[OP]
Contributor
I recently inherited a tablesaw , and have what is probably a very basic wiring question. The saw is obviously 220 volts, but the wires coming from the saw motor are red, white and green, while the wiring in my shop is black, white and green. I assume I should connect white to white, green to green and red to black -- could anyone with more electrical experience (not a high threshold, mind you) please verify?
Many thanks,
Dave
Member
From what you've written it's not clear that you understand enough about electricity to make this connection safely, so consider hiring an electrician rather than reading on.
Motor leads don't necessarily follow any standard for color. When you say it's "obviously" a 220 motor, does that mean it has a plate on it? Does it also show connections? If you absolutely know it's 220 single phase and it's a reasonably modern motor, then you most likely have two hot leads and a ground. Most likely the green is a ground, but you can test for sure with a multimeter or continuity tester. The ground will have continuity to the motor case, but not to any other lead. The other two wires should have continuity with each other, but not the motor case. These are the hots.
Now, if the wiring in your shop comes out black, white, green only, it's most likely a 110 circuit and not suitable for a 220 motor. If you know for a fact that black and white are in fact delivering 220, then these lines would go to the two hots, and the ground to the green.
Notice all the "most likely" above. If at all in doubt, hire an electrician. A few bucks spent on expert labor is a lot cheaper than your machine or your life.
Pete
Electricians will note that I'm taking some liberties with terminology to keep it simple. Please don't rant me.
Last edited by Pete Bradley; 07-26-2009 at 2:16 PM.
Member
The green wire is always the ground. For 110v, black(or red), is hot, white is neutral. For 220v black and white are both hot.
As Pete stated, if you aren't absolutely sure the motor is 220, don't connect anything. If you tie a 110v motor into a 220v circuit.... Actually I don't know what would happen, but I'm sure no good will come of it.
Contributor
This type of work does NOT require an "electrician" if you are not familiar with wiring motors, IMO.
1-2 hours of research, a mulitmeter, and some common sense is more than enough to complete this job.
Member
That assumes the saw was wired correctly by its original owner and any subsequent owners who made modifications.Originally Posted by Jeff Willard
I'd trace everything to make sure. Shop too for that matter, unless you are talking about a known working 220v outlet.
Member
Did they make a 110 volt saw?
Since this is not new - Matt's advise is the best.
And make sure any cords presently on the saw are properly sized -- replacements are often undersized.
Member
No its not. On Unisaw single phase bullet motors, green is one of the hots.
My advice was that assuming the motor is 220 1P, "most likely" this is the hookup. As Matt pointed out, an "inherited" machine can have all kinds of history including amateur wiring, missing leads, or other damage. Old machines often come with shorts to the motor body or machine. These problems are all solvable, but responsible advice requires more than "what color goes where".
Pete
I ran a new 220v outlet for my used Unisaw and it works great. The electrical guy at Lowes should be able to help you. Tell him you want to run a new 220v Romex # 10 outlet for your saw. The black and the red leads are interchangible BUT the motor will run backwards if you hook them up backwards.
Member
No again. For a basic two-lead connection, switching the hot leads will have no effect on motor direction. If you don't know why, you probably shouldn't be telling a newbie he can install a 220 circuit in his load center if he gets advice from the guy at Lowes.
C'mon folks, I know you mean well, but be careful what advice you give.
Pete
Last edited by Pete Bradley; 07-27-2009 at 1:59 PM.
Member
I gotta jump in here. Pete is 1000% right. If you don't know what you are doing and don't want to fry the motor, zap yourself, etc. etc. seek knowledgeable help- unfortunately that may not be from someone at a big box store! These electrical threads on all the WW forums contain more incorrect and sometimes downright dangerous electrical information than any other topic! In some cases posters offer advice when they have no clue, in other cases they may know, but don't explain it right.
Beware.
On reversing the leads to change direction- that is for 3 phase motors. A reversible motor (not all induction motors are reversible either) requires swapping wires around in the motor's connection box.
With 220V in many areas of the country (new NEC code?) if you are using 10-2 or 12-2 ROMEX with black, white, bare ground, for a 220V circuit you must mark the white with a colored tape at both ends to indicate it is now a hot lead because in 110V circuits the neutral is "normally" white and wired to the ground bar in the panel.
You can't assume anything about the wire color in an old used motor- maybe it was rewired etc.
If there is a motor plate with wiring diagram it should show you how to wire the motor for 110V or 220V. Motor wires "may" have numbered bands around each wire, be color coded, both, or neither. The colors/numbers should correspond to the wiring diagram.
Last edited by Alan Schaffter; 07-27-2009 at 2:12 PM.
[OP]
Contributor
All, thanks for all of your advice. Sorry that my original post was unclear: I do have working 220 volt outlets in my shop which were professionally wired with black-white-green 10 gauge Romex.
I know this saw has been run under 220 volt power in the past. I checked out the serial number at one point and understood it to be built in the late 1970's. I gather that the red-white-green cord is unconventional, but it is 10 gauge wire and in excellent condition, so I would like to avoid buying a new cord if possible.
In particular, Pete, thanks for your advice on the multimeter -- I'll use it this weekend to verify that green is the ground, wire a plug, and start it up.
Thanks again for all the great advice.
Dave
Contributor
Careful, careful...at a local Lowes here, one of the guys in the electrical department at Lowes is the county electrical inspector. Go ahead and tell him that you are going to rewire some 220 in your "shop" and I would bet money that he would somehow find out who you are, where you live, or whatever...and you would hear a knock on your door REALLY soon.
I drink, therefore I am.
Member
I was going to make a smarta** comment about intrusive governments but I think I'll hold off.
Back in the 70's my parents had an extension built onto the house. My dad was career Navy, but came off of a farm, and always enjoyed electrical work. So much that after retirement he went into the trade and spent the last years of his life as an electrician. He did the wiring himself. Today, it seems, you need a licensed contractor and a permit to do anything more than change a lightbulb.
Sorry for the thread hijack.
Member
Pete gives some great advice here if you didn't wire it or buy it new, I would never assume any wire color or take for granted that it was wired correctly. I purchased a saw from Ebay that before I was done, I found problems in both the motor and on the start contactor. Green was used for a hot lead to the motor but grounded on the contactor. Contactor had only two leads wired but it was a three phase motor. The motor was wired for something, just nothing the manufacturer had designed as the leads didn't match either 230V or 460V. Who knows what happened when the person who owned the saw before me wired it up and hit start. I'm hoping a breaker kept tripping and he decided to sell it. I'm shocked that 10 years later the motor still runs.
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