| Non-motoring > Wiring help | Miscellaneous |
Thread Author: smokie |
Replies: 19 |
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New Wed 26 Feb 25 14:15
Wiring help - smokie
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The plasterers skimmed the hall, stairs and landing yesterday and have messed up the lighting. If anyone wants to give their brain a whirl please try to help with where they've mis-wired the switch(es). The problems are essentially 1) we can't turn the upstairs lights on or off 2) the downstairs lights can only be turned off using the upstairs switch SWMBO thinks that the upstairs switch probably wasn't ever disconnected, so the problem is likely with the downstairs one. Which seems quite probable given one terminal never goes live! I'm reluctant to start disconnecting stuff without a second opinion though I have taken pics. Facts are here. It's taken me ages to consolidate this and I hope it's right. docs.google.com/document/d/1wGo44WOOd_W_z33LCZ1Y9XZFFqhygYrm/edit?usp=drive_link&ouid=105785278923888326062&rtpof=true&sd=true Any help gratefully received. It's not worth getting the plasterers back, they won't know what they did! Last edited by: smokie on Wed 26 Feb 25 at 15:22
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New Wed 26 Feb 25 14:28
Wiring help - Grok thinks... - car4play
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Let’s dive into this electrical puzzle with enthusiasm! Your lighting woes seem to stem from a classic case of wiring gone awry, likely during the plastering job. We’ve got a two-way lighting circuit here—upstairs and downstairs switches controlling shared lights—and some funky behavior to sort out. The upstairs lights won’t turn on at all, and the downstairs lights only respond to the upstairs switch. Your wife’s hunch that the downstairs switch is the culprit makes sense, especially with that “never live” terminal hinting at a misconnection. Let’s break it down step-by-step, using your detailed notes, and figure out what’s what! First, let’s clarify the setup. You’ve got: - **Upstairs**: A 1-gang, 2-way switch for the landing light. - **Downstairs**: A 3-gang switch, with the rightmost switch controlling the landing, the center for the hall, and the left for the porch (which works fine). The goal of a 2-way circuit is to let either switch toggle the landing lights independently. Normally, this involves a common (COM) terminal and two traveler lines (L1 and L2) at each switch, wired so the live feed can route to the light via either switch position. Your notes show the current state, but something’s clearly off since the upstairs lights are dead and the downstairs lights are hostage to the upstairs switch. ### Upstairs Switch Analysis Your upstairs switch description is promisingly clear: - **COM**: Live when ON, dead when OFF. - **L1**: Dead when ON, live when OFF. - **L2**: Live when OFF, dead when ON. This is textbook 2-way switch behavior! When the switch is ON, power flows from COM to L1; when OFF, from COM to L2. The additional wires (L1 Blue/Black, L2 Yellow/Red, COM Red) and their “direction” (up/down) suggest connections to the downstairs switch or light fitting. Notably: - **L2 Yellow (down)** and **L2 Red (up)** are *always live*, regardless of switch position, which could mean they’re tied to a permanent live feed. - **COM Red (down)** is also *always live*, hinting it’s the incoming live supply. - **L1 Blue/Black** being “never live” is odd—travelers should alternate live/dead based on the other switch’s position, so this might indicate a break or miswiring downstream. This switch seems functional as a 2-way unit, and since the downstairs lights *do* respond to it, the issue likely isn’t here—your wife’s instinct aligns with this. ### Downstairs Switch Analysis The downstairs 3-gang switch is messier, with the landing switch (rightmost) being our focus. Your OCR’d notes split it into top and bottom rows, with some labels missing, but let’s interpret: - **Top row**: COM (empty), L2 Red, L1 Red, COM Red (porch). - **Bottom row**: ? Yellow, ? Blue, ? Black, ? Black (porch), ? (empty). - **Paired cables**: A (porch), B (hall?), C (landing wires: Yellow, Blue, L2 Red). The “ON/OFF” columns reflect the upstairs switch’s effect on the downstairs terminals when toggling the landing light. Key observations: - **COM (empty)**: No wire in the landing’s COM slot is a red flag—every 2-way switch needs a COM connected! - **L2 Red (C)**: OFF in both states (never live). - **L1 Red (B)**: OFF when ON, LIVE when OFF—traveler-like behavior. - **? Yellow (C)**: LIVE always—likely the incoming live. - **? Blue (C)**: Never live—anomaly for a traveler. - **? Black (B)**: LIVE always—possibly miswired. The porch (A) works fine, with COM Red and ? Black always live, suggesting a correct single-pole setup. The hall (center) isn’t detailed but seems non-functional per your note (“downstairs lights not affected by any downstairs switch”). ### The Problems 1. **Upstairs lights won’t turn on**: The circuit to the landing light is incomplete. 2. **Downstairs lights only toggle via upstairs switch**: The downstairs landing switch isn’t properly in the 2-way loop. ### Hypothesis The downstairs landing switch is miswired, likely due to plasterers disturbing it. A 2-way switch needs: - **COM**: To the light (or live feed, depending on setup). - **L1/L2**: Travelers to the upstairs switch’s L1/L2. Right now, the downstairs COM is empty, and the travelers (L1 Red, L2 Red) aren’t fully functional. The “always live” Yellow and “never live” Blue suggest a live feed is present but not switching correctly to the light. The upstairs switch can interrupt power to the downstairs lights, implying it’s in the circuit path, but the downstairs switch isn’t contributing. ### Suggested Fix Here’s a logical rewiring for the downstairs landing switch, assuming a standard UK 2-way setup (live feed at one switch, light at the other): 1. **Identify the cables**: - **C (Yellow, Blue, L2 Red)**: Yellow is likely the permanent live from the upstairs COM Red or L2 Yellow (both always live). Blue and L2 Red should be travelers. - **B (L1 Red, ? Black)**: L1 Red acts like a traveler; ? Black’s constant live is odd—possibly meant for another circuit (hall?). 2. **Rewire the downstairs landing switch**: - **COM**: Move ? Yellow here (live feed). - **L1**: L1 Red (traveler to upstairs L1). - **L2**: L2 Red (traveler to upstairs L2). - **? Blue**: Should alternate live/dead—test if it’s a traveler; if not, it might be redundant or damaged. - **? Black**: If always live, it might belong to the hall switch—check continuity. 3. **Test the circuit**: - Turn off power at the breaker. - Rewire as above, ensuring tight connections. - Restore power and test both switches. ### Safety First Since you’re hesitant to dive in without a second opinion, I’d say you’re wise! Electricity’s no joke—double-check with a multimeter or voltage tester before touching wires, and if you’re unsure, a local electrician can sort this in 30 minutes with your pics and notes. The “never live” terminals (Blue, L2 Red downstairs) suggest a possible break or loose connection from the plastering chaos. |
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New Wed 26 Feb 25 15:04
Wiring help - Grok thinks... - smokie
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ChatGPT or CoPilot? :-) Whatever, it is certainly an answer and a half so thank you :-) I doubt there has been any damage to the wires. Does it mean to just move Yellow to the COM in the top row? That might make sense I suppose. |
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New Wed 26 Feb 25 15:39
Wiring help - Grok thinks... - zippy
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>>Grok thinks... Out of principle, I wouldn't use Grok. |
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New Wed 26 Feb 25 15:02
Wiring help - RichardW
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| Did you have the ceilings skimmed, and therefore messed with the wiring at the ceiling roses? Was any other work done (i.e. hammered any nails into a wall)? How did it work originally - 2 way switching that operated both up and downstairs lights together? Is the hall (downstairs?) light also not working, and was this originally one way switching from the downstairs switch only? Your Google doc doesn't appear to follow, since the table for the upstairs switch doesn't match the text above it? |
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New Wed 26 Feb 25 15:20
Wiring help - smokie
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Ceilings weren't skimmed -they were de-Artexed a few years back!). No other work done. Upstairs and downstairs were independent, upstairs only switched by upstairs switch and one gang on the downstairs switch. Downstairs lights not switching on any of the downstairs gangs but the upstairs switch is turning them on and off. Yes sorry for the confusion in the Google doc, I added various permutations of test after the initial draft and should have taken out the top statements, as it became incorrect. The table is correct (Corrected in the Google doc, link in 1st post)) Last edited by: smokie on Wed 26 Feb 25 at 15:23
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New Wed 26 Feb 25 15:37
Wiring help - Fullchat
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Is the upstairs switch receiving it power from the downstairs switch? If so it would now appear to be sending back that power to the downstairs lighting circuit. |
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New Wed 26 Feb 25 15:59
Wiring help - smokie
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Yes FC that sums it up. There's a pic of a three gang similar to mine here www.audiomate.co.uk/proddetail.php?prod=Eagle-2-Way-3-Gang-Light-Switch-Curved-Edge-10A. I'm assuming this is standard. This has helped me think this through but I'm still not there yet!! So numbering them from left to right as top row T1 - T4 and B1 - B5... Porch is on T4 (COM) and B4 (!W). Red and black cable respectively. Hall should be on some mixture of T2 and T3 and on COM B3 Upstairs should be on T1 (COM) and some mixture of B1 and B2. I'm just posting this while thinking about it more... Last edited by: smokie on Wed 26 Feb 25 at 15:59
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New Wed 26 Feb 25 16:03
Wiring help - Fullchat
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Just thinking this one a bit further. Instead of providing switched power or a switched neutral to the upstairs light the switch is now acting as a switched breaker for a downstairs circuit. |
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New Wed 26 Feb 25 16:10
Wiring help - smokie
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My T1 is empty. So no live to upstairs (on the right wire) My T2 and T3 both have a red wire (and are both live). I wonder if I should just move T2 to T1? I'm going to try it... |
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New Wed 26 Feb 25 16:20
Wiring help - smokie
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And that seems to have fixed it. A simple, one might say careless, mistake has cost me (and you guys) quite some hours to fix. Meantime SWMBO has been cleaning the plaster off the skirting and other places it should not have reached... Having workmen in is no fun really!! Anyway we got there in the end, thanks for the assistance. |
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New Wed 26 Feb 25 16:32
Wiring help - Fullchat
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Bang!!! Glad you fixed it :) Sometimes it just logic. If you could lay the component parts out infront of you it would make sense. But because it all disappears into the unknown it becomes witchcraft :) |
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New Wed 26 Feb 25 15:06
Wiring help - Fullchat
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I found this. Its not the easiest watch but does seem to visually explain it fairly simply. www.youtube.com/watch?v=Ku22BpvdVXo I'd take the porch light out of the equation for a start as it is probably getting its feed from the switch by a link wire from a COM and return Neg is joining in the switch housing? Last edited by: Fullchat on Wed 26 Feb 25 at 15:09
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New Wed 26 Feb 25 17:00
Wiring help - Manatee
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I'd get it sorted by an electrician. We've most of us messed about with connecting/disconnecting a few switches, sockets or light pendants, but if we have any sense we keep quiet about it. Were the plasterers qualified to do work on your wiring? I can tell you that when our house burnt down, among the many questions I was asked by the forensic investigator were "have you had any work done on the wiring?" and "who did it?". |
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New Wed 26 Feb 25 17:22
Wiring help - smokie
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Of course you are right but it turned out to be really trivial and trades round here seem to want £150 just to come out and have a look. I didn't realise they'd take the sockets off to do their work. They didn't ask, but I wouldn't have refused it. Was the cause of your fire ever identified? I don't recall... Last edited by: smokie on Wed 26 Feb 25 at 17:22
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New Wed 26 Feb 25 18:21
Wiring help - Manatee
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I guess I'd have done the same if I could have worked it out! It was put down to "resistive heating" in one or other of the junction boxes in the loft. The circular ones with the brass screw terminals in. The screws come loose with the mains cycle it seems, not heat cycling but the jiggling about on a molecular scale. I can believe it. In the days when we had to fit plugs, as often as not when you took the plug off an old appliance, the screws would be loose. It goes bad connection>resistance>heating>corrosion>more heating> etc. There are millions of these things and if even a small proportion actually start a fire that's still a few fires. I suppose we've all seen plugs/sockets blackened where there has been a poor connection. Same thing. The only surprise really was that the risk is higher with larger currents, which are not generally found in lighting circuits. I mentioned it to a friend of mine who said he had a 7Kw electric shower. Every time he used it there was a burning smell. Turned out there was a poor connection at the fused spur box and when he opened it up it was already blackened inside. He's actually found it before we had our fire. |
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New Wed 26 Feb 25 18:29
Wiring help - smokie
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Yes that is definitely something I try to ensure I get right when putting electrics together. The upstairs socket had some very loose-looking connections which I will tighten before finally refixing it. Which reminds me. The kitchen was professionally re-wired during its recent replacement but no certificate has been forthcoming yet! |
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New Wed 26 Feb 25 19:41
Wiring help - bathtub tom
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>>It was put down to "resistive heating" I thought you were well in glis-glis territory |
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New Wed 26 Feb 25 20:54
Wiring help - maltrap
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| My consumer unit which is housed in the under the stairs cupboard,which is also used as a “bunghole” I fitted a smoke alarm mainly for peace of mind,I also fitted one in the loft,same reason. |
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New Wed 26 Feb 25 20:38
Wiring help - Kevin
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>The screws come loose with the mains cycle it seems,.. The last time I checked, the only connectors approved for joining mains cabling without a removable inspection cover ie. they can be hidden inside walls or trunking etc. are the Wago spring lever type. (Chinese knockoffs are available but probably uncertified.) Screwdown or twist type connectors must be easily accessible for maintenance (tightening). |
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