Raceway systems such as EMT and rigid conduit are permitted by most codes to be embedded in concrete. The solid exterior of these conduits eliminates the possibility of concrete entrance, however, the termination with the connector or coupling can be susceptible to concrete entering the raceway.
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The UL 514B testing procedure requires the connector or coupling to be assembled to the conduit inside a special concrete form. Then Portland-type concrete is poured into the form and over test samples. Then the concrete slurry is vibrated to remove any trapped air, and allowed to cure. After concrete curing, the fittings are chipped out of the concrete and examined for concrete penetration.
Although compression style connectors and couplings pass these tests in all trade sizes because of the gland ring design, the set screw types may have difficulty conforming to UL or CSA concrete penetration requirements. When the set screw is tightened onto the conduit, the fitting and/or conduit material will “yield”, or stretch, enough to create an opening at the conduit/ fitting connection.
Set screw fittings in the smaller (1/2″, 3/4″, and 1″) trade sizes are less likely to stretch to the point that would permit entrance of concrete. However, 1-1/4″ and larger size fittings will yield enough so that concrete can enter the raceway. UL and CSA will accept product carton marking that specify “Concrete-Tight When Taped” on fittings that cannot pass testing, since the tape prevents entrance of concrete into the raceway. The taped joint must completely encircle the conduit/ fitting connection. We recommend using duct tape or similar type of durable tape.
Even the most experienced electricians and project managers need tips every now and again. We get questions all the time at our counters and via email about what types of conduit fittings will work in various situations.
Buying the right electrical conduit fittings for your project is as important as getting the right conduit itself. Fittings don’t just join lengths of conduit together. They also connect conduits to walls, boxes, and other enclosures. Depending upon which conduit you’re planning on using, the type of fitting can make or break the success of the installation.
Not Sure Where to Start? Start with the Application
The first step (and this is likely already a part of your project plan or permit pack) is to define the application for the conduit.
What regulatory aspects need to be met, for example, in order for your project to pass inspection and satisfy national and local safety regulations? Not only does the material need to meet NEC standards, but it also should be safe for the building itself.
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Conduit fittings are available in a variety of materials, including die-cast zinc, nickel-plated brass, nylon, and galvanized steel. The NEC’s standards don’t always specify which material you should use, but before you make your final budget (and your first order), always consider whether or not the material needs to be:
- Watertight or waterproof
- Corrosion resistant or resistant to harsh chemicals for petro/industrial/food applications
- Utilized for HVAC and/or ventilation systems
- Impact-resistant for industrial applications or motorized equipment
- Explosionproof or hazardous locations
Insulated fittings further ensure that internal wires don’t suffer any damage due to friction or wear alone. If and when you’re unsure, contact an experienced dealer for answers to your specific questions about materials, quantities, and more.
What Are the Common Types of Conduit Fittings?
This is by no means an exhaustive list (for that, you can consult our catalog), but the most common conduit types (and their applications) include:
- Metallic and nonmetallic couplers: Used to join lengths of non-flexible conduit.
- Connectors: Attach conduit to enclosures like electrical boxes. Many are designed to be snapped into an opening without a locknut for faster installation. Use metallic connectors for metal conduit, and PVC connectors for PVC conduit.
- Conduit bodies: Provide a service entrance to the interior of a raceway for inspection and maintenance. They can also be used to enable more bends in one section of conduit.
- Locknuts and insulating bushings: Used when attaching conduit to a box or enclosure.
- Reducing washers: Installed with a locknut to reduce the size of the knockout or opening to fit the size of a smaller length of conduit.
- Straps/hangers: Secure wire and conduit to walls, ceilings, etc. to prevent conduit and wires from sagging or buckling from their own weight.
- Nipples: Threaded lengths of conduit that make it easier to join pieces of equipment together.
- Elbow: Provides a needed angle or direction change in a conduit run. Available for both metallic and non-metallic conduit in either 22-,30-, 45- or 90-degree bends.
- Raintight hubs: Necessary for most outdoor applications, they have both internal and external threads to make connections that prevent moisture from seeping into the enclosure.
Most Popular Conduit Materials
Here’s a quick hit-list of the most popular conduit varieties that should satisfy most electrical applications:
- Electrical metallic (EMT)
- Galvanized rigid (GRC)
- Intermediate metal (IMC)
- PVC
- Liquid-tight non-metallic (NMLT)
- Liquid-tight metallic (UA)
Most conduit is available in custom lengths and is bent to spec on site by a professional. Have questions about conduit cutting and bending equipment, too? Let us know and we’ll connect you with an expert.
As Always: Stay Safe!
Since we are talking about electrical components and equipment, here’s a quick reminder that HOLT takes everyone’s safety very, very seriously. We deal mostly with trade professionals, but it bears repeating that failing to follow the right precautions when you’re working with electrical components can cause both injury and death.
Always follow the manufacturer’s instructions and wear all appropriate safety gear (a HOLT expert can tell you what you need there, too). If you’re trying DIY projects yourself, always verify what permits your municipality requires, and follow all codes for both commercial and residential safety.
HOLT is Your Electrical Supply Partner
We don’t build. That’s your job. We make sure that we have everything the electrical tradesperson needs to get that job done. The team at HOLT is always figuring out new ways to make your work go smoothly, especially when it comes to your budgets and timelines. Whether you need a site pod, last-minute delivery, or some friendly advice, contact us today and let us know what you need.
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