Plastic consumer units/enclosures etc

Still off topic, but to answer a few comments:

Yes it has gone a little feminine - perhaps a chinz or gingham border for future developments?

Great idea Legh Richardson! I've passed that on ?

...you can't read the support forum pages unless you are already successfully  logged in

Good point mapj1‍ but you can read the 'Feedback and question' pages so feel free to post in there if you wish ?

 ...I don't like the new logo (the one the browser puts on the tab or window title) - it seems to be black (and a bit of purple) on transparent - which looks OK on when the tab is active (and the tab label has a white background) but on an inactive tab (at least on Firefox) when the background goes black it's almost invisible...

Thanks AJJewsbury‍  I've passed this feedback on although I can't guarantee it will be be changed.


Now, back to plastic consumer units...

Is aluminium close enough?


I am not convinced on the BG unit.

It is doubtful it is pure aluminium.

It is apparently die-cast, and one of the alloying materials added to aluminium for die-casting is magnesium.

Building regulations do not allow the use of magnesium.

There is no specification in the building regulations information for a percentage of magnesium, it's a blanket ban.

So, how much is in the BG CU, if any, nobody knows.


I'd have no qualms in using a plastic CU personally if it was the right part for the job.

A solid magnesium CU would be quite awkward from a corrosion perspective and perhaps quite fun in a very hot fire. However, I do not believe that magnesium when bonded to other atoms has to always count  - if it did in a blanket sense, then magnesium oxide , present in fire resistant plaster board and as a inert whitener, would be  a problem (it is also the white powder inside pyrotenax cable).


I agree that at some point, magnesium with hint of aluminium might be an issue, but Aluminium with silicon and perhaps 3 to 8 % magnesium  in to stiffen up a soft metal, less so. It is an awful idea from the point of corrosion of course, as no doubt it will be fixed with steel screws, but the Mg content is not a big concern.  typical die cast alloy composition


This building regs ban you mention, I presume it is new,  - do you have a reference or link? It is always possible that once again our civil service (who are often neither) need reminding of some basic science, and that atoms in an alloy behave very differently to the pure element.

I think that there would be a difference in the atomic structure of MgO & an Al/Mg alloy that would mean the Mg is not as tightly bound to the Al is it is to the O after all the burning of Mg would result in MgO.


I'll have to lock back through my notes Mike, but I will find the reference for you, give me a few days please.

I would have thought that MgO is a stable compound and reasonably inert, like NaCl. Split either of them into their constituent elements (lots of energy needed) and you have some rather volitile components. I would have thought that an alloy combination of Al and Mg might not be as stable as the metal salts when heated.


Legh

The question of mgAlloy only related to the commercial serctor and was further related to building materials not components,,accessories and the like, 


Here is a quote from the notes relating to the AD(J)

• Any material which when tested to BS 476-11:1982 (2007) does not flame nor cause any rise in temperature on either the centre (specimen) or furnace thermocouples.

• Products classified as non-combustible in tests following the procedures in BS 476-4:1970 (2007).

• Any material classified as class A1 in accordance with BS EN 13501-1:2002 Fire classification of construction products and building elements. Classification using data from reaction to fire tests.

Typical examples of such materials to be found in buildings include totally inorganic materials such as concrete, fired clay, ceramics, metals, plaster and masonry containing not more than 1% by weight or volume of organic material. (Use in buildings of combustible metals such as magnesium–aluminium alloys should be assessed in each individual case.)'


This has now changed a lot since the introduction of AZ61 a non-combustible MgAlloy which was specifically designed for hurricane, earthquake zones and areas of high geophysical shifting like Dubai for instance because its ductile, light in weight and stronger than steel, this sort of alloy is used in components, mobiles, tablets, cameras, appliances, motors and many many other things, 


AZ61 has passed most of the approvals for non-combustibility worldwide as being safe, where most of the bans exist is aluminium compounds similar to what is used as cladding.


Rob

 

Thanks Rob,

It would have taken me days to find the reference, I'm not convinced that the wording restricted itself to building materials, but I guess that is down to interpretation, and I'm not going to labour the point, your explanation is fine.

Though I know that I didn't get my original evidence from Wikipedia or any the like it was from the original document, which could have been AD(J) or another, I honestly don't recall.

If you lot really are concerned about the fire safety of the BG "garage" CU, I have one that is surplus to requirements (having served its purpose temporarily) and will happily apply an oxy-acetylene torch to see whether it really will go off like a firework.

Actually I have yet to be able to find one for sale. A web search yields plenty of BG consumer units, but not of the alloyed variety............

Are they actually available in the UK?

This has now changed a lot since the introduction of AZ61 a non-combustible MgAlloy

AZ61 appears to have a melting point of below 610 degrees C - which is considerably below the 1400+ degrees C for steel. Can we have any confidence that such material really meets BS 7671's demands - which only gives steel as an example of what's acceptable? (Regardless of other standard's ideas of what constitutes non-flammable/fire-proof.)

 

Actually I have yet to be able to find one for sale. A web search yields plenty of BG consumer units, but not of the alloyed variety

Good point- the IP65 ones I've seen (e.g. https://www.screwfix.com/p/british-general-5-module-3-way-populated-garage-consumer-unit/1926g) seem to be steel, not Al alloy. We're not being led down a tangential wild goose chase are we?


  - Andy.