Log in to the online community

Want to post a reply? You'll need to log in

Plastic consumer units/enclosures etc

42 Replies

  • New Question

Plastic consumer units/enclosures etc

Posted by whjohnson on Aug 31, 2019 12:33 pm

I have a job where a small former outside toilet is being converted into a hobby pottery complete with water supply and small kiln.
I propose to fit a small plastic consumer unit with the appropriate IP rating for protection against ingress of water.
This will be a home brew job with a generic enclosure and a RCD main switch and mcbs from my spares stock.
I have seen many metal enclosures rusting quietly away in detached garages/w/shops/outbuildings and thought they would be better served by using plastic.

I think there is still a case to be made for fitting plastic consumer unit enclosures in outbuildings in order to prevent deteriation caused by external influences. Moist atmosphere, unheated spaces and the like.

Any other like-minded souls out there?
Comments welcome.

Re: Plastic consumer units/enclosures etc

Posted by Legh Richardson on Sep 6, 2019 5:55 pm

R.Davies BSc(UMIST) AMIMechE CIEH:
Crikey just logged in again and this forum seems to have been taken over by the 'girlies' or in certain circles known as the 'purple mafia' or the 'pink mafia', although the pink is generally the girlies and purple is associated with somewhat gay, shocking colour though somewhat painful to navigate for a red blooded male.😐.

Rob 

Yes it has gone a little feminine - perhaps a chinz or gingham border for future developments?
I have always thought that fires in consumer units, meters, switchgear are primarily caused by loose terminations associated with the supply intake and nearby. It would help if the people responsible for making these terminations were experienced and not part-time 'meter readers' - that's just a generalization.....

Legh
www.leghrichardson.co.uk

Re: Plastic consumer units/enclosures etc

Posted by AJJewsbury on Sep 6, 2019 7:15 pm

On the "purple" theme - 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 - making it tricky to find the IET tab again... The old one at least had a white square around the IET bit so you could see it whatever the background.

  - Andy.

Re: Plastic consumer units/enclosures etc

Posted by Lisa Miles on Sep 6, 2019 10:54 pm

😊 We're going a little #off-topic here...

If anyone wants to give us their thoughts re the new branding colours etc please feel free to pop your feedback in the Online Community Support forum.

Oh and it's not pink, it's purple... 😂
Lisa Miles - Online Community Manager, Engineering Communities

Re: Plastic consumer units/enclosures etc

Posted by Typiod on Sep 6, 2019 11:29 pm

Lisa Miles:
😊 We're going a little #off-topic here...

If anyone wants to give us their thoughts re the new branding colours etc please feel free to pop your feedback in the Online Community Support forum.

Oh and it's not pink, it's purple... 😂

Wether it be pink or purple its a b***** awful colour, so much so I now have a seperate browser for this site with the text colour changed. Also I have not bothered going to the Online Community Support forum as I am not one for surfing through loads of different pages on a single website.

Re: Plastic consumer units/enclosures etc

Posted by mapj1 on Sep 6, 2019 11:42 pm

Also you can't read the support forum pages unless you are already successfully  logged in, so not much use for anyone who cant find the buttons, and it is only slightly less of an abandoned back-water for dead topics than 'Calvin Asks'.
regards Mike

Re: Plastic consumer units/enclosures etc

Posted by Elizabeth Morgan on Sep 9, 2019 2:59 pm

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...

 
Elizabeth Morgan, Web Producer - Engineering Communities

Re: Plastic consumer units/enclosures etc

Posted by Paul Skyrme on Sep 10, 2019 7:50 am

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.
 
Paul Skyrme MEng, BSc(Hons), IEng, MIET, MSOE, MBES, SIIRSM, TechIOSH, CMSE®. #e5 Founder Member

Re: Plastic consumer units/enclosures etc

Posted by mapj1 on Sep 10, 2019 9:25 am

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.
regards Mike

Re: Plastic consumer units/enclosures etc

Posted by Paul Skyrme on Sep 11, 2019 8:45 pm

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.
Paul Skyrme MEng, BSc(Hons), IEng, MIET, MSOE, MBES, SIIRSM, TechIOSH, CMSE®. #e5 Founder Member

Re: Plastic consumer units/enclosures etc

Posted by Legh Richardson on Sep 11, 2019 9:09 pm

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
www.leghrichardson.co.uk

Re: Plastic consumer units/enclosures etc

Posted by R.Davies BSc(UMIST) AMIMechE CIEH on Sep 11, 2019 9:46 pm

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)

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
 

Re: Plastic consumer units/enclosures etc

Posted by Paul Skyrme on Sep 11, 2019 9:54 pm

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.
Paul Skyrme MEng, BSc(Hons), IEng, MIET, MSOE, MBES, SIIRSM, TechIOSH, CMSE®. #e5 Founder Member

Re: Plastic consumer units/enclosures etc

Posted by Chris Pearson on Sep 11, 2019 10:26 pm

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.

Re: Plastic consumer units/enclosures etc

Posted by whjohnson on Sep 11, 2019 11:28 pm

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?

Re: Plastic consumer units/enclosures etc

Posted by AJJewsbury on Sep 12, 2019 10:36 am

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.

Re: Plastic consumer units/enclosures etc

Posted by mapj1 on Sep 12, 2019 12:01 pm

AZ61 is not really an aluminium alloy fortified with magnesium - it really is mostly magnesium with less than 10% of other elements alloyed in to improve machining process and chip formation. We use it for things like metal laptop lids because of its lightness.
Certainly as far as the world of (Def Stan) Defence Standards go, it is not considered to be non combustible, I was assuming alloys with a majority of Al, and a bit of Mg for stiffening up such as we use for die casting.
Are BG really making  a CU out of AZ61 ? I'd like to think it was a mistake.
I have no difficulty with rules of the form quoted by Rob Davies - 'risks should be considered' yes, not blanket rule in/out.

edit

Adding Calcium at 1 to 2% helps suppress  the flammability, but of course not the melting
flame test. 

furnace test.
regards Mike

Re: Plastic consumer units/enclosures etc

Posted by Chris Pearson on Sep 12, 2019 5:30 pm

AJJewsbury:

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?
I can confirm that the BG unit is non-ferrous, or at least a magnet will not stick to mine.

Share:

Log in

Want to post a reply? You'll need to log in