How many sets of C7 or C9 Outdoor Christmas Light Strings can I plug in together?
When using C7 or C9 25-Lamp Strings, do not connect more than three strings in a series. You can connect two of our C7 or C9 100-Lamp Strings together IF you use a 3 Outlet Power Adaptor plug in between the two light strings. You should never connect 100-Lamp Strings together without the 3 Outlet Power Adaptor. The exception to this rule is our Low Energy/High Efficiency Lamps in which case you can run twice as many strings as stated above.