BELOW GROUND Conduit System for Electrical

A complete line of FRE® Below Ground fiberglass conduit products designed for either Encased Buried (EB) or Direct Buried (DB) applications. UL2420/CSA C22.2 No.2420

FRE Composites manufactures a complete line of Below Ground Fiberglass Conduit products designed for either Direct Burial (DB) or Encased Burial (EB) applications as described in the National Electrical Code (NEC) and Canadian Electrical Code (CEC). UL Listed and CSA Certified, FRE® Below Ground Conduit system products are used the world over by power and telecommunications utilities as well as commercial and industrial markets as an economical and longlasting alternative to PVC, HDPE and other types of rigid conduit.


  • Superior impact and crush resistance
  • Rot and rodent proof
  • Non-conductive, assuring a safe system
  • Highest strength to weight ratio of any conduit
  • Lightweight: A 19.68 ft. (6 m) section of 4" (102 mm) conduit weighs approx. 15 lbs. (7 kg.)
  • TriSeal eliminates the need for adhesive, saving time and cost on field assembly


  • Suitable for Direct Burial (DB) and/or Encased Burial (EB) applications
  • Available in 3/4’’ (19 mm) through 8’’ (203 mm) diameters
  • Complete line of fittings and adaptors
  • Quick push-fit assembly (TriSeal one piece injection moulded urethane gasket)
  • UL2420/CSA C22.2 No.2420


  • TriSeal joint is watertight up to 50 Psi
  • Conduit contains no chlorine, halogen or other toxic materials
  • Temperature range from -40°F to +230°F (-40°C to +110°C)
  • High temperature rating results in no cable fusion
  • Low coefficient of friction. Smooth inner wall results in longer cable pulls without burn through and fewer manholes
  • Chemical Inertness. Impervious to a wide spectrum of chemicals and fuels



Underground installations

Work Practice

Work practice for underground installations


For underground installations


Safety Data Sheet


What is FRE®? ?
Owned by FRE Composites, FRE® is a registered trademark both in Canada and the United States since 1970 for Reinforced Thermosetting Resin Conduit. .
What US and Canadian standards apply to FRE® Below Ground products?
Underwriters Laboratories’ and the Canadian Standards Association’s binationally harmonized Standard for Reinforced Thermosetting Resin Conduit (RTRC) and Fittings, UL 2420 / CSA C22.2 No.2420 provides the requirements for both Encased Burial (EB) and Direct Burial (DB) below ground products.
What is NEMA TC-14?
NEMA TC-14 is an industry standard published by the National Electrical Manufacturers Association (NEMA).
What is the difference between the UL 2420 / CSA C22.2 No. 2420 standard and the NEMA TC-14 standard?
None. Since October 18th, 2002, NEMA adopted the latest version of the RTRC harmonized standard between CSA & UL.
What are the differences between the Below Ground Encased Burial (EB) and Direct Burial (DB) products?
The only difference is the thinner wall thickness for EB products compared to DB products, which affects certain mechanical properties such as compression. However, all other product characteristics are identical.
How far should the spigot (male) end be inserted into the bell (female) end to make a good connection?
For conduit employing the TriSeal joining system: 5” (129 mm). For conduit employing an inside tapered bell without TriSeal: 4” (103 mm).
Is the TriSeal joint watertight?
Yes. Our proprietary design, one-piece molded urethane TriSeal ensures, when installed per manufacturer’s instructions, a watertight joint as defined by the National Electrical Code (NEC) and Canadian Electrical Code (CEC).
Will FRE® Below Ground conduit permit a cable to fuse to the conduit wall due to fault currents?
No. Since RTRC is a Rigid Nonmetallic Conduit (RNC), it is impossible for a cable to fuse to the conduit due to fault currents. Additionally, epoxy resins can sustain high temperature exposures and, unlike PVC, will not melt under fault conditions or weld to the side wall of steel.
Are all FRE® Below Ground products available in 10 foot lengths?
The standard length for all our 2” (53 mm) and larger trade sizes in both IPS and ID dimensions is 19.68 feet (6 meters). However, to accommodate specific project requirements, all such products are also available in 9.84 foot (3 meter) lengths.
Can FRE® Below Ground conduit be bent in the field?
In the U.S. FRE® Below Ground conduit can be bent in the field for larger radius elbows using standard RNC bending equipment and carefully following our manufacturer’s instructions, in accordance with 355.24 of the National Electrical Code (NEC). This installation advantage is made possible because of our 68 % ± 3 % glass to resin content. RTRC products with a higher glass content will severely restrict this capability.
Is Thin Wall (TW) conduit acceptable for a Direct Burial (DB) application?
No. Thin Wall conduit does not offer sufficient compression strength to withstand typical Direct Burial (DB) loads without the possibility of ovalizing beyond acceptable levels. This could severely impair cable pulling operations.
Are there any operations needed to be performed prior to making an adhesive joint between the bell and spigot?
A light sanding of both the inside of the bell and the outside of the spigot is necessary to increase the adherence of the adhesive. (See manufacturer’s adhesive instructions.)
Should you remove the TriSeal when using an adhesive for assembling the conduit?
It is recommended that the TriSeal joint system not be used with adhesive.
Can you install an expansion joint in a Direct Burial (DB) or Encased Burial (EB) application?
In normal circumstances, expansion fittings are not needed for Encased Burial (EB) installations since the movement of the conduit will coincide with the expansion and contraction of the concrete. The only location where an expansion fitting should be utilized is where the concrete itself has an expansion fitting. In Direct Burial (DB) situations, expansion fittings are not needed because the ground has relatively constant temperatures. However in cold areas, conduit must be installed below the frost line to prevent damage during freezing and thawing cycles.
What should you use to make joints go together when you try to mate a spigot (male) end and a bell (female) end and it is too tight to fit?
The use of a little water based pulling lube or soapy water on the spigot end will ease the drive of the spigot into the bell.
What is the pullout strength of FRE® Below Ground conduit with the TriSeal?
The minimum pullout strength of our TriSeal joint design is 500 lb. (227 kg) for all trade sizes.
What is the pullout strength of adhesively bonded FRE® Below Ground conduit?
The minimum pullout strength of an adhesively bonded joint is 1000 lb. per inch trade size (e.g. 4” trade size = 4 x 1000 lb. = 4000 lb.) or 454 kg per mm trade size.
Should you use a radius bell end fitting when you pull cable?
The use of a radius bell end fitting is highly recommended to prevent damage to the cable during pulling operations.
Can you use FRE® Below Ground products in a Class 1 Division 2 area?
In the U.S., FRE® Below Ground products can be used in a Class 1, Division 2 location if they are encased in a minimum of 2” (51 mm) of concrete and provided with not less than 24” (610 mm) of cover, in accordance with 501.10(B) of the National Electrical Code (NEC). However, in Canada, the Canadian Electrical Code does not permit any type of Rigid Nonmetallic Conduit (RNC) to be used in these locations.
What is the intended use of an FRE® sleeve?
An FRE® sleeve is intended to allow conduit to pass easily through pillars, concrete abutments, walls, etc. or to repair a damaged conduit section. It is not intended for joining lengths of conduit.
When you order a Thin Wall (TW) conduit, do you get Thin Wall fittings and accessories?
No, it is not always possible to reduce fittings to Thin Wall (TW) dimensions.
What is the temperature rating for the FRE® Below Ground products?
It is UL Listed and Certified for a temperature range of -40 °F to 230 °F (-40 °C to 110 °C). However, epoxies are known to perform well in high temperatures (up to 275 °F or 135 °C).
Is FRE® recognized by the National Electrical Code (NEC®) and the Canadian Electrical Code (CEC®) as an approved conduit?
Yes, FRE® is a Rigid Nonmetallic Conduit (RNC) that is covered by Article 355 of the NEC and as a Rigid RTRC Conduit that is covered by Rules 12-1200 – 12-1220 of the CEC.
Are all available ID and IPS Heavy Wall (HW) trade sizes UL Listed and CSA Certified?
No, in accordance with UL 2420 / CSA C22.2 No. 2420, only 4” (103 mm) Heavy Wall (HW) conduit and fittings are currently eligible for Listing and Certification in ID trade sizes.
How does the flexural strength of the FRE® Below Ground product compare with that of PVC?
FRE® Below Ground products offer twice the strength to weight ratio of PVC. The higher flexural strength allows FRE® to be used at the maximum spacing distance between supports permitted by the National Electrical Code (NEC) and the Canadian Electrical Code (CEC).
Can other manufacturers produce FRE® products?
No. FRE® is a registered trademark owned by FRE Composites and therefore no other manufacturer can make FRE® products.