AMD 3 - Hopefully busting the myth of metal DBs

[D Skelton]

So, I've been trawling through every bit of info available on AMD 3, specifically info regarding non-combustible DBs in domestic premises. Others may have further information regarding the decision made by JPEL/64 as to what was included in AMD 3 following the final draft and I welcome any comments or 'picking apart of' what follows, but it seems quite clear to me that the intent of the regulation is not quite followed through with what is now in print. The last we hear is that within the final draft, 960[SUP]o[/SUP]C glow-wire tested plastic will not meet the requirements of Regulation 421.1.201 and will not be considered non-combustible.

Below is Regulation 421.1.201 in its entirety:

421.1.201 Within domestic (household) premises, consumer units and similar switchgear assemblies shall comply with BS EN 61439-3 and shall:

(i) have their enclosure manufactured from non-combustible material, or

(ii) be enclosed in a cabinet or enclosure constructed of non-combustible material and complying with Regulation 132.12

NOTE 1: Ferrous metal, e.g. steel, is deemed to be an example of a non-combustible material.

NOTE 2: The implementation date for this regulation is the 1st January 2016, but does not preclude compliance with the regulation prior to that date.

Ok, so lets have a look at BS EN 61439-3, the product standard for distribution boards intended to be operated by ordinary persons:

BS EN 61439-3 (Low-voltage switchgear and controlgear assemblies. Distribution boards intended to be operated by ordinary persons) Regulation 10 essentially says that the clause of Part 1 applies (except from a few issues irrelevant to this subject), thus we refer to BS EN 61439-1 (General rules), which says:

10.2.3.2 Verification of resistance of insulating materials to abnormal heat and fire due to internal electric effects

The glow-wire test principles of IEC 60695-2-10 and the details given in IEC 60695-2-11 shall be used to verify the suitability of materials used:

a) on parts of ASSEMBLIES, or
b) on parts taken from these parts

...

The temperature of the tip of the glow-wire shall be as follows:

- 960[SUP]o[/SUP]C for parts necessary to retain current-carrying parts in position;

...

Got that, so let's have a look at BS EN 60695-2-12. This deals with the interpretation of glow-wire test results carried out in accordance with 60695-2-10 and 60695-2-11. It says:

10.1 Test criteria

The test specimin is considered to have withstood this test if there is no ignition, or if all of the following situations apply:

a) the longest sustained flames or glowing of the test specimin after the removal of the glow-wire, t[SUB]R[/SUB], extinguish within 30s;
b) the specimin is not totally consumed; and
c) there is no ignition of the wrapping tissue.

So this essentially tells us that if there is no ignition of the test specimin then the material is fit to be covered by the BS EN 61439-3 product standard. However, it still doesn't quite address whether or not that makes the material non-combustible.

For this reason, we turn to BS EN 13943 (Fire safety vocabulary). Lets look at some definitions:

4.46 combustion
exothermic reaction of a substance with an oxidizing agent

4.186 ignited
caused to be in a state of undergoing combustion (4.46)

4.43 combustible, adj.
capable of being ignited (4.186) and burned

4.239 non-combustible
not capable of undergoing combustion (4.46) under specified conditions

The crux of this matter I think comes down to those aforementioned 'specified conditions'. The fact is, almost any material is combustible if heated hot enough, therefore why does Regulation 421.1.201 not specify these specified conditions?

We can however look at BS EN 61439 which clearly stipulates these specified conditions (the glow-wire test as described in BS EN 60695-2) and it's requirement for plastic domestic distribution boards to pass these tests.

If as per BS EN 60695-2 a material passes the 960[SUP]o[/SUP] glow-wire test through non-ignition, it cannot by definition be called a combustible material, ergo sum - it is non-combustible.

This is of course my interpretation of all these standards and the definitions contained within, I do believe however that this is surely the only way it can be interpreted.

To summarise; if you install a plastic consumer unit within in a domestic property after 1st January 2016, as long as it conforms to the BS EN 61439-3 product standard, by definition, it will be non-combustible. Note 2 within Regulation 421.1.201 giving steel as an example of a non-combustible material is in my opinion nothing more than a red herring.

Hopefully, we might now be able to put this nonsense to bed once and for all!

 

[SPARTYKUS]

Oh dang it! Ive just invested heavily in a super secret ceramic DB manufacturing facility.

 

[baldsparkies]

I know this sounds like a crude test, and yes I guess it is.
But I had a spare BASEC 8 way board from Denmans.
Myself and a couple of guys used a blow torch on the poor thing (just for devilment).
It melted and distorted, but it did not combust or catch fire.
And boy did we try.
Ponged a bit though.

 

[GEOFF S]

So, I've been trawling through every bit of info available on AMD 3, specifically info regarding non-combustible DBs in domestic premises. Others may have further information regarding the decision made by JPEL/64 as to what was included in AMD 3 following the final draft and I welcome any comments or 'picking apart of' what follows, but it seems quite clear to me that the intent of the regulation is not quite followed through with what is now in print. The last we hear is that within the final draft, 960[SUP]o[/SUP]C glow-wire tested plastic will not meet the requirements of Regulation 421.1.201 and will not be considered non-combustible.

Below is Regulation 421.1.201 in its entirety:



Ok, so lets have a look at BS EN 61439-3, the product standard for distribution boards intended to be operated by ordinary persons:

BS EN 61439-3 (Low-voltage switchgear and controlgear assemblies. Distribution boards intended to be operated by ordinary persons) Regulation 10 essentially says that the clause of Part 1 applies (except from a few issues irrelevant to this subject), thus we refer to BS EN 61439-1 (General rules), which says:



Got that, so let's have a look at BS EN 60695-2-12. This deals with the interpretation of glow-wire test results carried out in accordance with 60695-2-10 and 60695-2-11. It says:



So this essentially tells us that if there is no ignition of the test specimin then the material is fit to be covered by the BS EN 61439-3 product standard. However, it still doesn't quite address whether or not that makes the material non-combustible.

For this reason, we turn to BS EN 13943 (Fire safety vocabulary). Lets look at some definitions:






The crux of this matter I think comes down to those aforementioned 'specified conditions'. The fact is, almost any material is combustible if heated hot enough, therefore why does Regulation 421.1.201 not specify these specified conditions?

We can however look at BS EN 61439 which clearly stipulates these specified conditions (the glow-wire test as described in BS EN 60695-2) and it's requirement for plastic domestic distribution boards to pass these tests.

If as per BS EN 60695-2 a material passes the 960[SUP]o[/SUP] glow-wire test through non-ignition, it cannot by definition be called a combustible material, ergo sum - it is non-combustible.

According to BEAMA, this will still not pass.

This is of course my interpretation of all these standards and the definitions contained within, I do believe however that this is surely the only way it can be interpreted.

To summarise; if you install a plastic consumer unit within in a domestic property after 1st January 2016, as long as it conforms to the BS EN 61439-3 product standard, by definition, it will be non-combustible. Note 2 within Regulation 421.1.201 giving steel as an example of a non-combustible material is in my opinion nothing more than a red herring.

Hopefully, we might now be able to put this nonsense to bed once and for all!

Cheers

 

[D Skelton]

Cheers

BEAMA don't write the rules, and even if they did, it isn't in the rules. It's one thing making your intent clear when working on legislation, but unless you illustrate that intent in the actual regulation it refers to, then the intent becomes irrelevant.

 

[Silly Sausage]

Purely for your enjoyment on this Thursday night, I read the latest issueing from the IET Wiring Matters earlier, ....

I quote, "There is no published definition for the term ‘non combustible’ that aligns with the intent of Regulation 421.1.201."

So, if the material is undefined, one can use anything one likes?!?!? :smilielol5::smilielol5::smilielol5:

 

[netblindpaul]

Damien,

This is the crux of my comments over the last few months.

The "metal" bit comes from BEAMA & their members deciding that ferrous metal is the only material that meets the intent of the regulation.

This I have always disagreed with.

Why is an installation standard interfering with a product standard?...

 

[stevey1983]

Wiring matters direct from the IET, should clear it up for everyone

http://electrical.------.org/wiring...consumer-units/index.cfm&utm_contact=94284970

 

[stevey1983]

Metal consumer unit for TT,

this podcast from the IET tells you of requirements of if you need to protect your tails, db, etc with rcd here.

Wiring Matters podcast series - IET Electrical

 

[shanky887614]

just got to wait till jan and see what the big manufacturer's decide

 

[netblindpaul]

Ended up duplicated. Don't know why so deleted.

 

[telectrix]

with the way the IET write some of their regulations, i'm surprised they've not got this guy as a proof reader.

https://www.youtube.com/watch?v=40-oo1S2WEw

 

[Ib≤In≤Iz]

just got to wait till jan and see what the big manufacturer's decide

Exactly, I'm not all that worried until then.

 

[GB.Kayak]

So, I've been trawling through every bit of info available on AMD 3, specifically info regarding non-combustible DBs in domestic premises. Others may have further information regarding the decision made by JPEL/64 as to what was included in AMD 3 following the final draft and I welcome any comments or 'picking apart of' what follows, but it seems quite clear to me that the intent of the regulation is not quite followed through with what is now in print. The last we hear is that within the final draft, 960[SUP]o[/SUP]C glow-wire tested plastic will not meet the requirements of Regulation 421.1.201 and will not be considered non-combustible.

Below is Regulation 421.1.201 in its entirety:



Ok, so lets have a look at BS EN 61439-3, the product standard for distribution boards intended to be operated by ordinary persons:

BS EN 61439-3 (Low-voltage switchgear and controlgear assemblies. Distribution boards intended to be operated by ordinary persons) Regulation 10 essentially says that the clause of Part 1 applies (except from a few issues irrelevant to this subject), thus we refer to BS EN 61439-1 (General rules), which says:



Got that, so let's have a look at BS EN 60695-2-12. This deals with the interpretation of glow-wire test results carried out in accordance with 60695-2-10 and 60695-2-11. It says:



So this essentially tells us that if there is no ignition of the test specimin then the material is fit to be covered by the BS EN 61439-3 product standard. However, it still doesn't quite address whether or not that makes the material non-combustible.

For this reason, we turn to BS EN 13943 (Fire safety vocabulary). Lets look at some definitions:






The crux of this matter I think comes down to those aforementioned 'specified conditions'. The fact is, almost any material is combustible if heated hot enough, therefore why does Regulation 421.1.201 not specify these specified conditions?

We can however look at BS EN 61439 which clearly stipulates these specified conditions (the glow-wire test as described in BS EN 60695-2) and it's requirement for plastic domestic distribution boards to pass these tests.

If as per BS EN 60695-2 a material passes the 960[SUP]o[/SUP] glow-wire test through non-ignition, it cannot by definition be called a combustible material, ergo sum - it is non-combustible.

This is of course my interpretation of all these standards and the definitions contained within, I do believe however that this is surely the only way it can be interpreted.

To summarise; if you install a plastic consumer unit within in a domestic property after 1st January 2016, as long as it conforms to the BS EN 61439-3 product standard, by definition, it will be non-combustible. Note 2 within Regulation 421.1.201 giving steel as an example of a non-combustible material is in my opinion nothing more than a red herring.

Hopefully, we might now be able to put this nonsense to bed once and for all!

D, thank you very much for bringing together the relevant standards in one place for analysis. Not withstanding the view that the changes to BS 7671 regarding electrical enclosures for the domestic market are an exercise in both treating the 'symptom rather than the cause' and 'shutting the stable door after a bolting horse', I comment only on the conclusions that you draw.

According to your text BS EN 60695-2-12 states:


10.1 Test criteria


The test specimin is considered to have withstood this test if there is no ignition, or if all of the following situations apply:


a) the longest sustained flames or glowing of the test specimin after the removal of the glow-wire, tR, extinguish within 30s;
b) the specimin is not totally consumed; and
c) there is no ignition of the wrapping tissue.


10.1 a) indicates that the test specimen may ignite but must be self-extinguishing within 30s.


Clearly this is not 'non-combustible'. You also rightly state:


'If as per BS EN 60695-2 a material passes the 960o glow-wire test through non-ignition, it cannot by definition be called a combustible material, ergo sum - it is non-combustible.'


This is true; however, a plastic enclosure could also pass the standard through the less strict route of 10.1 a), b) and c).


Therefore, without manufacturers' publishing the results of their testing regime to demonstrate compliance with BS EN 60695-2, the installer will not know whether an enclosure compliant with the standard achieved compliance by being truly non-combustible or by being self-extinguishing. Thus the changes to BS 7671 apply a more restrictive requirement than BS EN 61439-3.

 

[Andy78]

with the way the IET write some of their regulations, i'm surprised they've not got this guy as a proof reader.

https://www.youtube.com/watch?v=40-oo1S2WEw

Just listened to the whole thing Tel..... great backdrop for a paperwork morning. Cheers