Q: Why can’t TFN be also dual-rated as MTW?
A: Because the stranding is too coarse. TFFN, which is more flexible, can be dual rated.

Q: Does Cerrowire make a VW-1 version of TFFN?
A: No, it is not a popular item and the costs would be prohibitive.
THHN, THWN, and MTW are VW-1 rated in sizes 14 AWG through 1 AWG

Q: Is the nylon jacket on THHN for mechanical protection only?
A: No, it also serves as a barrier to the effects of gasoline and oil.

Q: Can the words “Cable Tray Use” be applied to all sizes of THHN type products?
A: No, only sizes1/0 AWG and larger are marked for use in cable trays.


Q: Can XHHW-2 be made with a 2000 Volt rating?
A: No, for 2000 Volt you would purchase an RHW-2 wire instead.

Q: Why purchase a thermoset insulated XHHW when you can buy a thermoplastic insulated product having the same rating?
A: The main reasons are: 1) the thermoset product has better low temperature properties and 2) a higher K Value (electrical properties, approximately 10,000 K Value vs. 4000). The short circuit current carrying capacity is also greater, providing greater protection from meltdown than THHN.

Q: Can XHHW-2 be rated gasoline and oil resistant?
A: Yes.

Q: Does XHHW-2 have to meet any flame test requirements?
A: As a minimum, it would have to pass a horizontal burn test or FT-2 flame test.

Q: Can XHHW-2 be rated for use in cable trays?
A: Sizes 1/0 and larger can be rated when marked for “CT Use” or “For use in Cable Trays”. Cerrowire’s 1/0 and larger XHHW-2 is marked “For CT Use”.

Q: Can XHHW-2 be rated for Sunlight Resistance?
A: Yes, Black XHHW-2 Conductors sizes 8 AWG and larger are marked “Sunlight Resistant.”

Bare Copper/SE Style U

Q: Why is the base color of both inners of SE Style U colored black?
A: Both the PVC insulation and the nylon jacket on the inners now have to pass a 300-hour weatherometer test, and black best meets the requirement.


Q: Can the inner insulated conductors of an NM-B cable be stripped out of the cable and used in a conduit?
A: No. Even though the conductors meet the thickness and other applicable requirements for Type THHN thermoplastic-insulated wire, they are prohibited from being surface marked with “THHN”, “-B”, or any ampacity or temperature rating.


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