You have new quote information. View My Dashboard ×
Customer #:
Ship To: {{vm.session.shipTo.lastName}} {{vm.session.shipTo.firstName}},
Change Customer/Ship To

In this installment of our This vs.That series, we will be comparing TFFN and THHN wiring. This series focuses on giving two different products a side by side comparison to share vital information about them, and help make any wiring decisions easier! 

THHN wire and TFFN wire belong to a category of electrical wire also known as building wire. TFFN and THHN wire are built in accordance with the National Electrical Code for general purpose wiring for installation in conduits or recognized raceways. THHN and TFFN wire are essentially the same wire except for specific ratings that pertain to each. The four letters in both wire names signify the approvals the wires have gone through and can help us uncover the slight differences between the two.

What is THHN Wire? 

THHN stands for Thermoplastic High Heat-Resistant Nylon. This wire is made of thermoplastic material, can withstand high temperatures, and features a nylon jacket.

THHN Wire Specifications: 

  • Single, annealed bare copper conductor (14 AWG to 1000 MCM)
  • PVC insulation
  • Rated to 75ºC in wet locations and 90ºC in dry locations
  • Rated to 600V
  • Oil and gas resistant

THHN wire is most commonly offered in stranded constructions but is available with a solid conductor from 14 AWG to 10 AWG. Most THHN electrical wire is also dual-rated as TWHN wire, adding water-resistance to the product's characteristics.

What is TFFN Wire? 

TFFN stands for Thermoplastic Flexible Fixture Nylon, meaning the wire is made of thermoplastic material, is highly flexible, and has a nylon jacket. TFFN wire is also classified as a fixture wire.

TFFN Wire Specifications: 

  • Single, annealed bare copper conductor (18 AWG or 16 AWG)
  • PVC insulation
  • Rated to 90°C in dry locations
  • Rated to 600V
  • Oil and gas resistant

TFFN wire also has a cousin: TFN wire. TFN wire is the same as TFFN, except TFN wire features a solid conductor instead of stranded, which is why it doesn't have the second "F" for flexible.

How Do They Compare?

TFFN is only available in 18 AWG and 16 AWG, while THHN can be as small as 14 AWG or as large as 1000 MCM. THHN wire and TFFN wire have essentially the same construction but achieve different ratings at different sizes. A smaller TFFN wire is more flexible than THHN wire, but it doesn't offer the same kind of heat resistance in wet environments as THHN wire does. 

Since TFFN and THHN wire have different ratings and are available in different gauge sizes, there are slight differences in their uses. While both can be used for machine tool, appliance, and control circuit wiring, the difference lies in the fact that TFFN is used in applications where the NEC designates fixture wire, while THHN is not. Although fixture wire can be used for control circuits, it can’t be used for branch circuits, but THHN can. Both wires are used for installation in conduits or recognized raceways, but raceways for fixture wire have restrictions.

They must be large enough to permit the installation and removal of conductors without damaging the insulation. THHN and TFFN wire have very few differences, however, it’s important to consider the differences they do have in order to choose the correct wire that can withstand the proper conditions and perform as needed.

To learn more about THHN wire vs TFFN wire, view our full specs on TFFN wire and THHN wire.