DIY Electric Car Forums banner

1 - 1 of 1 Posts

·
Registered
Joined
·
70 Posts
Discussion Starter #1
[Apologies for a tardy response: outbound email server problems!]

The 240V system in the UK (and hence in former colonies such as Oz, South
Africa etc.) could be SAFER than the 120V system. I've heard it argued that
a 240V "shock" will more reliably activate safety devices given the
inter-reaction with the human body resistance.

Ok, you damn well don't want to come into contact with a live conductor but
the chances of that are slim: for at least fifteen years, probably longer,
the neutral and phase/live/hot pins have been shrouded so that there is
virtually no chance of contacting a live connection with a plug half in/out
of a socket. I have weeded out all older plugs with unshrouded pins from my
family's houses. The respect/attitude towards electricity is different I
suspect too!

The neutral and live socket "holes" are shuttered on all our standard
sockets: this was a requirement from when they were introduced in the 60s:
some older ones relied on equal pressure on both the neutral and live pins
which twisted the shutter out of the way, but since ALL of our plugs have an
earth/ground pin (whether it is a Class I, grounded appliance or not) all
new sockets use the longer earth pin to push down on an inverted T-shape
shutter blocking the two "lagging" power pins... very safe and hard to
defeat (except, as I have recently found on trailing sockets/powerstrips:
the newer "low profile" versions of these you can insert the earth pin of a
plug "upside down" and open the shutter since the other pins aren't blocked
by the slim casing... bad manufacturers!! I think this is a requirement of
the dimensioning of fixed sockets though.

The plugs are robust, the pins are unbendable, as most people's bare feet
will testify when standing on a carelessly disgarded, upturned one! Very
"over-engineered." :) There is even a designation for rough service ones,
usually rubber backed etc. which I always use on EV cordsets* etc. The pins
are also held firmly in the sockets, giving mechanical strength. The
always-present earth pin means that the neutral and live/phase are not
interchangeable which means that single-pole switching on appliances is
possible since it cannot be inline with the neutral.

*But I nonetheless do not recommend regular usage of a standard domestic 13A
socket for EV charging without several additional precautions:
http://www.eco-drive.co.uk/doc/londonEVcharging.pdf for the document that
Evan referenced: aimed at warning against the adoption of using the sockets
for the EV charging network that is emerging, particularly in London.

It is the Euro plug/sockets, not the UK ones, that use the recessed outlets
to avoid being able to touch the pins.

Cables virtually always exit the plug at 90=BA (downwards) meaning that the
don't easily pull out - but for an EV that can be desirable. There is only
one manufacturer of a rear cable entry UK plug but this then won't fit into
standard weatherproof sockets which expect the cable to exit downwards!

There is no such thing as an ungrounded outlet. The only such case is the
transformer-isolated, low current outlet for shavers/toothbrushes in
bathrooms to prevent a single-fault-to-earth path for current. Other
territories (e.g. Oz) have permitted standard 240v outlets in bathrooms for
years, without GFCI! They are now generally requiring GFCI protection on at
least those outlets. It really annoys my Australian family when they visit
that they can't use hairdryers etc. in the bathroom - something any Brit
wouldn't even think about!

In bathrooms and similar the UK does not permit wall switches either, only
nylon pull cords to ceiling switches. Other countries with 240V or similar
do permit them but the "creepage" and "clearance" from the part of the
switch you can touch to the actual mechanism appears much greater, so maybe
it is just as safe even with wet hands?! It is funny watching my
aforementioned Australian kin groping around in half-light trying to find
the non-existent wall switch too!

Parts of Europe I have visited are quite lax about earthing - it appears
optional! They tend to rely on whole-house GFCI protection: very much
considered a supplementary measure in the UK, but required here when
earthing is via your own earth stake/rod/mat etc. Most "service panels" on
houses in the UK are now (since mid 80s) using circuit breakers and RCDs
(GFCIs) rather than replaceable fuses or wire fuse links: but these are
still around on older properties so I carry replacement fuses and fuse-wire
with me just in case when opportunity charging!

One thing that is lacking in the UK is that most GFCI protection doesn't
provide cover for faults from rectified supplies etc. as will be common in
EV charging hardware: in parts of Europe the type that DOES cover them is
all that is permitted: here, no-one knows what they are!

As someone who leases/rents EVs to people I carefully try to educate
customers about the particular dangers posed with an EV, whilst trying to
assure them it is safe IF they follow the procedures, use the portable RCD
(GFCI) that is provided etc. Still, the biggest danger would appear to be
where the earthing is provided to the supply using the neutral conductor,
which if it gets disconnected from the earthed centre point of the
transformer due to a fault will cause a live vehicle body.

It is so, so nice to have a minimum of 13A @ 240V from every socket outlet =
=3D
3kW (subject to the total load on the circuit) and often having 16A at
camping grounds etc.

Beyond 13A/3kW the perfect option is the BS4343/IEC60309 series: 16A/32A/63A
(North American ratings 20A/30A/60A) at 110V (yellow), 230V (blue), 400V
(red: three-phase, with or without neutral where each phase is 230V to
neutral/earth) Most common in the UK are 230V at 16A at camping grounds;
32A at some industrial/commercial properties; 63A at harbours and outdoor
event hook-ups. Three-phase, although used nearly everywhere for
distribution, is rarely available through a socket and if you can find it is
generally a 4-pole, 3-phase+earth socket at 16A. Europe seems to have 16A,
3P+N+E sockets as standard which means you can use 230V between a phase and
neutral if necessary.

I think that they are UL listed usually too: I am sure that I have seen the
UL logo and cUL symbol on at least some of mine: manufacturers like Hubbell
make them for the North American market.

Matt

-- =

Matthew Trevaskis
[email protected]



_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev
 
1 - 1 of 1 Posts
Top