Current capacity is different for single strand and for multi-strand wire. Current carrying capacity is also mitigated by how much heat the insulation covering the wire can endure before breakdown. I personally perfer to use PTFE 'Teflon' insulated silver plated copper multi-stranded wire for everything I wire. It gives a high-tech appearance, carries a higher current with less weight, it solders wonderfully, and takes years to oxidize but it is more expensive. There are vendors on eBay who supply this type insulated multi-strand wire via surplus sources.
Included below is a useful( PVC) wire gauge/capacity table for determining basic current carrying capacity derived from the circular mil diameters of individual unplated copper strands. Sounds complicated, but its actually not, however, it is an engineering strategy to determine the correct wire gauge size for a specific current requirement.
- Determine the amount current to be carried...the 'load',
- Allow 5 or 7 Amperes wiggle room (add this to the maximum current to be carried),
- Determine length of wire to be used, (long runs drop current, keep the runs as short as practical),
- Locate supplier for multi-strand wire, ask for the circular mil Ampere current carrying formula (better than relying on tables),
- Calculate wire gauge based upon current carrying capacity requirement or use a table
A PVC insulated wire, circular mil table is listed here:
Same size wire (circular mils) carries different current depending upon insulation covering, PVC for instance does not carry as
much current because the insulation will breakdown at lower wire temperature, while PTFE 'Teflon' insulated wire can carry more current because the insulation breaks-down at much higher wire temperature.
For PTFE silver plated copper wire, my favorite wire, can be found below, although there are also many other vendors around, (incidentally I am not affiliated with any of these other than I buy wire from them occassionally).
Here is a source for Mil-Spec Wire (PTFE) 'Teflon' Stranded Silver Plated Copper which I use:
eBay vendor: "SkipMalley", has many different (all surplus) gauge sizes and colors,
enter this number
for 20Ga: "292417410713" via eBay search field
for 16Ga: "291102551795" via eBay search field
For Alpha 5858 PTFE Wire information, see page 11,
Here is a useful current capacity and Voltage drop calculator:
Please don't make the mistake of using only one color wire for power wires, use at least two different colors. It is both useful and wise to create an accurate drawing of your wiring configuration, (a little picture of your SSR showing the color of the wires and where they are routed to and from, relying of DC42's layout drawings of the controller board for the other end reference locations, etc) and put the drawing in your printer document drawer for future reference.
Good luck (and please, don't burn down your house),