electrical experts help! question about 220 wiring

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Forum topic by rg33 posted 01-18-2014 06:07 PM 2561 views 0 times favorited 16 replies Add to Favorites Watch
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83 posts in 2024 days

01-18-2014 06:07 PM

Quick help from electrical gurus out there. I’m trying to wire up a 220 outlet to the wall for the plug pictured below. Does it matter which terminal I hook up the black and white wires to? When I’ve done 120 wiring the polarity seems to matter as the outlets have a gold and silver colored terminal but here theyre both the same.

thanks in advance

16 replies so far

View GaryL's profile


1099 posts in 2853 days

#1 posted 01-18-2014 06:14 PM

It does not matter. Either hot wire can be connected to either screw. Just don’t get the ground mixed up…lol

Are you changing an existing 240v outlet to the plug configuration that you need or did you run a new circuit?

-- Gary; Marysville, MI...Involve your children in your projects as much as possible, the return is priceless.

View Manitario's profile


2630 posts in 2905 days

#2 posted 01-18-2014 06:29 PM

no neutral (white) wire on (most) 220V circuits so both the black and red wires are “hot”; they each supply 110V to the plug so it doesn’t matter which side each of them goes.

-- Sometimes the creative process requires foul language. -- Charles Neil

View rg33's profile


83 posts in 2024 days

#3 posted 01-18-2014 07:46 PM

Thanks guys, second question. The tool cable is only about 6 ft, I’d like to make an extension for another 10 ft or so. The current cable is 14 gauge rated for 300V. Will there be any problems if I buy an extension cord with current 120 ends (also 14 gauge rated for 300V) and replace the ends with ones that will match what I currently have? The tool only draws about 10 amps. Otherwise the heavier gauge cable is much more expensive.

thanks again

View Fred Hargis's profile

Fred Hargis

4998 posts in 2516 days

#4 posted 01-18-2014 08:46 PM

There will be no problems, but you probably want to make sure you get 15A/ 240V plug and receptacle. If you get an extension made of #12 wire, then you can use the 20A/240V plug and receptacle. The outlet you pic’d can accept both the 15A and the 20 amp configurations. The tool almost certainly has a 15A plug on it, if it only has #14 wire.

-- Our village hasn't lost it's idiot, he was elected to congress.

View jonah's profile


1720 posts in 3321 days

#5 posted 01-18-2014 09:02 PM

Please don’t use a white wire for a hot wire if you can avoid it. If you do have to do it, wrap the white wire in black electrical tape inside the outlet box. You need to let the next guy know that’s a hot wire, since white is the universal color for neutral. Feeding that receptacle should be a 4 conductor wire with a bare ground, a white neutral wire, and a black and red hot wire. You should use the black and red to the two gold screws and the green to the ground. Don’t use the neutral.

View rg33's profile


83 posts in 2024 days

#6 posted 01-18-2014 10:41 PM

Jonah, the outlet came with only 3 wires: black, white, and bare for ground. The guy who did the wiring did not use 4 conductor wiring. I already put the cover on it but I will open it back up and wrap the white neutral with some black tape to let the next guy know its hot. thanks for the advise

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1720 posts in 3321 days

#7 posted 01-19-2014 12:55 PM

You’re welcome. As someone who has experienced lots of old house craptastic electrical work, I can speak for the next guy to open up that outlet when I say “thank you” for doing things the best way you can.

View toolie's profile


2134 posts in 2651 days

#8 posted 01-19-2014 01:32 PM

HD sells a 220v extension cord, usually in the electrical dept, that will handle your needs. I use it on a 220v 2 hp band saw, and have used it on a 3 hp unisaw, without incident.

-- there's a solution to every just have to be willing to find it.

View hydro's profile


208 posts in 1774 days

#9 posted 01-19-2014 02:47 PM


Please note that the “220V” is the additive voltage of two 110V circuits, and with normal tolerance is often up to 240V. While this makes no difference to your tool motor, it does matter when properly specifying a flex cord. The rating of the flex cord should be in excess of the peak voltage present on at the maximum of the electrical sine wave. Since the “240” volt number is a Root Mean Square (RMS) rating of the sine wave, it is somewhat like an “average” rating (not really but that puts it in understandable terms). The peak value of that additive sine wave is actually 1.414 X the RMS voltage, or in the case of 240v it is about 340V. With that in mind, I would suggest looking for a flex cord or extension cord with a 600V rating printed or impressed on the cord. That is the next step up in flex cord voltage rating and will keep your wiring properly protected.

You can go the electrical store or hardware store and ask for ST, SO, STO cord and it will be rated for 600V. Do not get the SJT, or SJTO as the “J” stands for a 300V rating (Junior hard service)

Confused yet? Isn’t this 240V stuff fun?

-- Minnesota Woodworkers Guild, Past President, Lifetime member.

View jonah's profile


1720 posts in 3321 days

#10 posted 01-19-2014 09:17 PM

When cords or receptacles are rated by UL they are rated for RMS voltage. I’m not sure what specific cord the prior poster was talking about, but I’m sure the thing at home depot is actually rated for 250V, which would be fine for this application. Most people use 220V and 240V interchangeably, including stores. Looking at the package and the UL mark would be the only way to know, but as far as I know UL only rates for 125V and 250V, not 220V.

View GaryL's profile


1099 posts in 2853 days

#11 posted 01-19-2014 09:26 PM

jonah and hydro got my curiosity going so I went out to the shop and checked some cords.
A mix of 300v and 600v. My heavier cords, 12/3 and 10/3, are 600v, 14/3 -300v.

-- Gary; Marysville, MI...Involve your children in your projects as much as possible, the return is priceless.

View oldnovice's profile


6895 posts in 3390 days

#12 posted 01-21-2014 06:51 AM

I know it is extra cost but I would consider a branch GFCI if possible, better safe that sorry!
I added a 220 line to my garage along with a local disconnect and a GFCI as the floor is cement and the GFCI only cost about $40.

Kudos for those commenting on voltage as many only consider the current rating but voltage is just as important!

-- "I never met a board I didn't like!"

View rg33's profile


83 posts in 2024 days

#13 posted 01-23-2014 01:22 AM

Hmm, heres whats puzzling, (I follow the rms example noted above, at least in theory; im an engineer), but like gary’s my 14 gauge cable is rated for 300V, more importantly this is the cable already coming out of the 220 motor from Grizzly that I pictured above. So Im going to assume that it will be safe to buy a 10 ft extension with 110 plugs (I saw them at HD the cable in them is 14 gauge rated for 300V just like the cable coming out the motor) and will cut off the ends and swap them for connectors; female and male that will connect to the wall and to the tool cable.

thanks all

View Jason White's profile

Jason White

114 posts in 3393 days

#14 posted 01-23-2014 04:43 AM

What others have said—

Both of those brass-colored terminals are hot, so it doesn’t matter.

View Whiskers's profile


389 posts in 2049 days

#15 posted 01-23-2014 05:32 AM

220V extension cords are extremely expensive. But you can make one cheaply with a hunk of 12 gauge wire and a couple plugs you can buy at an electrical supply house.

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