Checking your Home is Electically Grounded.   (Suspicious noise on Neutral) - Page 1
Forum section: electronics / repair

author: Zero_Ego
author_rank: Regular Contributor
timestamp: May 26, 2025, 06:20:02 pm
content: Howdy,I found some suspicious noise in my Mains Power.For a number of reason which I will not bore you with - I decided to check the integrity of my home Earth. At the time (Two days ago) all I had was a crapped out old Dick Smith multi-meter. (Me best one don't judge me) Sure wished it had a backlight meter when my other half turn the power off. Didn't see that comingSo my "Go to" was ChatGPT. Just to check my theory was correct, I asked it how to figure out which is active so I don't zap myself. (No crow yesterday - not that if I had one on hand I would of been confident to start probing home AC sockets) That's not my thing.I say way the danger. (Except when I sky dive) [Editors note: This guy has waffles - I hate waflerers] Freaks! (He doesn't sky dive either)So, figuring out the Active was easy enough with just a multimeter. (You guys know how) What I was interested in was the resistance between Neutral the Ground. I was looking for 1 Ohm or less. (GIven my flash Dick Smith such low reading is not it's strong point) It fancy becaue its got Dick written on it.I will leave that one alone.Now can I please put in a clause. Can you guy not come down heavy on the safety. I'm a pussy by nature.I say that because this next sentence will rattle some. I did not turn the mains off first. I know I should of but I didn't want everything in the house rebooting. (Spikes)I was confident I was safe, I had Identified my target sockets so I put my meter on Diode Mode. (It is supposed to trigger under 200 Ohms) I thought it was going to be a no brainer and would hear a continual solid beep signifying low Ohms. That is not what I heard.The Diode tester function was sounding off some low frequency. I could hear the way the pitch was changing there was something up with the path - or some noise. So I switched over to Ohms (It's a LCD DVM) and the meter was fultuating - from just above say 2 Ohms back down to less than 0,4 Ohm then up again down. That's when I turned off the power to get a solid reading for Neutral to ground.It was within Spec 1 Ohm or less and it was stable.Here's my question.Can I put a Shunt resistor across the Neutral and the (Earth) Ground at the socket - power back up the building - connect the crow across the resistor to read the noise on the line?I have no idea if its normal. It could be a dodgy USB charger any number of switch modes causing the noise.Does anyone know it its normal for the Neutral to Ground to fluctuate. With the power off - it was rock solid.I suspect noise coupled with a pour earth ground. My earth rod is old - not deep enough or corroded.Thanks, I really need some help on this one. Is a Shunt resistor a good idea or laughable? (Give it to me straight)If not what size ? 1M, IK , 10K I can then calculate the current.Thanks for reading.Really appreciate the help.ZE

author: helius
author_rank: Super Contributor
timestamp: May 26, 2025, 06:56:10 pm
content: Is there a split personality at work here (Editor's note?)Measuring the bonding between Neutral and Earth can't be done with a multimeter. The instrument used is a "Ground Impedance Analyzer" such as the unitshereandhere. It is designed as an impedance bridge to measure the ratio between a test shunt between Live and Neutral and the unknown impedance from Neutral to Ground. Less than 1 ohm is sufficient.The reason you were only able to get this <1 ohm reading when the main breaker was opened, is that the test current from the multimeter is swamped by resistive and reactive power in a live electrical network.This neutral to earth bonding is for safety only; it has nothing to do with noise. The PE (Protective Earth) terminal can only protect you from electric shock if it is (only) bonded to Neutral at the electric panel where the circuit breakers are. That way, a wiring fault inside grounded equipment will cause a fault current to flow, which is what trips the circuit breaker and de-energizes the faulty equipment. Any shunt resistor from Neutral to Earth is asking for trouble.Whether your building electrical network is properly grounded to the soil underneath is a separate issue and requires a different test instrument (aground resistance tester). This does have an impact on noise.

author: themadhippy
author_rank: Super Contributor
timestamp: May 26, 2025, 07:06:16 pm
content: Quotemaybe in your part of the world,else were the neutral-earth bond could be some distance from the consumers side

author: tggzzz
author_rank: Super Contributor
timestamp: May 26, 2025, 07:15:25 pm
content: You really need to characterise the noise... amplitude, frequency, reference point, measurement technique.As for fiddling with the mains supply: don't. Employ an electrician with appropriate certifications.Doing anything else could be dangerous in too many ways to enumerate, both to yourself (don't care!) and others. It might invalidate your insurance, and/or be illegal.FYI, I found parachuting boring, and switched to something interesting.

author: Zero_Ego
author_rank: Regular Contributor
timestamp: May 27, 2025, 02:39:29 am
content: Hi thanks for the comments - not all reads warm and fuzzy.C'mon more warm and fuzzy please. No one wants a big upset.I've been nothing but respectful is the forum and I get that asking dangerous high voltage electrical questions are fronded upon.But please a little respect and kindness as I'm only asking can it be done and would it work. I understand about liability and the balance between responsible advice you can give here online.But this is the way it has be - safety first for all. (But not me) Thanks tggzz. (Wow) Forget it!A person comes to these places to learn, hopefully from the best of the best - well at least one hoped.Do I have to show my qualifications? How do I know you guys know what you are talking about? Just saying, it goes both ways don't you think?I'm simple asking thought experiments to gain a better understanding of electronics.How do I know my electrician is smarter that a spark plug? Just because he has the fancy meter? That's like saying Katy Perry would be an astronaut if she blasted off into space for a full 11 minutes. People would laugh at her.What you don't like my jokes? [Editors Note: Horatio keep it pleasant ] Great, now every knows your real name act normal.I was simply asking could it be done?If I asked can I fix my leaking tape (and you guys were plumbers) are you going to say go away and get a plumber because its illegal and too dangerous? If you said yes to that. Slap yourself! There's a youtube guy who says that and it's still not funny.You need a licence plumber where I live - apparently they have had too many reports of people drowning when they forget to turn off the mains)All that potential, right in the eyeball.You even need a licence to own a cat. (I calibrate mine)No Script, No Fear, All Opinion. i thought that was Dave's job.You gave me the 'go away and hire a professional.' Unfair I was just asking can I get a refund? Or a second opinion.One thing about AI (Vs) GI it might get it wrong but it sure invites the curious mind. (Without the heavy's coming down on you)I put my safety hat on when I entered the beginners lounge and . . . I'm having a little trouble getting it off. . . it think it's stuck.I will consult a professional.Thanks for your time.Horatio.Germany

author: J-R
author_rank: Super Contributor
timestamp: May 27, 2025, 04:43:13 am
content: Since you're such a fan of ChatGPT, you should ask it to clean up your posts and remove anything not pertinent to the topic being discussed. If you want to be a comic, go do some standup at your local watering hole.But to answer your question, the reason the reading fluctuates or you think you have noise when measuring between neutral and ground at the outlet is because the neutral is the return path from the hot. It is the other half of the circuit which is a loop, coming from the breaker's hot, going out to the outlet, then back via the neutral.The hot side at the breaker is 230V and where the neutral bonds to ground in the panel is 0V. When you have a load connected in the middle, say a 2000W heater, the neutral at the middle/outlet will not be 0V, it will be perhaps 3V or 5V because of the resistance in the neutral wire. So that voltage is interfering with the multimeter's ability to measure resistance or check a diode for a voltage drop.You can go to other outlets in your house and see this for yourself by measuring the voltage between neutral and ground. Any circuit where there is a modest amount of load connected will have some voltage differential between neutral and ground.Also, this shows one reason why the neutral and ground are separate, and the ground wire should never be used to carry current. And the neutral should only be bonded to ground in one place in the house, typically at the service entrance or main panel.

author: tggzzz
author_rank: Super Contributor
timestamp: May 27, 2025, 05:42:02 am
content: Mains voltages aren't really high, and asking questions about them is absolutely not a problem.High energy circuits are dangerous in many ways, and we don't want well meaning beginners to accidently repeat old mistakes and hurt themselves.Have fun, safely

author: Fflint
author_rank: Frequent Contributor
timestamp: May 27, 2025, 06:25:38 am
content: This noise you speak of. I noticed that too with some of my meters, but only on continuity. It never crossed my mind to try measuring neutral to ground in the diode mode. The sound is this buzz that is somewhat recognisable as 50hz.I'm sure my bonding is fine. Still I do get few volts of AC on neutral, especially if measured pretty far from the main cabinet.I wouldn't assume your bonding is bad because of audible noise.The best way to check your bonding is to look inside the main electricity cabinet. Also you can get some idea what is going on with a normal low voltage ohm meter. Yes, you'll not get an impedance reading, but you'll get an idea if your bonding is there. If you see anything over 1ohm and you're not far from the main electric cabinet I'd be checking things further.

author: BennoG
author_rank: Frequent Contributor
timestamp: May 27, 2025, 09:19:14 am
content: using the meter in diode / resistance / continuity mode while there is voltage over the poins is of no use.It will disrupt the measurements you are doing and make no sense at all.Benno

author: tszaboo
author_rank: Super Contributor
timestamp: May 27, 2025, 09:49:50 am
content: You have an RCD fuse (also called GFCI) in your house's distribution box. There is a button on it. The button when pressed will run some 40mA or so current between phase and protective earth, then the fuse will open.Someone please correct me (no, really) if I'm wrong, but as far as I understand this is sufficient testing to see if the earth is connected, because if that current can form a circuit, then it is connected.Someone corrected me.

author: BennoG
author_rank: Frequent Contributor
timestamp: May 27, 2025, 10:25:30 am
content: Quote from: tszaboo on May 27, 2025, 09:49:50 amThat will not guaranty the PE from your distribution box is connected to the PE of your work desk.

author: themadhippy
author_rank: Super Contributor
timestamp: May 27, 2025, 11:33:27 am
content: Quote.Not necessarily so ,The vast majority of rcds dont have an earth connection so weres that earth current going to go? the test button puts a small load between the input and output of the device that causes an imbalance.The test button aint there to proof your earth is good,its there to test the mechanics of the device work

author: BILLPOD
author_rank: Frequent Contributor
timestamp: May 27, 2025, 01:11:44 pm
content: Good Morning Zero_Ego, I found your humor, (humour?), refreshing, and preferable to some of the anger displayed in some threadsSounds like you got some good responses also. I wish you success in your project.

author: tszaboo
author_rank: Super Contributor
timestamp: May 27, 2025, 01:34:39 pm
content: Quote from: themadhippy on May 27, 2025, 11:33:27 amYou are right, it has the circuit drawn on the device, for example: So it only makes an imbalance of current.How about one of these socket testers?They are after the RCD, and to form a circuit they can only use the earth connection. I think.

author: Haenk
author_rank: Super Contributor
timestamp: May 27, 2025, 02:01:17 pm
content: I don't think these are helpful with finding noisy devices.If thread opener really wants some help, he should first disclose, why he thinks the lines are noisy.I can see why a bad earth might cause noise issues (Y-caps), but there is just so much nonsense text and so little information.Oh - and don't play around with mains. It's noch technically "high voltage", but your heart/body might think otherwise.

author: themadhippy
author_rank: Super Contributor
timestamp: May 27, 2025, 02:35:24 pm
content: Quoteavoid like the plaque,its subtle difference but something likeis better