The message <
[email protected]>
from "RamRod Sword of Baal" <
[email protected]> contains these words:
England does use neutrals.
The active used to be red (Brown now?) and the neutral black (Blue
now?) and
the earth green (yellow and green now?)
Correct so far. ;-)
England does not have 120 volts as a standard voltage.
Not for domestic supplies.
The English system is 3 phase and single phase. Now it was 415 volts for 3
phase and 240 volts for single phase but I think that has been reduced to
230 volts to comply with European standards, not sure how much the 3 phase
voltage has been reduced.
Three phase and neutral distribution with every 3rd property fed red[1]
phase and neutral and the properties each side being fed blue[1] and
yellow[1] phases respectively along with a neutral. Phase to neutral
voltage being a nominal 240v despite the "Harmonisation"[2] of a
notional 230v european wide appliance rating plate standard.
This distribution philosophy considerably reduces the capital costs in
cabling to domestic properties. In the UK, urban areas are served by
local substations feeding into an underground LV 3 phase street
distribution system. The only areas where the quaint practice of
overhead cable and pole transformers are to be seen are in rural areas
serving remote properties and farms.
Three Phase supplies are generally only available to business premises
and factories.
In UK they have a ring main that is used for domestic plugs (13 amp) where
the cable starts at the 30 amp fuse and returns to the same fuse allowing
the current to flow both ways through the cable. The actual appliance plug
has a smaller fuse inside of it to protect the appliance.
In addition, the lighting is also fed off the same 240v source via 6
amp fuse bridge (maximum rating allowed per lighting circuit) but this
is simply a single run of 1mm FT&E PVC cable usually daisychained from
light fitting to light fitting with switch drops from each ceiling rose.
Most modern house builds have consumer units installed that only accept
miniature circuit breakers and generally utilise a whole house ELCB
breaker (typically 80A/30mA rating). Older properties are fed via a 60
or 80 or 100A service fuse feeding the older Wylex rewirable fused
consumer units via a watt hour meter.
The old Wylex fuse boxes accept different, colour coded fuse shrouds
over their identically rated knife contact gear with the width of the
fuse bridge slots sized accordingly with red allowing the maximum 30 amp
rated blade width to be inserted and white only permitting the narrowest
6 amp blade width rated fuse bridge to be fitted.
The fuse bridges are of the rewirable type but, provided the fuse
bridges haven't been miswired with a higher rating of fusewire, it's
impossible to plug a 30 amp fuse into a smaller rated fuse carrier.
Fitting a lower rated fuse into a high capacity circuit isn't a safety
issue, it just means you'll be replacing a fuse more often than once
every 30 years or so (maybe straight away if a 2KW fire is plugged in
and switched on when you insert a 6A lighting fuse bridge ;-).
Being able to fit a 15A fuse in place of a 30A one on a lightly loaded
30A ring main circuit is a useful feature in that it will improve the
protection against faults in the permanent wiring. If you have to
replace a blown 15A fuse on this circuit more than once a year, you
could always try a 20A one before reverting back to the 30A fuse.
The only disadvantage with using 240v for lighting relates to tungsten
filament lamps which require longer and thinner filaments compared to
their american counterparts which compromises their life versus
efficiency rating. However, since tungsten filament lamps are slowly
being ousted by newer CFL and LED technologies, this is becoming less of
a consideration.
[1] I'm referring to the traditional cable wiring colours for 3 phase
(black being neutral) but the EC have "Harmonised" the wiring colours
across all of the european nations, much to the detriment of safety in
most of the participating countries involved since they've chosen an
entirely arbitary colour coding scheme, seemingly to prove that they
aren't favouring any one particular country's standards. As an example
of the sheer stupidity involved, they've mandated the use of black as a
phase colour!
[2] Europe wide Voltage Harmonisation is simply an exercise in
specifying a common rating plate voltage on domestic appliances at a
compromise voltage that sits neatly between the UK's 240v and the
majority of Europe's 220v standard. Except for tungsten filament lamps,
this does actually bring a benefit without too great a compromise being
made.
Most appliances which utilise mains voltage directly for heating or to
power motors will work just fine over the rejigged Public Supply Utility
(PSU) voltage tolerances designed to prevent these new 230v rated
appliances from being subjected to voltages outside of their nominal
working tolerance range. Off the top of my head, this means a change in
the UK from 240v +/- 6% to 240v +3/-10% whilst in Europe, 220v +/-6%
becomes 220v +10/-3% (or thereabouts).
Other appliances which utilise switching regulators to derive internal
voltages (computers and entertainment devices) are immune to much wider
variations in supply voltage so never had any issue with supplies rated
at either of the two common voltages of 220 and 240.
Tunsten filament lamps are about the only domestic 'appliance' that
needs to be specifically rated for the voltage actually used in their
target country market.
Presumably, at some date in the future, probably when all GLS tungsten
filament lamps have been totally outlawed by the EC, the PSUs will
actually start to harmonise their domestic supply voltage to 230v +/-
6%.
However, the UK PSUs have nothing to gain by this move whilst the
european PSUs will see a benefit in going from 220v to 230v and it seems
more likely that the european PSUs will make the first move (if some
haven't already started doing so). Indeed, it's even possible that the
EC may eventually implement another "Harmonisation" exercise to
standardise on 235 volt (possibly ending up at 240v). It's even possible
that a 240 volt standard might be the long term plan in the EC's policy
on domestic mains supply voltage standards (but that's just my own dark
thoughts on the matter ;-).
