Do I Need a Neutral Line for a DC Motor?

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Forum topic by GrizzlyBagWorks posted 01-14-2017 05:11 PM 1092 views 0 times favorited 8 replies Add to Favorites Watch
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96 posts in 1920 days

01-14-2017 05:11 PM

Topic tags/keywords: inca 220v 110v dc servo motor speed control electrical inca jointer planer 550 570 570 510

Super random question here but I thought some users might have an insight into a problem I’m hoping to address on a machine I’m modifying.

I have an Inca 570 10” Jointer Planer Combo machine that runs on 220V (two hot 110 lines and a ground—there is no neutral). I’ve modified the machine’s planer feed assembly to run off of a 110V brushed DC gear motor with a speed controller. Right now I have the two motors wired separately—the main motor in a 220V outlet and the DC motor in a 110V. It’s kind of a pain. I was hoping to tap into one of the 110V hot legs and the ground from 220V line to power the DC motor. There is no neutral on the 220V but my question is, do I even need a neutral line for the DC motor since there is no alternating the current?

Here is the same setup shown on my old Inca 550:

8 replies so far

View TheFridge's profile


10852 posts in 1815 days

#1 posted 01-14-2017 05:22 PM

Technically it’ll work but it’s a big no-no. Grounds aren’t current carrying conductors. You need a separate source.

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

View GrizzlyBagWorks's profile


96 posts in 1920 days

#2 posted 01-14-2017 05:45 PM

Thanks for the quick response! Sorry, I should have been a little clearer in my original post. This is what I’m hoping to do:

From the 110V DC Motor:
-Black “Hot Line”: Tap into 110V leg of 220V line
-White “Neutral Line”: Cap it – Not plugged into anything
-Green “Ground Line”: Splice into proper Ground

I was wondering if the DC motor will run with just a single 110V Hot (Black wire) and a ground with no neutral hooked up.

View Carloz's profile


1147 posts in 921 days

#3 posted 01-14-2017 06:10 PM

That is one of the biggest no no in electric wiring work.
If you use the ground wire (which is connected to the chassis of the tool) as a neutral then any time there is a bad contact in the ground wire your whole tool is under 110v tension. If for example when you plug in if the hot prong touches the outlet first your tool becomes one killing machine for a short ( or not so short) time but still enough to make some big trouble.

View Fred Hargis's profile

Fred Hargis

5458 posts in 2823 days

#4 posted 01-14-2017 06:48 PM

I do not believe that will work. Most brushed motors are DC motors (drills, sanders, etc.) and they are all wired with the neutral connected (that’s why they are called “universal” motors, they run on both currents). I have to think your motor won’t run unless the negative (neutral) is connected to something.

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

View bigblockyeti's profile


5597 posts in 2050 days

#5 posted 01-14-2017 07:13 PM

That’s a very bad idea and it will not work. Bad because of the previously mentioned reasons. Won’t work because a DC motor needs power as a positive and a negative and 120VAC would have to first be rectified before it will run a DC motor. With only the hot connected it will do nothing, connecting the hot and neutral will have the motor oscillate back and forth at 60hz (in N. America). The most important is having the green wire properly attached to the motor and run to a dedicated ground NOT THE NEUTRAL. Make it safe first, make it work second.

-- "Lack of effort will result in failure with amazing predictability" - Me

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96 posts in 1920 days

#6 posted 01-14-2017 07:16 PM

Thanks guys, I went out and tested the motor to see if it would run if I pulled the neutral off the switch, it doesn’t. My very simplistic understanding of AC/DC motors led me to believe I may not need the neutral since it’s a direct current and not alternating. Turns out it doesn’t work that way. Have to have both to run.

THanks again guys!

View MrUnix's profile


7306 posts in 2528 days

#7 posted 01-14-2017 07:29 PM

What you have is not just a DC motor… it’s a DC motor being powered by a controller that runs on 120VAC wall power, and should be treated as such. Wire for the controller… the type of motor attached to it is irrelevant.


-- Brad in FL - In Dog I trust... everything else is questionable

View Lazyman's profile


3225 posts in 1717 days

#8 posted 01-15-2017 11:39 PM

I’m not a an electrician but I think it is considered dangerous to use the ground as your neutral for your 120v add on. You could technically use the ground as your neutral and the motor would work but you risk electrifying the entire machine since the ground is there in case one of the 2 hot wires shorts out. If you hook your 120v motor to the ground and you happen to be standing in water when you touch the machine for example, you may become the path of least resistance to complete the circuit.

My understanding is that you either need a 220-to-120 transformer or you need a 4-wire cord and outlet with black/red hot wires, white neutral and ground. With that you could tap, one hot, a neutral and the ground to get a safe circuit. The other option is run a separate 120v, 3-wire cord to the motor.

Of course the most dangerous thing may be to take electrical advice from some random guy (like me)on the internet.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

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