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This is an observation I am basing very much basing on anecdotal evidence. I have recently moved to the U.S from Europe, and have previously lived in New Zealand. I find that kettles (known as tea kettles here) take a lot longer to boil water in the United States.

Someone suggested to me that this is due to the lower mains voltage level (120 as opposed to 240V in NZ). Is this correct? I would have thought it would be easy to compensate for by increasing the current.

Chris Stratton
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  • There is also a significant influence of air pressure or height. The closer to sea level you are, the higher the boiling temp, and the slower the cooking in a boiler with the same rating. – posipiet Jan 11 '13 at 07:39
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    While this question, as phrased, it not really suited for EE.sx, the differences that *lead* to the OP asking the question (e.g. the difference in available power from an outlet in various countries) does seem appropriate for the EE.sx site. As such, I think it might need rephrasing, but it seems useful to keep around. – Connor Wolf Jan 11 '13 at 08:36
  • This is very much a real question which highlights the impact of electrical design decisions, in this case domestic outlet voltage. Electric kettles as discussed here may not be so common in the US (Boston tea party fallout making a countertop coffee maker more patriotic) but are well known and depended upon in much of the developed world. (Or at least the 240 vac regions). – Chris Stratton Jan 11 '13 at 15:00
  • @ChrisStratton This seems off-topic to me as a clear impact in consumer-electronics support. There is no design here, just discussion of what leads to a kettle boiling slower in one country then another. We would need detailed measurements on the kettle, if it is a case that it is the exact same kettle with a cable to the outlet I think the answer is relatively easy to explain, lower voltage-same resistance. While I agree this highlights impacts of electrical design decisions, do do many [su] questions discussing hardware choices, that does not make the question fit automatically. – Kortuk Jan 11 '13 at 19:48
  • If this question were on topic we would have to have detailed info on altitude, which kettles were used and full electrical specs on how they were implemented. – Kortuk Jan 11 '13 at 19:50
  • @Kortuk - the relevant EE design information is in the excellent answer below - many posters contributed the details of circuit current ratings which domestic appliance designers must constrain themselves by - it's not about the specific product, but about the *constraints on all such products which could be designed*. In most (though obviously not all) cases altitude is a minor factor. – Chris Stratton Jan 11 '13 at 19:54
  • @ChrisStratton breaker ratings for different countries is a useful piece of information for design, I agree. If there were a question about current limits in homes around the world for design purpose that sounds like a great fit. This is not asking about that, and the power rating of his kettle heating element might be much, and very plausibly is, lower then the maximum for a room. I am not arguing as to how interesting I find the question, just to the point that it does not fit. – Kortuk Jan 11 '13 at 20:13
  • @ChrisStratton The argument that this question is on-topic for this site is a stretch. It is not indicative of any intent or desire for electronic design or to engineer anything electrical. I would suggest it belongs to Physics or Skeptics more than EE. – Anindo Ghosh Jan 11 '13 at 20:31
  • @Kortuk - please see the answer which points out that the power rating of typical examples of such appliances in 240v countries exceeds the circuit rating in 120v countries - ie, it is a design issue in that **no one can design a comparable power rating appliance compatible with 120v domestic service** – Chris Stratton Jan 11 '13 at 20:51
  • @ChrisStratton If you would like to continue this discussion lets talk in [chat](http://chat.stackexchange.com/rooms/895/ee-ask-a-moderator) – Kortuk Jan 11 '13 at 21:26

1 Answers1

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It's not just you, and you are in fact correct.

What it boils down to is the available power on the local circuit breaker.

In the US, a house is normally broken up into various segments, each getting it's power through a 15A circuit breaker.

As such, the maximum available power for the circuit is 120V * 15A, or 1800 watts.
Furthermore, to prevent the breaker from tripping if a lamp or other device is also plugged into a circuit, the maximum power I have seen a single device draw is generally limited to ~1500W.

In a country with 240V mains, you only need to draw ~6.25A to get an equivalent 1500W.
A quick search for 240V electric kettles leads me to some devices that claim *3100 watt heaters.

I don't know what the standard/common breaker rating is in a 240V country, but if it's also 15A, that would mean that you can draw approximately twice the amount of power from any one outlet then you can in a 120V country.

That likely explains the difference you perceive.

Edit:

From @RJR in the comments:

Common breakers in Europe (NL at least) are 16A. 10A (older homes, lights) and 20A (power appliances like hotplates/hobs) are used also but not generally for normal power outlets.

As such, the maximum available power for a electric kettle is indeed twice the maximum available power in most 120V houses.

Connor Wolf
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    Common breakers in Europe (NL at least) are 16A. 10A (older homes, lights) and 20A (power appliances like hotplates/hobs) are used also but not generally for normal power outlets. – RJR Jan 11 '13 at 08:28
  • @RJR - Excellent! That nails it, then. – Connor Wolf Jan 11 '13 at 08:33
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    "What it boils down to" - heh :) – Martin Thompson Jan 11 '13 at 09:58
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    In the UK at least every mains plug is fitted with a <=13A fuse (3,5, and 13A are the common ratings), so you can't exceed ~3000W (taking into account startup kick on many devices). Most houses are wired on a ring-main system with a 16 or 32A breaker. – John U Jan 11 '13 at 09:59
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    @RJR Your observation is true for Germany, too. In my home, most breakers are B16. There is one for the washing machine, C16 (a bit more on the slo-blo edge). I use two B10 breakers for a room with old (1 mm^2) wiring, and I have seen B20 for big appliances, too. The standard outlets in the lab at the company I work at are fitted with C16, because our bench equipment would trip B16 all the time. – zebonaut Jan 11 '13 at 15:37
  • For new construction in the US circuits in the kitchen will have a 20A breaker for 2400W peak power. Unless they've been rewired older houses will still only have 15A circuits. – Dan Is Fiddling By Firelight Jan 11 '13 at 16:37
  • @DanNeely - If they wire kitchens with 20A breakers, do they use the 20A plugs too (The ones with one horizontal and one vertical prong)? I can see a customer-service nightmare coming from that, with stupid people not understanding why they can't plug their new electric gewgaw in. – Connor Wolf Jan 11 '13 at 20:23
  • @FakeName I assume they use outlets with sockets that can take both types of plugs. I live (and grew up in) older houses; and while I know the code's been updated have never gone "snooping" around when visiting someone with a new home. ex http://tinyurl.com/cnok9z9 – Dan Is Fiddling By Firelight Jan 11 '13 at 20:41
  • @DanNeely - The dual-type sockets were what I was (trying to) refer to. – Connor Wolf Jan 11 '13 at 20:53