Can I Ground Dust Syst. To Conduit

[gerryv]

Hi, I've just installed a steel spiral pipe dust collection system and am wondering if I can ground it for static to the steel electrical conduit that carries the 230v power lines in the shop.

[myxpykalix]

If by chance that conduit somehow gets charged with electricity like with a short then you are sending electricity thru the dust collection making it ripe for explosion or fire. That may be a far fetched possibility however.

I would run a copper wire thru the ductwork and ground it directly to your dust collection. That is how mine is set up and i have no problems. I'd keep the grounding seperate.

[gerryv]

The system has all of the grounds in place between flex ducts, steel ducting etc., with the exception of the final connection to ground. I can ask the landlord about boring through the concrete floor for a proper electrical ground if really necessary but, being that we're talking about static elec. I'm wondering if that's overkill or not. Jack, I hear 'ya but I suppose that if something that bad is going to whack my conduits then my dust collector is going to be exposed to it anyway because it directly connected. Anyone else lurking that can chip in?

[bleeth]

You don't need to install a ground rod. If you have metal electrical conduit in your shop running to the breaker box you can ground at any outlet box or even to the conduit itself. If you are all romex and/or PVC you can ground to any ground in a box or run ground to your ground in your breaker box. Having a seperate rod is super overkill.

Your DC conduit will be grounded via the ground on your DC motor unless you have isolating cushions (rubber gaskets) or plastic parts between the conduit and the DC.
Running a wire through the dc pipe is for plastic pipe or flex without a built in ground wire and not steel.

I wouldn't ground my bot to my DC. It may not be an issue but I just don't like the idea.

[frank134]

the conduit should be grounded to the panel so it can be used as a grounding conductor but it not the best way to go about it. you should run a wire from what every you want to ground back to you panel. In my case I put a small copper bus below my panel (1/4 x 2 x 6 ) which is grounded to the panel and three copper (3/4 x 8' ) ground rod outside in the ground. everything in my shop (frame steel of shop ) included is grounded to this bus bar. this is a little over but I know I am well grounded and most comerical build we wire to day are done this way.

[oddcoach]

If you have a copper cold water pipe nearby then you will not have to worry about any isolation.

[Gary Campbell]

The best ground available is the ground bus inside the panel. The panel enclosure itself may be grounded, as may be the conduit. Conduit is usually good, but due to many connections that can corrode, are not as reliable as running a wire to the bus.

Do not confuse the neutral bus with the ground. In a sub panel, they will be isolated. a neutral bus can carry current in a sub panel.

Contrary to popular belief, a ground rod is not a good place to locate a machine or static ground. Humidity variations in the soil can change the ground potential at the rod. Their main purpose is to provide a path for lightning.

[ken_rychlik]

The main thing to NOT do is run the copper wire inside the pipe. It will be a place for things to get hung up on and then the pipe will choke up.

Metal pipe will be it's own ground and should not need a wire in it. For the flex pipe, use the kind with the spiral wire built in the hose. Then take the end of the wire out and ground it to the metal pipe.

I use the ground bus in the panel and it works fine.

[dlcw]

Actually earth ground rods are a great way to ground IF AND ONLY IF all earth grounds rods that service the electrical supply are tied together with a large copper grounding strap (at least 2" wide) and the grounding strap is buried at least 4 inches below the surface of the ground and is in GOOD contact with the earth (pack it in tight!). If you have multiple ground rods that are not tied together properly, you can set up what are called ground loops and floating grounds. This is where the conductivity in the soil varies from one ground rod to another, thus providing a different level of proper earth grounding.

Grounding efficiency varies geographically. Salty marsh (coastal) areas provide INCREDIBLE ground systems. Dry sandy conditions (southwest US) provide OK but adequate grounding systems (need 1" x 10' rods instead of 1/2" x 8' rods). The majority of North America provides for very good grounding conditions (both electrical and RF). The wet seasons are better then dry seasons but overall the grounding is much more then adequate.

I've installed hundreds of miles of grounding radial systems for large radio and LORAN transmitters (23 years in electronics in the US Coast Guard). The one thing I learned very well is how to ground things. After the Coast Guard I got into Hazmat Emergency Response and worked to develop a very comprehensive nationally used grounding system when transferring highly volatile chemicals from an overturned vehicle to another, not overturned, vehicle outside on the road systems. I am also an amateur radio operator (Extra Class license) and have installed many grounding systems for both RF antennas and VAC.

Electrical service (and RF) grounding is a very exact science. The goal is to bring all grounding to a single point. Multiple grounding rods properly tied together form a SINGLE grounding point. Also, use copper. Clean all points of contact very well. Don't mix different metals in a grounding system (aluminum, copper, steel, brass, etc.). Over time electrolysis can reduce the efficiency of the system - this is especially relevant outside.

[curtiss]

Is it correct to place some rock salt in the hole with the copper rod, as that will enhance the grounding ???

[dlcw]

Curtiss,

Yes you can put rock salt from about 2" below the surface to 24" below the surface and it will enhance the grounding effects. The down side is you have to replenish the rock salt regularly, especially in the wet season. The dry season, not so much. But in the dry season, you will need to "water" the rock salt about once a week to keep it activated.

[gerryv]

Really good and helpful info; thanks much everyone. Should I assume then that grounding requirements are actually the same for both power (mains) and static electricity?

[dlcw]

Yes. Just tie everything together so you have a common ground point. You don't want to have one ground at a different potential (floating ground) then another ground. This can really cause problems and is a real PITA to track down. In digital electronics (controller and computer) these floating grounds are a killer.

[bcondon]

Having worked as an electrician, here is what I would do.

The conduit "should" be a good ground unless it is not properly attached
to the panel.

The cord to the DC should have 3 wires. There should be a green wire in the cord which goes to the ground pole of the plug. The ground pole of the recepticle is directly connected to the panel ground.

The green wire should be connected to the DC frame somewhere either at the motor or to the frame directly. If there is a screw with the wire connected to it on the motor, simply buy some green single strand wire, put a terminal end and put it under the same screw... Take the other end of the wire and attach it to the ductwork and you are done.

Thats it
make sure you use clips to hold the wire so it will not be tripped on or broken loose.

You do not need copper wire inside the metal pipe. The pipe is the ground.

Now, if you use plastic gates and metal pipe connecting the gate to the equipment and you think this is a ground, it is not because the plastic gate is not conductive.

Now if I want to start some contraversey, I will tell you that I used 4" plastic Sched 40 for my piping system. I have a copper wire running through the inside and another wire running around the outside. The wires are connected via small holes at the end of each duct. The DC end has these ground wire attached to the frame of the DC (and the ground off the plug).

Been running this way since 2006 without any issue. I never get a static shock if I touch the pipe so there is no buildup happening..

Thanks
Bob Condon