HOW TO KNOW THE DIFFERENCE

THHN/THWN-2 is a thermoplastic product, while XHHW-2 features thermoset insulation.

Wire Type	THHN/THWN-2 Thermoplastic (PVC)	XHHW-2 Thermoset (XLPE)
Insulation Type	Thermoplastic	Thermoset
Voltage Rating	600V	600V/1kV
Dielectric Constant (Hospital Grade must be 3.5 or less)	5.0-6.8	3.1
Minimum Temperature	-10° C	-40° C
Maximum Short Circuit Temp.	150° C	250° C
Resistance to Leakage Current (in water MegOhms in 1,000 ft.)	Low	Extremely High

ACRONYMS EXPLAINED:

THHN/THWN-2:	XHHW-2:
T = Thermoplastic	X = Cross-Linked Polyethylene (XLPE)
HH = High Heat Resistant	HH = High Heat Resistant
W = Water Resistant	W = Water Resistant
N = Nylon Jacket	(Not Required)
-2 = Temperature Rated 90°C Wet/Dry	-2 = Temperature Rated 90°C Wet/Dry

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THERMOPLASTIC:

1. Cheaper than Thermoset
2. Nylon Coating - Required for the Insulation System's Rating
3. Uses Thinner PVC Insulation
4. Lower Overall Electrical Insulating Properties

THERMOSET:

1. Hospital Grade (low leakage insulation)
2. Dual Rated 600V/1kV
3. Uses XLPE (cross-linked) Insulation Instead of PVC
4. Substantially Higher (better) Insulation Resistance

FACTORS THAT SET XHHW-2 APART FROM THHN

Thermoplastic and thermoset are two types of cable insulations commonly used for single conductors. It’s important to understand their strengths and weaknesses when designing and building a new facility, machine, or appliance.

THERMOPLASTIC INSULATION

THHN/THWN-2 is a thermoplastic product. It uses a thinner PVC insulation, which can lead to current leakage and dielectric breakdown in demanding circuits or from chemical or environmental exposure. The PVC insulation in THHN/THWN-2 emits a toxic smoke when burned and is less flexible at cold temperatures. However, it is lighter in weight and less expensive to manufacture.
Thermoplastic compounds can be heated, then shaped and cooled to maintain their desired shape. This process can typically be repeated by applying heat to remelt the insulation, which can lead to potential danger in some applications.
Examples of thermoplastic compounds include:

1. Polyvinyl Chloride (PVC)
2. Polyethylene (PE)
3. Polypropylene (PPE)

THERMOSET INSULATION

XHHW-2 is a thermoset product. Crosslink products like XHHW-2 have XLPE (crosslinked polyethylene) insulation instead of PVC. XLPE is more resistant to chemicals, ozone, and abrasions. Because of the chemistries involved, modern XLPE is far less toxic than PVC in the event of fire. In more applications, thermosets are more flexible than thermoplastics and are more advantageous for projects where complex, close-spaced bends are required.
Thermoset compounds utilize a curing process which causes a chemical reaction, allowing the polymers to cross-link. Once cured, the thermoset compounds retain their shape and will not remelt when heat is applied.
Examples of thermoset compounds include:

1. Crosslinked Polyethylene (XLP/XLPE)
2. Neoprene
3. Ethylene Propylene Diene Terpolymer (EPDT)
4. Chlorinated Polypropylene (CPE)
5. Crosslinked Polyolefin (XLPO)
6. Silicone Rubber