I'm attempting to shrink wrap wire connections for the first time and I am wondering what size of heat shrink is needed for i.e. a single 22 AWG wire. Could it be any heat shrink tubing that fits the wire? Or is there a certain size that it shrinks to so that I must purchase one not too large? Thanks!
I have some typical 22 AWG wire here and 1/16", 3/32" and 1/8" diameter heat shrink tubing that has a 2:1 shrink ratio. In the not shrunk state each fits over the wire. In the shrunk state the 1/16" and 3/32" grip the wire firmly, but, the 1/8" is just slightly larger in diameter and slips. Don't forget that you may want a fatter solder join or two wires to be under the shrink wrap. For that reason my recommendation is to buy all three sizes. The stuff is not that expensive and it is good to have a good selection around.
You can buy a kit that contains several diameters like this for under $20:
I got mine for $7 when it was on sale.
I usually keep an assortment of sizes on hand just go with the snuggest fit. That's the practical technician method.
The formal engineering way is to pick the smallest standard tubing size that fits over whatever you're covering. Then make sure that the recovered diameter of the tube is smaller than the wire bundle coming in on each side to ensure a snug fit. Most heat shrink has a 2:1 unconstrained shrink ratio, but there is stuff out there that can shrink 4:1 if your application requires it.