Decoding the markings '18/2 SJTW' on building light wires

Let's dissect a standard label found on reliable temporary work lights. Understanding each segment turns alphabet soup into a clear safety specification.

1. Conductor Gauge & Count: '18/2'

• 18: This is the American Wire Gauge (AWG) number, indicating the thickness of each individual copper conductor inside. A lower number means a thicker wire capable of carrying more current. 18 AWG is common for lighting circuits and light-duty power tools, typically rated for up to 10 amps.

• 2: This denotes the number of current-carrying conductors within the cable. '2' means a hot and a neutral wire. A '3' would indicate an additional ground wire.

2. The Cable Type & Rating: 'SJTW'

This is the core classification defined by UL (Underwriters Laboratories) and indicates the cable's intended service and environmental ratings. Breaking it down letter-by-letter:

• S: Service Grade. This is a hard-service, portable cord designed for flexible, heavy-duty use. It's a step above junior hard-service (SJ) cords.

• J: Junior. This might seem counterintuitive, but in this context, it indicates the cord has 300-volt insulation. The absence of a "J" (as in STW) would indicate 600-volt insulation.

• T: Thermoplastic. The jacket material is made of a durable, oil-resistant PVC compound. This material is robust and weather-resistant but can become stiff in extreme cold.

• W: Weather-Resistant. The jacket is suitable for use in wet locations. This is a non-negotiable feature for any outdoor construction application.

In Summary

An 18/2 SJTW cable is a 300-volt, weather-resistant, thermoplastic-jacketed portable cord suitable for powering lighting and light tools in damp outdoor environments. It's a versatile, cost-effective choice for many general construction tasks.