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American Kettles

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DrSimonB
1193903.  Fri Jun 03, 2016 10:07 am Reply with quote

An American kettle would not take twice as long to boil water. The power of a kettle depends on the voltage across it and the current through it. If the voltage is halved then you double the current by designing the kettle with lower resistance. UK kettles and US kettles will be designed with different resistances and both will work perfectly well.

Taking a British kettle to America would be problematic since it would have the appropriate resistance for the UK. In the USA it would have half the voltage across it and half the current through it resulting in on quarter the power.

 
Alfred E Neuman
1193906.  Fri Jun 03, 2016 12:09 pm Reply with quote

I think you'll find that American kettles have a lower power rating.

The domestic power outlets in the US are rated for 15A, so you can't actually double the current for half the voltage, and a quick survey of Walmart's website shows that the kettles on sale in the US are between 1kW and 1.5kW. My kettle is 3kW.

 
DrSimonB
1193910.  Fri Jun 03, 2016 1:12 pm Reply with quote

Interesting / they are designed to be lower power. Is there a reason behind that or is it just that they are not a nation of tea drinkers? Is there an efficiency difference?

 
Alfred E Neuman
1193912.  Fri Jun 03, 2016 1:54 pm Reply with quote

The reason is the current available from a domestic power socket, which is a factor of the thickness of the wiring.

To allow for the same power that you can get from a 230V supply, you'd need thicker wire, and copper is expensive. Basically, 230V is more flexible than 120V.

In the US the maximum power you can get for 15A and 120V is 1800W, but from a 230V supply at the same current you can get 3450W.

 
PDR
1193918.  Fri Jun 03, 2016 3:22 pm Reply with quote

In the UK essentially everything that plugs into the mains uses the same 3-pin plug system which is rated at a maximum of 13Amps (BS1363 refers). It would be normal practice (IET regs 17th edition refers) for anything requiring more than 13A to be wired directly - items like electric ovens and electric flash-heating showers would be in this group. There are minor exceptions which use two-pin only plugs (shaver sockets, fregsample) but they are a special case.

In the USA they operate a range of power sockets to the NEMA standard, with some rated at 15A, some at 20A and some at 30A (there is also a 50A version, but that's only for specialist things like ovens). The configuration of the socket receptacles and plug blades is such that you can plug a 15A plug into a 30A socket, but not vice versa.

The typical sockets you'll find in the walls and in kitchens will be the 15A ones, so the power available for plug-in devices is limited to 15A (1650-1800w depending on whether the specific area has 110v or 120v mains). the reason for having mainly only 15A sockets relates to the risk of overloading the wiring, which is exacerbated by the american preference for radial rather than ring-main installations.

The real question is why does america have 110/120v mains where most other places have 230/240V mains. You can blame this on Edison. He spent a long time trying to promote DC power systems (even though they needed generator plants on every street corner, which AC systems don't). DC voltages are far more dangerous than AC voltages as a source of electric shocks, and after much experiment it was determined that the maximum DC voltage that was not immediately lethal was 100Volts, so Edison power was specified at 100v +/- 10%.

When common sense prevailed and the colonies progressively moved over to AC power they retained this voltage so that the wiring could be retained without upgrading the insulation. So 120v is actually the maximum that can safely be pushed out on a single conductor to a domestic supply in America. Except that it isn't, but I'll come back to that in a minute.

In the UK and Europe the first large-scale electric power systems went straight to AC, and voltages between 200v and 250v were chosen independently as experiments on lethality came to slightly differing conclusions. Over the last 50 years this has been progressively standardised across Europe at 230v (+10% -6%). We've also standardised on 50Hz (where America chose 60Hz) although some of the original British electricity companies had used different frequencies - the London Electric Company chose 33Hz and I believe the Hull company used 100Hz. Some of the original LEC transformers are still in use after over 100 years because they don't wear out as such, but when used on 50Hz they are less efficient and they run a bit hot as a result.

Now I said the american home has 110/120v AC. This is both true and false. The internal wiring certainly runs at this voltage, but the supply to the house comprises a 3-wire supply - two anti-phased "live" wires and a neutral. Anything connected between either live and the neutral will see 110/120v, but things connected between the two live wires will see 220/240v, and this is used for some higher power fixed (direct-wired) appliances like air conditioners. Many years ago there was theory that the USA would progressively migrate to 240v, but I believe this is now seen as a commie plot and has been abandoned.

Does that answer the question?

PDR

 
suze
1193924.  Fri Jun 03, 2016 3:57 pm Reply with quote

PDR has explained the electrics, and there are a couple of societal things to bear in mind as well.

Firstly, the US is not a nation of tea drinkers in the same way as Britain. Coffee is very much the default hot drink, and only 7% of coffee drunk in US homes is instant coffee for which one needs to boil a kettle. Contrast with the UK, where 77% of coffee drunk in the home is instant. (Source: Mintel, 2014)

And secondly, when an American does need to boil a kettle she probably uses a stovetop kettle. The automatic electric kettle which turns itself off when the water has boiled was a British invention, invented by Bill Russell and Peter Hobbs in Croydon in 1955. (Bill Russell had earlier invented the pop-up toaster, but at that time he was working for Donal Morphy and Charles Richards in Orpington. After a falling out with them, he found himself a new business partner and went off inventing kettles.)

The Russell Hobbs type electric kettle has never really caught on in the US, and you'd have to look quite hard to find one in the shops. Whether that's because Americans have less use for kettles since they don't drink tea or instant coffee, whether it's because electric kettles are less useful on American voltage, or both or neither, I shall leave to the Americans among us.

 
PDR
1193925.  Fri Jun 03, 2016 4:16 pm Reply with quote

suze wrote:
Firstly, the US is not a nation of tea drinkers in the same way as Britain.


I dispute this.

Britain is a nation of proper coffee drinkers, a large number of whom have shown character flaws which have caused them to stray from the True Path. Forgiveness is available for those who repent and return to the One True Hot Drink, but those that don't will be cast into the Judecca round of the ninth circle for all eternity, compelled to perpetually warm the pot for the making of Beelzebub's Beverage, and to be showered with its dully metabolised postcursor.

Suffer thou not the tea-drinker to live!

PDR

 
Jenny
1193938.  Fri Jun 03, 2016 5:55 pm Reply with quote

You don't have to look far to find an electric kettle in the shops over here these days. I bought one recently from Bed, Bath and Beyond and had quite a few different makes to choose from. They do take about twice as long to boil as a British kettle though. Toasters have the same problem - they seem to take forever to toast a slice of bread.

We have to have special 240v circuits installed to run things like the washer, the dryer and the stove. All other circuits run on 110 or 120v.

 
PDR
1193953.  Sat Jun 04, 2016 3:03 am Reply with quote

If you'd had a word with the installers they could have fitted a 240v spur into the kitchen. then you'd just need a few british 13A sockets to run a british kettle & toaster...

When I was a student I saw a brand new (boxed) electric frying pan in a charity shop window for 20p. The reason it was so cheap was that it was an american (110v) one. I bought it and fitted a 10A diode inside the plug so it received half-way-rectified 230v, which to a heating element looks just the same as 115v AC. It was just right to make her bacon & eggs for breakfast before she scuttled back to her own digs...

PDR

 
Yokozuna
1225435.  Thu Feb 09, 2017 1:23 am Reply with quote

So, PDR, where did you fit that diode? In the place where the fuse normally goes?

On a less impudent note, I have a comment on US house wiring that you may not be aware of. The US code permits plug/socket connections for just about any connection. This includes lamps fitted downstream of a wall switch and large appliances such as 220v laundry dryers and roasting ovens.

I was surprised the first time I encountered a lamp that was hard wired to the wall just because it was controlled by a wall switch.

Just my two cents. Er, tuppence.

 
PDR
1225439.  Thu Feb 09, 2017 3:01 am Reply with quote

Yokozuna wrote:
So, PDR, where did you fit that diode? In the place where the fuse normally goes?


No - it was a stud-diode which was bolted through a holed drilled in the top of the plug, and then potted-over with RTV and then araldite

PDR

 
Jenny
1225818.  Sat Feb 11, 2017 2:49 pm Reply with quote

I do have a 240v spur in my kitchen for the oven, and one in the laundry room for the washer and dryer. However, you have to have a special circuit run for it (presumably for the reason of needing thicker wiring) and it seems a tad wasteful to do that just for a kettle and toaster. I just allow more time to make a cup of tea.

 
bobwilson
1286796.  Wed Jun 13, 2018 6:27 pm Reply with quote

Quote:
and it seems a tad wasteful to do that just for a kettle and toaster.

HERETIC

When it's time for tea or toast, you'll regret your penny-pinching as you wait...and wait......and wait.............

 

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