US 240V split phase supply cord - Page 1
Forum section: electronics / general

author: pcplatypus
author_rank: Newbie
timestamp: February 29, 2024, 10:54:55 am
content: We have an Australian 230V single phase piece of equipment that we want use in the US on 240V split phase (120 - N - 120). What supply cord is used for 240V in the US and is this mandatory under the US National Electrical code? I understand the US 240V colours are Hot L1 = Black, Hot L2 = Red, Neutral = White or Gray and Earth = Green/Yellow. As Neutral is not used is a 4 core cable required or is a 3 core, Red, Black, Green/Yellow suitable?

author: jonpaul
author_rank: Super Contributor
timestamp: February 29, 2024, 01:55:31 pm
content: Hello, a few points:1/ Regulation in USA is both NEC and local gov building electric .Eg Los Angeles differs from NYC.2/ Depending on the equipment KVA and portable/temporary/permanent the connectiond differ.3/ See Mike Holt forum or Professional Electricians forum, may have an answer.4/ Most USA AC, applicances washers, stove e 240V 2 wire, and use Line..Line connect, NO neutral.Thus a 3 pin connector L, L, Earth.5/ See Hubbel NEMA plug for chart USA r plug according V, I.https://image.regimage.org/hubbell-nema-plug-configuration-chart/6/ Import of some devices may be prohibited if nont compliant toUSA EMI or safety regs.7/ As safety, shock and fire hazards, Consult a lscenced electricina to install.Good luck,Jon

author: BrokenYugo
author_rank: Super Contributor
timestamp: February 29, 2024, 02:30:10 pm
content: How much current do you need and what sort of environment will it be in? I think there are about 6 or 7 different common ones off the top of my head between the 15/20 (NEMA 6-15/6-20) amp air conditioner outlets (looks similar to the usual 120V socket), 30 (14-30) and 50 amp (14-50) 4 wire with an extra neutral you can ignore, usually for stove/dryer, big RVs also use 14-50, the older 30 (10-30) and 50 amp (10-50) 3 wire stove/dryer with a shared neutral/earth (treat it like an earth wire for 240V load), and the 30 (6-30) and 50 amp (6-50) welder and big equipment socket. That's just what you usually see, if you look up a NEMA connector chart you will find more.For a plain old 240V load a 3 wire cord will be fine, ignore the neutral, that's for 120V loads, convenience outlets on stoves and such.Note some apartments will give you two phases of a 208 3 phase supply instead.So yeah, it's complicated, you'll want to do some work ahead with your hosts to see what they can provide and adapt from there. Aside from welders most 240 stuff comes without a cord for good reason.For lower power a 120-240 transformer is probably the easiest solution.

author: Stray Electron
author_rank: Super Contributor
timestamp: February 29, 2024, 03:14:21 pm
content: Quote from: jonpaul on February 29, 2024, 01:55:31 pmNot true any more. Stoves etc used to use straight 220 VAC so they left out the neutral but many modern devices use the 110 VAC connection for control circuitry, timers, clocks, interior lights, etc so they require the neutral. So all stove, washer and dryer cords and outlets are now 4 wire; L1, L2, N and Gnd. To my knowledge all water heaters are hard wired in and still only use L1, L2 and Gnd but that will probably change if/when they start adding Smart Controllers or other electronic controls to them.Otherwise I completely agree with the rest of your post.

author: ejeffrey
author_rank: Super Contributor
timestamp: February 29, 2024, 03:17:23 pm
content: Nema 6-15 would be the normal thing if you don't need neutral. It's somewhat common in industrial and commercial locations for moderately high power equipment -- espresso makers, computer racks, and vacuum pumps all often use this. It's pretty rare in residential settings although it's used in wood shops for tools like table saws and dust collectors.Excepting workshops, residential use is almost always either 120V or high enough power to use 30+ amp circuits such as electric stoves, clothes driers, and EV chargers. But that's probably not what you want.If your device is going to go in a commercial space there is a good chance the user will either have or be able to install a 6-15/6-20 outlet. In that case it will receive 208 not 240. But if you want more flexibility and don't really need the power it's much better to make it work off of 120.

author: pcplatypus
author_rank: Newbie
timestamp: February 29, 2024, 10:31:01 pm
content: Thank you all for your replies, this is most helpful and the Hubbel NEMA chart. I have posted to the Mike Holt forum as suggested. We will be working with local electricians for the installation as well as getting up to speed with the applicable local regulations. At this stage we don't know the location (which US state). This is a commercial application and we will be able to get 240V split phase. The supply in goes to a number of switch mode supplies, so the 240V split phase will be fine, there is no neutral required as nothing requires 120V. We don't want to use 120V as this would require larger conductors and would complicate our existing compliance. The cord is permanently attached and we would supply the equipment with a pre-wired cord to suit.The Australian (IEC) cord colours of Brown, Blue and Green/Yellow don't seem applicable as the US 240V has two live "Hot" connections and this would conflict with the Blue associated with Neutral in Oz. I believe that for US 240V Red (L1), Black (L2) and Green/Yellow (E) are typically used but I am looking for some input on this for those with local knowledge.Many thanks again.

author: bdunham7
author_rank: Super Contributor
timestamp: February 29, 2024, 10:38:32 pm
content: You haven't said how much power the unit needs and that is important.You also aren't clear as to whether this is a product that you want to import to US users or a one-off that you want to use while you are in the US.Nobody can give you a meaningful answer without that information. In the US if you mention 240V, everyone assumes you have a high power device (>1440VA) and if that isn't true you might want to go a different route.

author: cosmicray
author_rank: Frequent Contributor
timestamp: March 01, 2024, 12:42:14 am
content: Quote from: pcplatypus on February 29, 2024, 10:54:55 amMy concern about this theoretical piece of equipment, is how does the Australian mains wiring arrive to it ... neutral - 230v ? If the piece of equipment makes any use of that neutral, expecting it to be at 0v potential, then feeding it (120 - N - 120 = 240) might well work, but it may also put 120v hot onto something which the manufacturer did not intend to be hot. I would want to very carefully check the uses of the original wiring before applying a US 120 - N - 120 to it.

author: Someone
author_rank: Super Contributor
timestamp: March 01, 2024, 01:45:47 am
content: Quote from: cosmicray on March 01, 2024, 12:42:14 amNeutral could be live, or split phase, or 0V, and cant be assumed to be any one of those in advance. That's pretty standard electrical safety design outside of historic US.

author: ejeffrey
author_rank: Super Contributor
timestamp: March 01, 2024, 05:30:19 am
content: Quote from: pcplatypus on February 29, 2024, 10:31:01 pmThen assuming your power requirements are within the normal Australian 10/15 amp general use outlet a Nema 6-15 is what you want.Which state is for doesn't matter much. They have different versions of the electrical code, but that is mostly only concerned with the building wiring up through the receptacle. A local electrician asked to install a 6-15/20 outlet will be able to do that to the local code, and as long as your device has a cord with the proper plug it will be fine.QuoteBlack/Red/Blue are the standard colors for hot conductors in the US (depending on the # of phases). White is neutral and ground can be green, green w/ yellow stripe, or bare copper. Again this is mostly for building codes and a local electrician should get that right when installing the outlet. People usually follow these conventions in line cords and within their equipment, but it's much less controlled. For instance, if a piece of equipment doesn't care about the distinction between line/neutral, it's common to just use black for both.QuoteIt's been mentioned, but while this is not unheard of it is definitely uncommon. If you are counting on this make 100% sure. 240 VAC split phase is mostly used in residential areas. It also shows up in smaller commercial buildings, especially if they are in or by a residential zoned area. Most commercial electrical services has 3 phase 208, and a NEMA 6-15/20 outlet in those places will have 208 V not 240. 208 is the nominal voltage, and on one of our building it actually hovers around 199 VAC most of the time. If the building you are operating in has 3-phase service, it won't usually be possible to get 240 VAC without a transformer. I bring this up because we have had several pieces of finnicky equipment from the EU that didn't run on such a low voltage and needed a boost transformer installed by an electrician to operate.QuoteHave you considered just having a C14 or C20 power inlet and supplying an appropriate cord like this?https://www.digikey.com/en/products/detail/qualtek/226003-01/1466532along with a sticker saying "208/240 V only"?I don't generally like doing this unless your equipment could actually function off of either 120 or 208/240 since you can't really stop someone from replacing the cord. But it's not too bad as long as it isn't actually a hazard.

author: bw2341
author_rank: Regular Contributor
timestamp: March 01, 2024, 12:39:41 pm
content: That link to the web gallery of the Hubbell NEMA chart seems illegibly small in my browser.Here's a link to the original PDF.https://hubbellcdn.com/ohwassets/HCE/Hubbell%20Canada/Resources/NEMA_Chart.pdfA lot of industrial settings seem to prefer the round TWIST-LOCK style connectors.Watch out! The plug shape illustrations are all drawn to the same diameter which is incredibly misleading. The higher current plugs are much larger.