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THHN vs XHHW

THHN vs XHHW-2

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THWN-2 vs. XHHW-2: What's the Difference?

Written November 2018 | Lee Perry, Engineering Manager at Service Wire Company

A few factors set XHHW-2 apart from THWN-2.

Thermoplastic and Thermoset are two common types of insulation, and it's important to understand their strengths and weaknesses when designing and building a new facility, machine or appliance. 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 ◀BEST
Voltage Rating 600V 600V/1kV ◀BEST
Dielectric Constant
(Hospital Grade must be 3.5 or less)
5.0-6.8 3.1 ◀BEST
Minimum Temperature -10° C -40° C ◀BEST
Maximum Short Circuit Temperature 150° C 250° C ◀BEST
Resistance to Leakage Current
(in water MegOhms in 1,000 ft.)
Low Extremely High ◀BEST

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

KEY FACTORS:


THERMOPLASTIC:
Uses thinner PVC insulation. Lower electrical resilience can lead to current leakage and dielectric breakdown in demanding circuits or from chemical or environmental exposure.

  • Cheaper than Thermoset
  • Nylon Coating - Required for the Insulation System's Rating
  • Lower Overall Electrical Insulating Properties

THERMOSET:

Uses XLPE (Cross-linked) Insulation instead of PVC. Because of the chemistries involved, modern XLPE is far less toxic than PVC in the event of fire. Also more resistant to abrasion and substantially more electrically resilient.

  • Hospital Grade
    (low leakage insulation)
  • Dual Rated 600V/1kV
  • Substantially Higher (better) Insulation Resistance

OTHER ARTICLES:

2018 NFPA79 Requirements
by Lee Perry | September 2018

 


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