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. This is around the ideal voltage for filament lamps. 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. One of my radios is 110v positive earth dc.


NT