| General > General Technical Chat |
| Termites could burn your house down |
| << < (7/8) > >> |
| Cubdriver:
--- Quote from: amyk on October 12, 2019, 08:53:24 pm --- --- Quote from: Cubdriver on October 12, 2019, 04:28:01 am --- --- Quote from: vk6zgo on October 12, 2019, 02:23:45 am ---Certainly, in WA, even 100+ year old houses have been rewired with PVC over the many years since then. I had occasion to climb around in the roof of a "Federation" era house, & came across some "tramline" type wiring.(bare copper wire supported by porcelain standoff insulators). It had long ago been disconnected, & the wiring in use was all PVC. An interesting sidelight ---someone in the past had put a TV antenna inside the roof, which does work OK with tiles, but not with a metal roof like this house had. The antenna was resting across both sides of the old "tramline' wiring, so it's just as well it had been replaced. --- End quote --- That sounds like what's known in the states as "knob and tube" wiring. I've seen it in a few old houses (even still in use in a few lighting circuits at a friend's 1920s-ish house). The knobs are porcelain insulators used to support the wire, and hold it where turns were made, and the tubes were porcelain sleeves with larger heads at one end the were fitted in a hole wherever the wiring passed through a rafter, joist or wall stud. I'm happy that I can just pull a single cable with hot, neutral and ground all in one these days. MUCH easier! --- End quote --- K&T still had insulation over the wires. I've never seen it with uninsulated bare copper wires. If you're curious about the history of electrical wiring, archive.org has some good old books about it. --- End quote --- D'oh!! Good catch - I somehow missed that he said BARE wires. Yes, the K&T I've seen and read about was insulated. Uninsulated wire carrying mains through the walls and in the attic seems a bit alarming to me. Once again, vastly different standards in different countries. -Pat |
| tooki:
--- Quote from: Cyberdragon on October 12, 2019, 04:00:45 pm --- --- Quote from: Monkeh on October 12, 2019, 02:14:37 pm --- --- Quote from: Marco on October 12, 2019, 02:13:19 pm --- --- Quote from: Monkeh on October 12, 2019, 02:11:19 pm ---what earth? --- End quote --- Well I'm assuming with the talk of a theoretical earth leakage breaker he was also talking about theoretical earthed wiring. --- End quote --- Earth wiring is not necessary for operation of an RCD. --- End quote --- But an external path to earth is, and with no electrical box or any sort of metalwork, let alone a ground wire, I don't see how that would be possible. --- End quote --- You do realize that this “impossible” alternate path to earth is literally the exact raison d’être why RCDs exist? Whether an earth wire is present or not is actually not relevant to the RCD’s functioning. (The earth wire does, in grounded appliances, provide protection against some other failure modes.) |
| TerraHertz:
--- Quote from: Cyberdragon on October 12, 2019, 04:00:45 pm --- --- Quote from: Monkeh on October 12, 2019, 02:14:37 pm --- --- Quote from: Marco on October 12, 2019, 02:13:19 pm --- --- Quote from: Monkeh on October 12, 2019, 02:11:19 pm ---what earth? --- End quote --- Well I'm assuming with the talk of a theoretical earth leakage breaker he was also talking about theoretical earthed wiring. --- End quote --- Earth wiring is not necessary for operation of an RCD. --- End quote --- But an external path to earth is, and with no electrical box or any sort of metalwork, let alone a ground wire, I don't see how that would be possible. --- End quote --- Exactly. This is a light switch wiring. Two wires, one Active, the other to the light. When they are shorted, light comes on. There's no Earth wire, and even if bare conductors touch the wall woodwork, it's unlikely to draw enough current to ground (the actual ground on which the house sits) to trip an RCD. The 'slow burn' effect is due to the light being in series with the current path. Hence no thermal runaway to arcing, and the whole charred mess staying just below ignition temperature for wood. Luckily. |
| Cyberdragon:
--- Quote from: Cubdriver on October 12, 2019, 09:12:09 pm --- --- Quote from: amyk on October 12, 2019, 08:53:24 pm --- --- Quote from: Cubdriver on October 12, 2019, 04:28:01 am --- --- Quote from: vk6zgo on October 12, 2019, 02:23:45 am ---Certainly, in WA, even 100+ year old houses have been rewired with PVC over the many years since then. I had occasion to climb around in the roof of a "Federation" era house, & came across some "tramline" type wiring.(bare copper wire supported by porcelain standoff insulators). It had long ago been disconnected, & the wiring in use was all PVC. An interesting sidelight ---someone in the past had put a TV antenna inside the roof, which does work OK with tiles, but not with a metal roof like this house had. The antenna was resting across both sides of the old "tramline' wiring, so it's just as well it had been replaced. --- End quote --- That sounds like what's known in the states as "knob and tube" wiring. I've seen it in a few old houses (even still in use in a few lighting circuits at a friend's 1920s-ish house). The knobs are porcelain insulators used to support the wire, and hold it where turns were made, and the tubes were porcelain sleeves with larger heads at one end the were fitted in a hole wherever the wiring passed through a rafter, joist or wall stud. I'm happy that I can just pull a single cable with hot, neutral and ground all in one these days. MUCH easier! --- End quote --- K&T still had insulation over the wires. I've never seen it with uninsulated bare copper wires. If you're curious about the history of electrical wiring, archive.org has some good old books about it. --- End quote --- D'oh!! Good catch - I somehow missed that he said BARE wires. Yes, the K&T I've seen and read about was insulated. Uninsulated wire carrying mains through the walls and in the attic seems a bit alarming to me. Once again, vastly different standards in different countries. -Pat --- End quote --- The earlg Edison systems used bare wire even here, but that soon stopped after the introduction of the NEC in the 1890s. So if you see bare wires here it's a Victorian era DC system. |
| TerraHertz:
For completeness - I cut holes through the inner of the double brick wall foundation under the bathroom concrete slab. Expecting the termite trail between ground and the timberwork to be in there. And it was. |
| Navigation |
| Message Index |
| Next page |
| Previous page |