120 to 240 Volt Motor Wiring

[53superm]

I have 2 pieces of equipment I would like to wire from 120 to 240. No - not my ShopSmith - I know that's 120. I have a 1959 Craftsman Radial arm saw with a dual voltage motor and a Sandborn air compressor with a dual voltage motor that are currently (no pun intended) wired for 120. I want to give them each their own 240 circuit. For my line wiring, do I need to run 10 ga with a 30 amp breaker? Can I run 12 2 with ground? 12 3 with ground? I seem to remember that 240 does not have/use a neutral - is that correct?

Thanks,
David

[THOMRIDER]

240volt does not use a neutral, I would use 10/2 with a 30 amp breaker if I were wiring it.

[backhertz]

Corrected:
Typically, when you double the voltage, you halve the current. So if you have a 15 amp device using a 120 VAC, this circuited changed to 220/240 VAC, you'll draw only 7.5 amps of current. Ohms law pure and simple.

Your white Romex sheathed wire will handle is rated for 15 amps and will easily handle a 220/240 volt device. You can leave this Romex wire in place as it will handle up to 600 volts, providing the total load doesn't exceed 15 amps. If you reuse an existing wire, you must be sure of its path. If there are other outlets, then they too will become 220…unless you want them 220 (you then should remove those outlets, use 220 outlets & wrap the white wire in red). This is almost impossible if the wire is run inside a wall. I would suggest running new wire and leave the existing wire if you have the space in the circuit breaker panel for at least one new ganged circuit breaker. You could use 2 separate breakers, but if one trips, you still have 120 volts going to the motor.

If your need goes to 20 amps at 220/240 VAC then use yellow 12 gauge Romex. Orange or 10 gauge is used for 30 amps circuits. Romex colors: White= 15 amps, Yellow=20amps, and Orange= 30amps.

What to use? The answer is it depends on what type of service you have. But typically, on a 220 circuit, you will use a double ganged breaker along with 14-2 or 12-2 Romex wire. This type of Romex will have 3 wires- black conductor, a white conductor, and a copper ground. The ground is not counted as a conductor.

If you were wiring a 30 amp dryer, you'd use 10-3 wire which is a black, red, white, and a copper ground. 10-2 used to be allowed and is grandfathered in some older installations. But new dryers have 4 terminals- one for each wire. That is the only case I know of where a 220 VAC outlet uses the neutral in a typical home circuit breaker panel. 12-3 & 14-3 is used for 3-way switches or something called splitting the neutral which I'm not going to discuss.

Please be sure to understand what you are doing as it doesn't take much to cause an accident. I am not sure of what size motors you are using. But your total capacity along with the length of the outlet from the panel will determine the size wire & breaker you use.

Use the correct gauge wire and give yourself plenty of slack. Prior to connecting the wires to the circuit breaker in the box, wrap red tape around the white wire since it is no longer a neutral wire, but is now one of your two hot conductors connected to the ganged circuit breaker. You can daisy chain your outlets- or you can run a dedicated circuit to each outlet. That is often determined by how much work is involved in running the new wire along with the length of the outlet from the box.

I just watched a You Tube video where the person filming his 220 VAC outlet installation stated he had to do it hot because his landlord wasn't home and he'd use gloves to be safe. He is an accident waiting to happen in my opinion. If you are working in a hot box in an older house, it's almost like a Forrest Gump box of chocolates & you never know what you might find- especially in an old house. Wearing gloves though might not be a bad idea.

I reread my first post & realized I made some errors. Please realize I am not a licensed electrician however in NJ as a homeowner I am permitted to do my own wiring. I ran a 100-amp sub panel from my basement to my garage with 32 circuits. My township inspectors used my box to show other inspectors how they wished electricians would wire their boxes. I am not bragging, but I believe in keeping everything neat and not to code- but rather exceeding code which cost me a few extra bucks. You can not be too safe with electricity.

Most of the circuits I ran were for my wood workshop. The rest were for a new master bedroom addition and second floor laundry room I ran the subpanel so I didn't have to home run my circuits completely across the house which would of added an extra 50-75 feet to every circuit. If you are dealing with a subpanel, remember the neutral buss and the ground buss are purposefully kept separate.

Good luck and be sure ask questions or look up your electrical code in your area. Watch the You Tube videos and if you are not sure, then call an electrician or someone competent. I got the idea from reading your first post that you are knowledgable of electricity to understand motor wiring. So this should be a cakewalk for you.

It is very hard to offer assistance/advice without being able to see the entire picture. So please realize this and do not go by anything I've written as gospel.

[JPG]

IIWM, I would run 12-2 wg twice and use two 20A breakers.

OR 14-2 wg and use two 15A breakers.

[backhertz]

Here is something you might want to watch:
http://www.youtube.com/watch?v=OlGIHmqacgU

The guy means well, but I wouldn't have done it like he has. Typically a person will remove one of the knock outs on the top of a breaker panel and fish the wire up into the attic or down.

He shows a yellow wire inside his panel, but on the compressor, he has what looks to be gray wire that was not wired through the strain relief. I imagine he plans to install an outlet on the wall or maybe not.

I don't personally care for extension cords or wires hanging out of my attic. I do not believe it meets code. But the end result is he did it safe by first turning off his main 100 amp sub-panel breaker and gives you an idea of how to wiring in a ganged circuit breaker.

I didn't realize a large 6 HP 220 compressor would draw 15 amps. So I learned something. Another thing I learned was his TS also draws 15 amps, so if he were running both on a 20-amp breaker, the breaker would trip. So dedicated breakers are in his case essential.

The guy didn't use red tape on the white wire & uses some terms I've never heard before. But at least he wrote identified the panel on this breaker cover.

I'm sure there are more videos on You Tube.

[JPG]

Here is something you might want to watch:
http://www.youtube.com/watch?v=OlGIHmqacgU

The guy means well, but I wouldn't have done it like he has. Typically a person will remove one of the knock outs on the top of a breaker panel and fish the wire up into the attic or down.

He shows a yellow wire inside his panel, but on the compressor, he has what looks to be gray wire that was not wired through the strain relief. I imagine he plans to install an outlet on the wall or maybe not.

I don't personally care for extension cords or wires hanging out of my attic. I do not believe it meets code. But the end result is he did it safe by first turning off his main 100 amp sub-panel breaker and gives you an idea of how to wiring in a ganged circuit breaker.

I didn't realize a large 6 HP 220 compressor would draw 15 amps. So I learned something. Another thing I learned was his TS also draws 15 amps, so if he were running both on a 20-amp breaker, the breaker would trip. So dedicated breakers are in his case essential.

The guy didn't use red tape on the white wire & uses some terms I've never heard before. But at least he wrote identified the panel on this breaker cover.

I'm sure there are more videos on You Tube.

Tape marks a white wire NOT used as an 'identified neutral conductor'. Ok to do so(actually required) and black tape would be ok(main thing is to mark the white wire so it will not later be mistaken as a neutral conductor).

'Common' s.b Neutral.

Bare wires are ground.

Industry home run = dedicated branch circuit(single device/appliance).

Breaker size determines the 'minimum' wire size, not the wire size determines the breaker size.

Those screws are made for a square drive as well as the flat blade.

He installed the wires, then the breaker. Maybe my 'habit', but I install breakers first, then attach the wires.

He really covered the turn things off issues to an extreme, but better off/safe than sorry.

Cords dropped from ceiling are ok IF properly secured at the ceiling. Pendant is the magic word, but they are generally avoided. I do not see any in his video(Are you referring to his temporary non-clamped gray wire?).

I think he pushed the yellow wire down from the attic through a fairly large conduit that extends into the attic. He calls it a pipe. Interesting clamping 'arrangement'.


Take it all with in with a cocked eye. Lotsa good stuff among some lesser so.

[robinson46176]

I seem to remember that 240 does not have/use a neutral - is that correct?Thanks,
David

Not really... While I have seen some industrial uses of 240V (I'm old school I still call it 220V) with out a neutral wire I think every thing pretty much calls for a shell ground these days.
You should also be aware that "some" 220V appliances use both 110V and 220V in the same appliance. In those cases a white third wire is required as a neutral for the 110V application (either side [red or black] and the white neutral).
The two common ones are electric ranges and clothes dryers. Things like lights, timers etc. are often on the lower voltage but all heating elements are on the higher voltage.
Back in the days that I was in the appliance business we often had people call in and want a dryer service call because it would not heat. To avoid a service call just to change a cartridge fuse of flip a breaker we tried to always be sure that they had checked them. Many many times they would argue that they knew that the feed was OK because the drum of the dryer ran. It was very hard to get them to understand that the drum motor was often 110V but the coils were 220V and if one cartridge fuse of the pair was blown or one side of the breaker was tripped the dryer would run but not heat...
All to often the repairman would make a call and even though we had walked them through the explanation all he had to do was reset the breaker or replace the cartridge fuse.
One of my daughters and her other half own a maintenance business serving both homes and businesses (lots of stores and apartment owners). They go through the same thing... Make a service call (pretty $$$$) and cure the problem by resetting a breaker. Most of the time it is after someone on site has "supposedly" checked them. Good for their bottom line but really wasteful for their clients.


.

[backhertz]

Here's another video:
http://www.youtube.com/watch?v=XMgwZDtR4tw

This guy is funny.

Here is a guy doing just the breaker and is a bit more serious.
http://www.youtube.com/watch?v=LXQoOWbU3DE

I'm interested to see how you rewire the motors from 120 to 240. Sometimes it is as simple as moving the wires on a terminal block. There are many, many ways depending on the way the motor is manufactured. You might need to get inside the motor and take the windings which could be in parallel and simply wire them in series.

[53superm]

Hope this link works to show motors and wiring. My shop is in the barn. We have 220 service. I am very familiar with ac wiring. I included a pic of a box in the ceiling with a blue wire coming out of the strain relief. I will run 12 2 w/ground, remark the white to red.

http://s1352.beta.photobucket.com/user/ ... 20PAULA-PC

[backhertz]

Great pics. Thank you. I do not believe you will have any problem. Your total load looks like 12.4 amps total based on the motor plates. 12-2 wire with a 20-amp ganged double breaker should have you in hog heaven.

The one thing I don't know is how much current the compressor will draw when it first comes on. Years ago, refrigeration compressors would draw 400% of their running current when starting. A compressor with an 8 amp running current would draw 32 amps when initially starting. I believe most breakers are designed for this very brief period of time without tripping.

Perhaps one of the other members would care to share.

I get nervous sharing electrical advice- especially after watching one You Tube video today where the person got the job done, but he did not address things like strain relief and the inside of his panel was sloppy in my opinion.

I also saw a Mark V video where the guy ended up burning his motor. Stuff happens! http://www.youtube.com/watch?v=6OT-MevPk34 I'm not sure what the problem was, but it resulted in smoke…

Good luck.