New 17th edition amendment 3 consumer unit - metal or plastic?
- Thread starter ElliotW
- Start date
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First published in 2011, revised and corrected in 2012.
What the material is used for, ambient temperature range, possibility of contact with hot surfaces, etc, etc.
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More-or-less - it's title is "Low-voltage switchgear and controlgear assemblies. Distribution boards intended to be operated by ordinary persons (DBO)" - £152, or half-price for BSI members! It's predecessor (60439) had much the same title. I haven't got a clue as to what was 'new' in the 2012 version of 61439-3 (as compared with 60439-3).
Kind Regards, John
A requirement to use CUs complying with its predecessor, 60439-3 was in the initial 17th.
Indeed it did - so I wonder what, if anything, 60439-3 had to say about the combustibility of CU enclosures (and, indeed, what 61439-3 has to say about the matter).
Kind Regards, John
Very little. From IEC 61439-1:
8.1.5.3 Resistance of insulating materials to abnormal heat and fire due to internal
electric effects
Insulating materials used for parts necessary to retain current carrying parts in position and
parts which might be exposed to thermal stresses due to internal electrical effects, and the
deterioration of which might impair the safety of the ASSEMBLY, shall not be adversely affected
by abnormal heat and fire and shall be verified by the glow-wire test in 10.2.3.3. For the
purpose of this test, a protective conductor (PE) is not considered as a current-carrying part.
For small parts (having surface dimensions not exceeding 14 mm x 14 mm), an alternative
test may be used (e.g. needle flame test, according to IEC 60695-11-5). The same procedure
may be applicable for other practical reasons where the metal material of a part is large
compared to the insulating material.
The original manufacturer may provide data on the suitability of materials from the insulating
material supplier to demonstrate compliance with these requirements.
8.1.5.3 Resistance of insulating materials to abnormal heat and fire due to internal
electric effects
Insulating materials used for parts necessary to retain current carrying parts in position and
parts which might be exposed to thermal stresses due to internal electrical effects, and the
deterioration of which might impair the safety of the ASSEMBLY, shall not be adversely affected
by abnormal heat and fire and shall be verified by the glow-wire test in 10.2.3.3. For the
purpose of this test, a protective conductor (PE) is not considered as a current-carrying part.
For small parts (having surface dimensions not exceeding 14 mm x 14 mm), an alternative
test may be used (e.g. needle flame test, according to IEC 60695-11-5). The same procedure
may be applicable for other practical reasons where the metal material of a part is large
compared to the insulating material.
The original manufacturer may provide data on the suitability of materials from the insulating
material supplier to demonstrate compliance with these requirements.
Thanks. What is the "glow-wire test in 10.2.3.3" - 600°, 900° or what?
Kind Regards, John
I like that. It means that they think there is such a thing as normal fire.
Not necessarily. The English language is often ambiguous - does it mean "(abnormal heat) and fire" or "abnormal (heat and fire)". I actually suspect the former. Such ambiguity would obviously not be acceptable in mathematics or computer programming.
Kind Regards, John
There is. In, for example, the gas burner used in the needle flame test for flammability.
– 960 °C for parts necessary to retain current-carrying parts in position;
– 850 °C for enclosures intended for mounting in hollow walls;
– 650 °C for all other parts, including parts necessary to retain the protective conductor
I would say the latter, and would prefer "abnormal heat or fire" to express the former. When I get a moment I'll see if Mr Gowers has anything to say on the subject.
What I'd really prefer, and were I able to, insist upon, would be "fire or abnormal heat" to express the former.
It is, or BWOTB, just as unacceptable in legislation, regulations and standards.
Thanks - and I guess therein probably lies the problem. I presume that the enclosure of a CU comes into the third of those categories and that 650° C is not regarded by some (e.g. LFB) as being adequately high. Mind you, as I posted earlier, Hager seem to believe that even a 900° C glow wire test would not be adequate, hence their decision to go with metal.
Kind Regards, John
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