Curiosity Only, somewhat off topic.
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I noted recently several refs by USA users asking about 240 volt ac power
plugs etc. Now I have never even been to a 110v country - possibly only USA ? - and I can see a degree of (shock) safety offered with that system, but I can hardly imagine the mass of copper required to carry possibly 200 amps around the house. Nevertheless, I just wondered why there seems such interest in running 240v equipment, presumably via suitable transformer. David VK3DBD/G3SCD. . ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: Curiosity Only, somewhat off topic.
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David,
The standard residential service in the US of A is 120/240 Volts AC. It is provided by the center tapped secondary winding of the utility transformer. The center tap is grounded and becomes a Neutral such that in the home you have two 120 VAC legs, one from each of two ends of the secondary winding. The two legs are 180 degrees out of phase to each other, and separately are used with the grounded neutral to provide the 120 VAC service. For larger appliances such as stoves, ovens, hot water heaters, clothes dryers and Amateur Amplifiers, the current is sourced by connecting to both 120 VAC legs, resulting in 240 VAC being delivered to the appliance. No additional step-up transformer is required. There is no free lunch. The laws of physics cannot be changed. It is just a different scheme of power delivery which allows a grounded neutral to be carried to each small appliance or lighting fixture. I hope that helps a bit with your understanding. Milt, N5IA -----Original Message----- From: David Dunn Sent: Wednesday, December 14, 2011 3:04 PM To: [hidden email] Subject: [Elecraft] Curiosity Only, somewhat off topic. I noted recently several refs by USA users asking about 240 volt ac power plugs etc. Now I have never even been to a 110v country - possibly only USA ? - and I can see a degree of (shock) safety offered with that system, but I can hardly imagine the mass of copper required to carry possibly 200 amps around the house. Nevertheless, I just wondered why there seems such interest in running 240v equipment, presumably via suitable transformer. David VK3DBD/G3SCD. . ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ----- No virus found in this message. Checked by AVG - www.avg.com Version: 2012.0.1890 / Virus Database: 2108/4680 - Release Date: 12/14/11 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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*240 volt in USA*
Thanks to several folk who so promptly and sensibly repllied to my posting. Now I understand and can see why the local electricians do not have to use pipe benders to get the wire around the corners...... I have over the years wired several complete houses, both new and "rebuilds" and seen the requirements in a house change from a supply to light about half a dozen 100 watt lamps and a 1 kW heater occasionally, to the current trend needing hefty cable of sufficient capacity to run two 10 kW electric showers plus kettles and heaters Tvs and all the other gadgets we seem to require in modern living.! All comments much appreciated, Compliments of the Season to all and Happy Elecrafting...... David in Sunny Yackandandah On 14 December 2011 22:33, Milt -- N5IA <[hidden email]> wrote: > David, > > The standard residential service in the US of A is 120/240 Volts AC. > > It is provided by the center tapped secondary winding of the utility > transformer. The center tap is grounded and becomes a Neutral such that in > the home you have two 120 VAC legs, one from each of two ends of the > secondary winding. The two legs are 180 degrees out of phase to each > other, > and separately are used with the grounded neutral to provide the 120 VAC > service. > > For larger appliances such as stoves, ovens, hot water heaters, clothes > dryers and Amateur Amplifiers, the current is sourced by connecting to both > 120 VAC legs, resulting in 240 VAC being delivered to the appliance. No > additional step-up transformer is required. > > There is no free lunch. The laws of physics cannot be changed. It is just > a different scheme of power delivery which allows a grounded neutral to be > carried to each small appliance or lighting fixture. > > I hope that helps a bit with your understanding. > > Milt, N5IA > > > -----Original Message----- From: David Dunn > Sent: Wednesday, December 14, 2011 3:04 PM > To: [hidden email] > Subject: [Elecraft] Curiosity Only, somewhat off topic. > > I noted recently several refs by USA users asking about 240 volt ac power > plugs etc. > > Now I have never even been to a 110v country - possibly only USA ? - > and > I can see a degree of (shock) safety offered with that system, but I can > hardly imagine the mass of copper required to carry possibly 200 amps > around the house. Nevertheless, I just wondered why there seems such > interest in running 240v equipment, presumably via suitable transformer. > David VK3DBD/G3SCD. > . > ______________________________**______________________________**__ > Elecraft mailing list > Home: http://mailman.qth.net/**mailman/listinfo/elecraft<http://mailman.qth.net/mailman/listinfo/elecraft> > Help: http://mailman.qth.net/mmfaq.**htm<http://mailman.qth.net/mmfaq.htm> > Post: mailto:[hidden email].**net <[hidden email]> > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > > > ----- > No virus found in this message. > Checked by AVG - www.avg.com > Version: 2012.0.1890 / Virus Database: 2108/4680 - Release Date: 12/14/11 > Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: Curiosity Only, somewhat off topic.
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In reply to this post by Milt -- N5IA
On 12/14/2011 2:33 PM, Milt -- N5IA wrote:
> The standard residential service in the US of A is 120/240 Volts AC. Another very important difference between UK practice and North American practice is that in the UK, ring circuits are used, while they are not in the US. The central breaker panel in a typical home will have 15-30 branch circuits that go to various parts of the home. The breakers are set for 15A or 20A, and are carried on #14 or #12 copper with a phase, a neutral, and a protective earth. There's a FAR more extensive description of power wiring practices both in the US and Europe on my website that I was paid to write by a company that makes power protection products.. The did NOT tell me WHAT to write. :) http://audiosystemsgroup.com/publish.htm 73, Jim Brown K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by vk3dbd
Hi David,
I think Milt [he and I share the same family name, no relationship however] explained it well. Regarding safety, I'm not sure it makes a whole lot of difference. However, I distinctly remember reading somewhere that 450 VAC is the most lethal. I don't know why. That service in the USA is essentially all industrial, 3-phase, and depending on how the transformer is wired, seems to come in three flavors: 408, 440, and 480 V. Virtually all US residential wiring is 120/240 single phase. 73, Fred K6DGW - Northern California Contest Club - CU in the 2012 Cal QSO Party 6-7 Oct 2012 - www.cqp.org On 12/14/2011 2:04 PM, David Dunn wrote: > I noted recently several refs by USA users asking about 240 volt ac > power plugs etc. > > Now I have never even been to a 110v country - possibly only USA ? > - and I can see a degree of (shock) safety offered with that system, ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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