IEC/IEEE 60079-30-1:2025

Explosive atmospheres - Part 30-1: Electrical resistance trace heating - General and testing requirements

IEC/IEEE 60079-30-1:2025 is available as IEC/IEEE 60079-30-1:2025 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.IEC/IEEE 60079-30-1:2025 specifies general and testing requirements for electrical resistance trace heaters for application in explosive atmospheres with the exclusion of those for Equipment Protection Levels (EPL) Ga, Da, Ma and Mb equipment. This document covers trace heaters that comprise either factory or field (worksite) assembled units, and which can be series trace heaters, parallel trace heaters, trace heater pads, or trace heater panels that have been assembled and/or terminated in accordance with the manufacturer's instructions.
This document also includes requirements for termination assemblies and control methods used with trace heating systems. The explosive atmospheres referred to in this document are those defined in IEC 60079-10-1 and IEC 60079-10-2.
Annex F and Annex G outline the application of this document for those users applying the Division method of area classification
This second edition of IEC/IEEE 60079-30-1 cancels and replaces the first edition of IEC/IEEE 60079-30-1 published in 2015. This edition constitutes a technical revision.
The significant technical changes with respect to the previous edition can be found n the foreword of this publication.

Atmosphères explosives - Partie 30-1: Traçage par résistance électrique - Exigences générales et d'essais

IEC/IEEE 60079-30-1:2025 est disponible sous forme de IEC/IEEE 60079-30-1:2025 RLV qui contient la Norme internationale et sa version Redline, illustrant les modifications du contenu technique depuis l'édition précédente.

General Information

• Status: Published
• Publication Date: 14-Sep-2025
• ICS: 29.260.20 - Electrical apparatus for explosive atmospheres
• Technical Committee: TC 31 - Equipment for explosive atmospheres
• Drafting Committee: MT 60079-30 - TC 31/MT 60079-30
• Current Stage: PPUB - Publication issued
• Start Date: 15-Sep-2025
• Completion Date: 05-Sep-2025

Relations

• Revises: IEC/IEEE 60079-30-1:2015 - Explosive atmospheres - Part 30-1: Electrical resistance trace heating - General and testing requirements
• Effective Date: 05-Sep-2023

Overview

IEC/IEEE 60079-30-1:2025 - Edition 2.0 (Redline version available) is the updated international standard for electrical resistance trace heating intended for use in explosive atmospheres. It specifies general and testing requirements for trace heaters (factory or field assembled) including series and parallel trace heaters, trace heater pads and panels, plus associated termination assemblies and control methods. The standard excludes equipment intended for EPL Ga, Da, Ma and Mb. This second edition cancels and replaces the 2015 edition and contains technical revisions (see the foreword and redline for change details).

Key topics and requirements

• Scope and applicability: Defines covered trace heating products and exclusions; links area-classification to IEC 60079‑10‑1 and IEC 60079‑10‑2.
• Product types: Series trace heaters, parallel trace heaters, trace heater pads and panels - factory or field assembled.
• Design approaches: Requirements for stabilized design and controlled design methods for sheath temperature and safety.
• Testing regime: Extensive type tests and routine tests, including dielectric, insulation resistance, flammability, impact, deformation, cold-bend, water resistance, thermal stability, thermal performance, maximum sheath temperature verification, start-up current verification, and UV/condensation exposure.
• Termination and connection rules: Requirements and tests for integrity of terminations, splices, and integral components.
• Marking and documentation: Product marking, field-assembly marking, and comprehensive documentation and instruction requirements for installation, commissioning, maintenance and circuit design.
• Annexes for special methods: Normative annexes provide design verification, heat-loss calculations, electrically conductive covering, empty conduit use, and Division (Division 1/2) method application (Annex F and G).

Applications

• Freeze protection and process temperature maintenance on pipes, vessels and instrumentation in hazardous areas.
• Industrial heating systems in petrochemical, oil & gas, chemical plants, and other facilities with explosive atmospheres.
• Systems requiring certified trace heating components, verified sheath temperatures, and documented installation/maintenance instructions.

Who should use this standard

• Manufacturers of trace heaters, pads and panels for hazardous areas.
• Test laboratories performing type and routine testing to IEC/IEEE 60079‑30‑1 requirements.
• Design and safety engineers, electrical contractors and installers working on trace heating in classified areas.
• Asset owners, inspectors and regulators ensuring compliance and safe operation of trace heating systems.

Related standards

• IEC 60079‑0 (general requirements for explosive atmosphere equipment) - applicability table included.
• IEC 60079‑10‑1 / IEC 60079‑10‑2 (area classification - gas and dust).
• IEC 60079‑14 (referenced for EPL/Zone relationships in Annex A).

Keywords: IEC/IEEE 60079-30-1:2025, explosive atmospheres, electrical resistance trace heating, trace heaters, trace heater pads, testing requirements, sheath temperature, termination assemblies, Division method.

Standards Content (Sample)

IEC/IEEE 60079-30-1 ®
Edition 2.0 2025-09
INTERNATIONAL
STANDARD
REDLINE VERSION
Explosive atmospheres -
Part 30-1: Electrical resistance trace heating - General and testing requirements
ICS 29.260.20  ISBN 978-2-8327-0727-2

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CONTENTS
FOREWORD . 4
INTRODUCTION . 1
1 Scope . 9
2 Normative references . 9
3 Terms and definitions . 10
4 General requirements . 14
4.1 Applicability of IEC 60079-0 . 17
4.2 General . 27
4.3 Mechanical strength . 28
4.4 Terminations and connections. 28
4.5 Circuit protection requirements for branch circuits . 28
4.6 Temperature requirements . 29
4.6.1 General . 29
4.6.2 Stabilized design . 29
4.6.3 Controlled design . 30
5 Testing . 31
5.1 Type tests . 33
5.1.1 General . 33
5.1.2 Dielectric test . 33
5.1.3 Electrical insulation resistance test . 34
5.1.4 Flammability test . 34
5.1.5 Impact test. 36
5.1.6 Deformation test . 39
5.1.7 Cold bend test . 40
5.1.8 Water resistance test . 42
5.1.9 Integral components' resistance to water test . 43
5.1.10 Verification of rated output . 43
5.1.11 Thermal stability of electrical insulating material . 46
5.1.12 Thermal performance test . 46
5.1.13 Determination of maximum sheath temperature . 48
5.1.14 Verification of start-up current . 54
5.1.15 Verification of the electrical resistance of electrically conductive
covering . 58
5.1.16 Outdoor exposureUV and condensation test . 58
5.1.17 Connection Integrity (integral components) . 59
5.2 Routine tests . 61
5.2.1 Dielectric test . 61
5.2.2 Verification of rated output . 61
6 Marking . 61
6.1 Product markings for trace heaters . 61
6.2 Markings for Field assembled components . 62
6.3 Product markings for high temperature limiters and temperature controllers . 62
7 Documentation requirements . 62
7.1 General . 62
7.2 Circuit design documentation . 63
7.3 Trace heating system documentation . 63
7.3.1 General . 63
7.3.2 For trace heating systems according to the product classification
method . 63
7.3.3 For trace heating systems according to stabilized design method . 63
7.3.4 For trace heating systems according to controlled design method . 63
7.4 Instructions for installation of trace heating system . 64
7.5 Instructions for commissioning . 65
7.6 Instructions for maintenance / repair or modification . 65
Annex A (informative) Type test matrix for EPLs Gb/Gc/Db/Dc (refer to IEC 60079-14
for the relationship of EPLs to Zones) . 66
Annex B (informative) Checklist for installation . 68
Annex C (normative) Trace heater product design verification methodology . 69
C.1 General . 69
C.2 Design methodology and selection of trace heaters . 69
C.3 Stabilized design calculations . 69
C.4 Trace heater performance and equilibrium conditions . 70
C.5 Heat loss calculations . 72
C.6 Heat loss design safety factor . 73
C.7 Maximum temperature determination . 73
C.7.1 Theoretical pipe and sheath temperature calculations - Metallic
applications . 73
C.7.2 Theoretical vessel and sheath temperature calculations - Metallic
applications . 74
C.7.3 Sheath temperature - metallic applications utilizing a temperature limiter
control sensing the trace heater sheath or an artificial hot spot . 76
C.7.4 Theoretical sheath temperature calculations - Non-metallic applications . 76
C.7.5 Sheath temperature - Non-metallic applications utilizing a temperature
limiter control sensing the trace heater sheath or an artificial hot spot . 78
Annex D (normative) Calculation methodology for coverage of electrically conductive
covering . 79
Annex E (normative) Applications of trace heating in empty conduit . 80
E.1 General . 80
E.2 Maximum sheath temperature - trace heating internal to conduit . 80
E.3 Pull-strength test. 80
E.4 Rated output . 80
E.5 Verification of start-up current . 81
Annex F (normative) Requirements for Division 1 and Division 2 trace heating systems . 82
F.1 Application . 82
F.2 General . 82
F.3 Terminations and connections. 82
F.4 Control and temperature requirements . 82
F.4.1 General . 82
F.4.2 Stabilized design . 82
F.4.3 Controlled design . 83
F.4.4 Requirements for protective device in Divisions 1 and 2 . 83
F.5 Type tests . 83
F.5.1 Division 1 trace heating equipment . 83
F.5.2 Division 2 trace heating equipment . 84
F.6 Marking . 84
F.7 Instructions - Installation requirements . 84
Annex G (normative) Type test matrix for Division 1 and 2 explosive atmospheres . 86
Bibliography . 89

Figure 1 – Flammability test . 36
Figure 2 – Example of room temperature impact test . 38
Figure 3 – Example of minimum temperature impact test . 39
Figure 4 – Cold bend test . 42
Figure 5 – Integral components resistance to water test. 43
Figure 6 – Verification of rated output . 45
Figure 7 – Maximum sheath temperature using Product classification approach. 49
Figure 8 – Verification of sheath temperatures using pipe sculpture . 51
Figure 9 – Verification of sheath temperature, plate test . 54
Figure 10 – Verification of sheath temperature - plate test with serpentined sample . 55
Figure 11 – Plate test with two samples crossed over . 56
Figure 12 – Plate test with a single sample crossed over . 57
Figure 13 – Typical splice firm attachment apparatus . 60
Figure C.1 – Equilibrium conditions for workpiece maintenance . 70
Figure C.2 – Equilibrium conditions for upper limit evaluation . 71

Table 1 – Application or exclusion of specific clauses of IEC 60079-0 . 17
Table 2 – Sheath temperature design conditions based on Equipment Protection
Levels (EPLs) - Stabilized design approach . 29
Table 3 – Sheath temperature design conditions based on Equipment Protection
Levels - Controlled design approach . 31
Table 4 – Test voltages for the dielectric test . 33
Table A.1 – Determination of test samples . 66
Table B.1 – Trace heater installation record - Example . 68
Table F.1 – Division trace heating systems . 82
Table F.2 - Sheath temperature design conditions - Stabilized design approach . 83
Table F.3 – Sheath temperature design conditions - With temperature control device
controller and/or high temperature limiter . 83
Table G.1 – Applicable trace heater and trace heater pads and panels tests by
installation location . 86
Table G.2 – Applicable tests for integral components with trace heaters and trace
heater pads and panels . 87

Explosive atmospheres -
Part 30-1: Electrical resistance trace heating -
General and testing requirements

FOREWORD
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This redline version of the official IEC Standard allows the user to identify the changes made
to the previous edition IEC/IEEE 60079-30-1:2015. A vertical bar appears in the margin
wherever a change has been made. Additions are in green text, deletions are in strikethrough
red text.
IEC/IEEE 60079-30-1 has been prepared by IEC technical committee 31: Equipment for
explosive atmospheres, in cooperation with the Petroleum & Chemical Industry Committee of
the IEEE Industrial Applications Society under the IEC/IEEE Dual Logo Agreement.
This publication is published as an IEC/IEEE Dual Logo standard.
This second edition of IEC/IEEE 60079-30-1 cancels and replaces the first edition of
IEC/IEEE 60079-30-1 published in 2015. This edition constitutes a technical revision.
Users of this document are advised that interpretation sheets clarifying the interpretation of this
document can be published. Interpretation sheets are available from the IEC webstore and can
be found in the "history" tab of the page for each document.
This edition includes the following significant technical changes with respect to the previous
edition:
The significance of changes between IEC/IEEE 60079-30-1, Edition 1.0 (2015) and
IEC/IEEE 60079-30-1, Edition 2.0 (this document) is as listed below:
Type
Changes Clause Minor and Extension Major
editorial technical
changes changes
Redefined Maximum withstand temperature as it

X
3.20
applies to the performance benchmark test.
Separated maximum maintain temperature and

maximum continuous operating temperature to X
3.15 and 3.16
clarify the meaning of both terms.
Addition of requirements for controllers and high
C1
temperature limiters, added specific reference
4.6.3
standards.
Rewrite of the requirements for controlled design as
C2
it applies to the application of controllers and high
4.6.3
temperature limiters as for use in EPL's.
Addition of requirement for specifying various
C3
temperatures defined by the standard and including
4.2 and 7
them in user documentation.
Connection Integrity (integral components) X
5.1.17
Applications of Trace Heating in empty conduit X
Annex E
NOTE The technical changes referred to include the significance of technical changes in the revised IEC Standard,
but they do not form an exhaustive list of all modifications from the previous version.
Explanations:
A) Definitions
Minor and editorial changes
clarification
decrease of technical requirements
minor technical change
editorial corrections
These are changes which modify requirements in an editorial or a minor technical way. They
include changes of the wording to clarify technical requirements without any technical change,
or a reduction in level of existing requirement.
Extension addition of technical options
These are changes which add new or modify existing technical requirements, in a way that new
options are given, but without increasing requirements for equipment that was fully compliant
with the previous standard. Therefore, these will not have to be considered for products in
conformity with the preceding edition.
Major technical changes
addition of technical requirements
increase of technical requirements
These are changes to technical requirements (addition, increase of the level or removal) made
in a way that a product in conformity with the preceding edition will not always be able to fulfil
the requirements given in the later edition. These changes have to be considered for products
in conformity with the preceding edition. For these changes additional information is provided
in clause B) below.
NOTE 1 These changes represent current technological knowledge. However, these changes should not normally
have an influence on equipment already placed on the market.
B) Information about the background of 'Major technical changes'
C1 There are no additional requirements for temperature controllers and high temperature
limiters beyond those of the general industrial standards.
C2 The application of temperature controllers and high temperature limiters shall be as
specified.
C3 The documentation shall include the various temperatures specified in the standard.
The text of this International Standard is based on the following IEC documents:
Draft Report on voting
31/1867/FDIS 31/1893/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with the rules given in the ISO/IEC Directives, Part 2,
available at www.iec.ch/members_experts/refdocs. The main document types developed by IEC
are described in greater detail at www.iec.ch/publications/.
This document is to be used in conjunction with IEC 60079-0, Explosive atmospheres - Part 0:
Equipment - General requirements and IEC/IEEE 60079-30-2, Explosive atmospheres -
Part 30-2: Electrical resistance trace heating - Guidance on application for design, installation
and maintenance.
A list of all parts of IEC 60079 series, under the general title Explosive atmospheres, can be
found on the IEC website.
The IEC Technical Committee and IEEE Technical Committee have decided that the contents
of this document will remain unchanged until the stability date indicated on the IEC website
under webstore.iec.ch in the data related to the specific document. At this date, the document
will be
– reconfirmed,
– withdrawn, or
– revised.
INTRODUCTION
IEC/IEEE 60079-30-1 is intended to provide a comprehensive overview of the essential
requirements and testing appropriate to electric surface heating equipment used in explosive
atmospheres. The requirements of this part of IEC 60079 are considered to be the minimum
requirements for Equipment Protection Levels (EPLs) Gb, Gc, Db, and Dc in explosive
atmospheres for gases, dusts, and fibres/flyings. While some of this work already exists in
national standards or international standards, this document has collated much of this existing
work and considerably added to it. This document also contains the minimum requirements for
users applying the Division method of area classification.

1 Scope
This part of IEC 60079 specifies general and testing requirements for electrical resistance trace
heaters for application in explosive atmospheres with the exclusion of those for Equipment
Protection Levels (EPL) Ga, Da, Ma and Mb equipment. This document covers trace heaters
that comprise either factory or field (worksite) assembled units, and which may can be series
trace heaters, parallel trace heaters, trace heater pads, or trace heater panels that have been
assembled and/or terminated in accordance with the manufacturer's instructions.
This document also includes requirements for termination assemblies and control methods used
with trace heating systems. The explosive atmospheres referred to in this document are those
defined in IEC 60079-10-1 and IEC 60079-10-2.
Annex F and Annex G outline the application of this document for those users applying the
Division method of area classification.
This standard supplements and modifies the general requirements of IEC 60079-0, except as
indicated in Table 1. Where a requirement of this standard conflicts with a requirement of
IEC 60079-0, the requirement of this standard takes precedence.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies.
For undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60050-151:2001, International Electrotechnical Vocabulary (IEV) - Part 151: Electrical and
magnetic devices
IEC 60050-426:2008, International Electrotechnical Vocabulary – Part 426: Equipment for
explosive atmospheres
IEC 60079-0:2011, Explosive atmospheres - Part 0: Equipment - General requirements
IEC 60079-7, Explosive atmospheres - Part 7: Equipment protection by increased safety "e"
IEC/IEEE 60079-30-2, Explosive atmospheres - Part 30-2: Electrical resistance trace heating -
Guidance on application for design, installation and maintenance
IEC 60695-11-3, Fire hazard testing - Part 11-3: Test flames - 500 W flames - Apparatus and
confirmational test methods
ISO 4582, Plastics – Determination of changes in colour and variations in properties after
exposure to daylight under glass, natural weathering or laboratory light sources
ISO 4892-1, Plastics – Methods of exposure to laboratory light sources – Part 1: General
guidance
ISO 4892-2, Plastics - Methods of exposure to laboratory light sources - Part 2: Xenon-arc
lamps
ASTM D5025, Standard specification for laboratory burner used for small-scale burning tests
on plastic materials
ASTM G155, Standard practice for operating xenon arc light apparatus for exposure of non-
metallic materials
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60079-0,
IEC 60079-7, IEC 60050-151 and IEC 60050-426 (except as modified by this clause) and the
following apply.
NOTE Definition 3.40 is identical to definition 3.16 of IEC 60079-7: 2006.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
– IEC Electropedia: available at https://www.electropedia.org/
– ISO Online browsing platform: available at https://www.iso.org/obp
3.1
ambient temperature
temperature surrounding the workpiece including the trace heater and any
thermal insulation or weather barrier that may be applied the object under consideration
Note 1 to entry: Where a trace heater or surface heater is enclosed in thermal insulation, the ambient temperature
is the temperature external to the thermal insulation.
3.1.1
maximum ambient temperature
highest specified ambient temperature
3.1.2
minimum ambient temperature

lowest ambient temperature specified at which trace heating is operable and performs according
to specified requirements (and on which heat-loss calculations are based)
[SOURCE: IEC 60050-426:2008, 426-20-20]
3.2
branch circuit
portion of the wiring installation between the overcurrent device protecting the
circuit and the trace heater unit(s)
[SOURCE: IEC 60050-426:2008, 426-20-02]
3.3
connection
termination
termination or splice used to attach trace heaters or surface heaters to power wiring or to
connect sections of these devices
3.3.1
cold lead
electrically insulated conductor or conductors that do not produce significant
heat and are used to connect a trace heater to a branch circuit and designed so that it does not
produce significant heat
[SOURCE: IEC 60050-426:2008, 426-20-03]
3.3.2
end termination
termination, which may can be heat producing, applied to a trace heater at the
end opposite to that where the power is supplied
[SOURCE: IEC 60050-426:2008, 426-20-04]
3.3.3
power termination
termination applied to the end of a trace heater at which the power is supplied
[SOURCE: IEC 60050-426:2008, 426-20-05]
3.3.4
tee
electrical connection of trace heaters, in series or in parallel, to accommodate
a branch or a branch circuit of a trace heater
[SOURCE: IEC 60050-426:2008, 426-20-06, modified ("tee or branch" replaced by "branch or
a branch circuit")]
3.4
controlled design
design where the set point of the applicable temperature controller and/or high-limit device
temperature limiter is used in establishing/limiting the maximum sheath temperature
3.5
dead leg

segment of process piping segregated from the normal flow pattern for the purpose of providing
a heat loss reference
[SOURCE: IEC 60050-426:2008, 426-20-07]
3.6
design loading
minimum power that meets the design requirements, in the specified adverse conditions
(minimum ambient and maximum wind velocity), after voltage and resistance tolerances and
appropriate safety factors have been considered
[SOURCE: IEC 60050-426:2008, 426-20-08]
3.5
electrically conductive covering
metallic sheath, metallic braid or other conductive material
metallic braid, metallic sheath, or alternative covering with sufficient conductivity so that, when
bonded to ground, it will allow a ground fault protective device to operate under a fault condition
3.6
factory fabricated
assembled into units or sets, including the necessary terminations and
connections trace heater unit or set, including the necessary terminations and connections,
assembled by the manufacturer
[SOURCE: IEC 60050-426:2008, 426-20-09]
3.7
field assembled
trace heaters supplied in bulk unterminated with terminating components to be
assembled at the work site
[SOURCE: IEC 60050-426:2008, 426-20-10]
3.8
heat loss
energy flow from a workpiece, pipe, or vessel or equipment to its surroundings
[SOURCE: IEC 60050-426:2008, 426-20-11]
3.9
heat sink
part that conducts and dissipates heat away from a workpiece
Note 1 to entry: Typical heat sinks are pipe shoes, pipe supports and items of large mass such as valve actuators
or pump bodies.
[SOURCE: IEC 60050-426:2008, 426-20-12]
3.10
heat transfer aid
thermally conductive material, such as metallic foil or heat transfer compound
used to increase the heat transfer efficiency from trace heaters to the workpiece
[SOURCE: IEC 60050-426:2008, 426-20-13]
3.11
high limit temperature
maximum allowable temperature of the system, including piping, fluid and trace
heating system
[SOURCE: IEC 60050-426:2008, 426-20-16, modified (addition of "trace")]
3.12
high temperature limiter
safety device, or combination of safety devices, incorporating a means of sensing temperature
and a means of switching power to the trace heater before the maximum surface temperature
is exceeded
3.13
integral components
components such as heat shrink terminations, cold lead connections, moulded end seals, or
splices, which may conform to the general shape of the trace heater and are exposed to the
same environments (such as under the thermal insulation) as the trace heater, that are not
intended to be re-used in the event of a repair or modification, which may be factory fabricated
or field assembled
component such as a heat shrink termination, a cold lead connection, a molded end seal, or a
splice, which conforms to the general shape of the trace heater and is exposed to the same
environment as the trace heater, which can be factory fabricated or field assembled, and is not
intended to be re-used in the event of a repair or modification
3.14
maximum continuous exposure temperature (trace heater de-energized)
highest allowable continuous temperature to which the trace heating system
may can be exposed while de-energized as declared by the manufacturer
3.15
maximum maintain temperature / maximum continuous operating temperature (trace
heater energized)
specified maximum workpiece or process temperature that the trace heater
operates at continuously is able to maintain as declared by the manufacturer
3.16
maximum continuous operating temperature
specified maximum workpiece temperature; at which, the trace heater, can operate continuously
when energized as declared by the manufacturer
3.17
maximum intermittent exposure temperature (trace heater energized or de-energized)
highest allowable intermittent temperature to which a trace heater may can be
exposed, as declared by the manufacturer
3.18
maintain temperature
specified temperature of a workpiece or process that the trace heaters shall be
able to maintain continuously when energized as declared by the manufacturer
3.19
maximum sheath temperature
maximum temperature of the outermost continuous covering of a trace heater
3.20
maximum withstand temperature
maximum operating or exposure temperature that will not adversely affect the thermal stability
of the trace heater and its component parts
[SOURCE: IEC 60050-426:2008, 426-20-18]
maximum continuous exposure temperature or the maximum intermittent
exposure temperature (energized or de-energized) whichever is higher, as declared by the
manufacturer
3.21
minimum installation temperature
minimum temperature at which the trace heating system may can be handled
and installed
3.22
MI trace heater
mineral insulated metal sheathed trace heater typically containing one or more
heating conductors
3.23
operating voltage
actual voltage applied to the trace heater when in service
[SOURCE: IEC 60050-426:2008, 426-20-21]
3.24
outdoor exposure
exposure to outdoor conditions of ultraviolet light and moisture
3.25
overjacket
continuous layer of non-metallic material applied outside the electrically
conductive covering metallic sheath or screen to protect against corrosion
3.26
parallel trace heater
heating element that is electrically connected in parallel with another parallel
trace heater, either continuously or in zones, so that the watt density power output per lineal
length is maintained, irrespective of any change in length for the continuous type or for any
number of discrete zones
3.27
power density
power output for a trace heater expressed in watts per linear length or in watts per unit surface
area
3.27
rated output
total power or power per unit length or unit surface area of a trace heater, at
rated voltage, temperature and length or area
[SOURCE: IEC 60050-426:2008, 426-20-24, modified (removal of "which is normally expressed
in watts, watts per metre or watts per square metre")]
3.28
rated voltage
rated value of the voltage assigned by the manufacturer to which operating and
performance characteristics of trace heaters are referred
[SOURCE: IEC 60050-426:2008, 426-20-25, modified (addition of "assigned by the
manufacturer")]
3.29
routine test
test that is carried out by the manufacturer of the trace heater on all trace heaters during or
after the production process
3.30
series trace heater
heating element electrically connected in series with another series trace heater
with a single current path and with a specific resistance at a given temperature for a given
length
[SOURCE: IEC 60050-426:2008, 426-20-26]
3.31
sheath
uniform and continuous metallic or non-metallic outer covering enclosing the
trace heater used to provide protection against influence from the surroundings (corrosion,
moisture, abrasion etc.)
Note 1 to entry: See overjacket (3.25)
[SOURCE: IEC 60050-426:2008, 426-20-26, modified (addition of Note 1 to entry)]
3.32
sheath temperature
temperature of the outermost continuous covering (braid, sheath, or overjacket)
that may can be exposed to the surrounding atmosphere
[SOURCE: IEC 60050-426:2008, 426-20-28]
3.33
stabilized design
design where the temperature of the trace heater, by design and use, stabilizes
below the high limit temperature, under the most unfavourable conditions, without the need for
a protective system to limit the temperature
[SOURCE: IEC 60050-426:2008, 426-20-29]
3.34
start-up current
current response of a trace heater following energization
[SOURCE: IEC 60050-426:2008, 426-20-30, modi
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