Earth issue - Page 1
Forum section: electronics / beginners

author: PinheadBE
author_rank: Regular Contributor
timestamp: July 30, 2023, 12:22:10 am
content: Hi,Now that the kids are gone, I am refitting a bedroom of my house into an electronic lab. (At last !)It appears my house dates from the '70s and in those times in my country, an earth connection was only mandatory in rooms where water is available (kitchen, bathroom....)And so, I do not have an earth connection in the room I am repurposing.Electrical security issues set aside, I was wondering if there were problems to be expected with my equipment, such as oscilloscope, function generator not linked to earth, .....Getting an earth connection to that room means a great deal of work, including opening walls to replace electrical pre-wired tubes with only 2 conductorsIdeas ? Opinions ?Thanks !

author: Benta
author_rank: Super Contributor
timestamp: July 30, 2023, 12:31:46 am
content: There's no big issue on operating without PE. Test and measurement equipment is laid out to be floating. It may give you a small noise penalty, but a most 'scopes etc are in plastic housings today I don't think it'll matter.

author: Manul
author_rank: Super Contributor
timestamp: July 30, 2023, 12:41:47 am
content: In my opinion you absolutely need mains earth. In the old days, when everything had transformer based power supplies it was somewhat ok. Nowadays SMPS often include filter caps which make devices float at half mains voltage, it's annoying and it can even damage some sensitive circuits you are working on. Not to mention human safety in case something goes wrong or you accidetally connect scope ground to live. You can run a separate mains earth wire if that's easier. I've done that in my old apartment.

author: jonpaul
author_rank: Super Contributor
timestamp: July 30, 2023, 01:14:55 am
content: Been EE 55 yrs in power and HV1/ Earth: For safety and EMI , a must2/ no mains earth: Drive 3..5 m copper rods into the soil, space ~ 2m apart. Bond togather, use heavy braidor thick strnaded wire. Yellow/grn is IEC code for earth3/ Use 1:1 240:240 isolation transformer to float the bench power , Earth is STILL used4/ Use variable trsf (powerstat, Variac) to bring up maons gradually 0-240VBon ChanceJon

author: themadhippy
author_rank: Super Contributor
timestamp: July 30, 2023, 01:49:33 am
content: QuoteAre the tubes metal and is there good continuity between tube joints as in the uk at least,using metal conduit is permitted as the protective conductor

author: radiolistener
author_rank: Super Contributor
timestamp: July 30, 2023, 02:12:03 am
content: Quote from: PinheadBE on July 30, 2023, 12:22:10 amMissing ground leads to some issues with EM interference and safety also missing ground can damage some equipment in rare cases with specific configurations. As a temp solution you can put very thick copper wire (at least 3-5 mm^2 cross section) with ground from room where it is present. Keep wire length as short as possible

author: Roehrenonkel
author_rank: Frequent Contributor
timestamp: July 30, 2023, 09:19:52 am
content: Hi PinheadBE,use the existing supply for the lights.For the lab-outlets i would pull a dedicated line (3x2,5mm²) from the fuse-box directly.No need to open up the walls if you use plastic-tubes or -channels.If thats too much for you, try classical earthening (??) (DE: Klassische Erdung)by connecting N(eutral) and PE together at the outlets. Do you use Schuko in Belgium?If you'r not sure what you do, get an electrician please.Don't run your Class-1 (Metal case and 3-wire-supply) gear without PE, it can save your live.Good luck

author: Vovk_Z
author_rank: Super Contributor
timestamp: July 30, 2023, 10:10:51 am
content: Quote from: jonpaul on July 30, 2023, 01:14:55 amIf you are a pro an you really need earthing - then you need it. But as a DIYer I happily lived without PE 20+ years of DIYing and accomodated to it.Vice versa: I'm afraid to short circuit something if e.g. my oscill. will be grouded.I use 230:230 VAC 400VA isolating transformer at my bench table and its basically enough for me.

author: PinheadBE
author_rank: Regular Contributor
timestamp: July 30, 2023, 02:52:24 pm
content: As a reply to your comments (for which I thank you), here are some more info:- There is no earth at the lights circuit either. There really is no earth at all in the bedrooms, and they are situated two floors up from the electrical main board.- There is no Live/Neutral on my installation: it's a tri-phase without neutral. So, the two connection of the mains are interchangeable since there is no "neutral" connected to earth at any point. But if I measure between any of the mains pins and the earth pin (where available in my house), I get 115 VAC, half the mains voltage.- I have a ground leakage protection set at 30 mA on each circuit, and a global 300 mA protection. So I guess I am enough protected.- The floor in the room is covered by a (non-conductive) of vynilI re-watched Dave's video on the subjecthttps://youtu.be/xaELqAo4kkQand some others (Mr Carlson, SDG, ....) and I am coming to the conclusion that, EMI and noise problems set aside, I do not need to install an earth connection, neither an isolation transformer: Since there is no connection between the (inexistant) earth and one of the mains pin, the scenarios of blowing my equipement or the device under test is inexistant either, right ?However, one question remains: what about ESD ?How could I strap mysef and my sodering mat if there is no earth connection ?In the place where I temporarily was soldering (the kitchen table...), there was earth connection available, and I had a wrist strap and a soldering mat connected to an ESD connection point, connected to earth....What now ?Are there other solutions ?I have seen some "ESD dissipative" materials. Are they any good ?

author: themadhippy
author_rank: Super Contributor
timestamp: July 30, 2023, 03:14:36 pm
content: QuoteHows that going to work if there's no path to earth for the fault current to travel?

author: Vovk_Z
author_rank: Super Contributor
timestamp: July 30, 2023, 04:10:46 pm
content: It'll work anyways. Either you wan't have current through your body at all (that's unlikely) or it'll work.

author: madires
author_rank: Super Contributor
timestamp: July 30, 2023, 05:07:58 pm
content: Quote from: PinheadBE on July 30, 2023, 02:52:24 pmIn that case there could be a weak earth/ground as the line-to-earth voltage should be 230V / sqrt(3) = 132V, or an phase imbalance. IIRC, roughly half of all Belgian homes have this special three-phase setup without neutral (230V delta instead of 400V, neutral earthed at substation).

author: radiolistener
author_rank: Super Contributor
timestamp: July 31, 2023, 04:29:31 am
content: Quote from: PinheadBE on July 30, 2023, 02:52:24 pmIf you don't have ground, do not solder circuits powered from mains, keep in mind that your soldering iron tip have high voltage mains potential if it connected to mains without ground line.There is also issue with equipment connections, if you want to connect one equipment to another, first connect their GND wires, then signal wires. Otherwise you can damage it with overvoltage.

author: Terry Bites
author_rank: Super Contributor
timestamp: July 31, 2023, 06:55:30 am
content: This is a good oportunity to create a good technical earth in your lab.I'd run a separate 4mm or 6mm wire from each of your outlets to a commoning block.From there take a 4mm or 6mm earth wire back to your breaker panel.

author: jonpaul
author_rank: Super Contributor
timestamp: August 01, 2023, 12:31:48 pm
content: Please check your region/country regulations for electric wiring and safety/fire.In case of transients, lightning, utility fault the earth is required for transient/emi/leakage current /GFI pfortection.If you have an "incident" (shock, injury, fire, cause issue in mains utility, etcx) expect the wiring and earth to be examined by insurance/govenment/local authoritites.Lack of any earth may cause incicents and futire liability, regardless of use as a DIY/residenceJon

author: Bicurico
author_rank: Super Contributor
timestamp: August 01, 2023, 02:00:00 pm
content: Old houses, in Portugal at least, that are prior to a given year, are not required to have earth in the electrical installation and may continue to be used as is.

author: PinheadBE
author_rank: Regular Contributor
timestamp: August 01, 2023, 04:06:24 pm
content: It is the same in my country: as long as I am not doing big renovation of my house, adding a room..... my electric installation may remain as such.It is validate by the insurances companies.I installed solar panels 10 y ago, and the only part of the electric installation that was verified was the added line with the inverterThe same went with my heat pump: a new electric line was added, and was the only one verified.On the other hand, I will add some (good) lightning/transient suppressors

author: PinheadBE
author_rank: Regular Contributor
timestamp: August 07, 2023, 07:26:49 pm
content: I'm not sure I've understood correctly the responses to this question:QuoteTheir electrical installations are all of the Live-Neutral-Earth type.Mine has no neutral in the house, but only at the sub-station......And in the soon-to-be lab, there will be no earth connection eitherSo, for example, even if I probe an non-isolated device, the GND connection of my scope being not connected to anything, it cannot be damaged, right ?Can someone confirm, and/or someonewith the same kind of installation as meexplain how his lab is wired ? Does it have isolation transformator or not ?Thanks

author: TimFox
author_rank: Super Contributor
timestamp: August 07, 2023, 07:46:22 pm
content: Without a PE, and with the one line connection live with respect to local ground (including metal pipes) and a neutral connection grounded somewhere, a fundamental problem is that the line-PE and neutral-PE capacitors in any line filters place an AC voltage on the metal parts of any equipment with line filter equal to 1/2 the line voltage in series with a relatively small capacitance (a few nF).After an installation in a foreign country, we named that "the Dan effect", as in "Dan is hard to shock, but..." when he came in contact with the computer chassis and the metal framework of the mechanism that was grounded (the local electrician had neglected to ground the temporary 240 V Diesel generator).However, if the AC lines are balanced with respect to local ground, that effect is reduced, and the resulting AC voltage on the metal is relatively small.Are there any metal heating ducts or plumbing near the room you use as a lab?

author: PinheadBE
author_rank: Regular Contributor
timestamp: August 07, 2023, 08:03:54 pm
content: Yes, there are heating metal pipes, but it is not allowed to use them as PE (by regulation). But I'm not sure how good they are as a ground.My heating installation is a air-water heat pump. So I guess it is grounded somehow.But again, the neutral is not distributed in our houses. As I understood from above answers, the neutral is grounded at the sub-station only, and only the three "live" phases are distributed to the residences.I guess we may then say that they are balanced with respect to local earthMy main concernis to protect both my measuring tools and DUT from blowing up.PE or not PE ? Isolation Transformer or not ?I'm going on in circles....

author: TimFox
author_rank: Super Contributor
timestamp: August 07, 2023, 08:08:21 pm
content: If you have a PC with a normal 3-pin line filter for its AC input, try measuring the AC voltage between its metal chassis and any exposed metal pipes or ducts with a normal DMM, when the PC is plugged into your outlet.

author: m k
author_rank: Super Contributor
timestamp: August 07, 2023, 08:40:21 pm
content: Protect your life first.Your room is isolated, it can still kill you.There can be transients, so your scope can be damaged.Same with other high voltages, maybe from DUT, but that's different.For ESD you should create a load or drainage.Isolated floor is the worst, every step will create some potential.You come and go and every step will create some.Finally it will go somewhere.Are you zapped when exiting a car?Pink plastic is good, but can't stand heat.You can also create a habit of shorting your self, that's how field service must do as a last resort.Without earth you can't operate anything metal, sort of.If your doings are complex you may have opposite end live cases.Connect your whole lab from one wall socket and add 30mA ground leakage protection using your new heat pipe earth.Test your ground leakage protector regularly.

author: PinheadBE
author_rank: Regular Contributor
timestamp: August 07, 2023, 08:52:23 pm
content: OK, and what about protecting my gear ?Isolation transformer or not (since we doNOThave neutral referenced connections in our outlets) ?I have even seen isolation transformer notices where it was stated to cut off the PE from the output....

author: m k
author_rank: Super Contributor
timestamp: August 08, 2023, 05:36:10 pm
content: You use your room like your kitchen.Isolation transformer is protecting you, not your gear.How is that voltage Tim asked?How you do your hot tap water, partially through that heat pump?Is cold water from the same incoming pipe?If so then there you have a real earth, not good but still.When PE is connected through the isolation transformer transients have a route.It also connects all metal cases together, so one live metal case and you're closer to death, but opposite sides of isolated mains grounded and hopefully fuse will blow.New gear you only need when you're alive.If you're very afraid that you fry your gear you should use only isolated probes or connections.Even then you can still short something with your probe tips, but maybe that's acceptable.How your gear will fry, you put your scope ground to live mains?If so then where that point is?I'm from schuko land, we have Neutral blue and Live brown.But that is only one version and since the plug is symmetrical in practice all colors are live, excluding green/yellow PE.So do you think you accidently connect your scope ground to not so neutral blue?That is easy, you do not connect your grounded gear to grid side.If you do, like I did, you're absolutely sure it's a correct blue, but there's still a catch, if it was a scope the probe can still have ground and it is close.So nowadays you don't do it, you get a cheap handheld from far east or much more expensive high voltage differential probe from near west and be done with it.

author: EPAIII
author_rank: Super Contributor
timestamp: August 10, 2023, 06:18:57 am
content: I have a number of wires running on the exterior of my house: cable TV, internet, phone lines, etc. Some are vertical and some run along horizontally under the soffit.I would be tempted to run a ground strap up the outside wall and in through a window. You could use flat copper strap or a flat braid. A window with a rubber seal should allow a wide but thin copper strap to just run under that seal. On the outside wall, paint it to match the finish there and it will be less visible.

author: PinheadBE
author_rank: Regular Contributor
timestamp: August 10, 2023, 09:46:57 am
content: OK, thanks for your guidance.Let's suppose I find a way to install a PE, which I intend to do.Now, I still don't have the "Neutral-earth problem" (as described in the videos mentionned earlier in this topic) since we only have Live wires distributed in our homes. The neutral is only at the substation, and there, it is connected to earth.In that case, what about the isolation transformer ? Needed or not ?

author: madires
author_rank: Super Contributor
timestamp: August 10, 2023, 01:30:18 pm
content: Quote from: PinheadBE on August 10, 2023, 09:46:57 amDepends on what you're working on. Differential probes for your scope could be also an option.

author: m k
author_rank: Super Contributor
timestamp: August 10, 2023, 05:08:50 pm
content: Isolation is not needed, you are already isolated.PE and leak protector is there because one day your kitchen sink can become part of your electrical grid.An example situation can be a metal cased noisy audio setup that is "grounded" to heat pipe.But one is not enough, there must be two, maybe neighbors.Since both ends are floating the heat pipe current can be sort of what ever.Even if one distribution phase is dropped to ground it's still just one.With heat pipe grounded metal case the situation can be very different, but still not alone.Neighbors can also be close but at different sides of the border with different electrical systems.