Add Grounding to existing electric installation  - Page 1
Forum section: electronics / beginners

author: Bicurico
author_rank: Super Contributor
timestamp: November 30, 2024, 11:52:28 am
content: Hello,I have an old house that has an electric installation without grounding.Apparently, in the 70ies and 80ies, grounding was not mandatory.I now have a dish washer and a washing machine. On both you feel electricity if touching the metal case and for instance the tap. I am aware of the risks.Now I would like to add grounding, but here is the question:The easiest way to ground both machines would be to attach a wire from their case to the water pipe. I believe this is not allowed.The next best way is to dig a hole and insert a grounding rod made of copper. These are easily available, but I might have trouble digging a 1m deep hole, since the ground is mainly solid rock.Questions:1) How good a grounding would I achieve by drilling a 1m hole in the basement, which would be drilling into a rock?2) What extra safety would I achieve by connecting both machines to said grounding rod, considering there would be no differential switch?3) By having such a solution, wouldn't I increase the electric bill by continually feeding the excess current to ground/earth?Note: I cannot afford to replace the whole electric distribution in the house, it would be very difficult and expensive.I rarely use any of those two machines.I am not native English speaking, so some terms used might be wrong.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: November 30, 2024, 01:38:53 pm
content: Just putting a rod in a rock does not work. With a bit of bad luck your particular rock is an insulator, and it's just a waste of time.As far as I know, here in the Netherlands, you have to make two earth connections which are at least several meters apart, and then also measure the impedance between those two earthing connections to verify the impedance is low enough. But it's also a completely different situation here. There is no rock ground in the Netherlands, just sand and clay and ground water is also nearby. And that water is of course conductive.Whether your water pipe may be a suitable earth connection is not clear. This used to be common a bunch of years ago when all water pipes were metal, but it's being deprecated now. But you'd have to check with local regulations to be sure.The electricity you feel may be just normal leakage though the earth connection of a filter. If so, then it is capacitively coupled, and this blind current is not metered. Even if it's metered, it's probably just a few mA and costs would be negligible.

author: Roehrenonkel
author_rank: Frequent Contributor
timestamp: November 30, 2024, 01:57:16 pm
content: Hi Bicurico,have an electrician convert your N to PEN.Get a professional.Good luck

author: jpanhalt
author_rank: Super Contributor
timestamp: November 30, 2024, 02:54:07 pm
content: I do not know about soil conditions or building customs in Portugal. There's a system called "Ufer" grounding that may be considered.Here's a brief discussion, but a search for Ufer grounding might be more productive:https://www.dreiym.com/2024/02/29/ufer-grounding-a-cost-effective-and-reliable-method-for-electrical-safety/#:~:text=Ufer%20grounding%20is%20a%20technique,method%20during%20World%20War%20IIIn the US, once you have a ground connection, you can use a single GFCI to protect every outlet on the same circuit. However, for my daughter's older house, we just used a GFCI outlet for every outlet on the circuit. The cost difference is not that greatThere are specific labeling requirements such as this (Source: North Carolina code via Google):Quote

author: golden_labels
author_rank: Super Contributor
timestamp: November 30, 2024, 03:51:29 pm
content: As said above, I’d hire a professional company for that. The reasoning is as follows.Most notably because it’s possible neutral is already earthed outside your house (aTN system). A professional electrician is able to tell, and also determine if you need a separate protective wire or PEN may be used. The latter saves the work and cost of putting new wiring. This is something you can’t reliably do yourself, because it requires knowledge of how things are organized outside your own installation and of local code. Also both devices may draw high current, which may make a PEN wire unacceptable.The second reason is that making effective earthing is not trivial. I doubt you just want a pretense of it being earthed, right? You shouldn’t be worried about the cost. I don’t know what is the system used in Spain, but I guess it’s TN. In which case most of the work will be outside: binding neutral to earth. And then assuring a proper connection between neutral and device’s earth.Mind you pay for the advice and you’re free to never use their service. No need to sign any agreement on spot: just tell you will think for a week and call them back.

author: Bicurico
author_rank: Super Contributor
timestamp: November 30, 2024, 07:36:29 pm
content: The main problems in updating the installation is that all outlets are served only by two wires (phase and neutral) and to add the ground wire to the switch box certainly requires opening a new hole through 1m thick stone wall.I do have a 30mA differential in th switch box, but it is not connected to ground, of course.So, instead of rewiring everything, I would like to just ground the two washing machines.

author: jpanhalt
author_rank: Super Contributor
timestamp: November 30, 2024, 08:40:01 pm
content: Quote from: Bicurico on November 30, 2024, 07:36:29 pmThat's exactly the situation I faced in my daughter's home that was built in 1950. I am clueless about Portugal wiring. In the US, we have had live (L!) and neutral or "grounded" (not "ground") dating way back. That's where GFCI comes into play. Of course, your code takes precedence, and there is no arguing with it.If you have a basement with concrete floor, then Ufer grounding might apply. For any concrete floor, there is probably rebar or very heavy wire mesh. You will need a ground somewhere, but not at every outlet according to US code.

author: calzap
author_rank: Frequent Contributor
timestamp: November 30, 2024, 11:32:25 pm
content: Would have to know the size, length and connections of existing rebar in order to have a proper Ufer ground. That info is probably not available. Installing a new Ufer ground with rebar in an existing concrete basement floor would be quite a job. There should be at least 6 m of 13 mm or wider rebar imbedded horizontally with at least 50 mm of concrete all around. Bare copper wire 21 mm2 or larger could be used instead of rebar. Above requirements may vary depending on jurisdiction. That would be a lot of jackhammering or a new basement floor could be poured.I agree with others that the OP should have a professional look at his house.Mike

author: Terry Bites
author_rank: Super Contributor
timestamp: December 01, 2024, 03:37:53 pm
content: I've seen TN-S type wiring in most modern properties it is the prefered EU/ UK standard.Protective ground and neutral are bonded at the breaker panel. That ensures that you'll be protected by RCBO/RCD (GFCI) devices.All meatal pipework in the property must be bonded to ground too.No ground rod is needed. PE is not there to drain away leakage from dodgy wiring and appliances.See this great video, em Português:

author: themadhippy
author_rank: Super Contributor
timestamp: December 01, 2024, 04:04:29 pm
content: QuoteThat be TNC-S, combined neutral and earth on the suppliers side,separate neutral and earth on the consumer side,TNS (neutral and earth separate )does appear occasionally in the uk as does TT (earth is via a earth rod) but TNC-S is the most common.One very rare beasty is TNC were neutral and earth is combined.if spotted in the wild proceed with caution and leave yer double pole switches in the van.

author: m k
author_rank: Super Contributor
timestamp: December 01, 2024, 04:44:45 pm
content: Quote from: golden_labels on November 30, 2024, 03:51:29 pmI live on sand, maybe 10 floors of it.Under the house is considerable amount of copper.Worst day earth connection is about sort of.

author: soldar
author_rank: Super Contributor
timestamp: December 01, 2024, 06:29:47 pm
content: Quote from: Terry Bites on December 01, 2024, 03:37:53 pmI don't think that is right.In Spain we use TN-S which means PE and Neutral are only bonded at the distribution transformer.https://en.wikipedia.org/wiki/Earthing_systemIn rocky, poorly conductive ground I have seen grid, wiring, buried horizontally.

author: Poroit
author_rank: Frequent Contributor
timestamp: December 02, 2024, 05:33:09 am
content: G'day Bicurico,Talk to your neighbors. Particularly any who have built homes recently.How are their houses earthed?Are your electrical cables run in conduits?