Grounding a equpiment rack - Page 1
Forum section: electronics / general

author: queennikki1972
author_rank: Regular Contributor
timestamp: August 21, 2019, 12:05:33 pm
content: I know this is more of a electrician question, which is why i posted it here.. I didnt know where else to go..I have a house built in 1947. There is only Live and Neutral wires in the walls. I CANNOT AFFORD A HOUSE REWIRE! I do have GFCI outlets installed where needed.I have a Equipment Rack that has a ground lug on the rack and the rack mounted power strips. All the ground lugs are bonded with a heavy gauge green wire.The main outlet in the wall as well as the outlets on the rack all read "OPEN GROUND" or no ground.Can I either temporarily or even permanently, tie a heavy gauge grounding wire to a grounding rod to the racks grounding lug thus grounding the rack mounted outlets?This is the only area of my house that is of concern for grounding.

author: NiHaoMike
author_rank: Super Contributor
timestamp: August 21, 2019, 12:39:51 pm
content: If the water pipes are metal throughout, you can ground the rack to them. Or if that's not an option, install a ground rod outside.

author: Mr. Scram
author_rank: Super Contributor
timestamp: August 21, 2019, 12:49:19 pm
content: Quote from: NiHaoMike on August 21, 2019, 12:39:51 pmWater pipes aren't a substitute and using them poses a few specific risks. I don't know why this gets repeated in every thread about grounding.

author: Mr. Scram
author_rank: Super Contributor
timestamp: August 21, 2019, 12:51:53 pm
content: Quote from: queennikki1972 on August 21, 2019, 12:05:33 pmUsing an appropriately installed grounding rod should work as grounding pins in sockets should be tied to one anyway. Just make sure the rod is functional and not buried too shallow.

author: queennikki1972
author_rank: Regular Contributor
timestamp: August 21, 2019, 01:17:01 pm
content: six foot deep, correct?

author: soldar
author_rank: Super Contributor
timestamp: August 21, 2019, 01:17:16 pm
content: Quote from: queennikki1972 on August 21, 2019, 12:05:33 pmYou can and you should and that is the best option. Using domestic water pipes is only a bad alternative, never recommended and often prohibited.Before my building was upgraded and provided with protective earth I did exactly that: I dropped a wire out the back and connected it to several rods.While there are rods specifically made for this you can also bury as much junk metal as you can spread out and make sure is well connected. Steel andgle bar, wire, chain link, whatever. If it is free and spread in ground that you will keep moist it will help.

author: Mr. Scram
author_rank: Super Contributor
timestamp: August 21, 2019, 01:20:30 pm
content: Quote from: queennikki1972 on August 21, 2019, 01:17:01 pmIt depends a bit on your local conditions. Dry and loose soil or even rocks don't provide the same path as wet soil does. It's all about literally making a good conductive connection.

author: sokoloff
author_rank: Super Contributor
timestamp: August 21, 2019, 01:29:32 pm
content: Quote from: soldar on August 21, 2019, 01:17:16 pm5/8" x 8' copper clad ground rods are ~$13 in the US. Drive two of them at least 6 feet apart and connect with a continuous run of bare copper grounding conductor bonded to each rod and entering the structure somewhere near/in the lab. You can't reasonably dig up enough earth to bury chain link fence or scrap metal to justify not buying cheap and easily driven proper ground rods, IMO.

author: queennikki1972
author_rank: Regular Contributor
timestamp: August 21, 2019, 01:45:38 pm
content: Quote from: Mr. Scram on August 21, 2019, 01:20:30 pmFort Worth, Texas USA , mostly extreme dry, solid rock , have to get past the rocky ground for a good connection..

author: soldar
author_rank: Super Contributor
timestamp: August 21, 2019, 02:00:48 pm
content: Quote from: queennikki1972 on August 21, 2019, 01:45:38 pmQuote

author: pigrew
author_rank: Frequent Contributor
timestamp: August 21, 2019, 02:09:45 pm
content: The NEC updated their guidelines a few years back to allow running a single grounding wire to the outlets instead of replacing the entire cable.In a house of that age, metal cold water pipes are a reasonable solution.Does your house have a ground wire going into its fusebox or to the electric meter? If so, your "new" ground has to be shorted to your existing ground. There should also be a wire going from the ground to your water pipes.

author: soldar
author_rank: Super Contributor
timestamp: August 21, 2019, 02:10:38 pm
content: Quote from: sokoloff on August 21, 2019, 01:29:32 pmI agree of you have the money and your time is worth anything at all. OTOH, some people have a lot of time and very little money and can use alternative, cheaper methods. I have made effective earth connections using scrap lengths of galvanized pipe and angle steel for a total cost of pretty much nothing.

author: David Hess
author_rank: Super Contributor
timestamp: August 21, 2019, 02:39:35 pm
content: My preferred solution is to install an isolation transformer for the rack and then attach Earth ground to the isolated side.Quote from: sokoloff on August 21, 2019, 01:29:32 pmI buy a full length of copper water pipe instead of a copper clad ground rod, attach a fitting to one end for a water hose, and then use the hydraulic pressure to borrow it into the ground. Then the hose fitting can be removed and the pipe filled with salt and water to increase conductivity at the bottom.

author: Bud
author_rank: Super Contributor
timestamp: August 21, 2019, 02:59:07 pm
content: Quote from: Mr. Scram on August 21, 2019, 12:49:19 pmMy house had the electric box tied to the water input pipe right where it enters the house from the day the house was built.

author: sokoloff
author_rank: Super Contributor
timestamp: August 21, 2019, 03:51:52 pm
content: Was extremely common practice "back in the day" and with metal supply piping, it provided a generally good ground.Nowadays, lots of plastic pipe (both inside and outside of houses) and if you don't know what you have, it's no longer a safe bet. If you do know you've got hundreds of feet of buried metal pipe and no breaks prior to the service entrance, it's still fine, IMO.

author: MarkF
author_rank: Super Contributor
timestamp: August 21, 2019, 03:56:43 pm
content: Driving ground rods does NOT prevent electric shock.(Also, grounding myths starting at 35:00)More information (fault protection):

author: Mr. Scram
author_rank: Super Contributor
timestamp: August 21, 2019, 03:59:05 pm
content: Quote from: Bud on August 21, 2019, 02:59:07 pmThey used to run lead grounding "wires" too.

author: David Hess
author_rank: Super Contributor
timestamp: August 21, 2019, 05:09:38 pm
content: Quote from: MarkF on August 21, 2019, 03:56:43 pmI agree. They are more about protection from lightning, extreme overload protection, and sometimes EMI or noise control.Providing a dedicated ground to equipment which would otherwise not have it available also draws leakage current to a safe point and an extra way to reliably trip a ground fault interrupter in the event of a fault so it does prevent some types of electric shocks.

author: tggzzz
author_rank: Super Contributor
timestamp: August 21, 2019, 06:44:44 pm
content: Quote from: Mr. Scram on August 21, 2019, 03:59:05 pm"lead" is ambiguous in this context, since it could be pronounced "leede" or "led".Assuming you mean Pb grounding wires, I've seen them left behind under the floorboards. Actually the Pb ground was the outer sheath enclosing the single insulated live/neutral wires. The technique used to make a three-way junction still makes me shudderAnd a couple of years ago the old POTS cable was being stripped out from the road. I managed to get a 1 foot length of lead-sheathed 48(?) pair cable

author: queennikki1972
author_rank: Regular Contributor
timestamp: August 23, 2019, 03:08:02 pm
content: Quote from: pigrew on August 21, 2019, 02:09:45 pmDoes the Copper wire have to run to the panel, or just to earth ground? I would assume has to run all the way to the panel?

author: queennikki1972
author_rank: Regular Contributor
timestamp: August 23, 2019, 03:32:27 pm
content: So I did some test with a temporary earth ground and it seem to fix my issue.

author: sokoloff
author_rank: Super Contributor
timestamp: August 23, 2019, 03:36:32 pm
content: Reading this reference, it seems you can use an available earth grounding conductor that is not connected all the way back to the panel in a retrofit application like this, but I did not chase down all the referenced sections (as it’s not my house/lab...).http://www.electrician2.com/grndrec.htm

author: MarkF
author_rank: Super Contributor
timestamp: August 23, 2019, 05:13:13 pm
content: Have you checked your receptacle wiring?My parents house has 2-prong receptacles but has the 3rd (bare) ground wire in the cable that is not used.They just needed to be replaced and the ground connected. Slowly, the receptacles have been getting replaced...

author: queennikki1972
author_rank: Regular Contributor
timestamp: August 23, 2019, 05:27:17 pm
content: Quote from: MarkF on August 23, 2019, 05:13:13 pmSome of the wiring is modern 3 wire with ground wire not connected but the original wiring is 2 wire in romex. Some are metal boxes but no metal flex conduit in between outlets.. Honestly it all needs to be updated including the incoming amp service, but it will be a little while before we get to that..waiting on an estate settlement for that.I ran a temporary ground wire from earth to the (outlet)receptacle in question and it seem to read correctly grounded with tester in the outlet. This was only tested for a few minutes and removed. Ideally it would be to run from the panel or earth to "all" outlets but for now its not an option.Based on the post above and its related article, it seems earth ground can be safely grounded at the needed outlet..and/or the equipment rack power which has external ground studs but for now,I WILL one by one remove the outlets and mark with a sticker which ones have 3 wire available..and mark no equipment ground on those that dont.. so i can map out what needs resolved. Hopefully it would be not to much siding removed on my house to fix it..LOL

author: pigrew
author_rank: Frequent Contributor
timestamp: August 23, 2019, 10:08:35 pm
content: Quote from: queennikki1972 on August 23, 2019, 03:08:02 pmIt has to be electrically shorted (bonded?) to the existing grounds in the building (perhaps allowed though metal pipes, not really sure code-wise). The concern is that the voltage of the Earth on one side of your house is different than the Earth on the other side, so you could get a few volts (or more) between your various grounds. You can branch the ground wires as needed, even between circuits. Another thing to note is that your grounding electrode (water pipe, ground rod, etc.) is supposed to be connected to the neutral in your main fusepanel, which keeps ground and neutral voltages close together.In terms of code, it's usually improper to have a three-prong outlet with a floating Earth pin. There is an exception that allows it if the outlet is a GFCI-protected circuit and you have a label saying the Earth is floating.

author: queennikki1972
author_rank: Regular Contributor
timestamp: August 23, 2019, 10:29:03 pm
content: QuoteYes there are GFCI currently.