General > General Technical Chat
The real reason why North America uses 120v instead of 240v.
<< < (6/17) > >>
bdunham7:

--- Quote from: Monkeh on November 24, 2022, 09:28:58 pm ---Where's the data to suggest 120V systems and, as I originally stated, the accompanying attitudes regarding safety, are in fact safer?

--- End quote ---

I see no reason to think that certain attitudes 'accompany' 120V  systems and don't know why you'd lump them somehow as if Americans are less worried about shocks because the voltage is lower.  Would you be more likely to ignore the railway crossing lights if the train was a passenger train vs a freight train? 

What I said was that I don't think you are going to be able to tease out meaningful data that really shows you that one voltage is safer than the others using shock fatality stats from two different areas with other variables in play.  IOW, your statistics are meaningless for this purpose, IMO.  It could be that Americans, due to stupidity and neglect, get shocked 300X more often by 120V than Brits do by 240V, but only have 4X the fatality rate.  That would make 120V 75X safer.  Or maybe not.
Monkeh:

--- Quote from: bdunham7 on November 24, 2022, 10:06:08 pm ---
--- Quote from: Monkeh on November 24, 2022, 09:28:58 pm ---Where's the data to suggest 120V systems and, as I originally stated, the accompanying attitudes regarding safety, are in fact safer?

--- End quote ---

I see no reason to think that certain attitudes 'accompany' 120V  systems
--- End quote ---

https://www.eevblog.com/forum/projects/can-i-convert-a-atx-psu-to-run-directly-off-of-12v/msg4498369/#msg4498369

That's far from my only personal experience of how people treat 120V systems as 'safe' because it is 'safer'.


--- Quote ---Would you be more likely to ignore the railway crossing lights if the train was a passenger train vs a freight train?
--- End quote ---

I have just recently seen someone step out in front of a learner driver because they believe the instructor will stop them. So yes, people will treat dangerous situations differently based upon their misguided preconceptions.


--- Quote ---What I said was that I don't think you are going to be able to tease out meaningful data that really shows you that one voltage is safer than the others using shock fatality stats from two different areas with other variables in play.  IOW, your statistics are meaningless for this purpose, IMO.  It could be that Americans, due to stupidity and neglect, get shocked 300X more often by 120V than Brits do by 240V, but only have 4X the fatality rate.  That would make 120V 75X safer.  Or maybe not.

--- End quote ---

And I agree that it isn't easy to draw conclusions from the data - but I find it unlikely that the most commonly accessible voltage is in fact safer when fatalities are 20-30x higher for only 6x the population.
themadhippy:
maybe its down the shite quality of electrical work,look at the state of the american fuse boards posted in the "show your fuse board " thread,or compare the popular uk electrical youtube channels with american equivalent.Take a typical american electrical accessory,its either stab and pray,or wrap the wire around an exposed screw, or there the love of wire nuts.
mcovington:
There are at least 4 safety differences.

(1) 120 V is supposedly less lethal than 240 V, but I don't know if the difference is significant in practice.  I wouldn't want to be shocked by either one. 

(2) 240 V requires half as many amps to deliver the same amount of power, and thus, only 1/4 as much heat dissipated in a poor connection.

(3) To further mitigate the effect of poor connections in house wiring, Britain, as I understand it, commonly uses ring arrangements where there are two paths from source to load; North American never does.  (Is it even permissible in North America?  Does Australia use it?)

(4) Fuses in plugs or outlets and switches on outlets are, as I understand it, usual in the UK (also Aus?) but rare in North America.

As well as someone mentioned that in 240 V countries, both sides of the power line are expected to be well insulated from anything the user can contact.  (That is a reasonable expectation and normal practice in North America as well; I wouldn't build anything any other way.)
Monkeh:

--- Quote from: mcovington on November 24, 2022, 11:19:35 pm ---(3) To further mitigate the effect of poor connections in house wiring, Britain, as I understand it, commonly uses ring arrangements where there are two paths from source to load; North American never does.  (Is it even permissible in North America?  Does Australia use it?)
--- End quote ---

Double edged sword. The purpose is actually to reduce the amount of copper needed to provide flexible placement of loads - specifically, electric heaters. It's a bit out of date these days. While it will reduce the risk of fire from a single loose connection, it also hides the symptoms of said loose connection and can lead to excessive current in one leg for prolonged periods.

Basically unused outside of the UK and a few territories.
Navigation
Message Index
Next page
Previous page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod