[SystemSafety] Electrical Safety, Fire Safety

[Peter Bernard Ladkin]

Looking at the first pictures of the Grenfell Tower fire, it looked to me very much as though the
outside was burning, and indeed it was, as more recent pictures show. The initial reports said the
building had recently been renovated, and I immediately suspected burning exterior insulation (which
in the UK is called cladding).

Now, I would have thought that would have been a big deal, and it seems as if it could become one.
Apparently British building regulations don't prohibit the use of potentially flammable cladding on
large structures. US regs do. The US is a different kettle of fish, of course, because much
building, especially in the West, is wood-based, although recent larger structures are not
wood-based. I don't know about Germany, but see below.

Looking through the Wikipedia list of major building fires,
https://en.wikipedia.org/wiki/List_of_fires , it is notable that up through the 1960's, by far the
majority of reports are from the US. Obviously something changed in the US to reduce that (I guess
enhanced regulations after WWII?).

There are only about twenty major building fires listed in the UK since 1960. The Lakanal House fire
in 2009 seems to be missing. I was expecting to find some sort of precedent to aspects of the
Grenfell Tower, but there doesn't really seem to be one, except for the general problem of fires
spreading in large structures (e.g., Lakanal House in 2009). However, this is way more than are
listed for the rest of Europe. Is there some reporting bias?

Germany has been cladding buildings with polymer (styrofoam blocks, but I am sure there is a more
technical term) since I have been here (I came permanently in 1995), but I have had my doubts about
it. The more recent variant (within the last ten years) is fire-resistant mineral wool, and I would
be much happier with that. My building is wooden-framed with masonry walls, and has wooden floors,
which I love. I recently replaced the dining room floor (on the first floor of the building), and we
installed the mineral-wool between the beams holding the floorboards, both as insulation and also
explicitly as fire resistance. But when it is installed as building cladding, I understand the
frames enclosing the mineral wool are wooden, so that still seems iffy. There's a letter about this
situation in the Guardian from Alan Mitcham in Cologne
https://www.theguardian.com/society/2017/jun/14/grenfell-tower-fire-and-cladding-dangers

Given when the Grenfell Tower fire started, and that it appears almost the entire building burned
out, I was wondering about arson, and whether this could be the next "phase" of indiscrimate murder
technique, after suicide-bombing public places and driving trucks through crowds. But today's
newspapers suggest the fire services know where the fire started, in an apartment. That seems to me
to make it somewhat less likely that it was arson.

The other thing I wondered about is electrical safety, because a large proportion of building fires,
in both Germany and the UK (as well as elsewhere, I suppose) are caused by electrical faults.

The figures from Germany (ZVEI, the electrician's professional society, 2012) are that about 34% of
fires (and 52% of "avoidable fires") are caused by electrical faults; and in fires about 600 people
die per year (6,000 severely injured and 60,000 lightly injured; the risk pyramid with a factor of
10, as for road accidents. It's worth explaining this phenomenon). I got the UK figures from beama,
the manufacturer's association. It seems the same people make the protection kit in the UK as in
Germany: Moeller, Hager, Schneider Electric (which is French), Siemens, Eaton. Their RCD handbook is
available from http://www.beama.org.uk/resourceLibrary/rcd-handbook---dec-2010-.html It says that
typically there are 19 deaths per year due to electrical shock (Germany is about 15, I seem to
remember), and there are typically 23 deaths in fires caused by electrical faults, in about 10,000
such incidents.

(Those numbers seem to be radically different. If one-third of German building fires are due to
electrical faults, and 600 people die per annum in fires, one might imagine that about 200 deaths
are due to fires caused by electrical faults, which is an order of magnitude higher than the UK
figure. I really wonder if that can be right. I'll have to check.)

In any case, protecting against electrical faults means overcurrent protection, short-circuit
protection, residual-current protection and arc-fault protection. Wiring regulations seem to be
universal about overcurrent and short-circuit protection (required), and arc-fault protection (not
required for domestic buildings) but differ on residual-current protection.

I got into arc-fault matters after the conflagration of TWA 800 in 1996, when the NTSB discovered
the deteriorating-insulation issue with wiring in older aircraft, and the FAA technical center
reports on the amazing exploding Kapton started making the rounds. I talked to people at Schneider
Electric and other places who were trying to build arc-fault detectors/breakers at low cost for the
aviation industry. I lost track of what happened with that effort.

When I bought my house and "redid" the electrics in 2006, I had Type A RCDs installed on all
circuits. The ZVEI says that building electrics have a nominal 30-year lifetime, and that 70% of
installations in Germany have exceeded this lifetime. More detail about a small town near Bielefeld,
namely Lübbecke, can be found in Chris Goeker's Masters thesis - it's in German but non-German
readers can just look at Figure - Abbildung - 3.15 on p42, which contains a pie chart showing the
age of the electrical protection systems. The most eye-opening figure is that 8% were over 100 years
old! http://www.rvs.uni-bielefeld.de/publications/Theses/Masterthesis_Christoph_Goeker.pdf )

Installing Type A protection was standard practice by 2006, but the regulations were only changed in
2007 for newbuilds. But lots of other critters use my building as a home, without paying rent, and I
thought about arc-fault protection, given that some of them love to chew plastic (not just mice -
there is a standard story around here of martens getting into cars to chew up the insulation on the
wiring. Martens do install themselves in buildings, also, although you know you have one by the
smell). Interestingly, arc-fault breakers are called "fire protection breakers"
(Brandschutzschalter) in German electrical terminology. Nowadays, Type A protection costs €20-35 per
device and arc-fault protection €100-150 per device, so arc-fault protection is a financially
reasonable option if the devices are as reliable as the Type-A devices.

I tried to find the British regulations on building electrics. Apparently it's BS 7671, and the
regulations are set by the IEE (now IET).
http://electrical.theiet.org/wiring-regulations/index.cfm?referrer=/wiring-regulations/index.cfm A
timely query - there is a draft of new regulations aiming for publication in July 2018 and to come
into force in January 2019. Comments were opened a couple of weeks ago and the comments period
continues until 2017-08-23. So now is the time to comment for those of us who wish to do so. If you
have strong feelings about residual-current and arc-fault protection in building wiring, now is the
time to make them known. (The IET points you to the BSI WWW site, where you have to register to
download the draft.)

As I understand it, the current UK regulations require device-appropriate protection. So if you are
using devices subject to residual-current faults, you are supposed to have Type A RCD protection on
the circuit. And if your devices include some forms of common electronics which confuse Type A
protectors, you'll need Type B, which detect more subtle wave forms. But, unlike in Germany, it
seems to be left up to the judgement of the electrician. And who knows in advance to what use a wall
socket can be put in the future. Some bright spark or two is sure to try to plug in hisher electric
car........

Up to now, I would have said that lighting circuits don't necessarily need Type A RCD protection,
but utility circuits (those with wall sockets for electrical devices) do, as of course does your
electrical kitchen kit. Now there are "smart" light "bulbs", I'm not quite so sure about lighting
circuits, although it's hard to imagine how fiddling with the firmware could induce residual current
somewhere.

PBL

Prof. Peter Bernard Ladkin, Bielefeld, Germany
MoreInCommon
Je suis Charlie
Tel+msg +49 (0)521 880 7319  www.rvs-bi.de





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