One Outlet PE - Page 1
Forum section: electronics / general

author: Gcsillaz
author_rank: Contributor
timestamp: March 23, 2021, 02:03:27 pm
content: Hello everyone!Recently i've been getting in electronics and decided to buy a osciloscope for my bench.I live in a 60's apartment and thus my building does not have a PE on the electrical cabinet.Since my room is in the first floor of the building i was thinking if i could drill a 2,5m hole on earth and install a copper bar. Then i'd route the cable to my wall outlet.(pic attached)I know that it isnt the "proper" way, but its going to be pretty hard if i had to exchange all wiring and make a new electrical cabinet to accommodate to proper regulations.Now i'm using two-prong sockets, i'd exchange for 3 and just connect the earth to the central pin.What do you guys think? Would this be dangerous? Is it relatively viable?

author: Sal Ammoniac
author_rank: Super Contributor
timestamp: March 23, 2021, 03:47:22 pm
content: What's a "PE"?

author: Ian.M
author_rank: Super Contributor
timestamp: March 23, 2021, 04:02:20 pm
content: That would be a TT grounding system which is generally regarded as acceptable if its protected by a RCD (GFCI). Without one, the ground resistance is often too high to reliably trip the breaker in the event of a Line to PE fault, which makes the whole grounding system a potentially lethal hazard. Also, if there's any exposed metal pipes or structural metalwork in the room, or it has a concrete floor, faults elsewhere in the building may also cause a significant and hazardous voltage difference between the metalwork or floor, and your new PE, so you may need to cover exposed metalwork and use an electrically insulating floor covering (not just carpet - it doesn't insulate if you spill liquids on it).I certainly wouldn't modify the wall sockets unless you own your apartment outright or on a lifetime lease and are doing a full rewire to local electrical code under the supervision of a qualified electrician. The sensible option would be to wire the new PE to a socket strip on your bench, and to fit a RCD (GFCI) in the lead from the wall socket to the socket strip.

author: Benta
author_rank: Super Contributor
timestamp: March 23, 2021, 04:09:20 pm
content: Quote from: Sal Ammoniac on March 23, 2021, 03:47:22 pmProtective Earth.

author: BrokenYugo
author_rank: Super Contributor
timestamp: March 23, 2021, 06:11:56 pm
content: Quote from: Ian.M on March 23, 2021, 04:02:20 pmThis is the option I'd take, a GFCI/RCD feeding the bench is a good idea in any event, and you'll need several grounded sockets for any electronics bench anyway.

author: Gcsillaz
author_rank: Contributor
timestamp: March 23, 2021, 09:46:17 pm
content: Hello Everyone!Quote from: Ian.M on March 23, 2021, 04:02:20 pmWow! Great ideia Ian.M, we know it is not the proper way but it might just be a viable option this way.After you entered the comment i went to hardware store and bought a 2.5m height 13mm thick copper bar and 6mm² cable.I just finished installing in on a adjacent garden beneath my apartment.I have a certified tested microohmeter on my work i'll try to see the cable resistance from my room to the copper bar to ensure it is "within limits" (Around 2-200Ohms i think is ok right?)Also measured the PE in my room to the neutral wire and i have something like 2Vac.I'll get to work to try and find a GFCI/RCD for the bench!Is there a way i can test the ground system further?Thanks everyone!!!

author: Ian.M
author_rank: Super Contributor
timestamp: March 23, 2021, 09:59:51 pm
content: Its (usually) *NOT* the PE wiring resistance that's the problem. Soil conditions and ground electrode depth and surface area are the usual limiting factors. For a DIY methodology for ground resistance testing without specialized test equipment see '2. - Using a transformer, ammeter and voltmeter' here:https://www.tlc-direct.co.uk/Book/8.6.1.htmThe temporary electrodes and hookup wire don't have to be durable or of the quality of the permanent ground electrode so you can use cheap steel pipe or steel stakes, simply clean off any grease paint or rust immediately before use, and connect the voltmeter U directly to or as close as possible to X, the ground stake under test.The IEEE is of the opinion that TT system loop resistance should be under 200 ohms, so worst case, for testing, you are looking at having to drive a substantial current through twice that. OTOH for safety you don't want to go over 50V and personally I wouldn't use over 30V. The transformer *should* to be able to deliver 1A. Put one or two well chosen car bulbs, or a power resistor, in series to limit the current to less than the transformer's secondary current rating, and you can get away without having a power rheostat.The US NEC requires an additional ground rod if the ground resistance is over 25 ohms, (Seehttps://www.mikeholt.com/PopGraphic.php?id=4134) so that's a good target figure to have in mind.N.B. re-test it at the end of your summer or dry season!

author: Gcsillaz
author_rank: Contributor
timestamp: March 23, 2021, 10:23:24 pm
content: Hi @Ian.MQuote from: Ian.M on March 23, 2021, 09:59:51 pmI just looked and we also have at our office one Fluke 1664 multitester meter.On the manual it shows that it can do the earth test according to what you said but also another way that does not involve putting additional rods i believe."Earth Resistance Test by Loop Method" Maybe i'll bring it home and try it! That should give us an idea of the resistance you mentioned?Thanks!

author: Gcsillaz
author_rank: Contributor
timestamp: March 23, 2021, 10:28:10 pm
content: Sorry for the double post but i just stumbled upon one interesting phenomenon.I leaved my multimeter turned on the bench with one alligator clip on the PE cable and the other lead on the mattress.The other lead was close to the rubber cable of the soldering iron (hakko fx-888d) which is turned off but pluged in.It was showing around ~80VacCan anyone explain why?Thanks!

author: Cyberdragon
author_rank: Super Contributor
timestamp: March 24, 2021, 05:15:43 pm
content: Capacitive coupling, same way a non-contact voltage tester/Volt Stick works.Why is your soldering iron on your mattress?

author: Gcsillaz
author_rank: Contributor
timestamp: March 25, 2021, 12:12:03 am
content: Hi!Quote from: Cyberdragon on March 24, 2021, 05:15:43 pmI wrote it wrong, it's on my bench. i wanted to mean the anti static dissipative surface/carpet thing