Probably a simple/stupid question, but rather check with people who know before doing anything stupid....
No such thing as a stupid question, just stupid answers...
Is it OK to use Spade terminals on AC? And are there special terminals for use with AC? I'm guessing it's fine as I got a new take off 6' piece of 10ga SOOW wire a while back to use on my compressor and it had factory installed ring terminals on one end.
Ok to use? Yes, certainly. Spade, ring, faston and others are used all over the place with AC. Look at the control panel inside your dishwasher or washing machine or dryer or microwave. Or the main wiring inside your furnace. Crimped terminals all over the place.
As others have said, the terminals should be rated for 120v, but frankly, I challenge anyone to show me the difference between a 12v terminal and a 120/240v terminal. Pointless to manufacture one for 12v when a 120v one works as well. The only real issue IMO, is current carrying ability. Don't shoehorn a crimp meant for 16ga wire onto a 10ga wire. There may not be enough mass of metal to carry the level of current that 10ga wire is designed for(up to 40amps in some cases). The terminal ends up being the highest point of resistance, drops the most voltage, and melts.
What I'm thinking is it would be easier to put spade terminals on the 10ga SOOW to hook to my 30A Breaker vs try to get the wires under the plate which is really meant for solid wire....
The connection lug on the line side of a circuit breaker isn't meant for just solid wire. It's meant for either solid or stranded. Especially if it's the type that squeezes the wire between 2 plates, rather than the screw putting pressure on the strands directly, like the hole-and-screw you typically see on a ground or neutral bar. The squeezing-between-2-plates connection type is an excellent way to terminate a stranded wire. Whether it's the lug on a breaker, a back-wired switch or outlet(not backstabed!), or a piece of SJO going into the terminals on something like a pro-grade leviton plug.
That being said, the finer strands in a piece of SJO will require more attention that the 9 strands you'll encounter in THHN. I'd twist the stands together to make sure they all go under the plate and you don't have any strays.
If the connection has the screw bearing down directly onto the wire, a ground bar for instance, you should make sure that you're using a hole that is just big enough, so the screw doesn't spread the strands away from contact, but rather forces them to "fill up" the volume of the hole. Don't put a finely stranded 12ga wire into a hole that could take a 1/0 wire. Find a smaller hole.
Also, pull the screw out first and make sure the machining process left a smooth surface on the end of the screw. That way, the screw doesn't machine it's way through the fine strands as you tighten it.
As for solding: I'm a big fan of soldering, but there's been some discussion that tinned stranded wire can "cold flow" over time under the pressure of a screw and the joint will loosen. I'm not convinced of that, but there it is.
OTOH, I've always felt that the initial flow that occurs as the screw tightens onto the soldered strands helps them mold themselves to the screw to make for more surface area and a better overall contact. YMMV.
If you solder, make sure to use a solvent to remove all the flux so it doesn't act as an insulator, and use a tin/silver solder if you can get it. It's higher strength that tin/lead(so less likely to flow) and the silver should help with the conductivity.
