# Grounding problem?



## Dave Mills (Dec 4, 2019)

Ran into a situation this morning that I could use some help with. 

A few months ago, I bought a DeWalt 735 planer. At the time, I did "dust collection" by hooking up my shop vac plastic hose to it. I noticed, but ignored, that every time I planed a board, if I happened to touch the metal outfeed table, I'd get a static shock.

Roll forward to now, and the difference is I'm using an Oneida DC, Nordfab ducting, and a flex hosed hooked to the plastic dust port on the Dewalt planer. As I'm standing watching the board come through, I notice a flashing white light, I suppose a spark, jumping from the end of the wire in the flex hose to the metal Nordfab duct. The spark blinked pretty regularly, maybe every 1/2-second, and ended when the board got through the planer (i.e. before I turned off the planer).

The DC pipe may or may not be grounded, I'm not sure how to exactly tell. I have extended the standard ground they ask you to hook to the filter and the dust barrel, and hooked it in to a nearby duct clamp, but it does not extend by any means to every duct and every clamp, or somehow to the planer other than to the house ground.

The flex pipe connection to the planer is *plastic* if that's relevant.

The fact that I was getting a static shock before the DC installation tells me this issue is not related to the DC or pipes or it's own grounding, but related to the actual planer's grounding, or to my house grounding. The planer is plugged in to a 15A power strip, then into the wall, everything using 3-prong plugs, but I'm not sure how to test to see if that ground is actually *ground*.

Any help will be appreciated, thanks!


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## HoytC (Dec 30, 2019)

Connect the wire in the flex duct to the metal duct. That will eliminate the arcing. If other problems come up then deal with those next rather than speculate about them now.

Your previous experience with getting zapped by the outfeed may be more about you not being grounded than by it's grounding.


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## Pineknot_86 (Feb 19, 2016)

I have a Shop Vac and Oneida DD. I ran a wire from the lid of the DD to a washer soldered to a washer that is grounded to the wall
.


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## woodnthings (Jan 24, 2009)

*Both solutions above will work because ......*

The plastic wire wound hose does NOT provide an electrical connection between the dust collection and the planer. You can just run a separate wire, bare copper or insulated, either will work between the two units. 

I did the same between my Jet 1100 dust collector and the blower housing and it worked great. I was getting a static shock that would stop me cold and leave my hand singing. 

:vs_cool:


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## HoytC (Dec 30, 2019)

woodnthings said:


> The plastic wire wound hose does NOT provide an electrical connection between the dust collection and the planer.



Correct. That's not the intent. The intent is to ground the hose wire. If it's not grounded it just concentrates the induced charge and arcs to a grounded conductor if it's close by.


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## Dave Mills (Dec 4, 2019)

Ok, thanks guys. I connected the hose to the metal duct and ran some wood through, no sparks.

Dave


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## woodnthings (Jan 24, 2009)

*Having done this myself as stated above .....*



HoytC said:


> Correct. That's not the intent. The intent is to *ground the hose wire*. If it's not grounded it just concentrates the induced charge and arcs to a grounded conductor if it's close by.


I suppose if you connect just one end of the flex hose wire to either unit, it's "grounded' to that unit.......


My solution "connects" the two units, the metal planer cabinet and the metal blower unit with a wire, thus "grounding" the planer to the blower/motor. The flow of material through the flex hose creates static from the friction, and left "unconnected" that static charge will jump to your body. 

:vs_cool:


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## NoThankyou (Mar 21, 2018)

To test if a circuit is grounded:

The socket has three connection points. The magic words "Lower, Large, Left". Meaning, 'If the grounding lug is in the lower position, the large socket is on the left.' The large socket is the neutral leg.

With that knowledge, measure from the small socket to the large socket. You should read approximately line voltage. (I'm not going to get into 110 volts vs. 115 volts vs. 120 volts. For all intents and purposes in this discussion they are equal.) Now measure from the small socket to the grounding socket. You should read approximately line voltage. If you do not read approximately line voltage, your circuit may not be not grounded.

If you read appreciably less than line voltage, your circuit may be grounded differently than the rest of the house. This happens when a sub panel is grounded differently than the main panel. This is a nightmare problem because it is evidence of a ground loop. Any device with analog circuitry that uses building ground may have problems when a ground loop is encountered. If you create the ground loop and connect your cable TV to the circuit it will cause random pixilation. Simply, this happens when a remote sub panel is not grounded only to the main ground in the main circuit panel. 

Finally, if all is cool, use the Ohm meter function in the meter to measure the ground lug of the planer to the chassis of the planer. It should be less than 1 Ohm. If the measurement is not less than 1 Ohm, find out where the break is or more easily replace the power cord.


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## woodnthings (Jan 24, 2009)

*With all due respect .....*

This is a static issue, not an electrical issue. 


We just have to connect the flex hose's internal wire to a "ground" to discharge the static. Typically, a dust collector's separator "cyclone" is attached to the mobile base with legs and the blower motor is also attached to the base using bolts which will ground the separator even though there is no "electrical connection. A fabric bag above the separator and a plastic catch bag provide no electrical connection:










The flex hose does not provide an electrical connection either, so that's why the internal flex hose wire needs to be connected to either the blower motor or the separator. 

My dust collector uses a cardboard 30 gal drum and NO metal legs to provide an electrical connection to the base. Bungee cords are not good electrical conductors. So, I needed to use a wire from the separator to the blower motor to discharge the static, The wire is just barely visible under the flex hose against the door:

 Attached Thumbnails


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