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My goal is to have a house where all loads are powered by 240V, that is fully livable in all the normal ways. And this question concerns the hard, in-house, built-in wiring; we will armwave the availability of plug-in appliances.

Under NEC 2014/17, will it be possible to a) serve all built-in (ordinarily hardwired) loads with 240V supply?

I am willing to switch appliances (e.g. to all hard-wired lamps, and to all socketless, light emitting or discharge lights). There won't be a conventional forced-air furnace; it'll be mini-splits, baseboard emergency heat, and electricityless Empire heaters.

Let us presume I have either found US-legal 240V plug-in appliances, or decided to do without them.

Code calls out a number of 120V circuits and receptacles that specifically must exist: kitchen counter receps within 2' of any point on a countertop, wall outlets within 6' of any point along a wall, laundry room, bathroom, outdoor etc. I'm willing to physically install them as well and just leave them de-energized. With 240V circuits right next to them. 120/240V multi-wire branch circuits will not be used.

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Harper - Reinstate Monica
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  • Comments are not for extended discussion; this conversation has been [moved to chat](https://chat.stackexchange.com/rooms/111737/discussion-on-question-by-harper-reinstate-monica-would-it-be-code-legal-to-ha). – Michael Karas Aug 13 '20 at 02:20

3 Answers3

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Several have mentioned The required 120v circuits include 2 small appliances for kitchen counters, 1 for the laundry, 1 for the bathroom(s).

But I think the main problem you run into is 210.6.

210.6 Branch-Circuit Voltage Limitations. The nominal voltage of branch circuits shall not exceed the values permitted by 210.6(A) through (E).
(A) Occupancy Limitation. In dwelling units and guest rooms or guest suites of hotels, motels, and similar occupancies, the voltage shall not exceed 120 volts, nominal, between conductors that supply the terminals of the following: (1) Luminaires
(2) Cord-and-plug-connected loads 1440 volt-amperes, nominal, or less than 1∕4 hp

This limits the voltage to 120v nominal between conductors for luminaries and cord and plug connected loads 1440 nominal or less. This means all those 240V devices other countries use would not be code compliant in the US with regard to lighting and appliances as most are under 1500W.

SQB
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Ed Beal
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  • So if I have 240V receptacles in a garage workshop for tools, with no neutral in that box, I can't run some lighting fixtures on the same circuit? – manassehkatz-Moving 2 Codidact Aug 12 '20 at 19:24
  • @manassehkatz-Moving2Codidact there are provisions in 210.6(C) which allow luminaires on 277V circuits. – brhans Aug 12 '20 at 19:29
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    If I understand https://www.electricallicenserenewal.com/Electrical-Continuing-Education-Courses/NEC-Content.php?sectionID=806.0 correctly, it sounds like with the 2020 code, **cord-and-plug-connected or permanently connected utilization equipment** are permitted too. Which means that the only real limits of "120V only" (aside from required for kitchen, etc.) is the smaller sizes of Edison bulbs - which makes sense because you don't want to have a 240V light bulb socket where an unsuspecting user could screw in a standard 120V bulb. – manassehkatz-Moving 2 Codidact Aug 12 '20 at 19:35
  • You need to read that code exception it is a 277v step down to 120v fixture the light is still 120v with that exception in a residential setting, my shop was separate from the house so as a commercial building it could have 480v lighting if available. Most metal halide lamps and sodium vapor actually run under 120v at the lamp they strike at higher voltages but the operational voltage is 120 at the lamp exhibit 210.4 shows this with a nice example. – Ed Beal Aug 12 '20 at 19:43
  • @manassehkatz-Moving2Codidact the 2020 NEC has "210.6 (A) Occupancy Limitation." which specifies 120V outlets for "(2) Cord-and-plug-connected loads 1440 volt-amperes, nominal, or less or less than 1/4hp". The step-down option for lighting is covered by 210.6(C)(3). 210.6(C)(6) allows "Luminaires without lampholders", so an embedded 277V LED fixture should be legal. 210.6(C)(8) also allows 277V LED retrofit kits. – brhans Aug 12 '20 at 19:49
  • Wait a minute, 210.6(A) seems to apply to hotels. Your guy might have erred, the parsing is ambiguous. See also 210.6(C): Circuits exceeding ] 20 volts, nominal, between conductors and not exceeding 277 volts, nominal, to ground shall be pennitted to supply the following: (1) Listed electric-discharge or listed light-emitting diode type luminaires. That means fluorescent and LED :) – Harper - Reinstate Monica Aug 12 '20 at 19:49
  • @Harper-ReinstateMonica 210.6(A) - "In **Dwelling units** and ...". The same language is used in 210.6 NFPA 70A - the "NEC Requirements for One- and Two-Family Dwellings". So a "Dwelling unit" is a normal house. – brhans Aug 12 '20 at 19:55
  • And similar occupancies, the code handbook continues to explain to reduce the risk of shock to occupants 210.6.B 120v between conductors #1 lamp holders #: cord and plug or permanently connected That is a residential circuit sorry I real the entire article but still 210.6 covers it. – Ed Beal Aug 12 '20 at 19:57
  • @brhans "In dwelling units and guest rooms or guest suites **of hotels**..." Granted, "Dwelling Unit. A single unit, providing complete and independent living facilities for one or more persons, including permanent provisions for living, sleeping, cooking, and sanitation." So maybe. Still, 210.6(C) directly conflicts, and usually, the specific (calling out certain types of luminaires in 210.6(C)) overrides the general (luminaires in 210.6(A)). – Harper - Reinstate Monica Aug 12 '20 at 20:04
  • Again read the entire article, i gave the article and my experience. I am sure it will be spun however you want but in that case I would agree with closing as a waste of time. A) Dwelling unit: B:120v between conductors b.1 terminals of lamp holders within their voltage rating B.3 cord and plug . – Ed Beal Aug 12 '20 at 20:11
  • New to this. Do other countries have 240V phase to ground or 240v phase to phase. I +1'd you. – JACK Aug 12 '20 at 22:17
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    @JACK, most of Europe uses 230V phase-to-ground and 400V phase-to-phase. – Nate S. Aug 12 '20 at 22:51
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    For what it's worth, I would parse that as "in (dwelling units) and (guest rooms or guest suites of hotels)" but I agree it's ambiguous. Could indeed be parsed as "in (dwelling units and guest rooms or guest suites) of hotels" as well, or even "in (dwelling units and guest rooms) or (guest suites of hotels)". Would've been better if they listed it differently. – SQB Aug 13 '20 at 12:19
  • ... so what if you design the house for 5 air-conditioners per room, and 12V lighting only? (12V adapters fed by 240V of course) – user253751 Aug 14 '20 at 13:06
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Such a fun question deserves an equally fun answer.

Sure you can! And there's a neat trick that will help with all those troublesome NEC 2014/17 rules: simply make sure to build this house in a country where the NEC does not apply!

Most of the world uses 230V as their standard supply voltage, which is pretty close, but if that's not quite enough for you, there are 19 countries that use exactly 240V by default, and would make an ideal location to build a 240V-only house.

  • Brunei
  • Cook Islands
  • Cyprus
  • Falkland Islands
  • Fiji
  • Gibraltar
  • Isle of Man
  • Kenya
  • Kiribati
  • Kuwait
  • Libya
  • Nauru
  • Oman
  • Papua New Guinea
  • Qatar
  • St Lucia
  • Seychelles
  • Tonga
  • Uganda

(source: https://en.wikipedia.org/wiki/Mains_electricity_by_country)

Jim Stewart
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  • Comments are not for extended discussion; this conversation has been [moved to chat](https://chat.stackexchange.com/rooms/113357/discussion-on-answer-by-nate-s-would-it-be-code-legal-to-have-an-all-240v-house). – Michael Karas Sep 24 '20 at 03:44
  • This answer would benefit from any citation at all that indicates a 240V house is code-legal in the United States. Currently it just says "yes!", but then implies there are actually concerns w/ NEC compliance without detailing anything. As it stands, this post has no utility for anyone asking the question above. – TylerH May 28 '23 at 18:24
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Pointless exercise. The "armwave" of the existence of all possible loads being available in 240V is not insignificant. Most major appliances are already 240V, so you are only referring to things like lighting, small appliances, entertainment, personal items, PCs etc. Yes, you could buy them from overseas in 230V versions, but you would then have to change the plugs to match legal 240V plugs available here or buy adapters and why on earth would you want to go through that hassle? There is NO ADVANTAGE to using 240V for small loads.

JRaef
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  • Comments are not for extended discussion; this conversation has been [moved to chat](https://chat.stackexchange.com/rooms/113356/discussion-on-answer-by-jraef-would-it-be-code-legal-to-have-an-all-240v-house-i). – Michael Karas Sep 24 '20 at 03:44
  • This does not appear to address the question that was asked, which is "is it _code legal_ to do", not "is there a reason". – TylerH May 28 '23 at 18:26