When to Use Conduit & Fittings vs. a Liquid-Tight Cordgrip
März 19, 2019
Nowadays, the options seem endless when selecting a liquid-tight wire management solution for your application. With so many options, it’s easy to understand why someone might feel overwhelmed when selecting the right liquid-tight wire management device. Heyco hopes to eliminate that overwhelming feeling by answering a few common questions about liquid-tight conduit & fittings as well as liquid-tight cordgrips. By the way — the term cable gland is used interchangeably with cordgrip.
Conduit & Fittings
A common misconception made about liquid-tight conduit and fittings is that it provides strain relief on the cable. While liquid-tight conduit does provide some relief, it actually provides more of a protective barrier between the cable and whatever environment in which it may be installed. (Kind of like your jacket protecting you from rain or snow.) But you might ask how this differs from a liquid-tight cordgrip?
A liquid-tight cordgrip is different from liquid-tight conduit and fittings in that they provide strain relief directly to the cable. The industry standard established by UL is 35 pounds of pull force. That means 35 pounds of horizontal pull can be applied to the cable before the cable begins to pull out of the cordgrip or application.
In applications where movement, vibration and strain on a cable are expected, a liquid-tight cordgrip may be a better option.
Conduit & Fittings
Liquid-tight conduits are perfect for use in environments that are likely to get moist or wet. Used in conjunction with liquid-tight fittings, conduit can keep moisture at bay. If the application requires the use of liquid-tight fittings with conduits, make sure that the fittings are threaded onto the connection or, alternatively, use a junction box. This type of conduit can also be used in applications where the wires or cables may be exposed to corrosive elements. One example of such an application is using conduit for condensers of air conditioning units.
If installing wires or cables in outdoor applications, use a metal version of liquid-tight conduit with PVC outer sheathing as well as stabilizers that provide added protection against the elements, including the sun’s ultraviolet rays. This type of conduit is also suitable for applications that require bending or where vibration is expected.
Conduit with an inner core of electro-galvanized steel offers substantial resistance to both bending and vibration. The conduit’s core also features a plasticized PVC coating which provides oil resistance as well as optimal performance in high temperature applications.
Liquid-tight conduits can also offer ample protection against dust and some types of liquids. On top of that, these conduits have a high amount of mechanical strength, making them the preferred option when making a secure connection is essential.
Use these conduits if your application requires burying cables beneath the ground. Liquid-tight conduits can provide adequate protection against moisture as well as crushing, even when buried underground. However, it is crucial to note that the conduit you should choose to use must have a diameter not exceeding an inch. Why? Conduits with a larger diameter are not suitable for concrete encasement.
Finally, these conduits may be used for low heat applications – dry heat temperature not exceeding 80°C and damp heat not exceeding 60°C.
A nylon cordgrip may also bear the highest IP rating ― as high as IP68. What is IP rating? IP rating is Ingress Protection and defines the levels of sealing effectiveness of electrical enclosures against invasion from foreign bodies, such as dirt and moisture.
|Protection against solid objects
||Protection against liquids|
|1||Protected against solid objects over 50mm (e.g. accidental touch by hands)
||Protected against vertically falling drop of water
|2||Protected against solid objects over 12mm (e.g. fingers)
||2||Protected against direct sprays up to 15° from the vertical
|3||Protected against solid objects over 2.5mm (e.g. tools & wires)
||3||Protected against direct sprays up to 60° from vertical
|4||Protected against solid objects over 1mm (e.g. tools, wires & small wires)
||4||Protected against sprays from all directions – limited ingress permitted|
|5||Protected against dust – limited ingress (no harmful deposit)
||5||Protected against low pressure jets if water from all directions – limited ingress permitted|
|6||Totally protected against dust||6||Protected against strong jets of water (e.g. for use on ship decks – limited ingress permitted)
|7||Protected against the effects of temporary immersion between 15cm and 1m. Duration of text 30 minutes
Each number attached to the IP rating indicates the degree of protection; the first number, i.e., the number “6” in IP68, means intrusion protection. The number “0” means no special protection, number “3” means protection from entry by tools with a diameter of 2.5mm or more, and the number “6” means it is completely dust tight. The second number, i.e., the “8” in IP68, indicates the level of protection from different types of moisture. The number “1” means protection against condensation, number “5” means protection against low pressure water jets, and the number “8” means that it is protected against prolonged effects of immersion, under pressure. Another great benefit to using a nylon cable gland is that it may have a flammability rating of UL94 V0, which is the standard for safety of flammability and, in the event of burning, will stop within 10 seconds, on a vertical specimen. Many of Heyco’s cordgrips also have a NEMA rating, so if your application requires a NEMA rating, we offer cordgrips that are NEMA 3R, 4, and 4X.
Conduit & Fittings
Heyco offers a variety of conduits depending on the application. They are all constructed out of different materials to satisfy a variety of application requirements. The most common conduit is typically made either out of PVC or made with PVC, but lined with a zinc galvanized steel core to provide even more protection. The fittings used in conjunction with conduit are made out of a variety of materials including: die cast zinc, nickel plated brass, and nylon. Depending on the environment and ruggedness of the application. Some installations require a nickel-plated brass fitting to avoid corrosion or discoloring, whereas other applications can use either a zinc die cast fitting or nylon fitting.
Heyco’s line of liquid-tight cordgrips is quite extensive, as we offer a variety of materials and styles. Our most common/popular cordgrips are made out of a nylon 6/6 material and the sealing gland is typically made out of a Buna N or TPE material. For harsher environments, we offer 303 stainless steel cordgrips to better withstand the elements, as well as zinc-plated steel, zinc die-cast, aluminum and nickel-plated brass.
Conduit & Fittings
Over the years, as applications have become more sophisticated, so have the components that are used in them. Having said that, Heyco offers a variety of fittings to accommodate a variety of application requirements. The most common fittings feature threads (either NPT, PG, or metric) that engage with threads on the enclosure/application to ensure a liquid-tight seal. These fittings can also be installed on an enclosure/application without threads with the help of a locknut.
This locknut (usually stamped steel but sometimes nylon), is installed on the back-end of the fitting (inside the enclosure/application), and tightened to ensure a liquid-tight seal. Heyco also offers fittings that simply “snap” into the hole without any threads. These snap-in fittings have a limited panel thickness and hole diameter range they can work in, but are a lot easier to install than a threaded fitting. Depending on the application, you may require a fitting that allows for conduit to come straight out from the equipment (a straight-thru fitting), or other applications may require the conduit to be positioned 90 degrees from the enclosure (90° Sweep fittings).
Similar to the conduit fittings, Heyco’s most popular liquid-tight cordgrips also feature threads (either NPT, PG, or metric) that engage with threads on the enclosure/application to ensure a liquid-tight seal. These cordgrips can also be installed on an enclosure/application without threads with the help of a locknut. Like the locknuts for fittings, locknuts for cordgrips are usually stamped steel or nylon, depending on the application. The locknut is installed on the back-end of the cordgrip (inside the enclosure/application), and tightened to ensure a liquid-tight seal. Heyco also offers cordgrips that feature a similar “snap-in” style as the fittings. Similar to the snap-in fittings, snap-in cordgrips have a limited panel thickness and hole diameter range they’ll work in, but are much easier to install than a cordgrip with threads and a locknut. Heyco’s liquid-tight cordgrips are also available in a straight-thru style where the cable comes straight out of the equipment, or for applications requiring a quick turn out of the equipment, a 90° cordgrip may be the preferred solution.