Complex Ground Fault Issue in Kitchen Circuit: Seeking Insights and Advice - Page 1
Forum section: electronics / projects

author: mr_bigbrain21
author_rank: Newbie
timestamp: December 16, 2023, 03:11:31 am
content: Hello EEVBlog Community!I'm encountering a challenging ground fault issue in my home's electrical system, particularly within the kitchen circuit. I've gathered several measurements and observations and am seeking insights or advice on this perplexing situation.BackgroundLocation:Home kitchenMains Voltage:230V AC at 50 HzObservations and MeasurementsKitchen CircuitProtective earth to body voltage:60V─103V AC @ 50 Hz (varies with body position)Protective earth to phase voltage:113V ACProtective earth to neutral voltage:111V ACCurrent between kitchen circuit's protective earth and another circuit's protective earth:Avg 1.08 mA AC (peak 3.84 mA), negligible DCMains voltage between phase and neutral:223V ACResistance between kitchen circuit's protective earth and Living room's protective earth:1.26MΩLiving Room CircuitProtective earth to body voltage:Negligible (1-2V AC)Protective earth to phase voltage:223V ACProtective earth to neutral voltage:0V ACMains voltage between phase and neutral:223V ACDiscussion PointsFluctuating voltage between protective earth and my body in the kitchen circuit is concerning, especially with varying body positions.Abnormal voltage measurements in the kitchen circuit (phase to earth and neutral to earth) are puzzling.AC current presence between the protective earth connections of two different circuits indicates a potential grounding issue.The high resistance measurement between the protective earths of the two circuits is unexpected and adds another layer of complexity.QuestionsWhat could be the cause of the fluctuating voltage between protective earth and my body in the kitchen? (especially since it varies with the position of my body!)Are the phase to earth and neutral to earth readings in the kitchen indicative of a specific type of fault?Could the AC current and high resistance between protective earths of different circuits suggest a specific grounding problem?What are the potential risks associated with these findings, and what immediate actions should I consider for safety?Any recommendations for further diagnostics or specific areas to investigate?I'm planning to consult a professional electrician first thing tomorrow morning, but I'm also keen on understanding the technical aspects of these issues. In case this information helps, I;m located in the Netherlands, and any feedback, insights, or suggestions would be greatly appreciated. Thank you in advance for your help!

author: moffy
author_rank: Super Contributor
timestamp: December 16, 2023, 03:41:03 am
content: The resistance between the two earths is concerning but the problem of how the measurement was made is also an issue. The resistance measurement only makes sense if there is no voltage in the circuit but that doesn't appear to be the case looking at the difference between earth to neutral/active measurements. If the living room circuit is correct then you have the ground and neutral bonded together, the kitchen ground looks like it is floating i.e. it is not connected to the earth bar, but I am just surmising you need an electrician to have a look.

author: Limhes
author_rank: Contributor
timestamp: December 16, 2023, 05:34:00 am
content: Good morning (also from the Netherlands). It indeed looks like the kitchen PE connection is not connected. Trace it back to the your switchboard and make sure it's connected.The reason that it floats between L and N is because of filtering caps that form a voltage divider.

author: wasedadoc
author_rank: Super Contributor
timestamp: December 16, 2023, 03:05:02 pm
content: Quote from: Limhes on December 16, 2023, 05:34:00 am+1 (though not from NL).

author: CJay
author_rank: Super Contributor
timestamp: December 16, 2023, 03:45:20 pm
content: Quote from: Limhes on December 16, 2023, 05:34:00 amI wonder if there's been plumbing work done and something has been replaced with PEX or if there's an earth bond come loose

author: langwadt
author_rank: Super Contributor
timestamp: December 16, 2023, 03:47:37 pm
content: Quote from: CJay on December 16, 2023, 03:45:20 pmearth should be through a wire not some random plumbing

author: Microdoser
author_rank: Frequent Contributor
timestamp: December 16, 2023, 03:59:50 pm
content: Quote from: langwadt on December 16, 2023, 03:47:37 pmMetal plumbing pipe that goes into the ground is widely used in the UK to earth the electrics in a house. When that isn't used, a simple metal rod driven into the ground is required. Whether using plumbing pipe is still up to 'code' would be contained in the body text of BS 7671, unfortunately that requires purchasing as knowing what is the right and safe thing to do has, for some reason, to be behind a paywall...You do know that the wire you refer to just leads into the ground, right? It's why we call it 'ground'...

author: themadhippy
author_rank: Super Contributor
timestamp: December 16, 2023, 04:05:47 pm
content: Quoteis it?Quotewhat even on a TNC-S or TNS supply?QuoteAt least as far back as the 15th edition (1981) using incoming services as an earth was not permitted.

author: CJay
author_rank: Super Contributor
timestamp: December 16, 2023, 04:25:39 pm
content: Quote from: themadhippy on December 16, 2023, 04:05:47 pmYup, but it's entirely possible that properly bonded pipework through the property was providing earth continuity in place of a failed, deficient or entirely missing 'proper' earth wiring.Cutting out a section of that bonded copper and replacing it with PEX or similar non conductive water pipe then disconnects the earth, leaving it floating.Guess how I know...

author: CJay
author_rank: Super Contributor
timestamp: December 16, 2023, 04:27:18 pm
content: Quote from: langwadt on December 16, 2023, 03:47:37 pmAbsolutely, it should.Sadly we live in an imperfect world where wires get cut, corrode, were never installed properly or even at all.

author: Monkeh
author_rank: Super Contributor
timestamp: December 16, 2023, 04:33:24 pm
content: Quote from: Microdoser on December 16, 2023, 03:59:50 pmNo, it's not.QuoteNo, it's referenced to ground and in some types of installation will use the ground as the return path, but in fact it leads back to the neutral on the transformer.

author: temperance
author_rank: Super Contributor
timestamp: December 17, 2023, 01:19:13 pm
content: QuoteThe OP probably died meanwhile when trying to find the maximum voltage by performing some acrobatics on a chair stacked onto a ladder in an attempt at minimizing stray capacitance.

author: nightfire
author_rank: Frequent Contributor
timestamp: December 17, 2023, 01:41:27 pm
content: From the symptoms, one can conclude that:the PE is nearly broken at some point (PE(kitchen) to PE (living room) with >1MOhm is a prime indicator of thatIn the past, it was also quite common to put a PE on a metal pipe, newer regulations mandate that it has to be a cable directly to the mains cabinet.Some exemptions can be in the form of the net- mainly if it is constructed as a TN or TT network. The latter uses RCD to detect problems and relies on local grounding- but it should be unlikely if this has been mixed in with a TN network in the same house...For confirmation the resistance of the PE should be measured directly to the mains cabinet where the kitchen circuits are connected, so to be sure that the PE connection to the cabinet is not ok.(Trick: use a power outlet near the cabinet, measure that PE to the PE in the cabinet, then run a long extension cord to the kitchen)My take on this: Probably the cable leading to the kitchen should be exchanged.