En-Gauge

Sometimes called simply “vinyl,” Polyvinyl Chloride (PVC) provides cables with the ability to resist oils, acids alkalis, sunlight, heat weathering and abrasion.  This range of properties makes PVC a great outer covering for such wire types as underground feeders (UF), control, street lighting, direct burial wires and aerial.

It’s often used as an impervious jacket in installations that require cables to be highly protected.  Most PVC compounds do not have extremely high- and low-temperatures in the same formulation, and usually range from -20°C to60°C.  Different varieties also have different pliability and electrical properties.

PVC can be found on such copper wire products as Machine Tool Wire (MTW), Appliance Wiring Material (AWM) and TW/THW, among others.

If you work anything like we do around here, you’ve probably gotten into the habit of using all the wire acronyms in the book, but may not have spent a ton of time reflecting on what they mean in a while.

Well, we opened up our old manuals again to refresh our memories, and thought we’d remind everyone else while we were at it.

Wire Insulation Abbreviations

Let’s test it out:

RHW: Rubber insulated, moisture resistant, good up to 75°C

USE-2: Underground Service Entrance wire that can stand wet environments up to 90°C

XHHW: Cross-linked polyethylene insulation, moisture resistant and good up to 90°C in dry environments

Photo credit: Tom Magliery

The insulating materials commonly used to cover copper wire (and other) electrical conductors fall into two broad classes: Thermoplastic and Thermoset.

What’s the difference?

If we take a look at our Fundamentals of Rome Wire and Cable Manual (yes, it’s from a long time ago but yes, it’s still entirely applicable), we have the following descriptions:

Thermoplastic: This material is one that will soften and even melt when exposed to a sufficiently high temperature.  In other words, when the material is originally compounded, it becomes relatively hard yet pliable, much like most plastics we encounter in our daily lives.  However, if it is exposed to high temperature at some future time, it softens and melts. The major reason for selecting a thermoplastic material is because it is the most economical type of insulation.

Some of the commonly used thermoplastic insulations used nowadays:

PVC (Polyvinyl Chloride)

PE (Polyethylene)

ECTFE

PVDF

Nylon

Thermoset: This material, on the other hand, does not soften when exposed to high temperatures.  Once it’s compounded and cured, it becomes “rubbery” and retains its properties even when exposed to high temperatures….Thermoset insulations are usually used where the wire or cable will be exposed to high temperatures.

Some thermoset insulations often used are:

• XLPE
• CPE
• EPR

[UPDATE: We've added a few more pieces of useful information on this topic here]

Photo credit: John