On 20/11/16 02:34, wrote:
On Sunday, 20 November 2016 01:35:45 UTC, The Natural Philosopher
wrote:
On 19/11/16 22:15, Scott wrote:
On Sat, 19 Nov 2016 16:33:00 +0000,
wrote:

[snip]

The early Hoovers would have been used on DC supplies as well,
any one know if any area had DC sockets with an earth?

Drifting from the topic (as is often the way) it is interesting
you should mention DC supply. Was this commonplace in the UK (I
know it was in New York - battle of the currents) and if so when
did this change?


No, it wasn't, but ISTR being t0old about 205V DC or thereabouts
way back when.

http://www.vintage-radio.net/forum/s...ad.php?t=41380

suugests it hung on into the 60's in some areas.

Remember the CEGB wqas created post WWI, and the 'national grid'
grew out of that.

Prior to that time you got whatever voltage and frequency,
including DC, the local power company gave you.


In our old house some of the sockets had very heavy springs and
I remember being told at a young age this was because they were
designed for DC (to prevent arcing). I have Googled many times
since and been unable to find anything on any 'AC switchover'. I
was also told it was related to the closure of the municipal
generating station (for the trams) and introduction of the
National Grid but again I can find no support for this..

It almost certainly was. The rollout of 2540V A/C 50Hz as the
'standard' happened post War, and was intimately connected to the
construction of the 'national grid'

The original standard was 100-110v ac or dc.

My research indicates there was no original standard whatsoever.

It was down to the local power company.


This is around the ideal
voltage for filament lamps.

No, it isn't. about 3V is ideal for filament lamps. The lower the
voltage the fatter the filament and the less likely it is to burn out.

That's why slide projectors were equipped with 12V lamps. That's why LV
lighting was developed.

100-250V is a range that is suitable for domestic wiring because
currents are not too high and neither are voltages.

It was about as high as they could go without running into undue shock
risk and undue insulation requirements.

Keeping currents under 20A meant cheaper cable could be used.

Most moved on to anything in the 200-250v
region ac, but 100/110v dc areas remained into the 1950s.

To make matters worse there were negative and positive earth dc
supplies. Radios need mods to work with positive earth.

Not really. You just need not to touch the chassis....

One of my
radios is 110v positive earth dc.

Jolly good show.



NT



--
"What do you think about Gay Marriage?"
"I don't."
"Don't what?"
"Think about Gay Marriage."