What is the screw size used to hold light fixtures to box?
A normal junction box designed to hold a fixture that weights up to 50 lbs uses 8-32 screws. (Marked as "fine" or "UNF" at your local hardware store.) The NEC allows wall mounted (receptacle style) boxes having no fewer than (2) #6 for fixtures weighing 6 lbs or less. Boxes to be used as sole support for paddle fans up to 35 lbs must be marked and (UL) listed for the purpose, and maximum weight if listed for 35 to 70 lbs, These boxes will have whatever type of screw that was submitted with the box to the (UL) testing lab
If the light switch is off can I touch the electrical wires safely? If the light switch is off, can I touch the electrical wires behind the light socket? Or do I need to go the extra step to take out the fuse/circuit breaker to that socket?
Always turn the circuit off from the fuse box/circuit breaker panel before working on it. After turning it off, use a proximity voltage tester to verify that the circuit is not energized.Now, onto my edited answer:The hot wire (black) can come from the panel, through a switch, and then to the light. The neutral (white) wire would leave the light and make its way back to the panel. In this configuration, turning off the light switch would technically mean that there should be no energy at the light.Would I recommend working in that light fixture box? Nope. Just turn the breaker off.But there's another method to wiring a light that you have to watch out for too: the switch leg. This is where the hot wire comes into the light first and gets connected to the white wire that goes to the switch. From the switch, the remaining black wire comes back up to the light. Technically, if the connection in the light box is well done and the the switch is in the off position, you shouldn't be able to receive a shock in the light box.Would I recommend working in the light fixture box in this scenario? Not a chance. Just flip the breaker, and you're safe.In either configuration however, you could be shocked in the switch box.Have (safe) fun electrifying your world!
Where would you use a 14-3 wire vs. 14-2?
Electrical wire naming standards are similar in Canada and the USA.14–2 (said fourteen two) wire actually contains three wires. One ground (bare copper), one neutral (white coating) and one “hot” (black coating). We don’t count the bare ground wire, hence the name 14–2.14–3 contains 4 wires: one ground, one neutral and two hot wires (one black and one red).Fred is correct that a 14–3 wire should be used for what is called a three way switch, but it can be used in several other places as well. Another common use is to make “split” receptacles, which is a plug that has the top section and the bottom section electrically isolated from one another, with one powered by the red wire and the other by the black wire. They can share a common neutral and ground wire. This type of plug can be found in a kitchen where, before the advent of all these energy saving appliances, we used to blow fuses or trip breakers if too many items were on the same circuit. The red wire and the black wire in this instance will be connected each to their own circuit but the circuit breakers will be linked in the panel so that if one “trips” or goes off, then they both will (for safety).14–3 is generally more expensive than 14–2.