Is THHN/THWN ok for oily environments?

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wireman

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Can I use THHN/THWN wire in an oily environment?
The ratings for THHN/THWN in table 310.10(A) does not mention that it is ok for use in an oily environment, just damp & wet locations. Technically, I guess oil is wet so it must be ok????????

It does indicate in MTW's "trade name" that it is oil-resistant so it is ok to use.

I thought I knew the answer until looking it up in the tables.
 
wireman said:
Can I use THHN/THWN wire in an oily environment?
The ratings for THHN/THWN in table 310.10(A) does not mention that it is ok for use in an oily environment, just damp & wet locations. Technically, I guess oil is wet so it must be ok????????

It does indicate in MTW's "trade name" that it is oil-resistant so it is ok to use.

I thought I knew the answer until looking it up in the tables.
Click to expand...

Wet location rated does not imply oil resistant by design. Gasoline and oil resistance is another product standard, and the product has to be marked with this in addition to a wet location rating.

THWN-2 usually does have gasoline and oil resistance, if the nylon jacket remains intact. It is common that this will tear in most installations, and this is OK if you aren't interested in maintaining the gasoline/oil resistance. If this part of the product rating is important, the nylon jacket must remain intact throughout the length.
 
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Wet means with water in this context.
Oil, gasoline, and other hydrocarbons do not make something "wet", or even "damp".
They can, however, chemically attack many kinds of insulation.

THHN/THWN is not, by its UL listing alone, oil resistant.
But the manufacturer's spec it might be.
 
from southwire brochure

MTW or THHN or THWN-2
Conductors shall be UL-listed Type MTW or THHN or THWN-2* gasoline and oil resistant II,
suitable for operations at 600 volts as specified in the National Electrical Code. Sizes 14
through 1 AWG shall be rated VW-1, larger sizes shall be listed for CT use. Sizes 2 AWG
and larger listed and marked sunlight-resistant in black only. Conductors shall be annealed
copper, insulated with high-heat and moisture resistant PVC, jacketed with abrasion,
moisture, gasoline, and oil resistant nylon or listed equivalent, as manufactured by
Southwire Company or approved equal.
Click to expand...

310.10 (G) Corrosive Conditions. Conductors exposed to oils,
greases, vapors, gases, fumes, liquids, or other substances
having a deleterious effect on the conductor or
insulation shall be of a type suitable for the application.
Click to expand...
Note that the code does not say it has to be listed for exposure to these substances, only that the conductor has to be "suitable for the application".
 
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