US/UK Mains, kettles, etc.

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Owen Smith

Well-Known Member
I touched one of the live heat sinks in an HDR Fox T2 once by accident. Not an experience I wish to repeat, luckily it was "only" at mains voltage I think.
 
Owen Smith said:
Not an experience I wish to repeat, luckily it was "only" at mains voltage I think.
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Before 'elf and safety took over, I remember in my school days trying to unplug some stage lights and getting an interesting shock complete with sparks. I'm sure that circuit was off at the time. After that, I turned it off at the master switch and got some other mug to disconnect it - as in Not an experience I wish to repeat:D
 
I have in fact repeated it more than enough times already. I've had UK 240V mains shocks about 6 times in my life, and only once was it my own stupid fault (the HDR Fox T2 heatsink incident). It amuses me every time I see americans insist that a 240V mains shock will kill you. (Note I'm not saying it is safe, far from it, just that it does not kill every time.)
 
af123 said:
... and at least we can boil a kettle in a reasonable time.
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Having been to the US and Canada the steel hawser like thickness of their multi way mains extension leads always amuses me. It's like wrestling a python getting those cables to go where you want.

If you go to people's houses in the US and Canada, a lot of them still have traditional kettles with a whistle that they put on a gas ring. That boils a lot faster than the meagre wattage they can get into an eletric kettle.
 
Owen Smith said:
I've had UK 240V mains shocks about 6 times in my life, and only once was it my own stupid fault...
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I think I can beat that. The last time was my fault, when I forgot I was working with someone else...
It amuses me every time I see americans insist that a 240V mains shock will kill you.
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...and got a pretty good shock from one hand to the other. I'm still here.
 
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Owen Smith said:
If you go to people's houses in the US and Canada, a lot of them still have traditional kettles...
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Found myself talking to a USAnian engineer a few years back who, on an earlier visit to his daughter here, had been so impressed with the speed of our 230V kettles he'd taken one back home and put a 13A socket running off the 220V stove supply in his kitchen.
 
everthewatcher said:
...and got a pretty good shock from one hand to the other. I'm still here.
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Lucky. That's the most risky route.
My dad told me many years ago that naval radar techs were taught to keep one hand in a pocket when poking around live equipment; a principle I try and keep in mind to this day, though sometimes it'll mean steadying myself with a hand on an insulating wall rather than the metal ladder planted on damp soil :eek:
 
everthewatcher said:
Found myself talking to a USAnian engineer a few years back who, on an earlier visit to his daughter here, had been so impressed with the speed of our 230V kettles he'd taken one back home and put a 13A socket running off the 220V stove supply in his kitchen.
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Available for the next 28 minutes (according to the current BBC display) a programme on the John Taylor who has come up with a number of patents and designs that have been implemented for making kettles safer.
https://www.bbc.co.uk/programmes/b0b42z87

--pid=b0b42z87
 
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everthewatcher said:
he'd taken one back home and put a 13A socket running off the 220V stove supply in his kitchen.
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AIUI, the US system is actually 240V but with a centre neutral, so it's usually easy enough to find two wires 240V apart, often two adjacent sockets will do.
 
af123 said:
AIUI, the US system is actually 240V but with a centre neutral, so it's usually easy enough to find two wires 240V apart, often two adjacent sockets will do.
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And americans think our mains is unsafe?! At least we know we have 240V in all our sockets and everything is designed for such. Stealth 240V across disparate sockets is so much worse!

I am aware of the 240V "heavy mains" as they call it in the US for cookers, washing machines etc. I always thought it must be fed from a separate 240V feed into the premises.

The more I find out about mains outside the UK the more I wonder why they don't have more electrical fires. Oh wait, they do compared to the UK (alas I have no reference to hand).
 
The US and UK systems are both 3 phase. The nominal phase voltage (from any phase to neutral) is 120 in the US and 230 in UK. The voltage across any two phases is 200 in the US and 415 in UK.
Getting an accidental phase to phase shock (200V US, 415 UK) is comparatively difficult as it requires you to touch two phases simultaneously (and not be earthed). It's not impossible, but unlikely.
 
Owen Smith said:
The more I find out about mains outside the UK the more I wonder why they don't have more electrical fires. Oh wait, they do...
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Many years ago when I was involved in such things, it struck me that USA electrical and electronic equipment safety requirements had a bias towards protecting property by preventing fire, whereas UK/European ones were more focussed on protecting people by preventing shock.
 
MikeSh said:
The US and UK systems are both 3 phase. The nominal phase voltage (from any phase to neutral) is 120 in the US and 230 in UK. The voltage across any two phases is 200 in the US and 415 in UK.
Getting an accidental phase to phase shock (200V US, 415 UK) is comparatively difficult as it requires you to touch two phases simultaneously (and not be earthed). It's not impossible, but unlikely.
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And that isn't how 240V domestic heavy mains works in the US. 240V single phase comes into the house with a centre tapped neutral. Normal sockets are fed from one half or the other hence 120V (despite being nominally called 110V). Heavy mains takes the 240V, but it is all on one phase. A very odd system in my view.
 
Black Hole said:
AIUI?
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Had to look that one up myself - "As I Understand It".
MikeSh said:
Getting an accidental phase to phase shock (200V US, 415 UK) is comparatively difficult as it requires you to touch two phases simultaneously (and not be earthed). It's not impossible, but unlikely.
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Thankfully I never quite managed to do it even in the pre H&S university power labs. 240V is enough thanks.
 
Owen Smith said:
And that isn't how 240V domestic heavy mains works in the US. 240V single phase comes into the house with a centre tapped neutral. Normal sockets are fed from one half or the other hence 120V (despite being nominally called 110V). Heavy mains takes the 240V, but it is all on one phase. A very odd system in my view.
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That makes it two-phase rather than three-phase, doesn't it?

EEPhil said:
Had to look that one up myself - "As I Understand It".
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Ta. Another for the Netiquette section.
 
I haven't found a great reference, but this matches my memory: (reference)

(US) Voltage ... comes from a standard single phase system, with two hot legs coming from the transformer, each being 120 volts to neutral, where the AC sine waves are 180 degrees out of phase.
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and
With the 240V split phase system, we have the 240V available for all heavy duty appliances, and 120V for everything else. None of the wires carry more then 120V referred to earth, so there’s no increased shock hazard unless you’re careless enough to touch both hot wires. The power line from the transformer to the house is 240V, with only a small current in the neutral, so the only place where 120V circuits exist is the branch circuits within the house. So there is no loss of efficiency due to the use of 120V.
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The supply to most houses is Single Phase 3 wire configuration 180° apart
110 or 120 Volts between Phase and Neutral. (smaller appliances, lights, TV’s vacuum and normal sockets)
220 or 240 Volts between Phases. (used for larger appliances, (often fixed wired) heaters, airconditioning, ranges)
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So if two nearby sockets use different "hot legs" then they will have 240V between them - then all you need is..

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aha, once you know what to search for: https://en.wikipedia.org/wiki/Split-phase_electric_power
 
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Owen Smith said:
And that isn't how 240V domestic heavy mains works in the US. 240V single phase comes into the house with a centre tapped neutral. Normal sockets are fed from one half or the other hence 120V (despite being nominally called 110V). Heavy mains takes the 240V, but it is all on one phase. A very odd system in my view.
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I had to go do a bit of research on that. It seems they use both systems, plus another older one that is a bit of both. Given the size of the country and the relatively recent standardisation of these supply values that's not surprising.

I'm not sure they call it 110 though. I think we tend to say that because we associate it with our building site systems which are 110, but a different type of supply, much as many of us still call ours 240 and 440 volt which is generally incorrect for talking about the nominal voltage.
 
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