New Shop, looking for a ground

[mjindustry]

I'm sure this subject has been beat to death around here, but sometimes you get lost when that happens. Please forgive me for starting a new thread on this subject.

There is a ground rod sticking right out of the floor of my utility room, it's connected with some very thick gauge copper wire to a water pipe, and also my electrical box. Can I use this to ground my shopbot and dust vacuum, or do I need to go to something else?

[mjindustry]

FYI: My wife is on the way home with an additional ground rod right now. Have I answered my own question?

[sailfl]

The existing ground is good.

[dana_swift]

A shopbot should be grounded, as long as the ground you use is connected to both the power line neutral at some point, and a rod driven into the earth there is no point in creating new artificial ones. Noise immunity can be accomplished without any contact with the earth at all. (that is what aircraft and spacecraft must do) safety requires earth ground because of the configuration of the national power grid. Since you had your wife go get you one, I suggest you use it! Politics only, no science involved.. D

[rcnewcomb]

A quick easy way to tell if your ground is any good is to put a voltmeter between neutral and ground. It should read zero even on the lowest voltage setting.

[mjindustry]

Thanks guys.

Not sure I understand everything I'm being told, but I think at least one guy said go ahead with the new rod. It's 10' long, should I be worried about hitting plumbing, electrical, etc? Should I call the locators?

Thank you.

[michael_schwartz]

The bot as any equipment should be grounded to a grounding conductor that goes back to the service panel so that in the event the bot were to become energized you would be protected. That ground is in turn tied into the earth ground at the service panel. Unless you are absolutely sure and confident of what to do, and that you existing grounding system is to code and intact hire a reputable electrician.

The earth grounding system should be installed at an absolute minimum to code, but better to insure the lowest resistance practical/possible for the installation. Ground rods are cheap.


Source, Taunton's For Pros By Pros; Wiring a House, Completely Revised and Updated. Rex Cauldwell, 2002.

The author states according to code two rods spaced a minimum of 6 feet apart must be used unless a resistance of 25 ohms or less for a single rod can be proven. The author states he prefers to install up to 8 rods 8-20 feet apart.


Note I am not a an electrician nor did I sleep at a holiday inn express last night.

[dlcw]

I served 23 years in the Coast Guard as an Electronics Technician. 4 of those years were on LORAN transmitter stations. These are stations that suspend 4 miles of wire between 4 750' tall towers for an antenna to handle its 1,000,000 watt transmitters. LORAN frequency is 100,000 cycles per second. To get this antenna to be efficient, grounding is the most critical part of the system. I'm also a Extra Class licensed amateur radio operator where grounding is key in getting a radio system working well. I also worked on communications equipment aboard CG cutters where radio reception is a very high priority and bad grounding can be the difference in hearing and not hearing a MayDay call. In these adventures I learned more about grounding then I care to remember.

One thing that many people don't realize is that when you set up multiple grounding rods you have the potential of establishing polarity differences in your ground points. The more ground rods, the more potential for these differentials being brought into play. In the LORAN example, we had 360 16' ground rods. One each degree around the compass. All the ground rods were tied together with #4 copper wire. Then a 4" wide copper strap was buried about 6" in the ground and lead from each grounding rod back to where the transmission lines from the transmitters connected to the antenna (about 1/3 mile). To make sure the ground system was fully functional, another ring of #4 copper was attached in a great big circle connecting the 4" straps at 25' increments from the ground rods all the way back to the antenna connection point. Needless to say, each LORAN station caused a spike in copper prices. :eek:

The point I'm trying to make is that most electricians don't realize that multiple ground points that are not properly connected together can introduce ground differentials in your system. They might be slight but they are there. Make sure all of your grounding rods you sink into the ground are all connected together with at least #8 grounding wire. It's also a good idea to bury these wires in the ground to keep it at the potential of the ground rods and not act as part of an antenna.

I've found that the Shopbot - with USB for connectivity - is incredibly susceptible to ground problems and RFI (radio frequency interference - hence the reference to my communications background). Keep all your ground points common and securely connected together with good ground wire. All parts on the Shopbot that are not welded together or bolted together with bare steal at the joint should have a ground wire attached and led back to your common ground point. Going to this extreme has made my machine very reliable and I've not had any comms. problems since doing this.

Sorry for the long winded post but I thought it was very important for people to understand how critical grounding is and how much of a misunderstood subject it really is.

[Gary Campbell]

Guys...

I have a few notes to add to the above, all which is good.

If your electrical system is "up to code" then the earth grounding requirement has been properly taken care of. Getting a point that has a direct connection to the panel ground bus bar is your best bet. There is no better ground connection. I had my electrician install mine.

In my opinion there are NO reliable connections on the ShopBot frame that would ensure ground continuity. All of the "blue" parts are powder coated, which is an insulator. Most of the extrusions and aluminum parts are anodized, which can insulate. Each set of structural parts from the table to the gantry, the gantry to the Y car and the Y car to the Z extrusion have bearings between them. There is no reliable electrical connection through a bearing or painted connection. Notice I say reliable. There may be incidental contact, but without removing the coatings at bolt holes or other connection points and using ground straps or wires that bypass the motion points and bearings they are not connected electrically.

So, in my opinion, and even tho there may be incidental contact, unless you physically make a connection to a component with a ground wire, you can assume it is not grounded. This means use an abrasive wheel to get to bare metal, install the ground wire with a wire connector and star washer and run all these ground wires to a common ground point as I mentioned above.

I am definately not an Electrical Engineer, but would welcome one that might confirm or shoot down my educated guesses. I might buy him a nite at the Holiday Inn Express! :D

[curtiss]

So would it be more important to get a good ground connected on the y car & z ?? / that may be insulated from the other framework ??

Is one ground rod enough ? A bit rocky in most places for 10 foot rods I would think. Can they be laid in somewhat horizontal ?

off topic, but is Loran still used much with the new GPS ?

[dlcw]

Curtis,

Believe it or not LORAN is still on-air. It is remaining up and operational as a backup to GPS. I read a report a few months ago that several of the GPS satellites are starting to deteriorate with age and money has not been allocated yet to replace them. Typical Government long term planning (where are we going for lunch).

Anyway, like Gary said, many parts of the Shopbot are insulated from each other. One of the biggest generators of RFI (radio frequency interference) are between the roller bearings and the V track. I've got an RFI meter and used it to check and found that as the gantry and Z car roll along, there are RFI spikes coming from this "connection". I think this is where much of the communications problem with the ShopBot originates. When I was aboard ship in the CG, anywhere there wasn't a solid metal to metal connection between parts, we had to bridge the gap with ground wires. A good examples was sections of deck railings on deck that used chain. We had to bridge this gap with a ground wire because you could actually hear sparking in the sensitive HF radio receivers when the chains were rattled.

[bcondon]

I have a couple of comments.

I followed the code and installed 2 grounding rods from my 200 Amp service panel to pass code rules. I have a standard grounding bar which is part of the panel for all my return white wires. I installed a separate grounding bar for all my bare grounds which is an option you can purchase. My panels are all industrial grade Square D panels... more expensive, better quality, only plan on doing this ONCE in this house.

I have two more 100 Amp panels (one in my basement shop, one in the garage shop that contain my shopbot)

The 2-100 Amp panels comply with the code such that there is 3 wire (black/red) to power terminals, white to return feeds from all circuits,
ground wire to a separate grounding bar.

All bare wires from circuits (shopbot and recepticals) go to the grounding bar NOT the return wire (white wire bar)

My shopbot control panel is mounted to the frame of my shopbot so the control panel is grounding my shopbot frame. My speed control for the spindle is also bolted to the frame

My laptop uses the standard receptical with ground

I do not have any issue with losing communication to the shopbot
( please Lord, I am not tempting the grounding gods) but I have not had any issues with any of this.

The electrical inspector did comment that I could come work for him once I was done the house renovation because "I got the 2001 code correct except for those pesky updates in 2008"

There is a danger of installing different ground rods especially if they are
not attached by a common conductor. When I worked for Apollo Computer, one of the dangerous situations that we encountered was having a token ring network (Coax network grounded) running from building to building. We had to bury grounding conductors from building to building because we kept blowing up electronics (network cards) because the grounds were not the same voltage (there would be a voltage difference if you measured the ground difference between buildings).

[dlcw]

Bob,

It looks like you are pretty well setup. I would double check your connection between the the different panels and where they mount to the SB frame. Make sure it is metal to metal contact and not bolted on with paint in the way. If there is paint in the way then scrape a spot on the frame to bare metal and run a ground wire from the frame to your ground point. Glad to see you tied grounds to grounds and not grounds to neutrals. Some people do this and it's not the same. Another thing you might want to consider is to open up your laptop and connect a #14 grounding wire from the chassis to your common ground point. I did this with my SB computer and am glad I did. Yes, the receptacle ground will address the safety aspect but not the RFI aspect. The laptop chassis is the interceptor for RFI. You need to shunt this RFI to ground.

As far as electrical inspectors and IRC electrical code stuff - the grounding involved for IRC doesn't, and rightly so shouldn't, be concerned with RFI grounding (this is an FCC issue) to the point that we need to be aware of it and account for it when dealing with sensitive electronics equipment. IRC addresses residential safety needs.

I had an electrical inspector back in Ohio asking me why I was doing many things I did when I wired my shop back there. It was way above and beyond what IRC called for. He offered me a job as well....:rolleyes:

Interesting you mention the ground difference between buildings. This is what I was trying to get across in one of my previous posts. Floating grounds can be a real electronics equipment killer.

It looks like you are ready to fly.

[lemic_ray]

Well now I'm worried!

I'm building my new shop and I will start the wiring next week.

From the 200 amp panel in the house I ran (3) 00 cables to the barn (125') (220 1ph) (2 hots and a bare neutral ran over head)

It terminates into a 100A subpanel in the shop.

I am putting a 10" ground rod directly below the sub panel and a 4ga ground wire from the rod to the ground buss as it is my understanding if the buildings are not physically connected I should do so.

The neutral buss in the subpanel is ground lifted. That is to say it is mounted on a piece of plastic and insulated from the box.

There is a "missing" screw in the neutral buss and a green screw in a bag that came with the panel. I understand that if I install the green screw into the buss where the missing screw is it will then connect the neutral buss to the panel and thus the ground buss.

I had not planned on installing the screw.

Would this be wrong?

I was also going to add a second ground rod about 25' away in the area the ShopBot would be and run an isolated ground circuit (with all the orange plugs and all) for the digital stuff (computers and controllers)

Is this not advisable also?

Thanks for any direction.

[Gary Campbell]

Ray....

I think that when you install a subpanel, most codes require a 4th wire. You need the 2 240V hot legs, a neutral and a ground. Then at the subpanel, you must remove the screw and keep the ground isolated. All of your 110V neutrals go to the neutral buss and all the grounds go to the ground buss, which are isolated from each other on a subpanel, but not on a main. Code varies on the earth ground requirements. Some require it and some dont. Also some have a requirement for multiple rods with a space. CHECK YOUR LOCAL CODES! The local codes take soil conditions etc into consideration and are usually tried and true.

Also a note on ground rods. There is no better ground for equipment than taking one from the panel. PERIOD! the panel is required to have its own earth ground, which is mostly a path to earth for a current spike that could not be contained by the breaker and distribution system. (lightning?)

Again, usual disclaimer about electrical engineering and holiday in express