C9 500' String Light Spools (6", 12" or 18" Socket Spacing)
SPT1 or SPT2? Both wire types have a 18 awg coppper conductor. The difference is the thickness of the insulation. SPT1 wire is rated for 7 amps. Due to the thicker insulation on SPT2 wire, it is rated for 10 amps.
Using SPT2 wire, your finished strings can be 42% longer than with SPT1, but the cost of SPT2 wire is not 42% more, thus you get more bang for the buck using SPT2.
In situations where the amperage carrying capacity of the wire doesn't matter, SPT1 is a good choice.
General Description:
C9 500' bulk string light spool. Genuine commercial grade Wire & sockets only (Bulbs & plugs sold separately). Green or white wire. 6", 12" or 18" socket spacing. Requires bulbs with intermediate base (E17). Can be used with either LED bulbs or incandescent bulbs. Indoor / Outdoor use.
Electrical Specifications:
120 volt. SPT1/SPT2 both use 18 awg wire. SPT1 is rated for 7 amps / 840 watts. SPT2 is rated for 10 amps / 1200 watts (has thicker insulation). E17 intermediate sockets. These spools must be cut up into shorter lengths.
Physical Specifications:
500' per spool. 6" spacing  1000 sockets per spool. 12" spacing  500 sockets per spool. 18" spacing  333 sockets per spool. Sockets have heavy duty branch clips. Sockets have weep hole for water drainage. Indoor / outdoor use. Can be modified (spliced, cut, shortened, teed..).
Pricing Information:
Price is per spool.
Packaging Information:
1 spool per carton
Installation Information:
Spools must be cut up into shorter lengths. With SPT1, do not exceed 840 watts worth of bulbs per cut length. With SPT2, do not exceed 1200 watts worth of bulbs per cut length. Doing so will overheat the insulation on the wire. To determine how many incandescent bulbs you can have per cut length, take the wattage rating of the wire, and divide this by the wattage of 1 bulb.
Examples:
5 watt incandescent bulbs used on SPT1 wire: 840 watts (wire rating) divided by 5 watts (1 bulb) = 160 each 5 watt bulbs per cut length. 160 (sockets) @ 6" spacing = 80 feet. @ 12" spacing = 160'. @ 18" = 240'.
7 watt incandescent bulbs used on SPT2 wire: 1200 watts divided by 7 watts = 170 each 7 watt bulbs. 170 times 6" spacing = 85 feet. 12" spacing = 170'. 18" = 255'.
The above examples reflect the maximum limits of the wire. We suggest decreasing these figures by 10%.
When using LED bulbs, which are about .25 watts per bulb, you can't go thousands of feet  due to the drop in voltage caused by resistance in the wire itself. With long runs of wire, the further on down the wire you go, the lower the voltage is. With LEDs, a safe maximum length is about 400' +/. At 400', the voltage will be about 4% lower, which should still be enough power.
Handy formulas:
WATTS divided by VOLTS = AMPS
Examples: 1200 watts divided by 120 volts = 10 amps 7 watts (1 bulb) divided by 120 volts = .06 amps per bulb.
AMPS times VOLTS = WATTS
Examples: 10 amps times 120 volts = 1200 watts .06 amps (1 bulb) times 120 volts = 7 watt bulb.
