Setting up a work bench, room has no earth ground wiring - Page 1
Forum section: electronics / projects

author: kendalll
author_rank: Contributor
timestamp: March 15, 2016, 05:10:12 am
content: The room where I want to set up a work bench only has two prong outlets. (House in California, USA built in 1948) It has a modern circuit breaker box. The kitchen has a couple of outlets that at least have their grounds tied to each other.I'm thinking about the best course of action to tie things together for ESD protection / safety between my ESD mat, and the soldering iron, and everything else.Options I've thought of so far, not all of them wise...- Get the plug wired with a 3 wire cable back to the electrical box? (Would have to engage land lord, and probably an electrician to get it done)- Go under the house and drive a ground rod into the ground and run a wire up to my bench and attach to the power strip?- Not worry about it and just tie all the earth grounds together on my bench but leave them float relative to earth?- Just run a 10 meter extension cord from the other room that has grounded plugs and run my lab supply, o'scope, laptop, soldering iron etc on the extension cable?Anyone have advice?

author: Fungus
author_rank: Super Contributor
timestamp: March 15, 2016, 06:27:05 am
content: Quote from: kendalll on March 15, 2016, 05:10:12 amThis one.

author: Seekonk
author_rank: Super Contributor
timestamp: March 15, 2016, 07:08:23 am
content: Every house has a ground at the service entrance even if it isn't a good one. The other room may have outlets with a ground, but they might not be grounded. I had a house where all the grounds were connected together, but not to ground. This is more dangerous than no ground. I would test with a lamp to the ground pin to see if it will take any current. How hard is it to get 50' of 12/3 and run a dedicated line from fuse box to the work room and have a dedicated good outlet.

author: mongo
author_rank: Contributor
timestamp: March 15, 2016, 07:11:14 am
content: As someone who has been professionally working on electronics and computing systems for 25 years, I am going to give bad advice. ESD is not a huge problem, and all the protection in the world will not solve issues with an equipment ground. If you ground yourself to the Chassis, iron etc before touching sensitive items you should avoid most problems unless you have wool/shag carpet in your room which will cause more problems.As for your personal safety you are in the US it is legal and advisable to replace your two prong outlets in the lab space with Ground-Fault Circuit Interrupters (GFCI) or at least use a portable plug.QuoteGFCIs will not protect between line and neutral, but equipment grounds are more about protecting against fire than electrocution and/or ESD.https://www.nema.org/Products/Documents/NEMA-GFCI-2012-Field-Representative-Presentation.pdfThe real reason I would be careful running an extension cord is that older homes also may have the hot and neutral mixed so if you reach up to grab a light that is on the local circuit while holding your iron that is plugged into another circuit you may get a shock or there may be a potential between that ground and the local circuit. This is also potentially the exact definition of a ground loop as the equipment and wiring configuration will most likely have multiple paths for electricity to flow to ground.So in my opinion as a non-electrician, with no state or institutional credentials and whom may have just been "lucky" with ESD, you are putting yourself at risk with little benefit.Also note that in Data centers the main way we avoid ESD is to make sure there is enough humidity in the air. A cheap humidifier is an easy way to remove the dry summer time air issue.

author: Fungus
author_rank: Super Contributor
timestamp: March 15, 2016, 08:27:54 am
content: Quote from: Seekonk on March 15, 2016, 07:08:23 amYep. A fault in the wiring of one device can makeallthe devices dangerous.

author: Jeroen3
author_rank: Super Contributor
timestamp: March 15, 2016, 11:05:17 am
content: Quote from: kendalll on March 15, 2016, 05:10:12 amThe sum of the earth leakage of all devices can go up to several milli amp's really quick. And you will worry when touching any bare metal. It will hurt.

author: Seekonk
author_rank: Super Contributor
timestamp: March 15, 2016, 01:58:45 pm
content: Is anyone really worried about ESD?? I put that in a category of a terrorist at a grocery store. I can't attribute an incident to ESD. We had this old cattle prod we would arc to a board while it was running as part of our ESD testing.Many years ago I met a noted person in electronics at the Dayton Ham FEST. He said he never had any problems in his factory until he actually instituted accepted ESD prevention methods. That always makes me laugh.If ESD is your concern I would sink 1 foot of rebar in the soil. Just enough to shunt 1-2ma into the earth, not enough to make you a good current path. Probably nothing more dangerous than a well grounded metal bench.Am I the only one who hates grounded soldering stations. I like to work on things live. Most times I get away with it, but I will forget and have a grounded scope lead sometimes and ZAP. Just replaced an iron head on a stand. I placed a 1 meg resistor in the ground lead of the wand. Just enough for ESD.

author: donmr
author_rank: Regular Contributor
timestamp: March 15, 2016, 04:58:40 pm
content: Quote from: Seekonk on March 15, 2016, 01:58:45 pmIf you are handling bare FETs you should definitely worry about it. Modern CMOS ICs have fairly good protection but you can certainly damage them too. I have worked for IC manufacturers and seen plenty of parts that were damaged by static discharge. Assembled products are "usually" harder to damage but there is always a chance.A few days ago, here in a very wet climate, I walked across the room and felt the static discharge when I touched a grounded object on my bench.

author: Jeroen3
author_rank: Super Contributor
timestamp: March 15, 2016, 05:54:09 pm
content: Each time I stand up from my desk chair I can create a spark touching anything metal. It's really useful to have an ESD testing chair.

author: kendalll
author_rank: Contributor
timestamp: March 15, 2016, 05:59:12 pm
content: Thanks for the replies everyone!QuoteHad not thought of that. Thanks!QuoteQuoteI hear you guys! The primary reason for wanting to pay respects to the ESD boogie man is I'm doing some freelance work and some very high dollar boards are bound to land on my desk. I just wanted to be up to spec with the accepted practices to be able to tick the box that, yes I'm practicing good "ESD safe" techniques if I'm every questioned on it.QuoteNow that I think about it, just by using a normal power strip, all the devices are going to be tied together anyway. Might actually be harder to AVOID doing this than I thought.QuoteNow that I look back on it, my old boss putting the ground-cheater plug on the scope and showing me how to dive in live was something of a rite-of-passage!

author: apis
author_rank: Super Contributor
timestamp: March 15, 2016, 06:12:05 pm
content: Getting an electrician to do it properly for you is the best option:Quote from: kendalll on March 15, 2016, 05:10:12 amThe way I understand it, mains earth is there so that if a chassis (something the user might get in contact with) goes live the fuse will trigger and thus prevent anyone from being electrocuted when touching it.In order to be electrocuted a current has to flow through your heart: in the bathroom or kitchen, if you touch a metal tap, sink, water, pipe, etc, at the same time as a live chassis of some faulty equipment, a current can flow from the chassis, through your heart, to ground which means game over for you.In your living room there is probably mostly isolators: wooden floor, gypsum walls and so on, nothing earthed, so even if you accidentally touch a live wire there is no path to ground (it's an open circuit), current can't flow and chances are that you survive with only a painful shock.If you mix equipment that are both grounded and not, and one of them fail there are two scenarios:1. The grounded piece of equipment fails: chassis becomes live which means a large current will flow back into the ground wire and the fuse will trigger; you will realise something is wrong and avoid danger.2. A pice of equpment that isn't grounded fails, and it's chassis becomes live: you sit down to do some work and touch another piece of equipment that is grounded (the soldering iron for example) then you reach over to toggle a switch on the faulty piece of equipment (i.e. you touch a live wire). Your body then provides a path to ground, a current flows through you, you die. The fuse might trigger, but not before you die (that's why a ground fault interrupter is also a good idea, since they, unlike a fuse, supposedly trigger fast enough to prevent electrocution).So the rule is: never mix grounded and non-grounded outlets (and equipment) in the same room. Always ground equipment in the bathroom and kitchen since the sink and taps are connected to ground.If you don't know what you are doing you really should get an electrician to do it or you might put yourself and others at risk.Quote from: Seekonk on March 15, 2016, 01:58:45 pmDave has made several videos about ESD, it's a real thing you need to worry about, but maybe not be paranoid about (i.e. depending on how critical and expensive your application are). Static electricity can only build up on surfaces of materials that are good insulators, so anything that is a bit greasy/moist enough that it will dissipate a charge is going to be fairly safe. Clean plastic carpets, dry air, rubber shoes (things that isolate you electrically) will all make the problem much worse. This might be why some doesn't notice it much but others have a lot of problems with it? So yes, an air humidifier is a good thing, also for humans if the air normally is very dry. But get a version that evaporates the water, the ones that spray/atomize water into the air are bad because when the water-drops evaporate they leave small grains of minerals floating in the air and the resulting particle cloud is bad to breathe.

author: Zero999
author_rank: Super Contributor
timestamp: March 15, 2016, 08:58:08 pm
content: A good earth connection is not required, just for protection against ESD. Where I used to work, one room just had a 4m long foil strip glued to the wall which measured a few MOhms to mains earth. It worked because the plaster on the brick wall contains some water and salt, which is enough to conduct well enough for ESD protection. I don't know if this would work in the US, where buildings are made of wood, especially in California which is much more dry than the UK.As far as safety is concerned, your best bet is to run an extension lead to one of the other rooms and use that for everything which requires an grounded socket.

author: mmagin
author_rank: Frequent Contributor
timestamp: March 15, 2016, 08:58:49 pm
content: Quote from: kendalll on March 15, 2016, 05:10:12 amDo not do this unless you are prepared to also tie it to the main ground at the service entrance (with a gauge of wire appropriate to the size of electrical service -- typically 6 AWG or larger)The reason electrical code (in the US at least) mandates that all grounds be tied together is because in case of a nearby lightning strike (or other severe faults) there could be significant differences in volts per foot across the ground and the easiest path for high currents to flow could be in one ground (e.g. service entrance) and out another ground (this new ground rod), in the process doing considerable property damage or worse.

author: apis
author_rank: Super Contributor
timestamp: March 15, 2016, 10:14:11 pm
content: Quote from: Hero999 on March 15, 2016, 08:58:08 pmYes, that should also be ok as long as one ground everything via the extension lead: lamps, fans, etc as well as the test equipment. Or anything you could touch at the same time really.

author: Seekonk
author_rank: Super Contributor
timestamp: March 16, 2016, 01:08:11 am
content: There is always the possibility that the outlet box is "grounded" via metal sheath BX cable. Replacing outlet with grounded type would get you a reasonable ground. Follow that with a GFI and you will also ne protected from shorts to ground that the BX can not handle. Extension cords are cord violations too. There are those cheater adapters where the ground connects through the plate screw, $3.49 vs $.39 for replacement outlet.

author: mojoe
author_rank: Frequent Contributor
timestamp: March 16, 2016, 04:42:33 am
content: Some years ago, I was in a very small apartment in a very old building. Although the outlets were 3-wire, there were no grounds at all. I was getting bitten whenever I brushed against the outer shell of the mic connector on my HF rig (not while transmitting). I put a ground rod into the flower bed that was right outside the windows and ran a large ground wire inside to an outlet strip, where all the gear was plugged in. Not ideal, but it solved the problem.

author: jh15
author_rank: Frequent Contributor
timestamp: March 16, 2016, 05:31:16 am
content: House that old will have cold water pipes grounded, but who knows if plumbers have replaced sections with PVC by now.Just don't ground to gas pipes, hehe.

author: kendalll
author_rank: Contributor
timestamp: March 16, 2016, 06:27:37 am
content: Quote from: Seekonk on March 16, 2016, 01:08:11 amGood idea. I haven't removed the plate yet to see what's going on in there. The bathroom doesn't even have a GFI receptacle right now...

author: Photon939
author_rank: Regular Contributor
timestamp: March 16, 2016, 02:04:28 pm
content: Quote from: kendalll on March 16, 2016, 06:27:37 amYou could get lucky and have it be like my house (mid 50s) had two prong outlets all over but the boxes actually had a ground wire inside. The wire had plastic insulated conductors like modern wire but had a woven cloth outer sheath that may have been soaked in tar or something similar.

author: TimFox
author_rank: Super Contributor
timestamp: March 16, 2016, 08:04:35 pm
content: My house in Chicago was built around 1951 with 2-prong outlets. However, all of the wires (originals were fabric-covered rubber,and had deteriorated) were installed inside conduit. When the house was re-wired with a proper breaker box, the electricians pulled new plastic-insulated through the old conduits where possible and installed 3-prong outlets.Prior to the professional rewiring, I had replaced some of the 2-prong outlets with 3-prong outlets, which were grounded to the electrical box and conduit back to the house ground (cold water pipe). I did check the result with a voltmeter before proceeding.Take the face plate off your outlet and see if a 3-prong socket replacement is possible and safe.The electrical code had changed since the original wiring, and the electrician had to install a new ground connection near where the city water entered the building, replacing the original ground connection at the laundry tub closer to the fuse box.