Wire/Insulation Identifiers (THHN, THWN, etc.)

[Kidd6488]

Hi, can anyone explain to me, or give me a link that describes the system of identifying the types of wire? I know, like

THHN is the regular solid, 1 conductor wire
NM-B is the 12-2, 14/3... wire we use for inside houses
UM is outdoor wire
I think SEU stands for service entrance underground or somthing...

Thanks,

~Jonathon Reinhart

[LazyPup]

I am sure Hayzee or one of the guys will come forward with more detail but i will attempt to discuss some of the basics.

Technically speaking there is wire or cable.

Wire is a single conductor while a cable is two or more conductors in a common covering.

The wires commonly used in residential applications will be sized by the American Wire Guage Standard -AWG For most wires the AWG number indicates the wire diameter in fractions of an inch, thus a AWG 12 wire is 1/12 of an inch in diameter. Once a conductor size is greater than an inch is is listed as MCM or Mean Circular Mils,

In addition to the size, the insulation is also rated by temperature, resistance to water, oils and fuels, abrasion resistance etc.

When two or more wires are assembled into a cable the labels defines the size of the individual wires, number of wires in the cable, whether or not a ground wire is installed and the type of material or appication of the covering material.

IE awg12/2 wg NM-B is a cable having two awg 12 wires, With ground, and has a NON-metalic covering.

awg12/2wg-UF would be a cable having two awg 12 wires, with ground,but the type UF indicates is is listed for direct burial underground feed.

SE cables are Service Entrance Cables

MI cables are Mineral insulated cables.

The NEC is very specific in regards to what type of wire can or should be used in each application.

[kactuskid]

Here's a link that'll detail all the different types of wires and their uses.

http://www.essexep.com/electrical/handiwire/literature/WC%20Selection%20Chart.pdf

[Kidd6488]

Ok, thanks.

Do THHN, THWN, etc. stand for anything? Someone once started telling me, "triple heat ...." something but they weren't sure.


~Jonathon Reinhart

[kactuskid]

Yes, all the letters stand for something. This link will give you the entire scoop:

http://www.allaboutcircuits.com/vol_1/chpt_12/3.html

[HayZee518]

FEP - Flourinated Ethylene Propylene 90 degrees celsius 194 Fahrenheit
MI - Mineral Insulation - Insulation is magnesium oxide
MTW Moisture resistant thermoplastic 60 C or 140 F
PFA - Perfluoroalkoxy 90 C 194 F
RH - Rubber
RHH hear resistant rubber
RHW hear resistant rubber weatherproof 75 C 167 F
RHW-2 same - only thing changes is the temperature
SA - Silicone (external insulation - glass fiber)
SIS - Thermoset silicone
TBS - Thermoplastic with a fibrous outer braid
TFE - Extended Polytetrafluoroethylene - 250 C - 482 F
THHN - Heat resistance thermoplastic - 90C 194F
THHW Moisture and heat resistance thermoplastic
THW - same as for THHW
THWN - Same as above - change is temperature range
TW - Flame retardant thermoplastic - 60C 140F
UF - Underground feeder and branch circuit 60C 140F
USE or SEU - Underground Service Entrance cable 75C 167F
XHHW - Flame Retartdant thermoset Moisture resistant
XHH - Flame retardant thernoset
Z - modified ethylene-tetra-fluoro-ethylene 90C 194F, 150C 302F
ZW - same as Z but three temp ranges

(12, 14, 10 ga AWG) = American Wire Gauge standard in circular mils

MCM = thousand circular mils
KcMIL same as above

[HayZee518]

RHH etc - made a boo-boo "hear should be HEAT! Sorry

[Kidd6488]

Thanks, now I understand!

~Jonathon Reinhart