"Mortimer" wrote in message
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"Arny Krueger" wrote in message
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"Don Pearce" wrote in message
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Do the 120V and 240V system share the same high voltage distribution
lines? I mean is the transformation done per house, per street or per
district?

It is done as needed. In a residential neighborhood there may be several
transformers per block. There is a transformer in my back yard and I can
see the next one maybe 6-8 houses (on my side) down.

It just strikes me that with 240V available the requirement
for 120V should be dwindling.

240v has been widely avaiilable here since before WW2.

My expectations are that since power use is likely to decrease, and the
power drain of household equipment of a kind is generally decreasing,
there's no push for more 220 volt usage in homes.

220 volt portable houshold appliances are rare. Just a random thought but
the advent of 90-250 volt wall warts and other stuff with similar
switchmode power supplies are opening the door to future implementation
of more 220 volt house wiring.

The most recent *big* user of 240 volt power was air conditioning, but
almost all of that equipment that is going to exist has probably already
been isntalled, except of course new homes. I don't expect a lot of new
homes to be built for many years.

It really is too low for even distribution within a house.

I would say that its biggest problem is that 12 guage copper wire is
getting to be pretty expensive.

I have experienced lights dimming
significantly when appliances are turned on in many American homes.

Historical artifacts. I just rewired part of my daughter's ca. 1955
house and all I can say is that we added a ton of new circuits and I saw
many strange things that we made go away.

Several hundred dollars worth of 12 gauge Romex and accessories were
involved. Simple things like putting the garbage disposal, microwave,
and toaster oven each on their own circuits make a big difference.

In the UK, all of these could be driven from one ring main without the
need for separate radials from the fusebox for each one.

That makes sense if your rings are 10 gauge (2.5 mm),

There are two cables in parallel since its a ring.

The current is cut in half by the doubled line voltage.

Most houses I've seen just have two ring mains (one for upstairs, one for
downstairs), separate circuits for really high power devices (cooker,
immersion heater, electric shower circuit - if fitted) and one or two
lighting circuits.

My downstairs has something like ten 120 volt circuits, and there are about
another 8 circuits upstairs. As I mentioned, a typical modern US kitchen has
5-6 120 v circuits all by itself, not including the 230 v electric oven.

Electric stoves and ovens are always on their own 230 volt circuit, usually
fused for 30 amps with 10 gauge cable. Don't happen to have one - we cook
and heat with natural gas.


Things like microwaves would be fine in a ring main. Ring mains are fused
at 30 A which means you could have plug-in appliances to a total of 7.2 kW
downstairs and the same upstairs. Mind you, you have to be aware of the
electricity company master fuse which is (I think) around 60 A :-)

The 10 gauge wire, the ring configuration, and the doubled line voltage
explain all that.

I see the ring as being a bit of a problem. I guess you circumvent that
problem by fusing individual power cables on each appliance, if I'm
following your discussion.