230Vac welder where you don't have 230Vac?

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I am sure someone else has done this before, but it worked well for me and I learned a couple things, and thought I should share it here in case its useful to someone else. ^^^ WARNING: Proceed at your own risk. I hereby disclaim responsibility if you die or get an expensive fine trying this; you're on your own! Do not try this unless you are sure you know what you're doing and prepared to take responsibility and the necessary precautions. I imagine most [or maybe all] building departments and the NEC would probably frown on this. I am only suggesting this technique for a temporary use in the field. If you need a shop setup, of course, run the proper wiring. That said, ... the electrical theory is perfectly sound, and in a temporary setup it worked great for me to do some TIG welding at about 150A peak output. I didn't try to see how much power I could get, and that would depend on the efficiency of your machine. I needed to do some welding with a 230Vac TIG machine where I could not readily get 230Vac, so I rigged up a "combining adapter" to combine two separate phases of 115Vac power. I purchased a surface-mount 230Vac appliance receptacle because it was the simplest hardware, and wired it up with two stubs of neoprene 10GA SO cord with a couple of heavy duty 115V plugs. I happened to find some plugs with built-in LEDs that would tell me the circuit had the correct connections for L, N, G, which was convenient, not essential, but I still tested each line separately with a good DMM AC voltmeter scale before firing up the welder. I ran two 100 foot heavy duty extension cords to outlets that were empirically determined to have opposite phase. You do this by measuring the voltage between the two "L" (Line connection, the skinnier blade compared to the "N" neutral blade) connections of the two separate 115Vac lines. If they are the same phase it will read zero volts or something close to that, and if they are opposite phases, you will get about 230Vac (or 208Vac if you are working in a building that begins with 3 phase). One thing I discovered is that a GFI protected circuit will not like this hookup and will trip because it will see different current on the neutral compared to the line. Normally this would be a problem on a 115Vac circuit, because it would mean there is some current leaking into an appliance or some plumbing or something, which could pose a hazzard. In this case though, all the current is going between the two separate phase "L" wires, with little or no current traveling in the "N" wire. We're playing a nasty trick on the GFI that makes it very unhappy..The connections I used were as follows:1) Connect the Black wire from the L (Line) of one of the 115Vac circuits to one side of the 230V receptacle2) Connect the other side of the 230Vac receptacle to the black L (Line) wire of the other 115Vac phase. 3)  Then I tied the two 115Vac White N (Neutral) wires together for the ground pin of the 230Vac receptacle.4) Finally, I tied the two green ground wires from the 115Vac circuits to the appliance receptacle box. *** CAUTION: Be sure to measure the voltages of the two 115Vac lines with a good test meter as follows before proceeding to connect any working load:  Phase A "L" connection to Phase B "L" connection should measure 230Vac   (If you do not measure approximately 230Vac (or 208Vac in a 3phase building), then you found two 115Vac lines which happen to be on the same power phase, keep looking.)Phase A "L" connection to Phase B "N" connection should read about 115VacPhase A "N" connection to Phase B "L" connection should read about 115VacPhase A "N" connection to Phase B "N" connection should read zero or very close to zero volts. When you find two circuits that yield these measurements, you should be good to go. With that combiner box and two heavy-duty 100 foot extension cords (preferrably 12Ga or larger), I can get 230Vac almost anywhere for temporary use to do maintenance or repair welding where you could not otherwise easily get 230Vac. You will still be limited to the current rating of the smallest of the two circuit breakers you're attached to, and ideally you want to find two circuits that are at least 20A circuits if you can, but a properly wired electrical panel will still protect the building's wiring from a current overload just as it would normally.One more caution: To be on the safe side, I would generally want to do this with two 115Vac circuits that are fed from the same main electrical service panel, or at least the same 230Vac utility company service drop from the same utility company dropping transformer. I would not want two circuits attached to separate utility company transformers. Different utility company transformers introduce the potential for mismatched phase delays, mismatched neutrals, etc. Could probably still work, but more things to worry about, better to keep it simple.I want to stress again that if you're not comfortable working with electrical wiring at this level of complexity, DO NOT TRY THIS! Get help from someone who knows what they're doing.Cheers!Hypertherm PMX600, Miller AC/DC Stick, O/A Gas Rig -- looking for a 200A, AC/DC, TIG Squarewave Inverter, Pulse, (maybe Chinese...)
Reply:That's the dumbest idea I've heard of lately on this board.I'd suggest you delete the thread before some other idiot tries to do the same thing and burns his house down.Ever wondered why a 240V circuit breaker is linked so if one leg trips so does the other one?Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:For temporary supervised connection, this is not dangerous. It will not burn the house down! If either breaker trips, no current will flow in either branch. If a double failure of some sort occurred, both legs are protected against the total current they can handle. We don't protect both sides of a 115V circuit, because opening up a circuit anywhere stops current everywhere. The standard practice of linking 230V breakers poles is mainly a protection against a defective breaker that fails to trip.Hypertherm PMX600, Miller AC/DC Stick, O/A Gas Rig -- looking for a 200A, AC/DC, TIG Squarewave Inverter, Pulse, (maybe Chinese...)
Reply:Trscott, I totally understand what your doing, taking leg 1 of a 115 volt circuit and leg 2 of the same 115 volt circuit, eliminating the neutral and using the voltage from leg 1-2 for 230 volts. Really don’t like it.
Reply:The only real risk in this is if you failed to connect things correctly, hence my disclaimer. You are of course entitled to your opinion, but your response seems more than a little bit extreme. The house is happily standing even yet. YMMVHypertherm PMX600, Miller AC/DC Stick, O/A Gas Rig -- looking for a 200A, AC/DC, TIG Squarewave Inverter, Pulse, (maybe Chinese...)
Reply:Originally Posted by transitTrscott, I totally understand what your doing, taking leg 1 of a 115 volt circuit and leg 2 of the same 115 volt circuit, eliminating the neutral and using the voltage from leg 1-2 for 230 volts. Really don’t like it.
Reply:Originally Posted by trscottFor temporary supervised connection, this is not dangerous. It will not burn the house down! If either breaker trips, no current will flow in either branch. If a double failure of some sort occurred, both legs are protected against the total current they can handle. We don't protect both sides of a 115V circuit, because opening up a circuit anywhere stops current everywhere. The standard practice of linking 230V breakers poles is mainly a protection against a defective breaker that fails to trip.
Reply:Personally I have to agree SundownIII This should not be published on this board. You are really opening yourself up to problems if people decide to follow your plan and unfortunately have a problem. For some people you are giving them a loaded gun and asking them to play russian roulette. I understand the engineering may be sound but the execution by people may not and then the trouble starts. My suggestion to people reading the article is to stay away and wire everything according to code.Harold MulderMiller 211 AutosetHTP 201 Invertig with water coolerHardinge Cataract Quick Change Lathe
Reply:Originally Posted by transitTrscott, I totally understand what your doing, taking leg 1 of a 115 volt circuit and leg 2 of the same 115 volt circuit, eliminating the neutral and using the voltage from leg 1-2 for 230 volts. Really don’t like it.
Reply:Originally Posted by transitNO! The reason for the link is for SAFTEY. If one of the two breakers trip, the companion circuit is de-energized.
Reply:Originally Posted by haroldmulderPersonally I have to agree SundownIII This should not be published on this board. You are really opening yourself up to problems if people decide to follow your plan and unfortunately have a problem. For some people you are giving them a loaded gun and asking them to play russian roulette. I understand the engineering may be sound but the execution by people may not and then the trouble starts. My suggestion to people reading the article is to stay away and wire everything according to code.
Reply:Originally Posted by SundownIIIThat's the dumbest idea I've heard of lately on this board.I'd suggest you delete the thread before some other idiot tries to do the same thing and burns his house down.Ever wondered why a 240V circuit breaker is linked so if one leg trips so does the other one?
Reply:Anyone want to take a stab at describing a fault condition with the system I have described which would lead to an unreasonable hazzard?I am willing to be persuaded if someone wants to take a stab at explaining what they think the problem is, but seriously this is just like connecting two 12V batteries in series to get 24V; literally no different conceptually. As for the risk of someone doing this wrong, come on guys, I didn't post this to real estate agents (I can say that because my wife is one LOL), but to welders! We work around molten metal at thousands of degrees. I hadn't expected such timidity. If you can wire up a household receptacle or an extension cord, you can do this safely. It doesn't even require opening your breaker panel; its all cord connected and really quite safe. The worst that happens if you do it wrong and fail to follow my instructions is the breaker trips, just like it would if you hooked up that extension cord or receptacle wrong.Hypertherm PMX600, Miller AC/DC Stick, O/A Gas Rig -- looking for a 200A, AC/DC, TIG Squarewave Inverter, Pulse, (maybe Chinese...)
Reply:http://www.110220volts.com/220V-15A.htmlEd Conleyhttp://www.screamingbroccoli.com/MM252MM211 (Sold)Passport Plus & Spool gunLincoln SP135 Plus- (Gone to a good home)Klutch 120v Plasma cutterSO 2020 benderBeer in the fridge
Reply:Thanks Broccoli, Now I don't have to worry about wiring on up myself.
Reply:The connections I used were as follows:1) Connect the Black wire from the L (Line) of one of the 115Vac circuits to one side of the 230V receptacle2) Connect the other side of the 230Vac receptacle to the black L (Line) wire of the other 115Vac phase. 3) Then I tied the two 115Vac White N (Neutral) wires together for the ground pin of the 230Vac receptacle.4) Finally, I tied the two green ground wires from the 115Vac circuits to the appliance receptacle box.
Reply:Originally Posted by Grimm1Thanks Broccoli, Now I don't have to worry about wiring on up myself.
Reply:Originally Posted by trscottThe connections I used were as follows:1) Connect the Black wire from the L (Line) of one of the 115Vac circuits to one side of the 230V receptacle2) Connect the other side of the 230Vac receptacle to the black L (Line) wire of the other 115Vac phase. 3)  Then I tied the two 115Vac White N (Neutral) wires together for the ground pin of the 230Vac receptacle.4) Finally, I tied the two green ground wires from the 115Vac circuits to the appliance receptacle box. Cheers!
Reply:Originally Posted by SandyWhy in the world would you tie two seperate neutrals together then use them for a ground when a ground is already available? If you absolutely have to do this sort of thing leave those neutrals back there where they were. Unless you have up close and personal knowledge how these two seperate circuits run and any devices that may be attached, be aware that those neutrals could very well be current carrying conductors one or two receptacles downstream of the point(s) where you just tapped in.
Reply:Never said YOU didn't know electronics.What you described, in your somewhat confusing way, is not rocket science.  Actually very easy to accomplish for anyone used to working with 240V circuits and understanding where the 240V comes from.You're obviously new to the board.  We have a lot of new members that do not have that background (read some of the "how do I hook up my welder" posts).  These were the posters I'm concerned about.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:It goes without saying that if this does not make sense to you, you probably should not try to do it yourself, go buy the $135 adapter that Broccoli1 found, or get a cooperative electrician friend to do it for you. But this is not crazy, just a little bit "MacGyver-esque." LOLHypertherm PMX600, Miller AC/DC Stick, O/A Gas Rig -- looking for a 200A, AC/DC, TIG Squarewave Inverter, Pulse, (maybe Chinese...)
Reply:I don't understand why you used an Appliance receptacle and brought the Neutrals in to the mix in the first place.How can you be certain the 120v receptacle you are using is not fed from a Sun Panel?Ed Conleyhttp://www.screamingbroccoli.com/MM252MM211 (Sold)Passport Plus & Spool gunLincoln SP135 Plus- (Gone to a good home)Klutch 120v Plasma cutterSO 2020 benderBeer in the fridge
Reply:done it, if you know what your doing, and fully understand the system your dealing with, I'd say no big deal, except your running of off two seperate breakers, or in my case fuses, which might damage the machine if one pops, but if your going through all of the hassle to make up a plug and cord, and you have a 240 service which if you do have a 240 service you should have a 240 breaker and I'd just connect your cord right there, or get a breaker to do so oppose to making up the funky cord to plug into two seperate plugs on different legs, hell just put a fricken 240 plug and circuit right next to the panel"Obstacles are those frightful things you see when you take your eyes off your goal"   -Henry Ford
Reply:If you have ever wired up an electric service panel (aka a breaker panel) you would remember that back at the panel, all the grounds and neutrals are tied to a common buss bar. The green ground wire is really just an extra neutral in case the neutral fails. Frankly you could tie either the neutrals or the grounds to the ground pin on the 230Vac appliance plug with exactly comparable effect, they are all really just paths for returning the current back to ground electrically, assuming the 115Vac circuits in the building are correctly wired. In a normal 115Vac circuit, the neutral carries as much current as the line, but in our case, all of the current flows between the two 115Vac line wires (black wire, narrow blade, L, often a brass colored terminal on the plug) and no current will flow in the neutral. Just like a normal 230Vac circuit where the current flows between two breaker poles attached to the opposite phase busses in the breaker panel and no current flows back to the neutral/ground buss. We're connecting to exactly the same place in the breaker panel, just using non-standard hardware to do it.
Reply:Originally Posted by SundownIIINever said YOU didn't know electronics.What you described, in your somewhat confusing way, is not rocket science.  Actually very easy to accomplish for anyone used to working with 240V circuits and understanding where the 240V comes from.You're obviously new to the board.  We have a lot of new members that do not have that background (read some of the "how do I hook up my welder" posts).  These were the posters I'm concerned about.I had buddy who said his dad use to  have some insulted clamps made up with spikes that he would clip right on to the wires coming off of the pole into the weather head to steal power while welding, now that is highly dangerous (deadly) and illeagal too"Obstacles are those frightful things you see when you take your eyes off your goal"   -Henry Ford
Reply:Originally Posted by eyeball engineerdone it, if you know what your doing, and fully understand the system your dealing with, I'd say no big deal, except your running of off two seperate breakers, or in my case fuses, which might damage the machine if one pops, but if your going through all of the hassle to make up a plug and cord, and you have a 240 service which if you do have a 240 service you should have a 240 breaker and I'd just connect your cord right there, or get a breaker to do so oppose to making up the funky cord to plug into two seperate plugs on different legs, hell just put a fricken 240 plug and circuit right next to the panel
Reply:Originally Posted by trscottEyeball,Let's be real clear here. If you have a simple 230Vac circuit as I've described, tied between two breakers, and only one breaker trips, the circuit is completely disconnected, all current will stop flowing. You will not damage the machine if only one breaker opens.If you put two switches in series in a circuit with a battery and a light bulb, one switch on each side of the light bulb, and open only one of the switches, the light bulb will go off just fine. You don't need to disconnect both sides of the circuit to stop the current from flowing.I am talking about a temporary field situation where you do not have any way to conveniently set up a 230VAC circuit. Another option would certainly be to open up the panel and hook up direclty to the panel with a new 230V breaker, maybe needing to take some breakers out to make room, etc., but goodness that is not nearly as easy to do, and the panel may not be anywhere near as close to where you need the power as the two wired 115Vac circuits.
Reply:Originally Posted by Sandy... What does or should happen back at the panel doesn't explain tieing two neutrals (current carrying conductors) ....
Reply:Eyeball, Just call me "target"Just tryin to help some other folks. Cheers!Hypertherm PMX600, Miller AC/DC Stick, O/A Gas Rig -- looking for a 200A, AC/DC, TIG Squarewave Inverter, Pulse, (maybe Chinese...)
Reply:Originally Posted by trscottEyeball, Just call me "target"Just tryin to help some other folks. Cheers!
Reply:Eyeball,I would a lot rather have someone do this, than try to connect directly to the service panel, or wire up their own 230Vac circuit if they're not sure what they're doing (much less jumper cables at the weathertop). At least with this setup once you get the adapter wired up correctly, it is just plug and play and will work anywhere you have correctly wired 115Vac circuits, and in any case, even if you do it wrong all the people and wiring are fully protected by the existing service panel breakers. It either works as intended, or it trips the breakers quite harmlessly (if you did something wrong or the existing 115 circuits are wired wrong), A lot of the objections here are simply uninformed.Hypertherm PMX600, Miller AC/DC Stick, O/A Gas Rig -- looking for a 200A, AC/DC, TIG Squarewave Inverter, Pulse, (maybe Chinese...)
Reply:Originally Posted by trscottEyeball,I would a lot rather have someone do this, than try to connect directly to the service panel, or wire up their own 230Vac circuit if they're not sure what they're doing (much less jumper cables at the weathertop). At least with this setup once you get the adapter wired up correctly, it is just plug and play and will work anywhere you have correctly wired 115Vac circuits, and in any case, even if you do it wrong all the people and wiring are fully protected by the existing service panel breakers. It either works as intended, or it trips the breakers quite harmlessly (if you did something wrong or the existing 115 circuits are wired wrong), A lot of the objections here are simply uninformed.
Reply:We could make the argument that its better to hash all this out here than have folks who know less than they think they do, try to do this without understanding the issues, and do it wrong. This is a VERY convenient accessory to have around.Hypertherm PMX600, Miller AC/DC Stick, O/A Gas Rig -- looking for a 200A, AC/DC, TIG Squarewave Inverter, Pulse, (maybe Chinese...)
Reply:Here's a simple schematic drawing: Attached ImagesLast edited by trscott; 02-09-2010 at 05:10 AM.Hypertherm PMX600, Miller AC/DC Stick, O/A Gas Rig -- looking for a 200A, AC/DC, TIG Squarewave Inverter, Pulse, (maybe Chinese...)
Reply:TRSCOTT(Let's be real clear here. If you have a simple 230Vac circuit as I've described, tied between two breakers, and only one breaker trips, the circuit is completely disconnected, all current will stop flowing. You will not damage the machine if only one breaker opens.)         Maybe I'm missing something here but if only one of your 115V ccts trip the breaker the other cct is still feeding power to one side of your 230V cct you built. In the picture above if Phase A Blows Phase B could still be pushing 115v through the wires to L2 in your 230V cct. If this happens what's going on inside that 3000$ plus machine you have hooked up to it.Harold MulderMiller 211 AutosetHTP 201 Invertig with water coolerHardinge Cataract Quick Change Lathe
Reply:trscott I think the point here many seem to be making is that if people don't understand electricity, they shouldn't do this. If they DO understand it, then there is no reason to post this, because they already know the basics of what you have suggested.What worries them and me is that there are those here who will read this and decide they can "cheat" and make something work, that they don't understand and never should have attempted if you hadn't given them the information. It's sort of like either and diesel engines. In general you "never" use either to start a diesel. That said I know some who have done it. You don't stand there and spray the whole can into the intake however unless you want to see the motor go BOOM!. A little info is more dangerous than no info in these cases.I also wonder if this has any real practical purpose for most. You show a 20 amp 110v outlet. In reality I've found very few 20 amp lines in most homes, although they are becoming more frequent. If you do find 2 20 circuits, you'll end up with 2 100'  lengths of extension cord draped thru out the house, that will cut into that 20 amps you are trying so desperately to get. So on average you have 2 15 amp circuits to work from giving you at best 15amps of 220v. This might run an inverter tig machine, or a bottom level 220v mig on low power, but thats not what most people want to run. This is useless to run a 220v stick machine like a tombstone, or  a 220v mig even close to max. I can't practically run my 220v mig from a 4500w genset and thats basically what it puts out 230v @15amps.I see all sorts of potential here for problems if you happen to have a bad breaker. Since I've had to replace at least 8 breakers in different homes in the last 2 years because the breaker shorted and locked "on" I don't see this as a "remote" possibility. A machine that wants to pull 30 amps+ feeding from a 20 amp and a 15 amp mismatched system that your idea can easily create, with 16g extension cords (most noobs don't own 12g+ cords) draped thru the house, has FIRE written all over it if you happen to pick a bad breaker.So what have you accomplished with this "info"? You've told someone who's already has no idea what they are doing (whom you have said shouldn't do this yourself), how to do an electrical tie in that you won't get a licensed electrician to install (because they know better), and that in all practical purposes won't run anything they probably will want to run. That can possibly burn their house down..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Although the idea will work, there are some issues. First of all, you should not have tied those neutrals from different circuits together. It allows parrallel paths for the neutral current from other loads on those circuits, a code violation.Secondly, the grounding conductor is NOT just a spare wire in case the neutral fails, the neutral (actually called the GROUNDED conductor in the NEC) is a CURRENT CARRYING CONDUCTOR, which is why it is INSULATED. It is there to COMPLETE THE CIRCUIT. It is forbidden to use it as a grounding conductor past the first disconnect, as under certain conditions it can have a potential and cause any metal connected to it to become ENERGIZED (like your welder cabinet).The GROUNDING CONDUCTOR is there to operate the overcurrent device in the event of a GROUND FAULT, never to carry neutral current. That is why it is bonded to the neutral, or GROUNDED CONDUCTOR, at the service entrance. It operates the overcurrent device by acting as a short circuit, delivering massive amounts of current to open the OCPD immediately before conductor damage can occur.Third, NEC requires that all conductors of a circuit be run in the same cable or raceway. This is to prevent INDUCTION, which can 1.create heat and 2. delay the opening of an overcurrent device.And fourth, in a line to line circuit, a common trip breaker is required. No we don't open both sides of a 120 circuit because it uses only ONE LINE, the other half is GROUNDED. Opening only one half of a line to line (240V) circuit will stop the load, but still leaves a potential at the load for user injury/death.If you notice the manufactured device is not approved by any listing agency.If it works for you great, just wanted to put some code/safety info out there, so that others will have more info in case they are contemplating something like this. Why not just make up a pigtail and hook it up at the panel to a two pole breaker?Miller Challenger 172Miller Thunderbolt AC/DC 225/150Miller Maxstar 150 STLVictor 100CVictor JourneymanOxweld OAHarris O/ASmith O/A little torchNo, that's not my car.
Reply:Originally Posted by trscottDescribe a failure mode for which this setup would cause an unreasonable hazzard.
Reply:Originally Posted by trscottAnyone want to take a stab at describing a fault condition with the system I have described which would lead to an unreasonable hazzard? . . .
Reply:The reason we don't switch the neutral (besides being against code) is because when you switch the neutral, the load ceases but there is still potential existing at the load. Same as when you only switch one side of a L2L circuit, a lethal potential still exists.The code only allows switching of the neutral when "all grounded conductors (neutrals) and ungrounded conductors (hots) are switched simultaneously".Miller Challenger 172Miller Thunderbolt AC/DC 225/150Miller Maxstar 150 STLVictor 100CVictor JourneymanOxweld OAHarris O/ASmith O/A little torchNo, that's not my car.
Reply:So what kind of damage can this do to an inverter welder if current from another load (lights, tv) is energizing the neutral which is being used for a ground at the 240v end of this adapter? If some one turns on a vacuum cleaner and energizes the welders ground suddenly, will it fry the welder, or have no effect, or what? What will happen to the tv, lights or vacuum if the welder has to shunt some current through the ground to the neutral?
Reply:trscott,As I previously stated, and not to "pick on you", but the posters who know what they're doing didn't need your "guidance".  The ones that don't know what they're doing, shouldn't be trying to jerry rig a "welding machine hookup".Actually what you're proposing is done quite often in marina applications.  Most new marinas (those built in the last 10 yrs or so) have either a 50A 125/250 receptacle, or two (2) 30A 125V receptacles at each slip.  If properly wired (most are) the two 30A receptaces use different legs in the power panel.  Marinco and Charles both make "Smart Y's" which use two 30A 125V male plugs and one 50A 125/250V receptacle to feed a 50A cord.  The "smart" part of this adapter comes into play when one of the 30A plugs is disconnected, the power is immediately shut off to the 50A receptacle.  These adapters run about $500.Also, for marine applications, the neutral and ground are not bonded at the panel.  In fact, if you test for continuity between the neutral and ground at a receptacle, it should show open.  If not, you can be assured you're going to have problems with electrolysis with the boats in that slip.  Even then, you have to be careful of the "smart guy" who thinks he's saving money by not buying an approved marine converter (battery charger) and goes to Sears and buys a cheap battery charger with a two conductor (no ground) cord.  Here the neutral and ground are bonded in the charger and WILL cause electrolysis, not only for that particular boat, but also for other boats in the immediate area.Some of the other posters have pointed out (much better than I could have) some of the other pitfalls of your "handy tip".PS.  Not a sparky but I am an engineer and have been dealing with electricity for "a lot more" than 30 years.  You probably wouldn't believe some of the "field expedient" fixes we used in Viet Nam and I sure as heck wouldn't post them here.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:I guess this is a good point to tie a knot on things and let it go:As a temporary field expedient, where no other convenient source of 230V power is readily available, this is a perfectly reasonable temporary configuration. 1) Combining the neutrals in this case is not a problem, no current is flowing through the neutrals in this particular branch, and the neutrals are all tied together back at the service panel ground buss anyway, The welder load is not tied between Line and Neutral, as it would be with a 115V load, but between the two Line connections. The Neutrals are not carrying any current. Each branch circuit has current flowing from this load only in the black wire, not the white. If there are other loads on either of the branch circuits, their current is still going to end up at the ground buss in the panel. You should preferably turn these loads off temporarily, just to preserve max available current for the welding application, but they pose, and are exposed to, no special hazzard by virtue of this setup.2)  As for one breaker tripping, in this case, once again, the load is not tied between Line and Neutral like a 115V circuit, but Line Phase-A and Line Phase-B, If one breaker trips, no damage can occur, the circuit will not have 115V remaining on it, but 0V. You could measure 115V between the remaining line and ground, but that is not where the load is connected. And, the unit safety ground still remains grounded. That one side of the input is still connected is of no more particular consequence than one side of your car battery attached to the car once you've disconnected the other; no current can flow through the system until both terminals are connected. 3)  I used the neutral white wires as safety grounds in this case because the third green or bare ground wire in 115V circuits is notoriously unreliable in many real-world installations. It is often neglected, defeated, or poorly connected, without anyone realizing because it normally carries no current. In this application, no significant current will be flowing in the white wires as I've connected them, just as no significant current normally flows in the third wire of a 115V circuit. As anyone who has wired a panel will know, all of the bare ground wires from 115V circuits, and all of the neutrals from these 115V circuits, are tied to the same ground buss back at the panel, and any of these conductors can serve as the safety ground connections for this particular circuit, which presents no current flowing back to ground. 4) If another device sharing one of the branch circuits is turned on, its current will flow on its neutral conductor back to the ground buss in the panel and that neutral conductor will remain at ground potential, or within a few volts of, and cause no harm to the welder. Our neutral, having no current flowing on it, connected as it is in parallel with the other loads on the branch, will have no meaningful effect on the peripheral load, and the peripheral load will have no meaningful effect on the welder. As previously stated, it would be preferable to turn these peripheral loads off if possible, just to preserve the max available current for the welding application. 5) There is one negative effect due to running the current between two separate branch circuits, due to inductive impedance which does cause some additional heating in the wires. With parallel wires run together in romex or conduit, their magnetic fields, being in opposite phase, tend to cancel each other and reduce their inductive losses. That is indeed a limitation of this technique, but we're dealing in intermittent, low duty cycle loads, and not a permanent application. On the other hand, only one wire in each circuit is carrying current, so the others will not be contributing any resistive heating in the conduit or cable. You are not going to be significantly stressing the design margins for properly wired circuits on this low duty cycle temporary basis. 6) Nobody is recommending this as a normal shop connection, or for unsupervised or permanent use, but as a few here have noted this is a well known technique for getting 230V power where you only have 115V (as long as you have two branches on different phases). The Marina practice is something I was not familiar with, as is the comparable commercial product posting by Broccoli1. These make sense and represent further confirmation that this is not so crazy as some would like to suggest.7)  I remain confident that if you follow the precautions I've specified, wire the adapter as I've recommended, and test the branch circuits as specified, this works quite well, poses no particular hazzard, and doesn't take a rocket scientist to implement safely. This is a temporary, cord-connected, field-repair-expedient which can be very useful. 8) I used an appliance receptacle in this adapter, because its what I use in my shop, they are very beefy, inexpensive, and often available elsewhere for temporary use by unplugging an appliance, so that's what I put on the end of the cords on my personal shop gear. You could of course substitute a circular twist-lock or other type connector of suitable rating. I believe that pretty well covers the field of issues raised. I will try to humbly allow others here to have the "last word" on the subject. I am sure this suggestion will continue to be excoriated mercilessly by some. On the other hand if anyone would like to discuss it further with me, feel free to contact me with a private message; I am at your service and happy to help any way I can. I stand by the principle that more knowledge is better than less and hope that some have benefitted from this thread. Cheers all!Hypertherm PMX600, Miller AC/DC Stick, O/A Gas Rig -- looking for a 200A, AC/DC, TIG Squarewave Inverter, Pulse, (maybe Chinese...)
Reply:Combining the neutrals is not safe.  Can you guarantee that they return to the same panel.Suppose one plug is connected to a subpanel with a loose neutral.  You could easily have dangerous neutral currents on your wire, which is not sized for the subpanel's main breaker size.Aside from that, we separate plugs and receptacles, for the reason, that once a plug is disconnected, power is not present, so that the bare metal of the plug is not energized, when not connected.  In your setup, once one plug is inserted, the other becomes hot.  I suppose with a special connector that is insulated on both sides, this particular hazard can be avoided, but there are MANY other issues here, and I really don't have the time or inclination to debate them.The point is, IF YOU WANT TO BURN YOUR HOUSE DOWN, NOBODY CAN STOP YOU, BUT PLEASE DON'T PROVIDE THIS ADVICE TO PEOPLE WHO DO NOT KNOW ANY BETTER.
Reply:Trscott - You asked for a possible failure scenario. In post #40 I spelled out just one. I can think of other realistic possibilities. If you wish to ignore the possibility and not comment on it further, that's fine. But if you're saying it's not so, and that you don't believe it, I must strongly disagree. And since you've posted the following, I have a feeling that you haven't carefully though this all through.  Originally Posted by trscott 2) As for one breaker tripping, in this case, once again, the load is not tied between Line and Neutral like a 115V circuit, but Line Phase-A and Line Phase-B, If one breaker trips, no damage can occur, the circuit will not have 115V remaining on it, but 0V. You could measure 115V between the remaining line and ground, but that is not where the load is connected. And, the unit safety ground still remains grounded. That one side of the input is still connected is of no more particular consequence than one side of your car battery attached to the car once you've disconnected the other; no current can flow through the system until both terminals are connected.
Reply:I just hope whoever reads this thread in the future also reads all the posts. I'd hate to think of some guy who doesn't know enough trying this and getting confused thereby injuring/killing himself or others. I once got bit by 120 v w/ my knees on rainsoaked ground and, needless to say, it was something I don't want to repeat.                             My 2 pennies,                                                   MikeOl' Stonebreaker  "Experience is the name everyone gives to their mistakes"Hobart G-213 portableMiller 175 migMiller thunderbolt ac/dc stick Victor O/A setupMakita chop saw
Reply:Quote:Originally Posted by trscott  For temporary supervised connection, this is not dangerous. It will not burn the house down! If either breaker trips, no current will flow in either branch. If a double failure of some sort occurred, both legs are protected against the total current they can handle. We don't protect both sides of a 115V circuit, because opening up a circuit anywhere stops current everywhere. The standard practice of linking 230V breakers poles is mainly a protection against a defective breaker that fails to trip.**************************************************  **************************************************  *******NO! The reason for the link is for SAFTEY. If one of the two breakers trip, the companion circuit is de-energized. ++++++++++++++++++++++++++++++++++++++++++++++++++  +++++++++++++++++++++++Denrep, I pointed to the same safety issue back in post # 7. I’ve been sitting back and letting others comment. I was thinking of drawing a diagram of the failure modes but decided against it because someone may think I’m approving of the wiring. I’m not going to comment on the diagram to correct the interconnection of neutral and ground.Would you use acetylene gas in your gas stove because you could connect the hoses?Last edited by transit; 02-09-2010 at 06:41 PM.
Reply:I've never had a problem and have done it 5 times.
Reply:Originally Posted by tankeedogI've never had a problem and have done it 5 times.