Question about voltage in U.S. house built in 1890 - Page 1
Forum section: electronics / repair

author: niemand
author_rank: Contributor
timestamp: May 14, 2024, 04:29:00 am
content: Most of the electrical outlets in this house is the 2-slot type with one slot wider than the other. I plugged in a grounded extension to a 3-slot outlet (valid grounded). I have a digital voltmeter set to AC volts, the black probe inserted into the ground of the extension, and the red probe inserted into the narrow slot of the 2-prong outlet. The reading I got was 62 V. The reading I got when I put the red lead into the wider slot of the 2-prong outlet was 59 V. Why not 120 V (the U.S. standard household voltage)?When I measured only the 2-slot outlet (i.e., inserted one probe into the narrow slot and the other probe into the wider slot of the same 2-slot outlet), the meter read 120 V.

author: bdunham7
author_rank: Super Contributor
timestamp: May 14, 2024, 04:51:07 am
content: What does your service panel or fusebox look like? Unless this has wiring from the 1920's that hasn't been updated, something isn't right. The neutral (the large slot side) should be bonded to ground at the service panel. I'd suspect you don't actually have real grounds and perhaps your system isn't actually ground referenced (this would be extremely unusual in the US).

author: BlownUpCapacitor
author_rank: Frequent Contributor
timestamp: May 14, 2024, 04:51:55 am
content: The electrical wiring in that house is not ground referenced, meaning neutral is not connected to ground; that's a big no no.

author: Whales
author_rank: Super Contributor
timestamp: May 14, 2024, 05:34:13 am
content: Quote from: BlownUpCapacitor on May 14, 2024, 04:51:55 amIt sounds more like the ground wiring is not ground referenced. The neutral wiring may or may not be grounded.If a house full of appliances has its ground wiring disconnected and floating: measuring the ground wiring to be halfway between active & neutral sounds like a plausible symptom.I recommend you get a sparky to check this out niemand.They'll have the tools and skills to diagnose the problem quickly.Out of curiosity I'd love to see pictures of your fuse boards, BUT, given what you have described any metal cased appliances in your house may be unsafe to touch.Even the metal cased fuse boxes might be UNSAFE to touch or open.Could also just be a high-impedance phantom voltage, but don't take the risk.

author: BrokenYugo
author_rank: Super Contributor
timestamp: May 14, 2024, 12:00:54 pm
content: Pretty typical in a place like this you'll find people have added 3 prong sockets to the 2 wire circuits, leaving the ground floating (this is acceptable if a GFCI is used and marked appropriately) or worse yet connected to neutral to give a "bootleg ground" those are illegal for good reason and should be removed if found.Assume nothing with power in old houses, you can often find a different era of hacked up old wiring in every room. Sockets with live/neutral reversed are also dirt common.

author: niemand
author_rank: Contributor
timestamp: May 14, 2024, 01:22:55 pm
content: Quote from: bdunham7 on May 14, 2024, 04:51:07 amThe service panel is on the side of the house. Just circuit breakers; no fuses. What should I be looking for?

author: niemand
author_rank: Contributor
timestamp: May 14, 2024, 01:39:11 pm
content: The 3-slot outlets were tested to have valid ground with this.

author: niemand
author_rank: Contributor
timestamp: May 14, 2024, 01:44:06 pm
content: Quote from: Whales on May 14, 2024, 05:34:13 amWhat's a "sparky"?

author: wasedadoc
author_rank: Super Contributor
timestamp: May 14, 2024, 01:52:30 pm
content: Quote from: niemand on May 14, 2024, 01:44:06 pmA colloquial term for an electrician.

author: bdunham7
author_rank: Super Contributor
timestamp: May 14, 2024, 02:04:57 pm
content: Quote from: niemand on May 14, 2024, 01:22:55 pmStart by taking that cover off so you can see the wiring inside and post a good photo of that. Carefully, of course. Is there a grounding rod nearby?QuoteWith the voltage readings you are seeing, I would expect all 3 lights to be on at least dimly. Try measuring from the ground of your socket to a plumbing pipe.

author: Whales
author_rank: Super Contributor
timestamp: May 14, 2024, 02:15:40 pm
content: Quote from: niemand on May 14, 2024, 01:39:11 pmDo not trust those testers, they make assumptions. If your testing with a multimeter revealed the ground wiring voltages to be strange then maintain suspicion.

author: coromonadalix
author_rank: Super Contributor
timestamp: May 14, 2024, 02:17:19 pm
content: same here, see a master electician NOW and get everything sorted out and put an earth rod in the ground .... if there is notAs insurance(s) side if it was done by an master electrician, and anything bad happens you'll be covered, if "they learn" you did some job yourself, you may end with more problemsdont play god please

author: BrokenYugo
author_rank: Super Contributor
timestamp: May 14, 2024, 02:31:06 pm
content: A 3 light tester only works correctly on single faults, making them mostly useless, it's just 3 neons and 3 resistors. Dangerous compound issues can read all good, e.g. hot-ground reversal+bootleg ground will give a full pass.

author: niemand
author_rank: Contributor
timestamp: May 14, 2024, 03:21:04 pm
content: Quote from: bdunham7 on May 14, 2024, 02:04:57 pmPerhaps this thick painted wire is the grounding rod:

author: bdunham7
author_rank: Super Contributor
timestamp: May 14, 2024, 03:24:36 pm
content: Can you take a zoomed-out photo so we can see the entire installation including the other boxes nearby? I'm not seeing any ground wires in the box. The bus bar where the white wires are going to should be the neutral/ground bond. There's one big black wire going to that bar at the top, where does that come from?Also, this looks like a sub-panel, not a main service panel. There's no main breaker. Is there any other sort of accessible panel anywhere? Where does the service entrance come from--overhead or underground?

author: Stray Electron
author_rank: Super Contributor
timestamp: May 14, 2024, 03:54:48 pm
content: Is that your main breaker panel or is it a sub-panel??In the 3rd and 4th pictures in post #13 you can see the Ground bus bar on the LH side of the box and there's nothing connected to it. It's mounted directly on the metal box so the box should be directly connected to Ground. That is IF the Ground wire was connected to the Ground Bus Bar, but from what I can tell nothing is connected to that bus bar. The Neutral bus bar is on the RH of the box and is visible in photos 3, 4 and 5. Note that it is insulated from the metal box.If your house was wired to modern standards ALL of the ground contacts in ALL of your outlets should rundirectlyback to that Ground Bus Bar and if it is your Main Panel then the bare ground wire that connects to your Ground Rod should also connect to it.The wire that you point out in photos 1 and 2appearsto be a ground wire but it's attached to a different box than that shown in photos 3, 4 and 5. It's been painted over but it should a bare, solid copper wire and it should be clamped to a ground rod but some people merely shove them into the ground. You need to dig into the soil and see what's there.A agree with a previous poster, even though you have a three contact outlet I don't think that the ground contact in it is actually connected and the voltage that you're seeing from L1 to Ground is just from leakage.

author: Stray Electron
author_rank: Super Contributor
timestamp: May 14, 2024, 04:09:02 pm
content: Quote from: bdunham7 on May 14, 2024, 03:24:36 pmI agree, it looks like a sub panel. You can follow the feed wires out through the hole in the lower left side of the box and in photo #1 you can see that that conduit feeds back to box #2. The OP's "ground wire"? in photos 1 and 2 also goes into box #2. But based just of these photos it's impossible tell if it's connected to anything.BTW not all houses in the US have a 'Main Breaker". Mine doesn't. The incoming power lines directly feed the L1 and L2 bus bars.OP I will point out that unless a previous owner did some weird and illegal trickery somewhere in the wiring after it leaves the box, then none of the circuits coming from box #3 are grounded. You can follow every wire in that box and and they all connect to the 3 incoming power lines or to the Neutral Bus Bar or to a circuit breaker so there are NO Ground wires anywhere on those circuits.

author: niemand
author_rank: Contributor
timestamp: May 14, 2024, 04:47:25 pm
content: Quote from: bdunham7 on May 14, 2024, 02:04:57 pmThe ground I have been using for this comes from this 4-outlet type receptacle that is being used by computers:This is located right on the other side of the wall where the service panel is. All the original readings came from the bottom right outlet of this receptacle. The black plug on the upper left is an APC UPS system (Smart-UPS 1000) for computers and router. I don't have an extension long enough to reach plumbing pipe from here. (Behind the wall in the back is the kitchen where a 2-outlet receptacle is being used by the refrigerator and stove. I've been presuming that this is wired to the same ground as the 4-outlet one being used by the computers.)Per your advice to get a reading from a plumbing pipe, I had to use the 2-receptacle GFCI outlet located in the bathroom, which is on the opposite end of the dwelling unit:I used the ground slot from this with the black probe and got the correct 122 V when I inserted the red probe into the hot (narrow) slot on the ancient 2-slot outlet out in the hallway (the hot slot of both 2-slot outlets gave me 122 V; the neutral slots gave me 0 V). Touching the plumbing pipe with the red probe gave me 0.009 V; lifting away the probe gave me 5 V (perhaps due to capacitative coupling?). So it appears that this receptacle is properly grounded, whereas the 4-outlet receptacle being used by the computers is questionable.

author: niemand
author_rank: Contributor
timestamp: May 14, 2024, 05:47:07 pm
content: Quote from: bdunham7 on May 14, 2024, 03:24:36 pmI don't know how to tell a main from a sub panel.Service entrance? Perhaps behind the wall? The 4-outlet receptacle I mentioned above is behind this wall about 5 ft to the right.Other boxes nearby:Main service panel perhaps (I can't open the long one with the wing nuts at the bottom of it):

author: bdunham7
author_rank: Super Contributor
timestamp: May 14, 2024, 06:06:57 pm
content: Is this a townhome and the other meter is for the other owner/tenant? Those are two "main breakers" under the meters so that all makes sense, but there are still no ground wires anywhere so I've no idea how your outlets are getting grounded. That big, painted wire going into the ground probably goes to a ground rod of sorts and perhaps the wire going back into the house is cobbled into some sort of ground wire network going to the outlets, but that would be pretty hacked work. The only other possibility I can think of is that your house has conduit throughout and the ground bonding goes through that. I don't see any NM sheathed wires, so perhaps that is what they did, in which case you can pull the covers off your outlets and you should find a metal box that is grounded. Your bad ground at your 4-plex outlet could be due to a break in the conduit or a bad ground bond between the box and outlet ground terminal.

author: BlownUpCapacitor
author_rank: Frequent Contributor
timestamp: May 14, 2024, 06:20:02 pm
content: Use a DMM to measure the potential of those boxes to ground. Should be near zero or under 10v. I wouldn't go touching those boxes if they are at an elevated voltage.

author: tooki
author_rank: Super Contributor
timestamp: May 14, 2024, 06:31:03 pm
content: Quote from: niemand on May 14, 2024, 01:39:11 pmNote that these do NOT actually prove the outlet is wired correctly with a proper ground: one thing slimeballs do is to fake the ground by bridging the ground and neutral terminals on the receptacle itself, with no actual ground. This is called a bootleg ground, and BrokenYugo mentioned them above. A tester will show it as correct, but it’s actually dangerous, and even worse if multiple outlets have been wired this way, but some with the line and neutral reversed. In that case, you can end up with a device housing (or cable shield) at 120V. Connect two “grounded” devices that on different outlets and you’ve got a dead short (for example, a TV and a DVD player).If you ever find an outlet with a bootleg ground, which is an attempt to deceive inspection, you must assume the entire electrical installation is unsafe until it’s been inspected by an electrician, whom you should give a heads-up about the bootleg ground so they know they’re dealing with a questionable installation.I randomly had a video about this very thing suggested to me the other day:

author: Stray Electron
author_rank: Super Contributor
timestamp: May 14, 2024, 06:46:02 pm
content: Quote from: bdunham7 on May 14, 2024, 06:06:57 pmI agree, the two disconnects makes this look like it's duplex with both homes being fed by a two meters in a common box.FYI I'm pretty certain that the NEC doesn't allow houses to be grounded simply via the metal conduit. The joints are too unreliable. If the outlets are going to be grounded then they must be grounded via a wire. OTOH not every jurisdiction in the US requires compliance to all of the NEC, particularly in older homes so grounding may not be a requirement for the OP's house. OTOOH, under certain conditions the local authorities may require that the home be brought up to the current NEC requirements. So it depends.OP, I would follow Tooki's advice and pull out one of the outlets (after turning off the breaker and double checking that there is no power at the outlet) and physically looking at the wires connected to the outlet.. There should be three wires including a bare or green colored ground wire. But I think that you will find that the only wires are the black "Hot" leg and the White Neutral.

author: bdunham7
author_rank: Super Contributor
timestamp: May 14, 2024, 07:12:06 pm
content: Quote from: Stray Electron on May 14, 2024, 06:46:02 pmConduit-as-ground used to be fairly common and I'm not sure the NEC actually prohibits it even today. However, typical modern practice would be to include a ground wire. Properly installed conduit does include fairly robust ground bonding devices and the failures I've seen have been either a bad job or a corrosive environment. In dairy barns, for example, regular NM was allowed even though it was exposed (typically not acceptable) because it was safer than conduit that would rust and separate. That installation doesn't look to be modern, it could easily be 60+ years old and it would have been a retrofit even then.

author: niemand
author_rank: Contributor
timestamp: May 15, 2024, 03:38:52 am
content: Quote from: bdunham7 on May 14, 2024, 06:06:57 pmYes.

author: niemand
author_rank: Contributor
timestamp: May 15, 2024, 03:47:48 am
content: I tested the last grounded receptacle in my dwelling unit, which is the one in the kitchen being used by the refrigerator and the stove. The two outlets on this receptacle (non-GFCI) measured correctly: 122 V from ground to hot, and 0.005 V from ground to neutral.

author: bdunham7
author_rank: Super Contributor
timestamp: May 15, 2024, 04:17:51 am
content: Quote from: niemand on May 15, 2024, 03:47:48 amDid you test that 4-plex outlet with the stuff plugged into the other sockets? If so, you probably just have a disconnect in the ground somewhere and leakage currents inside the various devices (like the UPS) are working like a voltage divider with the ground pins at the center. A low-impedance (Low-Z) meter would give you a different result and there probably isn't enough leakage current to zap you too hard.

author: niemand
author_rank: Contributor
timestamp: May 15, 2024, 04:19:37 am
content: Quote from: Stray Electron on May 14, 2024, 03:54:48 pmWhat is "L1"? The hot contact on the outlet?

author: niemand
author_rank: Contributor
timestamp: May 15, 2024, 04:27:47 am
content: Quote from: bdunham7 on May 15, 2024, 04:17:51 amThanks. Not yet. It's got a very heavy desk right beside it, giving me only 4" of space. It's going to take some effort for me to gain adequate access. I don't know anything about a low-impedance meter. My DMM is just a cheap Kaiweets HT118A.I'm trying to understand your idea that leaky currents inside devices can work like a voltage divider.... What are "ground pins at the center"? What do you mean?

author: bdunham7
author_rank: Super Contributor
timestamp: May 15, 2024, 05:10:13 am
content: Quote from: niemand on May 15, 2024, 04:27:47 amHere's a schematic of a typical IEC AC inlet filter. Imagine you have 120VAC across L and N. What would you expect to measure across L and PE or N and PE? The capacitors form a voltage divider and if there is no other leakage and the PE is isolated (note that both PE terminals are connected to the case of the filter here) then the voltages across L/PE and N/PE would each be 1/2 of L/N.

author: CaptDon
author_rank: Super Contributor
timestamp: May 15, 2024, 01:20:14 pm
content: Conduit as a ground conductor or current carrying conductor is outlawed in the U.S. for good reason. Apparently in the O.P.'s house the wiring through the walls is mostly two conductor. As a matter of convenience many of the two prong outlets were replaced with grounded outlets but with no actual ground wire available. This is very typical of 'homeowner upgrades' when they have no clue about safety. I personally got thrown to the ground at a public swimming pool. I got out of the pool and went to play the jukebox standing on wet concrete. An inspection was made and it was a grounded outlet connected with no ground. The failure was internal to the jukebox putting the hot conductor directly to the metal frame of the jukebox. The owners of the pool said "We checked and didn't feel any shock although we had complaints". (They were obviously wearing shoes when they 'checked for shock').

author: bdunham7
author_rank: Super Contributor
timestamp: May 15, 2024, 02:31:34 pm
content: Quote from: CaptDon on May 15, 2024, 01:20:14 pmDo you have a cite for that? I don't think it is prohibited, at least not in the general case. It certainly was acceptable and common in the past, no more than a few decades ago. Receptacles used in metal boxes still have a feature where they 'self ground' to the box without any wires needed, although everyone bonds them with a wire and a clip nowadays. It is totally plausible that whoever installed the current system in the OP's house didn't use any ground wires at all except for that one large one going to the meter box and that it passed an inspection that way.

author: themadhippy
author_rank: Super Contributor
timestamp: May 15, 2024, 03:07:15 pm
content: Quotemany would have you believe thats also the case in the uk.Out of curiosity how is american conduit joined together,anything ive seem on line seems to be a clamp type arrangement,same for termination into a box? Over here metal conduit is threaded and screwed into a coupler to join lengths ,for boxes we use a brass bush and coupler

author: bdunham7
author_rank: Super Contributor
timestamp: May 15, 2024, 03:40:49 pm
content: Quote from: themadhippy on May 15, 2024, 03:07:15 pmThere are two types of "conduit", EMT and rigid. EMT is lighter and uses various devices such as single-screw retainers and compression clamps while rigid has pipe threads and couplers as the basic connection method.https://www.eaton.com/content/dam/eaton/products/conduit-cable-and-wire-management/crouse-hinds/catalog-pages/crouse-hinds-connectors-couplings-emt-catalog-page.pdf

author: niemand
author_rank: Contributor
timestamp: May 16, 2024, 02:24:00 am
content: Quote from: BlownUpCapacitor on May 14, 2024, 06:20:02 pmFor ground, I used my neighbor's grounding rod:Probing the screw at the bottom of the panel......I got less than 0.5 V and a duty cycle of 300 Hz:Probing the inside of the box......I got less than 0.1 V and a duty cycle of 60 Hz:Compare with probing the plumbing pipe in the bathroom using the ground from the GFCI outlet(like I did yesterday in my reply #17):I got 0.005 V and a duty cycle of 60 Hz.

author: ArdWar
author_rank: Frequent Contributor
timestamp: May 16, 2024, 03:52:40 am
content: PE getting to half line voltage is almost certainly a ground wiring fault (or that particular socket is not grounded at all), and some appliances connected to the same socket (or same network with faulted ground) are backfeeding the PE.I'm almost certain with that since the other likely explanation, your utility failed to ground their transformer properly, is fairly unlikely (it *do* happen however, and deliberately done in IT system which isn't usually used for residential).

author: SeanB
author_rank: Super Contributor
timestamp: May 16, 2024, 12:40:08 pm
content: Quote from: ArdWar on May 16, 2024, 03:52:40 amHard to do in the USA, as the pole pigs ( house supply transformers) almost always have the neutral connection not isolated from the case, and a ground wire for both the incoming and outgoing supplies, along with ground bonds at each service point. Thus even if the transformer has lost ground, it will be completed via all the other houses, which can make for some hot ground cables on them, and a large neutral earth drop.Here the house got upgraded to 3 wire outlets but was not rewired, and the only solution is to keep the meter, and replace all the rest with new. If it is rented the landlord is responsible to provide a safe electrical supply, and if it is owned by OP then the seller was responsible to have the house upgraded to comply to the minimum modern scec before transfer.

author: CaptDon
author_rank: Super Contributor
timestamp: May 16, 2024, 02:02:09 pm
content: It looks like my statement of EMT being disallowed as a ground conductor by NEC rules is wrong. It seems EMT is allowed with certain parameters like "Tight fittings" or "Steel Couplers" etc. My information (which I sadly accepted as being an NEC rule) came from and is because of the fact that local municipalities and fire ordinances are allowed to be applied over and above the NEC codes. Generally speaking, no one in their right mind would allow installing a 20 amp receptacle in a steel box 30 feet away from a main panel including 3 10ft pieces of EMT and 4 couplings and being fed with 12/2 and using the conduit and couplings as the sole source of grounding as being reliably safe over the long term that a house may last! Local codes (which I state as sensible) mandate a ground conductor of 'Not less than one AWG size smaller than the current carrying conductors' or as we all do, just wire the receptacle with 12/2 CU with 12 CU ground NM-B run inside the conduit. NEC section 250.118 and related also 310.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: May 16, 2024, 03:34:37 pm
content: My only comment is that while previous posts have stated that poor ground bonding is uncommon or rare, I have found it in more than a quarter of the places I have lived, only one of which was built prior to 1950.The only way to know is through measurement, and don't be too surprised at what you find.

author: tooki
author_rank: Super Contributor
timestamp: May 16, 2024, 04:55:45 pm
content: Quote from: niemand on May 16, 2024, 02:24:00 amFYI, Hz is the frequency. Duty cycle is a completely different thing (expressed in %) that applies mostly to square waves.300Hz is noise of some type. The line frequency in USA is 60Hz and won’t vary to any meaningful degree, so it’s not something that has any diagnostic value in household mains wiring.

author: BlownUpCapacitor
author_rank: Frequent Contributor
timestamp: May 16, 2024, 05:29:12 pm
content: So it looks like just a simple break in the ground connection somewhere in the building. I recommend hiring an electrician to do the job for you if you're uncomfortable doing it yourself. The fix is fairly simple. Just run a new ground line to that socket. Why not use the old one? Well, first of all it's gonna be a pain to get it out, fix it, then run it back. Plus if it's a broken conductor, it may not be in good condition to continue being used as a ground.

author: Stray Electron
author_rank: Super Contributor
timestamp: May 17, 2024, 02:40:14 am
content: Quote from: niemand on May 15, 2024, 04:19:37 amThe hot leg.L1, l2, L3 actually apply to multi-phase power systems that have multiple hot legs 120 degrees out of phase with each other. But I tend to think of U.S. residential power systems simply as a single phase systems or two phase power system with the phases 180 degrees out of phase with each other so I use the term L1 although it's actually N.A.

author: Stray Electron
author_rank: Super Contributor
timestamp: May 17, 2024, 02:52:00 am
content: Quote from: niemand on May 16, 2024, 02:24:00 amHaving no, or very low, voltage doesn't necessarily mean that the two points have a good connection. One of them may simply be floating i.e. not connected. You would have to put some sort of significant electronic load on the test point to be sure that it actually IS connected to ground.BTW your neighbors ground rod looks the way that ground rods should look. They are required by code to extend above ground and the wire and clamp be clearly visible so that the connection can be verified by an inspector. Years ago some people did just shove a wire in the ground andsometimesit would ground the system but usually the wire didn't go deep enough in the ground and the ground was very poor so people still got shocked.

author: CaptDon
author_rank: Super Contributor
timestamp: May 17, 2024, 02:00:49 pm
content: I am living on a rural street in the states and our power situation seems to be very strange. I see one leg of what appears to be a 4160VAC circuit (2400VAC referenced to ground) and I see absolutely no return line what so ever? Only one single feed line crosses the main road to our road and amazingly it doesn't even have the protective lightning protector ground wire run above it!! There are 5 pole pig transformers on our road (25KVA each) with 3 to 5 houses on each one. I see only a 'home use' style ground rod at the bottom of each pole that has a transformer. I suppose the ground rods at each of our homes as well as the connection to our city iron water pipes (how's the electrolysis on those pipes I wonder) is forming the return? Is this typical of the U.S. power grid?? Seems like a poor way to do a power return and I wonder if it also leads to an early demise of the city water pipes?? Obviously, with only one feeder the whole neighborhood goes dark when a significant tree limb falls onto the feeder which seems to happen about three times each year. There is some sort of a fuse device out at the main road for our neigborhood which also seems to fail at least once each year.

author: niemand
author_rank: Contributor
timestamp: May 17, 2024, 06:27:20 pm
content: Quote from: Stray Electron on May 17, 2024, 02:52:00 amIs this true even if the meter reads 5 V when I take the probe away from the plumbing pipe?

author: Xena E
author_rank: Frequent Contributor
timestamp: May 18, 2024, 06:38:17 pm
content: Quote from: CaptDon on May 17, 2024, 02:00:49 pmVisiting some folks in a rural area of MS once it seems that this is, or at least was, a done thing to economise on feed line, I'm talking 10 miles of single feeder going to a settlement of sixteen properties... if this is the case in your location I'm guessing it is a small community?The neutral return is the dirt!

author: kjpye
author_rank: Contributor
timestamp: May 19, 2024, 04:30:20 am
content: SWER (single-wire earth return) lines are widely used across Australia and other countries in less densely populated areas.

author: soldar
author_rank: Super Contributor
timestamp: May 19, 2024, 05:33:54 pm
content: Quote from: CatalinaWOW on May 16, 2024, 03:34:37 pmA couple years after I bought this house I noticed the computer case giving me the tingles. After much investigating I found out the entire upper floor was not correctly connected to Earth. Downstairs there is a register box near the ceiling which goes to a register box near the floor upstairs. This is a development with hundreds of identical houses so they prepared the bundles of cables, passed them through and connected them in each register box. Except that they had cut the earth cable just a bit too short so when they pulled the bundle through they pulled the far end into the conduit. Then they connected all the cables correctly except that the earth cable was not showing and was not connected. At first it was a mystery to me how a cable could go into a conduit at one end and not show up at the other end. It took me a while to think of the possibility they had cut the cable too short.They work fast and often make mistakes.

author: soldar
author_rank: Super Contributor
timestamp: May 19, 2024, 05:37:48 pm
content: It is good to know and understand the different types of earthing systemshttps://en.wikipedia.org/wiki/Earthing_systemIEC terminologyInternational standard IEC 60364 distinguishes three families of earthing arrangements, using the two-letter codes TN, TT, and IT.The first letter indicates the connection between earth and the power-supply equipment (generator or transformer):"T" — Direct connection of a point with earth (Latin: terra)"I" — No point is connected with earth (Latin: īnsulātum), except perhaps via a high impedance.The second letter indicates the connection between earth or network and the electrical device being supplied:"T" — Earth connection is by a local direct connection to earth (Latin: terra), usually via a ground rod."N" — the earth connection is supplied by the electricity supply network, either separately to the neutral conductor (TN-S), combined with the neutral conductor (TN-C), or both (TN-C-S). These are discussed below.

author: themadhippy
author_rank: Super Contributor
timestamp: May 19, 2024, 05:39:28 pm
content: Quotebiggest mistake was taking short cuts on the test and inspection of the finished job.

author: amyk
author_rank: Super Contributor
timestamp: May 19, 2024, 08:23:22 pm
content: Quote from: CaptDon on May 17, 2024, 02:00:49 pmIt's AC. If it was DC, even the ground rods would also corrode away rapidly.https://en.wikipedia.org/wiki/Single-wire_earth_return

author: chrisclarke
author_rank: Newbie
timestamp: May 20, 2024, 03:45:18 pm
content: My house in Cape Town, South Africa was built in 1900 and renovated in 1949The gent who renovated was the City Electrical Engineer. In 1949 they used ungalvanised steel pipes. About 2/3 of them have gone rusty, some areas completely corroded away.I bought the house as a deceased estate in 1984 and have been replacing the cloth and rubber cable with PVC and/or "Flat twin and earth" or "Surfix" which is also a 3-core cable but with an aluminium shield as well. Its a 230VAC mains and the cable is 2.5mm diameterIn 2020 the electrician replaced the outside earth rod which is a 2 metre x 25mm copper rod, with 2 rods, each 15m apartAt the other end of the house, which is 35m away, I also fitted an "earth mat" to ensure a completely quiet and safe earth.

author: themadhippy
author_rank: Super Contributor
timestamp: May 20, 2024, 04:21:18 pm
content: hope you bonded the rods and earth mat together

author: CatalinaWOW
author_rank: Super Contributor
timestamp: May 20, 2024, 06:10:29 pm
content: Wiring and electrical codes were initially quite local, and thus based on local conditions. An adequate earth return can be quite different. An area with sandy soil that is heavily contaminated by sea water and an area with almost solid granite and what little water there is is quite pure. Also it has only been a little over a century since electrical distribution got started and many things about corrosion have been learned in the meantime. So everyone should be cautious about applying their expectations in a new location. What was done historically may be quite different than what you have found previously in a different location. Even without throwing in the long history of DIY bodges. I have done many things knowing that they will not last forever. Sometimes I intended to do a better job later, sometimes I knew it would last as long as I would be using it. When I remember I warn future users/owners of these temporary fixes, but my memory is no better than most so some escapes have occurred.