Do's and don'ts in home lab with no earth ground - Page 1
Forum section: electronics / beginners

author: bottledwater
author_rank: Contributor
timestamp: December 08, 2022, 05:09:10 pm
content: Hi, there's no earth ground in my plugs at home. Driving a stake into the ground is not an option and nulling in the box outside is not allowed.If this is what you had to work with:1) How would you connect test gear and power supplies that ought to be grounded to earth? What would you do with their chassis grounds?2) What are some practices you'd adopt around handling static sensitive components from the moment they arrive in the post?3) Are there some types of projects you wouldn't do in this earth-deficient "lab", like mains connected power amp repairs?My concern is the safety of my components, my gear, and myself. I have a relatively nice power supply and oscilloscope, and I'm in the market for a good function generator, but I'm not sure how much I should try to do here. Failing logic ICs I can handle, but I'd be sad to see any of my gear blow up.I mostly play around with breadboards and the occasional PCB. My main interest is basic battery powered amplifiers, CMOS logic, playing around with MCUs. For a year I haven't had anything fail on me so I wonder how much is theory and how much is practice.Thanks!

author: bdunham7
author_rank: Super Contributor
timestamp: December 08, 2022, 05:11:57 pm
content: Quote from: bottledwater on December 08, 2022, 05:09:10 pmDo you simply have two-pin sockets or is there an earth/ground terminal that just isn't connected?

author: Grandchuck
author_rank: Super Contributor
timestamp: December 08, 2022, 05:12:17 pm
content: Can you access a metal water pipe? You would need to verify that it is indeed safe to do so!

author: themadhippy
author_rank: Super Contributor
timestamp: December 08, 2022, 05:16:24 pm
content: I'd be jumping for joy if i had a totally earth free location to work in

author: bottledwater
author_rank: Contributor
timestamp: December 08, 2022, 05:20:23 pm
content: Quote from: bdunham7 on December 08, 2022, 05:11:57 pmYes, 2-pin sockets everywhere and no earth coming into the building anywhere, I've looked. The building is old so it's technically legal.Quote from: Grandchuck on December 08, 2022, 05:12:17 pmI do have heat and water pipes coming in but it would be a long wire. In a pinch maybe I could access the main water pipe downstairs. But I heard it isn't safe to get your earth ground this way, at least for test gear? Maybe it would be safe/good for my ESD mat?

author: bottledwater
author_rank: Contributor
timestamp: December 08, 2022, 05:21:18 pm
content: Quote from: themadhippy on December 08, 2022, 05:16:24 pmHæhæ, nice

author: CatalinaWOW
author_rank: Super Contributor
timestamp: December 08, 2022, 05:29:13 pm
content: Remember that all voltage is relative. Draw a diagram, in your head or on paper, of the gear, devices and components you are worried about and how they are connected electrically. This diagram will show how potential differences can arise between various parts. And give you ideas how to control them.Example: For static safety the problem comes when your body is at a different potential than your parts, and the current that arises when you touch the part and force them to go to the same potential.Solution: Put a grounding mat on your bench. It doesn't have to be grounded. Now touch the grounding mat before you touch your parts. Touching the grounding mat forces your body and the mat to be at the same potential. Current has flowed between them to achieve this condition. But both the mat and your body are robust to this current and the only damage is a mild tingle you may have felt. After this, you and your parts are at the same potential and you can handle them freely.The same principal applies everywhere, but there is an added problem. Grounding on equipment is often as much for safety purposes as it is for noise control. A fault in the equipment could allow the chassis or other touchable places to be connected to either the hot or neutral lines. When grounded this failure either results in a blown fuse or non hazardous situation depending on which side the fault comes from. Without the ground you don't have this safety backup.Another problem arises if the floor surface is partially conducting (not open but high resistance). In cases like this it is possible for there to be a voltage between neutral and the floor, which is the potential your body will most likely end up at. Measure the voltage and be aware of this in the mental map identified in the first paragraph. A little thought will also suggest how you can evaluate the impedance between the floor and wherever the ground and neutral actually are connected, which can give you more information on precautions you can take. The danger zone lies in the middle. Very low and very high impedances will not usually be a problem.While your situation does expose you to some additional risk, it is not inherently terribly hazardous, and the risks can be controlled by thoughtful use. There are literally millions of people who have worked successfully and safely under these conditions.

author: Siwastaja
author_rank: Super Contributor
timestamp: December 08, 2022, 05:36:25 pm
content: Are you going to build or repair any mains powered designs? If not, any of this does not matter the slightest. What comes to lab equipment, it's no different from normal home electronics: the same regulations apply, the products must be safe to be legally sold. Beware of Ebay China imports or very old antique gear, though.For ESD, if you find any kind of steel pipe etc., you can attach the 1Mohm resistor to that and use it to ground your ESD mat. (Mat is really all you need; as you rest your hands on the mat, a special strap offers little additional help.)

author: bdunham7
author_rank: Super Contributor
timestamp: December 08, 2022, 06:13:08 pm
content: Quote from: bottledwater on December 08, 2022, 05:20:23 pmOK, are there RCDs (GFIs) at the outlets or in the service panel?

author: Ian.M
author_rank: Super Contributor
timestamp: December 08, 2022, 06:20:31 pm
content: Look up "equipotential bonding". If your work area has full equipotential bonding, and you take precautions against coming into contact with unbonded conductors and potentially conductive surfaces (e.g. bare concrete floors reinforced with rebar), and you take precautions against contact with the bonded conductors from outside the area, its at least as safe for YOU as if you had a proper PE conductor ('earth' ground).However do not ground to metal water pipes or other metal pipes if it passes through any area outside your control between its point of entry into the building and your proposed grounding point, as if any part of the pipes gets replaced with plastic, and a fault subsequently occurs in your work area there is a high risk of the pipes becoming mains 'live', risking electrocuting other occupants of the building.Exception:If *ALL* mains supplies to your bench pass through isolating transformers, and you do not extend their secondary side circuits outside your equipotential bonding zone, its impossible for them to make the bonding conductor 'live', so you can ground the bonding conductor to water pipes that pass outside your control. If you do so, remember that an isolating transformer removes all upstream RCD (GFCI) protection from its secondary side.

author: bottledwater
author_rank: Contributor
timestamp: December 08, 2022, 06:58:22 pm
content: Quote from: bdunham7 on December 08, 2022, 06:13:08 pmI have hot and neutral coming into a RCD in the service panel. One phase then goes into the apartment via old cloth-style wires. That's all. I could/should get some more to have things separated but I wanted to know about the earth issue first.Quote from: Ian.M on December 08, 2022, 06:20:31 pmI don't have any pipes that fulfill this criterion so I guess connecting to one of them is not an option.

author: bottledwater
author_rank: Contributor
timestamp: December 08, 2022, 07:02:58 pm
content: Thank you, this is very helpful. Let me summarize what I think I understand:My test gear and I will be fine, the same way my stereo is "fine" in a thunderstorm, as long as I don't do mains repairs.To keep my components safe I can stick them in an ESD box which I keep at the same potential as the ESD mat that I work at. That way, any time I sit down by my mat, my components and I will slowly be brought to the same potential through the 1M resistor.What if I then come in with my un-earthed oscilloscope ground to probe my sensitive component? Since chassis ground of my oscilloscope (and thus its input ground) floats, I'll zap the component. I guess if I touch the oscilloscope ground to my mat before I probe the component, the component will be ok when I do.The chassis grounds of my test gear will be connected to each other ("equipotential") through the power strip that I connect them to. But they will be floating. Would I connect my ESD mat and ESD component box to this floating power strip as well?

author: Ian.M
author_rank: Super Contributor
timestamp: December 08, 2022, 07:21:55 pm
content: If you 'ground' your ESD mat and other ESD prevention equipment to your bonding conductor(through the usual 1Meg safety resistors), and *ALL* your test equipment with three pin power leads have their PE ground connected to the *same* bonding conductor, along with all exposed metal nearby of significant size(i.e. don't bother with draw handles etc. but a metal bench or desk frame should be bonded), your parts and boards will be at no higher ESD risk than if you did have a PE conductor to true 'earth' ground.The bonded zone will probably have enough leakage to 'earth' ground to prevent the build-up of high static charge voltages, but if you can, a 1Meg resistor (actually 3x 330K in series to reduce the risk of it ever shorting out) between your bonding conductor and a waterpipe will discharge static charge without risking energising the water pipes with mains if anything faults to the bonding conductor.

author: langwadt
author_rank: Super Contributor
timestamp: December 08, 2022, 07:43:31 pm
content: Quote from: bdunham7 on December 08, 2022, 06:13:08 pmhere that is a requirement is all residential installations no matter how old

author: langwadt
author_rank: Super Contributor
timestamp: December 08, 2022, 07:48:41 pm
content: Quote from: bottledwater on December 08, 2022, 07:02:58 pmin my experience the biggest issue is when somethings are earthed and some not, the things that are not earthed will have their "earth"floating on mains/2 realtive to true earth via the y capacitors in most supplies. That can give you a tingle or fry electronics

author: JustMeHere
author_rank: Frequent Contributor
timestamp: December 08, 2022, 07:54:03 pm
content: If you're really worried, put a GFCI breaker in your panel. Other than that most of the time your DUT is on an ungrounded, isolated power supply anyway.

author: jonpaul
author_rank: Super Contributor
timestamp: December 08, 2022, 08:03:41 pm
content: 240v mains>>1:1 isolation transformer, of desired KVA.We floated our entire benches and lab that way to safely design and debug KW SMPS and electronic ballastsNever had any problemsSearch for 240/240V isolation transformersJon

author: TimFox
author_rank: Super Contributor
timestamp: December 08, 2022, 08:08:33 pm
content: Quote from: langwadt on December 08, 2022, 07:48:41 pmPrecisely. If you simultaneously come into contact with the metal case of an ungrounded box (with a normal IEC-connector line filter) and something that is grounded (radiator, faucet, water pipe, etc.) you will encounter 1/2 the line voltage through a medium-size capacitor (maybe 4.7 nF) and get a (normally) non-lethal shock.If you are on a ladder, or live in a 220 V country, that shock can still be hazardous.

author: bottledwater
author_rank: Contributor
timestamp: December 08, 2022, 08:23:04 pm
content: Quote from: TimFox on December 08, 2022, 08:08:33 pmInteresting. So if I connect myself to the metal case of a mains powered piece of gear through my ESD mat, I'll be floating at 1/2 the line voltage, but this is not a problem?

author: themadhippy
author_rank: Super Contributor
timestamp: December 08, 2022, 08:36:16 pm
content: Quoteand if the incoming supply is not referenced to ground?

author: langwadt
author_rank: Super Contributor
timestamp: December 08, 2022, 09:06:12 pm
content: Quote from: bottledwater on December 08, 2022, 08:23:04 pmyour connection to the ESD mat has a large resistor limiting current and anyway you wouldn't feel it unless you touch something that is really earthedI suspect quite few TVs and sound cards have been zapped by plugging the audio of an unearth PC into a TV that is earthed through the cable TV antenna connector

author: TimFox
author_rank: Super Contributor
timestamp: December 08, 2022, 09:56:34 pm
content: Quote from: bottledwater on December 08, 2022, 08:23:04 pmIt's only a problem when you complete the circuit (e.g., by touching some heating or plumbing metalwork).A bird can sit on an uninsulated high-voltage wire without damage.

author: bottledwater
author_rank: Contributor
timestamp: December 08, 2022, 10:03:44 pm
content: Quote from: TimFox on December 08, 2022, 09:56:34 pmI understand, although it was suggested earlier to connect myself and my chassis grounds to a metal pipe through a current-limiting 1M resistor (or 3x330k). Is that still the recommendation if the chassis grounds bring us to 1/2 the line voltage?

author: Doctorandus_P
author_rank: Super Contributor
timestamp: December 08, 2022, 10:30:31 pm
content: Quote from: themadhippy on December 08, 2022, 05:16:24 pmMaybe go practice your jumping skills beyond the Kuiper belt?

author: Ian.M
author_rank: Super Contributor
timestamp: December 09, 2022, 12:46:19 am
content: The resistors I suggested between bonding conductor and grounded waterpipe if available are to discharge DC static charge build-up to prevent the (small) risk of ESD induced flashover inside any nominally grounded equipment's PSU. They will do so successfully in the presence of AC leakage current driving the grounding conductor to approximately half the line voltage but wont ground out the leakage current, which would need a low impedance dedicated grounding conductor, marked as such where it passes through any common areas.

author: mag_therm
author_rank: Frequent Contributor
timestamp: December 09, 2022, 01:18:56 am
content: Is that the old type E France plug?More basically,initially,I would get a 100 kOhm 1 ~ 5 Watt Resistor:(220 ^2) /100000 =0.48 WattConnect across the pins of an old , spare plug.Now you can check with a multimeter, which side is lowest voltage and which side is "hot" to ground.That is assuming you know how to do it safely, and there is a ground like embedded water pipe, steam heater pipe etc.With old Test Equipment, Radios , other appliances,the first thing is to check that the On/Off switch and appliance fuse (if fitted) is on the "hot" side.With newer equipment I presume somebody already connected the outdated plug? So you can open it and check tightness and no splayed strands. And how is the ground wire terminated.The ground test will also tell if there is residual voltage on the side that is supposed to be at ground potential.

author: BillyO
author_rank: Super Contributor
timestamp: December 09, 2022, 01:40:41 am
content: Quote from: langwadt on December 08, 2022, 07:43:31 pmInteresting. If this is the case, then there must be access to ground for them to work. Since you and the OP are form the same country... it follows he does too.@bottledwater, do you have access to the basement? Back when I was a kid and lived in a basement apartment I also did not have access to the ground outside, however, it was easy enough to drill a hole through the concrete in the basement floor and pound a rod in there (with the landlady's permission in my case).

author: JustMeHere
author_rank: Frequent Contributor
timestamp: December 09, 2022, 01:49:21 am
content: Quote from: themadhippy on December 08, 2022, 08:36:16 pmThis was how I had my.old house. The panel was grounded. The bathrooms and kitchen were grounded. We didn't rewire anything else. Just dropped in some GCFI breakers. It passed.code. it worked.It might have worked too well. A close lightning strike would pop about half the panel. If probably did save my house when it flooded though.

author: themadhippy
author_rank: Super Contributor
timestamp: December 09, 2022, 01:57:46 am
content: Quoteso the installation had a reference to ground,if the supply has no connection,or a high impedance path to ground then your rcd aint gonna work

author: bdunham7
author_rank: Super Contributor
timestamp: December 09, 2022, 03:53:08 am
content: Quote from: BillyO on December 09, 2022, 01:40:41 amQuote from: themadhippy on December 09, 2022, 01:57:46 amAn RCD/GFI does not require a ground to operate. There may be some models that will not cooperate and others that are labelled to indicate that they are intended to be used only with ground connections, but there are many that don't and there's no reason that their basic principle of operation would require a ground. Do service panel RCDs have a ground wire in the UK or Denmark?

author: langwadt
author_rank: Super Contributor
timestamp: December 09, 2022, 08:37:20 am
content: Quote from: BillyO on December 09, 2022, 01:40:41 amit doesn't need an earth (ground) it triggers on a difference in phase and neutral current

author: bottledwater
author_rank: Contributor
timestamp: December 09, 2022, 10:11:49 am
content: Quote from: BillyO on December 09, 2022, 01:40:41 amThis was my first idea, but there's a concern that we'll hit ground water and get water coming up into the basement. I think the risk is low but I can't really accept any risk in that direction.Quote from: bdunham7 on December 09, 2022, 03:53:08 amIt doesn't have/need a ground wire. It probably works the way @langwadt explains.

author: bottledwater
author_rank: Contributor
timestamp: December 09, 2022, 10:16:15 am
content: Hi again, thanks again. Have been ruminating over this for a long time, so it's very nice to get some other eyes on it.I drew up the way I understand what you're saying so far. Please comment.

author: paulca
author_rank: Super Contributor
timestamp: December 09, 2022, 10:26:16 am
content: To answer your original question. What would I do?I'd move house.

author: themadhippy
author_rank: Super Contributor
timestamp: December 09, 2022, 01:07:47 pm
content: QuoteIts doesn't need a ground wire,but the supply feeding it needs to have a reference to ground.Quoteand where's that difference going to go to complete the circuit if there's no earth?Why dont rcds work on isolation transformers? and whats the difference between an isolation transformer and an incoming supply that has no connection to earth?

author: bottledwater
author_rank: Contributor
timestamp: December 09, 2022, 01:31:27 pm
content: Quote from: themadhippy on December 09, 2022, 01:07:47 pmFound the data on the model I have, if you're interested:https://support.industry.siemens.com/cs/pd/472574?pdti=pi&dl=en&lc=en-DK

author: Doctorandus_P
author_rank: Super Contributor
timestamp: December 09, 2022, 02:06:41 pm
content: There is no absolute "earth". It is just a convenient convention.Current always flows in loops, and Voltages are always differential measurements between two points.As a result, if you have no "real earth" you can just simply create your own.Just feed all your electronic equipment from the same extension cord, and use an extension cord which does have "earthed" sockets, even if the earth on the other side of the extension cord is not connected to anything.Then also connect your ESD mat to the "earth" connection of your extension cord.If you want to go real fancy, you can scrape the wallpaper off your walls put aluminium foil on it (also connected to your self created earth) and then put the wallpaper back. Now you have created a local faraday cage and anything outside it is then pretty much irrelevant.If you then also connect the metal doorknob to your ESD mat, you will (dis) charge yourself to the same level as your "local earth" when you enter the room.You can also have a look at how a RF measurement test setup is created with a LISN. (Line Impedance Stabilisation Network) It's mainly a fancy mains filter, combined with big steel plate that represents the local "earth" for RF measurement purposes. A "real" LISN is pretty expensive. Reason is probably that it is a relatively rare piece of test equipment and that its used for certification purposes, which demands close tolerances. Diy-ing a "usable" device is a lot easier, but you don't even have to do that. Just read a bit about the theory behind it and how it's supposed to be used.

author: Terry Bites
author_rank: Super Contributor
timestamp: December 09, 2022, 02:54:48 pm
content: Have your landlord sued for reckless endangerment and for failing to comply with HD 60364?So are neither side of your incomming mains supply earth referenced?

author: langwadt
author_rank: Super Contributor
timestamp: December 09, 2022, 03:29:15 pm
content: Quote from: Terry Bites on December 09, 2022, 02:54:48 pmThe supply is earthed somewhere, but afaik houses build before 1975 do not require an earth connection andoutlets from before 1994 do not require earth, but a GFI is required in all installations

author: paulca
author_rank: Super Contributor
timestamp: December 09, 2022, 03:44:34 pm
content: If you have no earth you have no G for a F to be I'edYes, I know it will detect other leakage, but without an Earth there be no leakage. Our friend will be the full current path and no GFI or he wont.

author: langwadt
author_rank: Super Contributor
timestamp: December 09, 2022, 04:08:03 pm
content: Quote from: paulca on December 09, 2022, 03:44:34 pmthe supply is earthed at the transformer/powerstation, the house doesn't need an earth for a GFI to work.and if the supply isn't earthed somewhere a GFI will not work no matter what because the only current path is like a normal load that won't trigger a GFI

author: bottledwater
author_rank: Contributor
timestamp: December 09, 2022, 04:51:45 pm
content: Quote from: Terry Bites on December 09, 2022, 02:54:48 pmI believe Neutral is earth referenced at the power distribution center. Old houses are not required to have a local earth but if you renovate you're required to make one. I'm just in a situation where it appears impossible to make a local earth.Quote from: langwadt on December 09, 2022, 04:08:03 pmI think both statements are true: The RCD works without a ground because it detects if what goes in comes back out. If there's a difference, there's a leakage current going through me to earth instead of straight to earth.This is the explanation on wiki [https://en.wikipedia.org/wiki/Residual-current_device]:Quote

author: BillyO
author_rank: Super Contributor
timestamp: December 09, 2022, 05:05:46 pm
content: Quote from: bdunham7 on December 09, 2022, 03:53:08 amWell, I do know how they are activated. What I mean is, if there is no ground/earth for current to flow into, thus causing the current difference between the two power lines, then they would never trip. In essence, they need a ground to work (or other connection where current can flow out of the circuit). There would be no point in installing them if there was no ground anywhere in sight. So, likely there is a ground coming into the building. Possibly terminated at the entry panel?Of course, they could just be requiring installation of them everywhere regardless whether or not they will ever offer any protection. You know, like a screen door on a submarine. It sounds like the sort of thing a government would ask for.

author: TimFox
author_rank: Super Contributor
timestamp: December 09, 2022, 05:08:23 pm
content: Quote from: BillyO on December 09, 2022, 05:05:46 pmIf there is no local ground connection in the building, but if you take an electrical appliance and drop it into a bathtub with water in it, some current will flow from the line through the water back to the ground connection at the substation, thus giving an imbalance that will trip the RCD.

author: bottledwater
author_rank: Contributor
timestamp: December 09, 2022, 05:13:49 pm
content: Quote from: Doctorandus_P on December 09, 2022, 02:06:41 pmThis is exactly my plan so far. My remaining questions are:1) What are the risks to me and my gear if I connect myself and its (chassis) ground connections through an ESD mat?As far as I understand, this may bring me to half the line voltage due to the caps in the power supplies, so if I touch anything that's actually earthed, I could be in trouble. There was also a comment that the fuses on my gear won't protect it if there's no real earth connected.2) Should I create an unconventional earth connection by connecting to a metal pipe?Here, the suggestion is to at least put a current-limiting resistor in between. But I could also be charging pipes going elsewhere in the building.Quote from: Doctorandus_P on December 09, 2022, 02:06:41 pmI love the idea of living inside a Faraday cage. This should alleviate any spiritual grounding issues

author: BillyO
author_rank: Super Contributor
timestamp: December 09, 2022, 05:15:58 pm
content: Quote from: TimFox on December 09, 2022, 05:08:23 pmIf he has metal drain plumbing, as would be the case here, then he has a really good earth ground. He could use that.My bathtubs are plumbed with plastic on both the supply and drain. If you drop a toaster into it, you better hope you are not in there. RCD/GFI or not.

author: BillyO
author_rank: Super Contributor
timestamp: December 09, 2022, 05:18:59 pm
content: Quote from: bottledwater on December 09, 2022, 05:13:49 pmIf you have metal drain pipes, they will make pretty good earth grounds. Copper supply pipes can be good, but if you don't have access to a real earth it may not be possible to test them properly.

author: TimFox
author_rank: Super Contributor
timestamp: December 09, 2022, 05:21:52 pm
content: Quote from: BillyO on December 09, 2022, 05:15:58 pmMy point was to what trips an RCD, which are quite sensitive to the imbalance in currents between L and N (low mA).Unless your plumbing uses de-ionized water, there is a substantial conductivity through it, even in plastic pipes.I would not trust plastic plumbing as a grounding method, however.In the US, appliances such as hair dryers must contain a GFI to deal with archaic houses that lack GFI outlets in the bathroom.

author: BillyO
author_rank: Super Contributor
timestamp: December 09, 2022, 05:42:45 pm
content: Quote from: TimFox on December 09, 2022, 05:21:52 pmNot here. I'm on a well. The water is chuck full of mineral and metal ions.Quote from: TimFox on December 09, 2022, 05:21:52 pmNo, for sure don't do that.

author: themadhippy
author_rank: Super Contributor
timestamp: December 09, 2022, 05:51:00 pm
content: QuoteBut will that current be enough to operate an rcd? If the bath is on a wooden floor and all the pipe work is plastic can you be certain the loop impedance is low enough for 30ma to flow without the potential rising above 50v to earth (uk rules)

author: TimFox
author_rank: Super Contributor
timestamp: December 09, 2022, 06:11:03 pm
content: Quote from: themadhippy on December 09, 2022, 05:51:00 pmThe US requirement for a GFI in a bathroom is to trip at 6 mA, and not to trip at less than 4 mA.30 mA seems far too high a trip point, especially in 240 V countries, but maybe that spec is for a whole building?US code requires a GFI built into any outlet in a bathroom or similar location.The US television program "Mythbusters" did a show about dropping an appliance into a bathtub, a common trope on criminal/mystery TV shows.They could not purchase a hairdryer without GFI (even at junk stores), so they had to use a simulacrum.They found that without a GFI, a lethal current could flow through their dummy, but that the GFI would trip.https://mythresults.com/episode19

author: bdunham7
author_rank: Super Contributor
timestamp: December 09, 2022, 06:11:24 pm
content: Quote from: bottledwater on December 09, 2022, 05:13:49 pmHaving your ground connections float up due to Y-caps is a real issue if you truly have no ground. However, fuses are not really an issue.It's hard to advise you because almost all alternatives havepotentialdrawbacks. Even if you find a nice pipe or something to ground on, unless you have some way of knowing that it hasreliablelow impedance to actual earth (the one that your supply is referenced to) you run a real risk of some problem in your lab creating a dangerous situation where metal things in your house that should be at ground are actually energized. OTOH, letting your grounds float isn't really desirable either. I'd suggest both running a wire to the best ground you can find and using an isolation transformer for your entire lab. However, I'm sure someone will jump in and point out that this defeats your RCD protection, which is true but unimportant in my view (but that's an ongoing argument I don't want to revive here). Note that this is not 'floating' anything as the ground between all of your instruments and hopefully an actual ground is still intact.Essentially in your case a whole-lab isolation transformer is a tradeoff between not having RCD protection on things you have apart in the lab and leaving the risk that an issue in your lab could result in energizing your plumbing or whatever you've chosen as a ground.

author: paulca
author_rank: Super Contributor
timestamp: December 09, 2022, 06:15:25 pm
content: Quote from: BillyO on December 09, 2022, 05:18:59 pmIf they aren't grounded of course they are just big antenna and I wouldn't want to be in the path between them and ground... or anywhere near it in a lightening storm.

author: BillyO
author_rank: Super Contributor
timestamp: December 09, 2022, 07:10:56 pm
content: Quote from: paulca on December 09, 2022, 06:15:25 pmI honestly cannot think of a situation where drain pipes would not eventually be buried in the ground. I guess a builder could go the all the trouble of making some sort of isolated chambers/tunnels to suspend their drain pipes in until they connected to the main concrete sewer, but that seems a little insane. Especially in a residential situation.

author: bdunham7
author_rank: Super Contributor
timestamp: December 09, 2022, 07:13:41 pm
content: Quote from: BillyO on December 09, 2022, 07:10:56 pmThere could be a nonconductive section or coupler somewhere...

author: themadhippy
author_rank: Super Contributor
timestamp: December 09, 2022, 07:47:49 pm
content: Quoteburied in the ground aint the problem,but plastic pipes that are very common for drain pipes in the uk dont conduct very well,nor does the ceramic pipes often found on large main drains

author: TimFox
author_rank: Super Contributor
timestamp: December 09, 2022, 07:56:25 pm
content: Plastic pipes used for drains are very common nowadays.Usually PVC, since the required glue joints work well.However, the liquid contained in them should be somewhat conductive.Moral: historical improper grounding should be replaced by proper grounding.(In high-school competitive debate, we always defined "should" as "ought to, but not necessarily will".)

author: BillyO
author_rank: Super Contributor
timestamp: December 09, 2022, 08:06:18 pm
content: Quote from: bdunham7 on December 09, 2022, 07:13:41 pmTrue. That would have to be pretty much in the house though. You don't need much length of a 3" or 4" pipe to be in contact with the ground to make a good earth. 10' would be plenty and give about 1500 sq. in. of area for a 4" pipe or 1100 sq. in. for a 3" pipe.

author: BillyO
author_rank: Super Contributor
timestamp: December 09, 2022, 08:07:15 pm
content: Quote from: themadhippy on December 09, 2022, 07:47:49 pmThat's why I specifically said "metal drain pipes"

author: paulca
author_rank: Super Contributor
timestamp: December 09, 2022, 08:53:40 pm
content: Quote from: BillyO on December 09, 2022, 07:10:56 pmWhy would you connect a roof drain to the ground? Most them empty out onto a gutter or some form. Including the metal ones. The only down pipe that goes under around here is the "soil stack".

author: BillyO
author_rank: Super Contributor
timestamp: December 09, 2022, 09:43:54 pm
content: Quote from: paulca on December 09, 2022, 08:53:40 pm?Roof drain? Maybe I'm being punked here, but no roof drain. I was referring to the septic (sewer, black/grey water, shower/tub/basin/toilet) water drain, indeed the "soil stack". Why would you assume roof drain?BTW, I do collect mine in a pipe that goes down to the creek near my house. The pipe is plastic though.

author: langwadt
author_rank: Super Contributor
timestamp: December 09, 2022, 10:32:44 pm
content: Quote from: TimFox on December 09, 2022, 06:11:03 pmthere is a single GFI for the whole house/ apartment

author: bdunham7
author_rank: Super Contributor
timestamp: December 09, 2022, 11:12:05 pm
content: Quote from: langwadt on December 09, 2022, 10:32:44 pmWow! The whole house goes dark?!? And then you have to figure out where the fault is?We have per-circuit AFCI (combination) breakers where needed and where GFI is required, at least one per circuit (typically the first wall socket in a chain). I don't even chain them, I use one GFI per socket location so that when something trips it I know what it was. That and I have some old wiring that may leak a bit on damp days.

author: themadhippy
author_rank: Super Contributor
timestamp: December 10, 2022, 12:36:52 am
content: Quoteyep great fun,especially if its a neutral-earth fault.In the uk we've slowly gone from no rcd protection to either the whole board protected by 1 device or split boards were part of the installation is protected by an rcd and the rest,normally lighting circuits, aren't, and are now moving to individual circuits having there own rcd.Coming to a dis board soon,if the iee get there way will be afd's,either whole board protection,or individual circuits,combined mcb/rcd/afd's are available,at a price

author: BillyO
author_rank: Super Contributor
timestamp: December 10, 2022, 01:08:26 am
content: Quote from: themadhippy on December 10, 2022, 12:36:52 amHere in Canada it is not usual to have the lights on different circuits from the outlets. There is no law against it, it's just not done but it makes great sense. If I ever build another house I will sperate the lights from the outlets.As for GFIs, we are only required to have them on: Bathroom outlets, outdoor outlets, whirlpool bathtubs and hot tubs.

author: Handskemager
author_rank: Newbie
timestamp: December 10, 2022, 06:17:34 pm
content: Not home at the moment but pretty sure we have 2x 13 amp fuses (1 for light and 1 for outlets), RCD (can’t remeber the wiring atm) and 16 amp fuse for “kraft stik” (3 phase 400v) for oven and stove.Living in a 91 spuare meter apartment in Denmark.Earth protected outlets in the bathroom and kitchen only.Building is from 1967

author: SL4P
author_rank: Super Contributor
timestamp: December 12, 2022, 08:09:26 pm
content: OP, does your GFI have aTESTbutton?Problem solved… if that button works, there is a mains earth on the bavpck of the GFCI.

author: langwadt
author_rank: Super Contributor
timestamp: December 12, 2022, 09:08:37 pm
content: Quote from: SL4P on December 12, 2022, 08:09:26 pmehh no, the test button just puts a resistor between live after the GFI and neutral before the GFI

author: themadhippy
author_rank: Super Contributor
timestamp: December 12, 2022, 09:09:38 pm
content: QuoteThe test button causes an imbalance by putting a load across the input side and output side so will still work regardless of earth.

author: langwadt
author_rank: Super Contributor
timestamp: December 12, 2022, 09:10:54 pm
content: Quote from: Handskemager on December 10, 2022, 06:17:34 pmsame, building from 1898, electrical installation from sometime in the early 70's

author: bottledwater
author_rank: Contributor
timestamp: December 13, 2022, 03:45:15 pm
content: I have two different electricians coming later in the week to see if they have some creative ideas to get earth in..!

author: CatalinaWOW
author_rank: Super Contributor
timestamp: December 13, 2022, 05:22:27 pm
content: Quote from: bottledwater on December 13, 2022, 03:45:15 pmWith all due respect to the electrical trades, be cautious about what they suggest. Make sure it makes sense to you, and lines up with all of the cautions identified in this thread. While there are many excellent electricians, only a few can deal with situations that are off the beaten path. And unfortunately there are a significant number that don't know their own limitations.

author: bottledwater
author_rank: Contributor
timestamp: December 13, 2022, 05:49:37 pm
content: Quote from: CatalinaWOW on December 13, 2022, 05:22:27 pmNote taken, thank you. It's part of the reason I'm asking two, maybe three.Since we most likely can't drill the stake down the basement floor (due to risk of hitting ground water), a specific concern I have is if I'll get a proper earth ground connection if we just put it down a few meters out, next to the basement, if that makes sense. Will it be deep enough and far enough away from the foundation of the building.I think there's an earth ground connection over in another part of the building that we could try to find to check against. Haven't been able to find it myself. Otherwise, I guess we can at least check the potential difference between neutral and the earth ground we can get, since neutral is supposed to be earth ground referenced at the power station.

author: Ian.M
author_rank: Super Contributor
timestamp: December 13, 2022, 06:08:29 pm
content: If your electricians are any good, they'll know how to put in temporary test ground rods and how to use them to measure the effective ground resistance of any ground rod they install. The only thing that could make that impractical is if the building is surrounded by a large area of concrete or thick tarmac with absolutely no access to the underlying soil anywhere nearby.

author: BillyO
author_rank: Super Contributor
timestamp: December 13, 2022, 06:36:59 pm
content: Quote from: bottledwater on December 13, 2022, 05:49:37 pmYes, you should. Here in Ontario Canada I had to put two 10' ground rods into the ground not more than 2 feet from the foundation for my service installation and they had to be connected to the panel with a #6 AWG stranded bare copper wire. I don't recall if there was a specification for how far apart they had to be. The ground I put in for my lab is pretty much the same. I just used re-bar for the rods. A bout .5m from the foundation (basement).Edit: found it in a book:QuoteBTW: Meatal pipes, both supply and drain are acceptable as grounds under the Canadian Electric Code. Your country may have different rules.

author: Sherlock Holmes
author_rank: Frequent Contributor
timestamp: December 13, 2022, 07:02:03 pm
content: Quote from: bottledwater on December 08, 2022, 05:09:10 pmWell there likely is an earth of sorts. The neutral is (effectively) connected to ground, the ground (at the substation and at the local address). But the ground/earth wiring is meant to be distinct from neutral, and have the capacity to endure large currents in the event of short circuit faults.In a situation like you describe, I wonder whether it would be prudent to connect your equipment not to the wall outlets, but to a1:1 isolating transformer(which eliminates galvanic current flow to the outside electricity system).Then, if you were standing on the floor even wet floor in bare feet, you'd not get a jolt if you did accidentally touch a metal exposed part of equipment that had accidental come into contact (internally) with the "live". No current could flow "to ground" in such a setup, so its safe. (So long as the equipment itself has no exposed metal that could ever come into contact with live internally).I was thinking of getting something like that myself for repair of some old tube radios I have here, a simple 1:1 ratio isolating transformer.Another advantage of isolation too, is that transformers have a very high impedance to HF signals, noise and spikes so you'd be reducing any of that getting through to your equipment.

author: Sherlock Holmes
author_rank: Frequent Contributor
timestamp: December 13, 2022, 07:07:55 pm
content: Quote from: bottledwater on December 08, 2022, 05:09:10 pmI'd also like to ask, can you share some photographs of this? of these outlets and any related parts like the breaker boxes or fuse boxes? you might well have a truly historic setup here that would be worth documenting, once its ripped out and updated that history will be lost.I recall as a kid in Liverpool our house had little well made (dovetail!) wooden boxes mounted on each floor, above a door. When we unlatched the door we'd see these large ceramic user-repairable fuses, all gone now).

author: Sherlock Holmes
author_rank: Frequent Contributor
timestamp: December 13, 2022, 07:25:07 pm
content: Quote from: jonpaul on December 08, 2022, 08:03:41 pmI've read that many "isolation transformers" actually connect one side of the secondary winding to the incoming ground/neutral (internally) this makes no sense to me.

author: bottledwater
author_rank: Contributor
timestamp: December 13, 2022, 09:09:27 pm
content: Quote from: BillyO on December 13, 2022, 06:36:59 pmVery interesting, thank you! Do you know why two are you required? I've been assuming just one.

author: bottledwater
author_rank: Contributor
timestamp: December 13, 2022, 09:18:39 pm
content: Quote from: Sherlock Holmes on December 13, 2022, 07:02:03 pmI can't say I understand the details of running the whole bench on a 1:1 isolation transformer. I looked into it a bit because other people in this thread suggested it. It seems it would make me safebut the gear I have is still spec'ed to need a connection to earth ground, to protect itself and for noise and whatever else, and the transformer doesn't provide that, and then I run into having the floating grounds in my gear float to arbitrary levels.So I decided to have another go at getting an actual earth installed. Fingers crossed it can be done and that it won't cost a fortune.Btw for anyone else finding this thread, I found this video on isolation transformer safety helpfulI also watched this video