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). =A0The > 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=3D238 ) > (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 =A0for 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? =A0Assuming > these plugs are available quickly. > > Google hasn't yet given me any definitive answer. =A0I 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