°C |
| Impregnated glass fibre (E-glass) | from 320°C to 400°C | TS2V 320°C, S2VGA 400°C |
| Mica | up to 500°C from the catalogue, up to 600°C with special constructions | MVV 500°C |
For silicone, PTFE, glass fibre and mica, the values are those of the Caviterm range, stated in the name of each product: they refer to the complete construction of the cable, not to the material itself. With special constructions some materials can go further, which is why the datasheet of the individual cable always prevails.
PVC is the insulation used in general-purpose cables: cheap, flexible and easy to process. In standard versions it works up to 70°C, the limit of common PVC-insulated installation cables. The Caviterm range also includes a PVC R3 rated up to 105°C. Above these thresholds the insulation softens, deforms and ages rapidly.
This is the most common mistake: installing a standard cable near a heat source “because it is not in contact anyway”. The radiant heat of a furnace or an exhaust manifold is enough to push the insulation beyond its limit.
Extruded silicone rubber is the first true insulation for high-temperature cables. Silicone is very flexible both when hot and when cold, and is suitable for wiring machinery, household appliances and equipment exposed to moderate heat.
In the Caviterm range, silicone cables reach 180°C, in single-core, multi-core and shielded versions: for example the GS 180°C and the FG4OH2G4 180°C with braided shield.
PTFE (polytetrafluoroethylene, also known as Teflon) is a fluoropolymer that withstands higher temperatures than silicone and has excellent chemical resistance. It is used when the heat rises and the environment is aggressive, as in the PP 260°C from the Caviterm range.
To go beyond 300°C, you move to glass fibre cables, referred to as E-glass in datasheets. The fibre is impregnated to bind the filaments, give the covering compactness and limit fraying.
But be careful: “glass fibre” alone does not define the temperature. What counts is the complete construction of the cable, i.e. how the fibre is combined with the other insulating materials. In the Caviterm range, for example, it ranges from 320°C for the TS2V to 400°C for the S2VGA. This is why the datasheet of each individual cable should always be read.
Mica is an insulating mineral that keeps its properties even at very high temperatures. It is the choice for the most extreme applications, where special glass fibre and mica are combined. In the Caviterm range this is the case of the MVV 500°C, while special constructions on request go up to 600°C.
All solutions are gathered in the Caviterm products section.
Temperature is the first criterion, but not the only one: a high-temperature cable must also perform in relation to other external factors. Three factors to consider.
The shield is a copper braid or an aluminium-polyester tape placed around the conductor to protect it. Its main function is to protect the signal from the electromagnetic and/or electrostatic interference generated by motors, inverters and power controllers. It is needed when power cables and signal cables are installed in the same environment, or near machines that generate interference.
To learn more: interference in electrical cables.
Armour is an external metal protection, generally made of galvanised steel or stainless steel, which protects the cable from impacts, abrasion and crushing. It should not be confused with shielding: the first protects the cable from impacts and wear, the second protects the signal from interference. The Caviterm range includes armoured versions even for the highest temperatures, such as the S2VGA 400°C.
The high-temperature cable for furnaces is the typical case, but not the only one. High-temperature cables are also used in:
In each of these contexts, besides heat, there may be vibration, oils, chemicals, dust or repeated bending. All factors that guide the choice between one insulation material and another, and between a bare, shielded or armoured version.
5 questions, asked in this order, are all it takes to choose the right cable.
If none of the cables in the catalogue answers one of these questions, it is time to consider a custom cable.
Since 1981 Caviterm has been designing and manufacturing special cables for industry. For high temperatures, the range goes from -40°C to +500°C with catalogue cables, and up to +600°C with special constructions, with:
Beyond the catalogue cables, custom cable manufacturing makes it possible to combine insulation, conductor, shielding and armour according to the application, even starting from an existing cable to be replicated (reverse engineering), and in customised batches. If you work with temperature sensors, also read the guide on how to choose a thermocouple cable: compensating or extension.
Do you have a high-temperature application to assess? Discover the Caviterm products or write to us using the form below: our technicians will help you choose the right cable.
Among Caviterm catalogue cables, the highest limit is reached by the MVV, with mica insulation and nickel conductor: it operates from -40°C up to +500°C. Special constructions in special glass fibre and mica go up to +600°C.
It depends on the temperature at the installation point. In the Caviterm range: up to 180°C a silicone cable is enough, up to 260°C a PTFE cable, between 320°C and 400°C impregnated glass fibre cables are needed, up to 500°C mica cables, up to 600°C special constructions. If the cable is exposed to impacts or rubbing, an armoured version is preferable.
Silicone is flexible and withstands up to 180°C. Impregnated glass fibre raises the limit to between 320°C and 400°C, but it is less flexible and not suitable for humid environments. If mechanical protection is also needed, versions with metal armour are available.
Only if the temperature stays within the PVC limit, which is 70°C in standard versions and 105°C in special ones. Near furnaces, heating elements or exhausts, radiant heat is enough to exceed it: in these cases a high-temperature cable is needed.
The first value (Uo) is the rated voltage between conductor and earth, the second (U) the voltage between two conductors. A 300/500 V cable can operate up to 300 V to earth and 500 V between phases.
Above certain temperatures, yes. Bare copper oxidises with heat, so as the temperature rises, nickel-plated copper or nickel is used. The MVV 500°C, for example, uses only a pure nickel conductor.
