Today I spoke with an electrician, who confirmed that yes, this is the way 220V single-phase is in the U.S -- 3 wires (ground and two 110V legs). So I took the chance and wired up a plug, then ran a test with a handful of resistors on a PCB and ... it works!!! I can reflow a board with the fixed profiles, but now I need a code to configure the profiles, etc, so hopefully the seller has it. Much thanks, -Neil. Quoting Bob Ammerman : > In the US, many 220V loads (like baseboard heaters) are wired with a 3 > conductor cable: white and black are the two phase wires, green is a safety > (frame) ground. No neutral. > > -- Bob Ammerman > RAm Systems > > ----- Original Message ----- > From: "Sean Breheny" > To: "Microcontroller discussion list - Public." > Sent: Wednesday, December 09, 2009 7:30 PM > Subject: Re: [EE] Oven wiring help > > > On Wed, Dec 9, 2009 at 6:41 PM, PICdude wrote: >> I did some basic testing... >> - Referencing this link again ( http://www.ezdiyelectricity.com/?p=238 >> ), I get 120V between X and G, 120V between Y and G, and 209V between >> X and Y. Both outlets are the same. >> - On the oven, the green-wire to ground resistance is effectively zero. > > This suggests that your building has 208V three phase power and those > outlets are wired between two of the phases. The third pin is ground. > >> >> I'm confused by your last paragraph -- why would I not be able to use >> the 209V across the two terminals that supplies 209V? Are you saying >> that a neutral is required? > > Well, in principle, no neutral is required. However, the fact that the > wire colors are as they are, (i.e., black, white, and green) would > indicate that the white should be at the same voltage as ground (i.e., > neutral). In many countries (like the UK), 220V standard circuits are > wired that way (one hot line which is 220V with respect to ground, one > neutral which is nominally at ground potential, and then the safety > ground). There is no way for you to provide exactly that configuration > (which the colors suggest), since you have no source of 220V with > respect to ground, only 220V between two wires which are each only > 120V with respect to ground. > > Most likely, the neutral line is completely isolated from ground in > the device itself and it would be OK to connect it to one of the > phases and the device would never know the difference. However, there > is a chance that doing so could damage it or make it malfunction, > since it may expect the voltage between the white and green lines to > be small. > > Sean > > >> >> Cheers, >> -Neil. >> >> >> Quoting Sean Breheny : >> >>> Hi Neil, >>> >>>> From your description, it sounds like it is single phase. I would >>> check conductivity (with an ohmmeter) from the green wire to the >>> chassis. The green wire should be ground. If that is the case, then it >>> is certainly single phase. White is for neutral and black for hot >>> (line). >>> >>> HOWEVER, if you are in the US, I do not think that hot-neutral single >>> phase 220V is available. Is this oven meant for US electrical >>> standards? 220V outlets in houses in the US usually use two hot lines, >>> 180deg apart in phase, plus a ground wire. One hot wire is black and >>> the other red, typically. Such outlets will often have only the two >>> hots and ground, but there are types which have a neutral, too. >>> However, the voltage from each hot to neutral is 110V. >>> >>> In US industrial installations, the primary power source is usually >>> 480V three phase, which is then stepped down to 208V three phase. 120V >>> for lighting and outlets is derived by running circuits between one of >>> the 208V lines and a neutral which is connected to the wye center >>> point tap on the secondary of the 480V to 208V transformer. >>> >>> 220V devices are usually designed for residential use, but when they >>> must be installed in an industrial environment, they are typically >>> wired between TWO phases of a 208V three phase supply. If they require >>> a neutral, the wye point is once again typically used. This is a >>> little bit funky because (A) the total phase to phase voltage will be >>> 208 instead of 220, but that is usually within tolerances and (B) the >>> phase to ground voltage will not be 50% of the total but a little >>> higher (58%, that is 1/sqrt(3) instead of 1/(2)). >>> >>> So, it sounds to me like your oven, provided that it uses the standard >>> wire colors, and is designed for the US, is probably designed to use >>> 120V. Do you know what the total required wattage is? Isn't there an >>> electrical spec plate on the unit somewhere that would tell you about >>> how it should be wired? >>> >>> If your office receives 220V single phase service (two hot lines, each >>> 110V with respect to ground), similar to a US house, then I'd say your >>> L6-30 recepticle probably has connections to the two 110V hots and one >>> connection to ground. There should be no neutral on this plug. This >>> would NOT be able to supply your oven because the three wires coming >>> out, at least as indicated by color, have only one hot line and does >>> have a neutral. >>> >>> The Hubbell twist-lock plug could be any of several types. It should >>> also have an Lxx-xx number on it somewhere. That would allow us to ID >>> it. How many pins does it have? >>> >>> Sean >>> >>> >>> On Wed, Dec 9, 2009 at 4:22 PM, PICdude wrote: >>>> Hi all, >>>> >>>> Need some quick wiring assistance please... >>>> >>>> I recently picked up a used reflow oven (APS GF-12) and it does not >>>> have a plug -- just 3 bare wires (12ga white, green and black). The >>>> prev owner said it was hardwired and thinks it was 3-phase, but IIRC >>>> 3-phase requires 4 wires... or not??? >>>> >>>> I have 2 options for outlets here at the office... >>>> (1) a Nema L6-30 ( http://www.ezdiyelectricity.com/?p=238 ) >>>> (2) Another similar outlet, but the prongs are in a smaller circle. >>>> It says "Hubbell twist-lock 20A 250V plug". >>>> >>>> So I ask... >>>> - Is this oven a single-phase oven? (APS only made these as 220V >>>> single-phase or 220V 3-phase). >>>> - Is there a standard for the colors on the plug wires? >>>> - Is there any way to check the oven for the correct phase >>>> requirements (resistance tests, etc) before I damage the oven? >>>> - Are both of these outlets single phase? >>>> - Which wires should I connect to which prongs on the plug? Assuming >>>> these plugs are available quickly. >>>> >>>> Google hasn't yet given me any definitive answer. I have a few days >>>> left on my DOA warranty, so need to test fast, and APS won't speak to >>>> me unless I give them $2000 first. >>>> >>>> Much thanks, >>>> -Neil. >>>> >>>> >>>> >>>> -- >>>> http://www.piclist.com PIC/SX FAQ & list archive >>>> View/change your membership options at >>>> http://mailman.mit.edu/mailman/listinfo/piclist >>>> >>> >>> -- >>> http://www.piclist.com PIC/SX FAQ & list archive >>> View/change your membership options at >>> http://mailman.mit.edu/mailman/listinfo/piclist >>> >> >> >> >> >> -- >> http://www.piclist.com PIC/SX FAQ & list archive >> View/change your membership options at >> http://mailman.mit.edu/mailman/listinfo/piclist >> > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist