What’s the difference between SPT-1 wire and SPT-2?
When making and installing Christmas lights or making your own extension cords, SPT wire is often used. These are usually made from 18/2 wire. When identifying the two numbers for the wire – 18/2 – the 18 refers to the size of the wire which in this case is 18 gauge. The 2 indicates that the wire is made with two wires.
The SPT-2 wire has a thicker insulation. Because of the thicker insulation with the SPT-2 wire the user can power more lights and decorations than the SPT-1 wire
SPT-1 is rated a 7 amps or 770 watts and has an insulation thickness of .030″.
SPT-2 is rated at 10 amps or 1100 watts and has insulation that is .045″ thick.
Use this information to help you evaluate your power needs. Do not exceed the recommended amperage, this will absolutely cause the wire to fail and be a hazard.
If you are using LED’s to make your customized light strings, we recommend that you do not run more than 400’ of the 18/2 wire. The reason for this is that your chances of getting some voltage drop is likely and your bulbs will not illuminate to the best of their ability.
If you are using Incandescent bulbs we recommend that you do use the SPT-2 wire.
In a Nut Shell – The difference between SPT wire is the thickness of the insulation over the wires, not the amperage of the wire. The wire gauge or AWG rating is how much current the cable can carry in amperes.
Other useful information.
SPT is an acronym for Stranded Parallel Thermoplastic
The smaller the number, the thicker the wire. A 16 gauge cord is thicker than a 18 gauge.
SPT wire is also known as zip cord or light line.