En-Gauge

Are you looking for Direct Burial Wire? Take a look at our Tracer Wire or USE-2 for more information.

Direct Burial rated wire is approved to be run in the earth in accordance with the National Electric Code (NEC), usually without the use of conduit to surround it. The combination of the insulation material and its thickness keeps out moisture and other harsh factors to protect the wires inside.

As long as it’s got the right insulation, it’ll be just fine in the ground by itself.

The most commonly referred to types of Direct Burial wire are USE (Underground Service Entrance) – with a thermoset insulation – Tracer Wire and UF, or “Underground Feeder” – both with thermoplastic insulations.  (Note: you might remember some of these terms from our post on wire abbreviations and wire insulation types).

Examples of use for Direct Burial wire use are running electricity to your home (USE-2),  connecting post lights, locating buried pipes with tracer wire, laying the sprinklers along golf courses (next time you’re playing a game, remember there are sometimes 1,000,000’ of wire running underneath you!), and, if you get fancy in the back yard, hooking up your propane grill to a propane tank in the garage!

Usually, Direct Burial wire should be buried at least 18′ underground, but check with the local enforcement officer (usually the electrical inspector) before laying anything down. Oh, and as always, make sure the power is shut off to anything electrical before working with electrical equipment , devices, or wiring!

If you need Direct Burial wire, you can call us or send in a quote on the form to the right!

This month’s (or two month’s) edition of Wiring Harness News had a good article written by Anixter on “Thermoplastic vs Thermoset Wire and Cable Materials.”  Since we highlighted this subject last month, we thought we’d give you some more information.

Firstly, Anixter created a nice reference graph listing general characteristics of the two material types and their implications to users:

“The variety of materials available to modern wire and cable manufacturers is immense.  This results in a wide range of properties within each material type.  The table is a generalized summary that does not apply to every material.  It is important to understand how the properties impact the performance of the product in the intended application.  Generally speaking, within a given material type, the old adage, “You get what you paid for,” still applies.”

Aside from describing the main characteristics of the two materials, which we did in our original post, they offer some thoughts in response to the question of how do I choose a material for my application?

“Knowing that the key difference between a thermoplastic and thermoset is in the way they respond to elevated temperatures can be an important aspect of which material to choose.  For example, thermoset materials are often chosen for circuits that may experience and overload.  This is because thermoset materials have a reduced likelihood of failure if momentarily operated at the higher temperatures that often accompany an overloaded conductor.  Comparatively, thermoplastics are often easier to strip, which makes them easier to process on automated equipment for large volume applications.”

Some great additions, thanks to Anixter.  You can find their full article here (.pdf format)

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

There are many tests used to measure the flame resistance of various copper wire and cable products. Flame Resistance is usually defined as the ability to stop burning once the source of heat is removed.

The following tests are most commonly used in North America.

Vertical Tray Flame Test

UL 1581/IEE 383
This test is performed on cables attached to a 1′ wide, 8′ tall vertical metal ladder tray.  A 10″ ribbon burner with an air/propane mixture applies 70,000 BTUs/hour of combustion for 20 minutes, 24″ from the bottom of the cable.  The cable must self-extinguish before the flame reached the top of the tray.

CSA FT-4
This test is a later version of UL 1581 and is more strict.  To pass, the resulting char can’t be greater than about 4.5″ (1.5m).

IEEE 1202
The newest version of UL 1581, this is essentially identical to CSA FT-4.

UL 1685
This is more or less UL 1581 with an added smoke emission requirement.  If it passes, a wire can be given a “Limited Smoke” listing.

ICEA T-29-520
Yet another version of UL1581, the only difference is that the BTU value is 210,000 instead of 70,000 and the cable spacing increases.

Vertical-Wire Flame Test

UL 1581 VW-1
This was the first flame test developed for studying how flames spread on wire and cable.  The test is performed with a 24′ wire and a Tirrill burner.  Two clamps hold the single sample vertically.  The burner is mounted at a 20° angle and applied for 15 seconds, then reapplied four more times each time the wire stops burning.  If the sample doesn’t burn more than 60 seconds after any of these burning sessions, or if less than 25% of the indicator flag burns, or the cotton batting is ignited during the test, the wire passes.  A “tray rated” cable must pass this test as well.

CSA FT-1
The Canadian version of the VW-1 test.

Are you looking for information on Kris Tech’s status as an American manufacturer? If so, you can visit our website.

Passed last February, the American Recovery and Reinvestment Act of 2009 was full of provisions to preserve and create jobs, invest in infrastructure, as well as energy efficiency and science, offer assistance to the unemployed, and stabilize the State and local economies.

Suppliers, manufacturers, distributors and contractors all have to consider what this means if they’re working on any ARRA-funded project.  As a copper wire manufacturer, we certainly have to think about this, and have gotten plenty of questions from our customers about “Made in America.”

There’s a lot of information out there on the subject, and sometimes it can be difficult to sort through.

The portion of the ARRA that we’re interested in is the Buy American Provision Section 1605.   To start off, it is a combination of two already-existing pieces of legislation: the Buy America Act of 1933 and the Buy American law of 1964.

Buy American Act of 1933

• Applies only to “US government procurements and construction projects” – or when the federal government directly buys products or itself builds public buildings or works that are followed-through on behalf of a public authority, as covered by the Federal Acquisition Regulation (FAR).
• Requires that any manufactured good used in these projects must be assembled in the US with US and foreign material and have more than 51% of their content produced in the US.

Buy America law of 1964

• Applies mostly to Federal Transit Authority (FTA) grants given to states and localities.
• Address the use of manufactured goods and construction materials components (parts and supplies incorporated directly into the final manufactured product or construction material).
• Requires that 100% of the components mest be made in the US for it to qualify. This is much more stringent than the Buy America Act.

Section 1605 of the ARRA – the Buy American Provision – brings aspects of both of these past laws together. It states the no funds given under this Act can be used for a public building or public works project (anything federally funded, as well as all state or locally-funded projects) unless “all iron, steel, and manufactured goods used…are produced in the US.” FAR Subpart 25.6, which implements Section 1605 above, says that “there is no requirement with regard to the origin of components or subcomponents in other manufactured construction material, as long as the manufacture of the construction material occurs in the United States.”

What does all this mean?  Where are the lines drawn?

Foley & Lardner Law Firm gives a good rundown of certain parts we’re concerned about:

“Subpart 25.6 curiously avoids defining precisely what is required for manufactured construction material to be considered “produced” or “manufactured” in the United States. But given Subpart 25.6′s definition of “manufacturing,” by implication construction material will be considered “produced/manufactured” in the United States when it results from processing into a specific form and shape or combining of raw material into a property different from the individual raw materials, and that processing/combining occurs in the United States…..Even more important, Subpart 25.6 specifically provides that there is no component or subcomponent origin requirement for domestic “manufacturing” status. Thus, for purposes of the ARRA, construction material will acquire domestic origin status when manufactured in the United States without regard to the origin of its components.”

Keep in mind, there are stricter guidelines for some projects under the FTA and FHA, as they’ve decided to comply with the existing Buy America law for all ARRA grants, which makes it easier for them to qualify projects. Therefore, they go by the “100% domestic” requirements.

What all of this means to us is that we’ll need to work closely with our suppliers and our customers to make sure the requirements are met appropriately on any ARRA-funded project.

The government keeps information on the ARRA up-to-date if you’re interested.  Or you can read the entire text of the Act

Are you looking for our Tracer Wire? We don’t believe in THHN, so you won’t find it here….

We found this article on an old experiment we did in 1993, but the information still applies.

[This is more or less the original text from 1993!]

Tracer Wire – also known as Locating Wire – is without question underrated and underused. Used primarily by Gas, Water, Fiber Optic, and Sanitation companies, its main use is for locating buried plastic pipes and fiber optics.

Unfortunately, a lot of contractors will mistakenly use THHN for this function, although you’ll see it’s a poor choice for many reasons.

Many times, plastic pipes or fiber optics are buried underground to connect to houses and buildings.  They’re used because of their strong flexibility under adverse conditions such as excess heat or cold, rainstorms, etc.

When one of these is used underground, you’ve got to have a wire that’s durable, flexible, and has strong insulation next to the plastic pipe or fiber optics in case you ever need to locate them (hence the name Locating Wire).  For instance, if there was a gas leak, the gas company needs to dig up the pipe in order to find the exact location of the problem.

Here’s where THHN is problematic. THHN doesn’t have the insulation necessary to hold up over time. Typical underground installations are expected to last up to 30 years. Nylon, the main covering of THHN, is very susceptible to water and moisture, causing additional breakdowns in the wiring under adverse conditions.

This takes a toll on THHN, which starts to wear down and erode, becoming more-or-less useless over the course of several years (fewer years than you’d like). In all likelihood, THHN will often need to be replaced once or even twice over the course of a building project’s life span.

The solution?  Tracer Wire.

With 30 to 45 mils of Polyethylene, Tracer Wire has all the flexibility of THHN, but with far better insulation and protection against underground conditions. Therefore, when the going gets tough on underground installation, Tracer Wire will still be there in the end.

Polyethylene offers a very strong insulation, often double or even triple that of THHN, so it can withstand even the toughest of underground conditions. Just as important, companies will save thousands of dollars and hundreds of valuable labor hours because they won’t have to dig up and replace Tracer/Locating Wire the way they will with THHN.

The only real case for using THHN for direct burial (even

thought it isn’t rated for it) is that it’s inexpensive.  But when you consider future costs to repair and replace it, long-term costs often end up skyrocketing.

In addition, Tracer Wire/Locating Wire is much more affordable than a lot of people think. Even with all the added benefits, Tracer Wire costs only a touch more than THHN, with a huge upside in terms of increased insulation, heat-resistance, and durability.

Tracer Wire saves Fiber Optic, Gas, Water, or Sanitation companies thousands of dollars in the replacement of wire, and also valuable time and energy in the form of labor hours and wasted material. With Tracer Wire’s increased durability over 30+ years in an underground setting, it is by far the better choice long-term for any underground wiring project you might undertake.

Looking for our solar products?  Visit our USE-2 Solar Wire page and our Photovoltaic (PV) Wire page.

Photo Credit: Wayne National Forest

The Underwriters Laboratories (UL) recently put out a brief overview of the solar panel market and the copper wire requirements needed to serve that industry.

We took some time to brush up on the current standards for our own PV wire products, and the distinction between PV wire and USE-2 wire in photovoltaic modules.  We thought you might be interested.

In summary, UL says “PV wire has superior sunlight resistance and low-temperature flexibility in addition to a thicker insulation or jacket and a proven level of flame resistance.”

Overall, only wires or cables highlighted in the National Electric Code (NEC) can be installed in modules that will be sold in the US.

Requirements for North American PV module interconnecting wires

• Single-conductor Type USE-2 cable and photovoltaic (PV) wire are both ok to use in exposed outdoor installations.
• Because these installations are usually found in more extreme environmental conditions, the insulation for these conductors must be sunlight resistant and rated for wet conditions, and must be able to handle temperatures of up to 90°C.

The main differences between PV wire and USE-2 wire

• USAGE
  • PV wire is solely used for interconnecting PV modules, and was developed to be able to handle 90°C in wet conditions and 150°C in dry conditions.
  • USE-2 wire is usually used for connecting terminals of service equipment, and is mostly found underground, and is therefore only rated to handle 90°C in wet or dry conditions.
  • Both can be UL rated at 600V.  However, PV wire can also be rated 1000V or 2000V if needed.
  • Both wires can be used in grounded PV arrays, but only PV wire can be used in ungrounded ones.

• CONSTRUCTION
  • PV wires have thicker insulation for added protection.
  • USE-2 is often used in places that don’t require a high level of movement out of the wire, and can therefore be made out of either stranded or solid conductors.
  • However, since PV wire is used only in solar panels, it needs to be flexible, so is only made from stranded wires.
  • The smallest size available for USE-2 wire is 14 AWG, however PV can get as small as 18 AWG.

• TESTING
  • PV wires must go through a flame test, USE-2 does not (since it isn’t usually installed in places where flames would be found). On the other hand, USE-2 must go through various abuse tests that PV wires aren’t subject to.
  • PV wire must go through more strict sunlight resistant tests.
  • Both of these tests are part of the UL 4703 specification requirements.

You can find out more about the solar market on the first page of the report, “Designing UL Compliant Photovoltaic Wire” (.pdf format).

Are you looking for our Tracer Wire?

Tracer wire, which is also called locating wire or locator wire,  is used to assist in locating pipes and other lines after they’ve been buried in the ground.

Once a pipe is laid down, tracer wire is placed along it’s length and buried next to the pipe.  This wire is what’s actually searched for if the pipe itself needs to be located (hence the name).  A Wire Tracer – an above-ground device with the ability to locate non-energized wire – is used so there’s no need to send electricity through a tracer wire in order for it to be detected.

After the wire is found, crews can start a much more accurate dig to reach the pipeline for maintenance, repairs or replacement, and site destruction is greatly reduced.

Used most commonly in the utilities industries (water, gas, sewer, fiber optics, etc), tracer wire can also be used in directional drilling applications, as well as irrigation systems and golf course sprinkler systems (Little Known Fact: Kris Tech Wire got it’s start by selling tracer wire to the golf course developers!).

You may be interested in more information on how tracer wire is installed or what types of tracer wire are the best to use in certain situations.