Household wiring must always use screw fittings, wire nuts, etc. Solder is not "generally approved" on dc, either, unless inside an approved housing, and then only when done in certain ways.* Household wiring is all the construction codes usually bother to cover, and they apply to 120/240Vac up to the switch, socket or outlet. Lamps, stereos, etc. are covered by code in some areas, like LA county, but by "Underwriter Labs Approval" in most others, in the US. A "UL" label (o/e) on the power cord is required for sale in most larger US communities.
120VAC can be attached by solder to an approved type of glass or phenolic circuit board inside the correct kind of enclosure. UL generally will not approve its use just about anywhere else for power-line connections.
This is something to keep in mind when doing any DIY project. Get a copy of the UL construction-code book. You'll find that all connections should be inside a non-meltable (fire-retardant) enclosure, via screw terminals, wire nuts, or compression fittings of some kind. Heat and humidity can quickly cause electrolytic corrosion on any soldered joint, eventually causing enough resistance for it to get hot and melt down.
Solder is great for some low-voltage dc purposes. When a connection might get subjected to heat (as in a house fire, resistive connection, etc.) the mischief that running solder can cause is just too great for it to be a good idea, so codes do not approve it in most areas. [Sorta like teflon tape in high-pressure gas lines. :-)] Over time, electrolysis slowly destroys soldered copper connections that aren't hermetically sealed, too. Some fungi accelerate that.
> Household wiring must always use screw fittings, wire nuts, etc.
This is for reasons of mechanical strength. Naive soldered connections can be pulled apart with your bare hands, and will not stand up to being snagged, tripped over, used as an acrobatic toy by a toddler, etc. This is especially true for the single-strand cable used in building wiring, which can apply a lot of leverage to a soldered joint.
Electrolysis and fungi? No, solder is chemically very stable. It's used to great effect to join copper water pipes, where the large surface area and built-in strain reliefs allow solder to be strong enough.
Household wiring must always use screw fittings, wire nuts, etc. Solder is not "generally approved" on dc, either, unless inside an approved housing, and then only when done in certain ways.* Household wiring is all the construction codes usually bother to cover, and they apply to 120/240Vac up to the switch, socket or outlet. Lamps, stereos, etc. are covered by code in some areas, like LA county, but by "Underwriter Labs Approval" in most others, in the US. A "UL" label (o/e) on the power cord is required for sale in most larger US communities.
120VAC can be attached by solder to an approved type of glass or phenolic circuit board inside the correct kind of enclosure. UL generally will not approve its use just about anywhere else for power-line connections.
This is something to keep in mind when doing any DIY project. Get a copy of the UL construction-code book. You'll find that all connections should be inside a non-meltable (fire-retardant) enclosure, via screw terminals, wire nuts, or compression fittings of some kind. Heat and humidity can quickly cause electrolytic corrosion on any soldered joint, eventually causing enough resistance for it to get hot and melt down.
Solder is great for some low-voltage dc purposes. When a connection might get subjected to heat (as in a house fire, resistive connection, etc.) the mischief that running solder can cause is just too great for it to be a good idea, so codes do not approve it in most areas. [Sorta like teflon tape in high-pressure gas lines. :-)] Over time, electrolysis slowly destroys soldered copper connections that aren't hermetically sealed, too. Some fungi accelerate that.