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IEC TS 60695-2-20
Edition 3.0 2021-04
TECHNICAL
SPECIFICATION
colour
inside
Fire hazard testing –
Part 2-20: Glowing/hot wire based test methods – Hot-wire coil test method –
Apparatus, verification, test method and guidance
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IEC TS 60695-2-20
Edition 3.0 2021-04
TECHNICAL
SPECIFICATION
colour
inside
Fire hazard testing –
Part 2-20: Glowing/hot wire based test methods – Hot-wire coil test method –
Apparatus, verification, test method and guidance
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 13.220.40, 29.020 ISBN 978-2-8322-9707-0
– 2 – IEC TS 60695-2-20:2021 © IEC 2021
CONTENTS
FOREWORD . 4
INTRODUCTION . 7
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 9
4 Principle . 11
5 Apparatus . 12
5.1 Test chamber . 12
5.2 Heater wire . 12
5.3 Power supply and test circuit . 13
5.4 Test specimen fixture . 13
5.5 Test specimen winding and pressing . 13
5.6 Conditioning chamber . 14
5.7 Timing device . 15
5.8 Micrometer . 15
5.9 Measuring scale . 15
6 Test specimens . 15
6.1 Test specimen preparation . 15
6.2 Test specimen dimensions . 15
7 Conditioning . 16
7.1 Requirements . 16
7.2 Test specimen conditioning . 16
7.3 Heater wire conditioning . 16
7.4 Test conditions . 16
8 Test procedure . 17
8.1 General . 17
8.2 Apparatus . 17
8.3 Determination of the test current, I . 17
c
8.4 Calculation of test current, I . 18
c
8.5 Determination of time to ignite, IT and/or time to drip, DT . 18
9 Observations and measurement . 20
10 Evaluation of test results . 21
10.1 Assigning a HWCT PLC classification . 21
10.2 Precision data . 21
11 Test report . 21
Annex A (informative) Guidance on how to effectively wind the heater wire on to the
test specimen . 22
Annex B (normative) Hot wire coil test (HWCT) – Performance level category (PLC)
classes . 23
B.1 General . 23
B.2 Reporting a classification . 23
Annex C (informative) Calibration curve to determine test current (I ) in a spreadsheet
c
program . 24
Annex D (informative) Precision data . 25
D.1 General . 25
D.2 Results of preliminary inter-laboratory round robin . 25
D.3 Evaluation of test results . 28
Bibliography . 30
Figure 1 – Test fixture arrangement (example) . 11
Figure 2 – Test specimen winding pattern . 12
Figure 3 – Test specimen fixture (example) . 13
Figure 4 – Heater wire winding device (Example) . 14
Figure 5 – Test circuit arrangement for heater wire calibration . 17
Figure 6 – Calibration curve . 18
Figure 7 – Decision tree . 20
Figure A.1 – Illustration of type a) behaviour . 22
Figure A.2 – Illustration of type b) behaviour . 22
Figure C.1 – Calibration curve in a spreadsheet program used to determine I . 24
c
Table 1 – Nominal thickness tolerances . 16
Table B.1 – Hot wire coil test (HWCT) – Performance level category (PLC) classes . 23
Table D.1 – Results for material 1A . 26
Table D.2 – Results for material 1B . 26
Table D.3 – Results for material 2A . 26
Table D.4 – Results for material 2B . 27
Table D.5 – Results for material 3 . 27
Table D.6 – Results for material 4 . 28
Table D.7 – Occurrence of PLC classes in the round robin . 29
– 4 – IEC TS 60695-2-20:2021 © IEC 2021
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
FIRE HAZARD TESTING –
Part 2-20: Glowing/hot wire based test methods –
Hot-wire coil test method –
Apparatus, verification, test method and guidance
FOREWORD
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