I searched the forum for this and did not find much. So I tried to make the title searchable for my project.
I want to create a timeline and ultimately an alert system for homes built or remodeled at certain times.
To that end, this question is about any known timeframe when I would typically see the tin or nickel coated copper service entrance conductors.
One of the homes that I inspected during my certification training was an older home with tin coated copper conductors. I’m not saying that tin coated copper is a problem, its just for my to understand the correlation between what I may oftentimes see and the homes age.
In other words when I fill out an inspection form (I am building in Excel)before even getting on location, I can create alerts to watch for. For example fire retardant roof panel, Aluminum wiring, regulations that were not required at the time … etc.
Glad to share my little creation when it is done. But that may be a while.
This is interesting, could track down the dates when the insulation technology changed maybe. BTW I do understand that tinned copper conductor is available to this day. I’m just wondering when it was more common place.
Tinning was originally developed to protect insulated copper wire from corrosive chemicals – primarily sulfur – released by wire-insulating materials. While no longer used in most wire insulation, these materials do sometimes show up in cable produced for a few high-environmental-stress industries, including waste-water treatment and paper milling. Tinning makes it easier to solder copper wire because it readily bonds to solder, which is itself largely made of tin. Tinned copper wire also suffers less corrosion at high temperatures than untinned copper.
Tinned copper wire is copper wire coated with a thin, electroplated layer of tin. This type of wire may be composed of a single tin-coated copper cable or many individually tinned strands of copper wire bound together. It is available in insulated versions and in uninsulated, or “buss wire,” versions.
Armoured cables with two rubber-insulated conductors in a flexible metal sheath were used as early as 1906, and were considered at the time a better method than open knob-and-tube wiring, although much more expensive.
The first rubber-insulated cables for building wiring were introduced in 1922 with US patent 1458803, Burley, Harry & Rooney, Henry, “Insulated electric wire”, issued 1923-06-12, assigned to Boston Insulated Wire And Cable. These were two or more solid copper electrical wires with rubber insulation, plus woven cotton cloth over each conductor for protection of the insulation, with an overall woven jacket, usually impregnated with tar as a protection from moisture. Waxed paper was used as a filler and separator.
Over time, rubber-insulated cables become brittle because of exposure to atmospheric oxygen, so they must be handled with care and are usually replaced during renovations. When switches, socket outlets or light fixtures are replaced, the mere act of tightening connections may cause hardened insulation to flake off the conductors. Rubber insulation further inside the cable often is in better condition than the insulation exposed at connections, due to reduced exposure to oxygen.
The sulphur in vulcanised rubber insulation attacked bare copper wire so the conductors were tinned to prevent this. The conductors reverted to being bare when rubber ceased to be used.
About 1950, PVC insulation and jackets were introduced, especially for residential wiring. About the same time, single conductors with a thinner PVC insulation and a thin nylon jacket (e.g. US Type THN, THHN, etc.) became common.
The simplest form of cable has two insulated conductors twisted together to form a unit. Such un-jacketed cables with two (or more) conductors are used only for extra low voltage signal and control applications such as doorbell wiring.
The first widespread use of non-rubber insulated conductors within cables was with type TW insulation which is a thermoplastic, 60 degree conductor. Next came THW which was primarily used in raceways and had a 75 degree C insulation. 90 degree C conductors like THHN came after those with their widespread use beginning in the early 80’s.