240 AC to 120 AC step down converter help

[scrapcan]

I would like to mount a step down converter on my lathe to run a machine mounted lamp. The main reason is to clean up the number of cords around the machine and not have to run another 120 volt circuit (I really do not want to open the wall up and have to re-sheet it).

I think I can pull from the main power lead for the lathe by splitting in a junction box. circuit for 240 to lathe is 30 amp circuit. Machine mounted lamp is wired 120 and uses a 100watt incandescant bulb.

Can anyone offer some advice on this?

[454PB]

You can pick 120 volts off of the 240 volt circuit. Use one leg of the 240 volt and ground.

[harrya]

Also change the 100 W bulb to a 100W curly saver one and it'll draw less amps also. I know this is nit picky but what the hey.......
harrya

[scrapcan]

454PB
Thanks for the input.

I had thought about doing it that way, I even left a loop in the wall to cut in a box should I need to and could easily peel off a leg. But then I thought about what would happen if you have varying load on the two legs feeding the motor when requiring higher torque? I hate flicker or dimming of the lights.

It may not be an issue, but that is why I ask.

[lavenatti]

The load on the legs varies any time you turn something on or off in the house. The proximity of the light will have negligible affect. 454PBs suggestion is the best one. Unless you wanted to wire 2 lights in series and just run them on 240.

[daschnoz]

454PB
Thanks for the input.

I had thought about doing it that way, I even left a loop in the wall to cut in a box should I need to and could easily peel off a leg. But then I thought about what would happen if you have varying load on the two legs feeding the motor when requiring higher torque? I hate flicker or dimming of the lights.

It may not be an issue, but that is why I ask.

You're going to get flicker no matter what - if your light is running off of the same feed as the machine - weather you are running a single 120V leg, or using a step down x-fmr. The only way you are going to eliminate the flicker totally is if you go with a regulated supply - which is hardly worth the effort (if you ask me).

Working in my grandfather's shop, the only time the lights ever dimmed was when the motor was switched on. It was rare for the lights to flicker during a cut (mill or lathe).

I would hang a light off of a single 120V leg.

[scrapcan]

Hearing the same thing 4 times makes me think the idea wa a good one to begin with. It will be no problem to drop into one leg via a junction box mounted beind the lathe.

I also thought it could be useful to have a double plug so I could use a tool post grinder without having to find another place to plug it in.

I will just have to see what time I have this weekend.

[454PB]

50 years ago, everything 120 volt was two wire, and it worked well, but present day "code" calls for three wire 120 volt and four wire 240 volt. Just be aware that you will not have that third wire (the neutral).

You may want to wirenut in an additional ground wire to the box IF it is metal.

[deltaenterprizes]

You can pick 120 volts off of the 240 volt circuit. Use one leg of the 240 volt and ground.

That is against the National Electrical Code. There should be NO current flow on the ground wire. You are creating the potential for electrical shock like when we were kids and would touch the refrigerator bare foot. The neutral wire is insulated and carries electricity. Current flowing on the ground wire can cause problems with every GFIC you have in your house because they sense current on the ground wire.
Just because they did it in the old days doesn't mean it was safe. People got killed that is why we have the 3 wire system.

A 220v to 12v transformer will allow you to use an automotive headlight or a spot light from the low voltage landscape lighting section at the box stores. They run about $60 at Grainger or look on Ebay.

It only takes 1/10 of an amp at 120 volts to kill you, less if you have a weak heart.

Is your life insurance policy paid up?

[shaune509]

connection to 'one'leg and neutral and or ground will work fine.
the ground and neatral ARE tied at the circuit box and as such are the same.
yes grounds may be lighter gauge in three wire systems mainly because we now use plastic condute instead of the older metal that was used as a ground secondary.
3phase would be totally different to get your 120v but can be done

[Catshooter]

I allways shudder when I see these types of questions here.

DeltaEnterprizes is correct.

The two posters above are also correct, at least in saying that the ground and the neutral are tied together in the panel. However, that has nothing to do with the fact that at the lathe the ground and neutral should never be tied together. The panel is one of just a very few places they are ever tied together, and for very good reason. If you use the ground to get 120 volts to your light bulb then they will be tied together at the lathe. If you then lose the grounding connection, very likely the lathe itself will become a current pathway. This can be very bad.

Is the lathe sitting on a concrete floor? With lots of oily dirt around it? Maybe some coolant? Excellent electrical pathway.

Most of the fine people who responded in this thread are giving you 100% wrong advise and I hope you don't follow it. Electricity is ruthless.

You guys with half an idea of how to make things electrical work are looking to get someone killed. There is a huge difference between running some Romex and making a plug work and understanding the fucntionality of a grounding system.

manyljt,

From your description there may or may not be some easy simple solution. If it was me and I wanted to use the 240 volt suppling the lathe I would set a junction box, install a small transformer/fuse set up and then use that power to run a light. A 150 va control transformer isn't that hard to find and would give you the power you need. If you weren't two states away I'd come over and help ya!

This is 34 years in the trade talking to you, just so you know.


Cat

[garandsrus]

Catshooter,

How is the lathe grounded with a three wire 220V system?

Thanks,
John

[Old Grump]

No-no-no-no. There is a reason you sepearte the lighting circuit from the utility circuits. If you get a power failure on your machine and it causes your lights to go out and your hands are in there when things are still spinning you are an accident about to happen. If you run an auxilary light on your machine do it right, ground is not a return.

Just dos centavos from an old electrician who got old by not being stupid.

[Frosty Boolit]

Neutrals and grounding conductors might both go to the Earth groung but they are not connected together in a sub-panel. I would definately not use the the grounding system to carry current. I have seen this on a water pipe and I'm glad I was not holding both sides when the pipe was cut.

[Hometek]

Catshooter,

How is the lathe grounded with a three wire 220V system?

Thanks,
John

On a 220v 3 wire, the green or bare wire is the ground. The ground wire should be attached to the frame of the lathe. It doesn't need the 3rd wire (ground wire) to function, it's there to reduce the potential diffence in case of a fault to ground. Please don't use the ground wire for a neutral. It will "work" but is unsafe.

All you need is old Murphy to raise his ugly head in the form of a loose connection on the ground wire and chances are when that happens you'll help make the connection by providing a path to ground leading back to the ground rod tied into the neutral bar.

[scrapcan]

OK boys the current talk is exactly where I was at. I know about bonding common at the panel. I also know not to go the other route. I have 4 wire to the outlet. I am not sure yet what I have on the lathe I have not pulled it open to see.

I would much rather have it safe. That is why I thought I could put a a stepdown in the main line prior to the lathe, branch circuit. I had thought about putting a service disconnect with a couple of circuits where the current outlet terminates.

I have not done anything yet as I am still pondering what step to take. Electricty and a hack job does not go well when your house or your life could be at stake.

Catshooter,

When I get a chance to look at this in more depth I will send you a pm. I know what has been done from the panel to the current outlet. I am just hoping for somehelp in deciding if I should open the wall, run new circuit in surface conduit to new box, or try to work with exisiting circuit.

[garandsrus]

On a 220v 3 wire, the green or bare wire is the ground. The ground wire should be attached to the frame of the lathe. It doesn't need the 3rd wire (ground wire) to function, it's there to reduce the potential diffence in case of a fault to ground. Please don't use the ground wire for a neutral. It will "work" but is unsafe.

All you need is old Murphy to raise his ugly head in the form of a loose connection on the ground wire and chances are when that happens you'll help make the connection by providing a path to ground leading back to the ground rod tied into the neutral bar.

Hometek,

Thank you for the reply.... I don't have experience with 220V which is why I am asking. Does 220V not need a neutral wire to work correctly?

Thanks again,
John

[Frosty Boolit]

220-240 volt is what you will read between the two "hot" wires. Either of those two "hots" will read 110-120 to the "neutral".

[Beekeeper]

Having spent most of my life as an electrician I will try to help some.
Is the lathe single or 3 phase?
Single phase is the most common in a home enviorment.
Check the plug on the cord coming from the lathe. How many wires are there?
Usually there are 2 black wires and a green one
If there are 4 wires they are usually 2 black, a white , and a green one.
The black wires are the 220 volt wires and will read 220-240 between them.
The green is ground and should be used only for that purpose.
The white if there is one is called the neutral and if you read between it and one of the black wires you get 110 volts.
If the white is not there do not use the ground as a neutral as it will cause problems throughout the rest of the electrical system.

Personal opinion, worth 2 cents.
Get a small voltage dropping transformer 220/110 and install it according to directions and use it for the light..
It makes a safer and better installation all around.
A little more expensive but a whole lot safer.


Jim

[Hometek]

Hometek,

Thank you for the reply.... I don't have experience with 220V which is why I am asking. Does 220V not need a neutral wire to work correctly?

Thanks again,
John

No. A 220v motor does not need a neutral wire to work correctly. The ground just goes under a frame screw. Some units such as a range/oven combo has 220v and 120v circuits. The neurtal is there to provide a current path for the unbalanced 120v current. The old system used a 3 wire but the 3rd wire was a ground that they also used for the neutral.