plasma cutter operation trouble , help

thank you Thor,

your explanation is very clear and very helpful, thanks for the pictures

I did go and purchased a ground bar which i will install to the sub panel, , the one the plastic bar is already isolated and could be used as neutral bar, and my new bar will be ground.

when i did the sub panel wiring , i also updated the dryer outlet and plug to current code ; 4 wire

now that we are at the subject , I like to ask an other question. the garage has an other metal sub panel which was in the house at the time of purchase. it also only has 3 main terminals i like to add a ground bar to it as well , the existing bar will be used as a neutral bar (jumper to metal box will be removed ) and a ground bar will be screwed to the metal box.

since my new plastic sub panel has bare copper ground wired to it and the old sub panel does not , can I bring a ground form the plastic panel to this existing metal sub panel?

thanks

Might, might not. Lots of torches don't have the axis of the internals precisely aligned with the axis of the outside of the torch. So holding the torch *straight* means holding it whatever way is required to get a straight cut.

Well, yes it can. But the way you say you have it wired below is correct.

Ok, it seems the extension is wired correctly. But the plasma cutter is telling you it isn't getting enough voltage (that's what the blinking light means). We can now say that means there's an internal problem.

The 120/240 switch could be bad, or the transformer could have a bad primary winding (one of two). I'd check both possibilities with an ohmmeter before boxing it up and shipping it off to be serviced. The switch is the most likely culprit, and those are simple enough to change out yourself.

If it is the transformer, Miller will have to replace it (hope it is still in warranty), or you'll have to live with operating it only off of 120 VAC. You really don't want to know what a replacement transformer costs.

It is also possible that something is wrong on the control board, fooling it into thinking there's a problem with the input voltage when there really isn't one. The board is a real class A bitch to repair at home. So replacing it is the more realistic option. That costs $241 (been there, done that on mine), if it is out of warranty.

Gary

Article 110-12. Mechanical Execution of Work. Electric equipment shall be installed in a neat and workmanlike manner.

What you are asking is can you string a wire from one sub-fed panel to another sub-fed panel and that is not a neat and workmanlike manner nor is it the way to do it. You would be sub-feeding an already sub-fed panel with an equipment ground from a sub-fed panel. So the answer is no.

You have said before that these sub-feb panels have a shielded cable running to them, I don't know if that is just that you are unfamiliar with terminology or what. The "shield" on those cables, usually a bare aluminum "braid" wrapped around the other conductors is actually the ground. If those sub-fed panels have a cable, versus separate wires feeding them then that cable is usually called triflex. You would twist the "shield" into a wire and put that in the grounding lug. If your sub-fed panels are fed with separate wires, not exactly neat and workmanlike then they should have included a separate ground wire of the propped size.

So far you have said the sub-fed panel that your plasma cutter is on is a 50 amp panel and it has a #10(copper?) wire for ground. #10 copper is the correct minimum sized ground wire for the 50 sub-fed panel. I am not sure what size your metal sub-fed panel is so I cannot advise you on the proper ground size. For 30 to 60 amps the ground should be #10 copper, 100 amps the ground should be a #8 copper and these are minimums. You may have to run a separate ground wire back to the main panel. If you have access to the aluminum "shield" in the metal panel then you could see if that is long enough to go to the ground buss.

I am going to suggest you get an electrician out there. There are other issues besides just tightening a wire under a screw, aluminum needs oxidation inhibitor and sometimes it needs to be tightened twice. If you were just running a cable to an outlet in the garage I would say go for it but since you are missing neutrals in sub-fed panels I say call an electrician as you can have a very real fire hazards there and me not being able to actually see what is going on can lead me to give you improper advice.

Thor

I don't know that this will help with your immediate problem (the plasma cutter not working), but as far as wiring a subpanel goes: When wiring the MAIN panel in a house, the ground and the neutral are tied together at the box. However, when wiring a SUBPANEL, you should run separate wires for the ground and for the neutral, and they should NOT be tied together in the subpanel box. As others have said, you should never run current through a ground wire, nor should you ground a neutral anywhere but at the MAIN panel.

Hi Thor, thanks again for the great reply,

I guess you are right i am unfamiliar with electrical termianlagy, hence I am not an electrician. there is no aluminum wire of any kind in my home. (thank god) when I may have said shielded, what I was referring to is that the wires do not run induvidually the are enclosed in an other plastic shield. I should of said ROMEX.

with that being said , the plastic 50 amp sub-fed panel has all 4 wires routed to it in the correct size and matter.

sub-fed panel 2 (original panel ) need some attention. I understand that it is hard to give advice when you do not see the whole picture. the original metal sub-fed panel was possibly installed as a 220 V only panel for a waste grinder pump and who knows what else, and i guess later on since the panel was nearly empty 110 circuits were added without bringing a seperate neutral so all the ground and neutral was in 1 bar , it is not complience with code and dangerous, as we know it now. so i will take care of this by seperating neutral and and adding a ground bar and bringing a correct size groung wire from the main panel to this sub -fed panel as well. and all will be in correct order. sould i call an electrician ? probably not since the want $60 just to drive by my house.

But I can say , i am truly glad that you and others engaged in this topic , i have learned a lot form it. and i thank you for that. same goes to anybody else that helped me with other wleding issues i had and have. that is what the forum is for ask questin get some answers..learn, help others.

thank you

PS: please disregard any typing errors , it is late and still got to take the dog for walk.

You never did say if the garage is attached or not? I left the stuff bellow because in there I tell you what size wire to run for the ground back to the main panel. Run your ground wire as neat as you can and secure it where it enters the main and the sub-fed panels, a romex connector would be ok, I don't mean tighten it to the ground lug but make sure it can't be cut or damaged by the metal of the panels and then tie it to the ground buss. The actual wire has to be protected from physical harm where it is exposed. You should also have a bit more wire than you need in case something happens to the wire or you later decide to move the ground lug.

To make sure the neutral is separate from the ground you could turn off the panel and pull the main ground off the buss in the sub-fed panel and then continuity test from neutral to the ground buss or something that you know is grounded like the metal case of the panel, it should not ring out. If it rings out then you have to fix that,err.

If you run any new outlets from these panels or if you already have outlets from these panels and you use a metal box then that box has to be grounded. All exposed metal parts need to be grounded.

When you get done, look at your work and ask yourself if it looks like it was done in a factory. If not then clean it up. Sloppy is fast and it works but quality can be done fast and it is MUCH easier to come back to later on to add or repair. While working with electrical TURN THE POWER OFF if it does not absolutely need to be on. Make your connections tight but not too tight, don't reduce the size of the conductor by over tightening.

There, a few more bits of advice. Let us know how it goes. Above all let everyone here know what the problem is/was in that plasma cutter. The reward to trouble shooting is to find out what was actually wrong.

This page gives some specifications. I did a google search on "residential wiring" and didn't get a whole lot of good hits, mostly people selling cd's or courses. If you google then be aware of European sites, you can't use much of that information. If you get your lingo right then you could easily call your local electrical inspector, but you would have to have a specific question and not be asking how to instal. Your city, not college, may also have a quick home owners course in electricity too. But, for what you are doing I think we have already covered most of what you need to know.

Take care, Thor

this was a brand new miller plasma cutter , and form day one it had problems with the powerlight start flashing and machine shuts -off only on the 220V positon.

2 weeks past by , and had many tips and advise from different surces, including miller technical support, and the dealer. none has solved the problem. the machine still had this intermittent problem of shutting off when ever it wanted.

today I brought it back to the dealer , to have the onsite tech do a basic check on it and order what ever it needs and have it ordered up .. but wanted the machine back, because I was still able to use it on

110 V till parts arrive.

after the tech called miller, it turns out that it has a recall !!! for about a week miller has pumped out defective cutters, and they know it by serial nmber which ones are effected. according to the tech. some has bad primary coil and PC board fault.

the dealer was nice enough to swap out the main unit only , but he wanted me to keep the torch (used ) so it got removed and wapped to the new unit.

I am glad it got resolved, even tho I lost half of my day driving and waiting.