Pizzawheel

I was considering this to run a 240V soldering iron, comforted by the fact that the iron would be supervised in use (IE never left on) and would only be used by me. The plan was kaiboshed because a spare dryer plug- which I was going to swap onto the lead in place of the 13amp one- cost over $30, more than a new soldering iron (albeit a small electronics one) on sale at crappy tire (think that was under $10)

Davita

I can see that swopping the soldering iron plug to fit the US 240VAC dryer outlet would work, as it is a simple resistor circuit but...if a UK dryer's plug was similarly swopped .....would the UK dryer motor work?

Pizzawheel

Yes, as people have reported in this thread, you put a delta of 240V across a motor and it runs, albeit 20% faster than intended due to the frequency.

The fact that the system was designed to have 240V/0V across it rather than +120V/-120v (excuse the simplification of AC there) is why I'd never recommend anyone do this at home.

Davita

Doesn't a delta connection require three-phases?

Pizzawheel

In this context I used Delta to mean differential; a voltage is always a differential. But don't get me started or I'll drift on to non-zero ground bonding.

Davita

Thanks Pizza...my question about the motor was rhetorical as I know it cannot be done by simply swopping the plug, and using the 240VAC split-system, as it can with a soldering iron or a kettle.

Therefore, I think we are in agreement with my response to Weve's post #23 where I suggested simply wiring his house from the N. American 240VAC system to enable using UK appliances, was a non-viable, and possibly dangerous, idea.

btw...trying to get a 240VAC kettle to steam using 120VAC, as someone suggested, seems to me like watching paint dry...

MikeUK

On the last part do the math...
if R is fixed and V is reduced by 1/2 then I is 1/4


for a 3kw in the UK we can fairly assume a resistance of 20ohms
the same kettle on 120v would function at approx. 750watt


allowing for the same amount of energy required to boil and losses being insignificant then it would take 4 times longer to boil the same kettle




isn't it interesting that most kettles in the US/Canada are around 1kw so a UK 3kw unit would only take 25% longer to boil than a local unit

MikeUK

FWIW


I have run several units on the US/Canadian twin phase 240v without issue

Mainly resistive (kettles/soldering irons/heater)but some inductive (drills)without any issues

I had a garage/workshop wired for both 120v and 240v with a couple of 250v 3 pin sockets (two live one earth> two horizontal pins one round earth) -'-

Never bothered trying a switch mode unit as most could handle the 120v's

Davita

That's why I sarcastically suggested if waiting for a UK kettle (240VAC) to boil on 120VAC it would be like watching paint dry....I understand the math.

Are you saying you used a UK 240VAC drill on the edison split 240VAC system or the 4 wire twin-phase system.....or a Canadian 240VAC drill?

MikeUK

Clear not on the maths front, 25% longer isn't waiting for paint to dry
Uk Kettle ~20ohm CAN kettle ~14ohms


UK Black and Decker on CAN 250Vac at 60HZ

Pizzawheel

People have done that here, and Mike has stepped up as one of them. You slap your +120 in the 240V live, and your -120 in the UK neutral, and everything works... electrically it's actually OK.

The risks and ramifications are somewhat more complicated, my concerns rests on energizing a neutral cable.

If you want to read more, here's a good start:

https://en.wikipedia.org/wiki/High-leg_delta

It's a north american thing.

MikeUK

In term of the appliance and (also to a point the house wiring to the junction box), the neutral is normally carrying current
The difference is its potential in relation to earth


But... In a UK system we'd only have a breaker on the live phase for 240v
a North American set up for 250v would have a dual breaker on both phases (or mine did)

Pulaski

As I see it, the greatest danger in using UK-sourced appliances on a jerry-rigged 240v North American supply is when the appliance has its own switch. That switch will isolate power from all the circuitry when supplied with UK-style 240v, but if the appliance is plugged in in North America, turning "off" the same switch will leave 120v feeding all the circuitry "backwards", through the neutral wire!

MikeUK

That a rather obscure way of looking at it
As you can and do get 250v sockets three pin -'- in NA ,.. normally in workshops for higher power tools where the 120v just can't give the push so its doesn't need to be jerry rigged

Yes one side of the circuit would still be live, but still off with no current flow
It would prove interesting if your 'domestic' appliance circuitry allowed a live feed to interact with the earth
Then it might be much more fun .... as current would still flow and it might be 'half' on


I look at its in a simple transformer view (as thats what your getting)
UK earth's one side of the 240v transformer and ignores the centre tap
US earth's at the centre tap/point and uses either side or both lives


In either case you don't 'dick' around inside with it plugged in but switched off ... unless you know what you're doing
Otherwise were moving from Electricity 101 to Darwin


Disclaimer However If this isn't clear and obvious then using UK appliances on anything other than a transformer shouldn't be an option for you !!!

weves

So, if North American 2-pin plugs have 1 live and one neutral and they appear to not care which orientation they are plugged in, this situation of live going through the neutral must happen half the time anyway on North American devices?