Electrical FAQs

What is TEWN?


TEWN is a Canadian General Purpose Wire, the Canadian equivalent of TFFN.

Why can't TFN be also dual-rated as MTW?


Because the stranding is too coarse. TFFN which is more flexible can be dual rated.

Does Cerrowire make a VW-1 version of TFFN?


No, it is not a popular item and the costs would be prohibitive.

THHN, THWN, MTW, T90 Nylon and TWN 75 is VW-1 rated in sizes 14 AWG through 1 AWG.

Is the nylon jacket on THHN for mechanical protection only?


No, it also serves as a barrier to the effects of gasoline and oil.

Can the words "Cable Tray Use" be applied to all sizes of THHN type products?


No, only sizes1/0 AWG and larger are allowed in trays per the NEC provided they pass the UL 1581vertical tray flame test or the CSA FT4 flame test.

What would be the CSA equivalent product to XHHW-2?


Cerrowire’s XHHW-2 is marked “RW90”.

Can XHHW-2 be made with a 2000 Volt rating?


No, for 2000 Volt you would purchase an RHW-2 wire instead.

Why purchase a thermoset insulated XHHW when you can buy a thermoplastic insulated product having the same rating ?


The main reasons are: 1) the thermoset product has better low temperature properties and 2) a higher K Value (electrical properties, 10,000 K Value vs. 4000). The short circuit current carrying capacity is also greater, providing greater protection from meltdown than THHN.

Can XHHW-2 be rated gasoline and oil resistant?



Does XHHW-2 have to meet any flame test requirements?


As a minimum, it would have to pass a horizontal burn test or FT-2 flame test.

Can XHHW-2 be rated for use in cable trays?


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”.

Can XHHW-2 be rated for Sunlight Resistance?


Yes, Black XHHW-2 Conductors sizes 8 AWG and larger are marked “Sunlight Resistant.”

Bare Copper/SE Style U

Why is the base color of both inners of SE Style U colored black?


Both the PVC insulation and the nylon jacket on the inners now have to pass a 300 hour weather meter test, and black best meets the requirement.

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