What is spt1 wire?
Emma Martin
Published Feb 13, 2026
What is spt1 wire?
For those of who don’t know what SPT-1 wire is – it is also known as lamp wire or zip cord, and is commonly used by decorators to build custom lengths of extension cords. It allows for a clean display installation by elimination excess extension cords that can be unsightly.
What is the difference between spt1 and SPT-2?
The main difference between SPT-1 and SPT-2 electrical cord is in the thickness of insulation. SPT-1 gives you insulation that’s 0.03″ thick while SPT-2 is 0.045″. With 50% thicker insulation, SPT-2 is the Wire of choice for anything that is reaching close to 7-amps. Both SPT-1 and SPT-2 have the same maximum amperage.
What is a SJTW extension cord?
SJTW is an industry abbreviation used on wire and cable. S is for service; J for junior (which means hard service instead of extra hard); T is the coating (thermoplastic/vinyl); W is weather approved. It is a hard service, thermoplastic cable rated for 300V and approved for outdoor use.
How do I know if I have SPT-1 or SPT-2?
The bottom line, the only difference between the two SPT numbers is the thickness of the insulation. SPT-2 has 50% thicker insulation than SPT-1. It does not change the maximum amount of power the wire can handle.
What type of wire is used for Christmas lights?
Mini lights use 22 gauge wire. C7s and C9s generally use 18 gauge wire. Specialty bulbs have a large base that requires them to be on 12 gauge wire. Heavier wire is usually more expensive, but it can support many more amps.
Which bulb is bigger C7 or C9?
Here is what you should keep in mind, along with a few decorating tips. C7 bulbs are smaller than C9s. C9 bulbs are larger, over 2 inches long, and fit an E17 base. They are usually available in 7 or 10 watts for incandescent bulbs and are generally used in the same ways as a C7 bulb.
Can you use lamp wire for Christmas lights?
Plain wire is the commonly used wired for custom lighting. Plain lamp wire is offered in two options, both use 18-guage copper. SPT-1 is typically used on Christmas lights, and has an insullation thickness of . 03 mm and is rated for 7amps.
What is the difference between C9 and C7 bulbs?
C7 bulbs are smaller than C9s. They have an E12 candelabra base, the same size as a night light bulb. C9 bulbs are larger, over 2 inches long, and fit an E17 base. They are usually available in 7 or 10 watts for incandescent bulbs and are generally used in the same ways as a C7 bulb.
How many amps is #8 SO cord good for?
| Types of Cord | Gauge Size Range | Ampacity of Current-Carrying Conductors (amperes) |
|---|---|---|
| 0 – 50 ft. (0 – 15.2 m) | ||
| SOOW – Service Oil Resistant Insulation/ Jacket Weather-resistant | 8 AWG | 40 Amps 35 Amps |
| 6 AWG | 55 Amps 45 Amps | |
| 4 AWG | 70 Amps 60 Amps |
How can I tell what gauge my extension cord is?
Gauge is typically listed along with the number of conducting wires in the cord. For example, a 14/3 cord contains 14-gauge wire and has three conductions inside. Extension cord lengths determine the cord’s power capacity.
What gauge extension cord do I need for Christmas lights?
16-gauge
For running Christmas lights, you want to make sure that any cord you use is rated for outdoor use. Pick a 16-gauge extension cord for light runs of 25 feet or less and go with a heavier duty 14-gauge cord for runs over 25 feet.
