General
What does the PPI Power & Communications Division do?
PPI is the major North American manufacturers’ trade association of advocacy and education for plastics use in pipe, conduit and infrastructure solutions. The mission of the Plastics Pipe Institute is to advance the acceptance and use of plastic pipe systems through research, education, technical expertise and advocacy. PPI has divisions representing the different end use applications for pipe and conduit. The Power & Communications Division (PCD) mission is to expand knowledge of the uses and benefits of HDPE conduit for Power and Communications applications.
Where can I find terminology specific to duct and conduit?
PPI Handbook of PE Pipe - Chapter 14 on Duct & Conduit has a useful glossary: link
What is the voltage of mainline power distribution and can HDPE conduit handle that voltage?
HDPE conduits up to 8 inches in diameter have had solid dielectric, high voltage cables, rated at 345kV installed inside them. Further, conduit through 6 inches is commonly used to protect underground distribution cables having voltage ratings from 600V to 35kV. Cable voltage ratings have not been a deterrent for utilities choosing to use conduit made from HDPE for underground power cables.
Is all plastic pipe that is orange conduit?
No. While modern gas pipe is yellow, when excavating piping infrastructure workers should be aware that certain older plastic gas pipe material was colored orange or tan. The predominant color for conduit today is orange but many other colors do exist. See FAQ question What colors are available? The American Gas Association has published a historical list of plastic gas pipe manufacturers which includes colors where pertinent. Contact the local gas company for further information. See also:
- PPI Statement V - Recommended Color Code for Solid Wall Plastic Pipe and Conduit - link
- American Gas Association Plastic Manufacturers Chart - link
Conduit Sizing
What size conduit do I need?
The size of the conduit you will need will depend on the type of cables to be installed, the method of cable installation, and method of conduit installation.
For further discussion on the sizing of conduit based on cable fill and cable installation method, see:
- PE Handbook of PE Pipe – Chapter 14 on Duct and Conduit – Section 8.1 - link
For further discussion on sizing of conduit based on conduit installation method, see:
- TN-63 Safe Pull Strength Calculations for Conduit– link
- TN-48 Guidelines for Choosing Wall Thickness for HDPE Conduit Based on "Mini-HDD" (Horizontal Directional Drilling) – link
- PPI Conduit Design Calculator for mini-HDD applications – www.conduitcalc.com
- PPI eLearn™ Conduit Design Calculator – Short Course – link
- See external article Electrical Cable Basics and Selection (Water Well Journal, 10-19-23) - link
Why are there many sizing systems for conduit?
There are a number of different sizing systems for conduit. These define the outside or inside diameter, wall thicknesses and tolerances. These include outside and inside diameter controlled sizes where the outside diameter, or inside diameter in the case of inside diameter controlled sizes, is fixed for a given size, and the wall thickness varies depending on the needs of the installation. Common sizes are IPS, SIDR, True Size, Schedule, EPEC and SDR. Selecting the right size of conduit is important so to ensure that the conduit is properly sized for the cable(s) to be installed and sufficiently robust for the installation and long term performance in the application. The PPI Power & Communications Division is working to harmonize the sizes across the ranges of standards. A more complete discussion of sizing systems is available within:
- PE Handbook of PE Pipe – Chapter 14 on Duct and Conduit – Section 8.2 - link
What do SDR and SIDR stand for?
SDR and SIDR values are indicators of wall thickness. SDR is the Standard Dimension Ratio, sometimes also referred to simply as DR (Dimension Ratio). Technically, it is the nominal outside diameter divided by the minimum wall thickness per specification. Similarly, SIDR is the ratio of the inside diameter of the conduit to the wall thickness of the conduit. The larger the SDR or SIDR, the thinner the wall thickness. The smaller the SDR or SIDR number the thicker the wall of the conduit.
Smaller SDR or SIDR numbers also mean that the conduit has higher tensile strength and greater resistance to deflection than a comparable product with a higher number. The combination of the outside diameter (OD) or inside diameter (ID) with the SDR or SIDR will define the ID of the conduit and the available space for the cables. See tables within conduit standards for available sizes and specific dimensions. A more complete discussion of sizing systems is available within:
- PE Handbook of PE Pipe – Chapter 14 on Duct and Conduit – Section 8.2 - link
Need help sizing the wall thickness for conduit in mini-HDD installations?
The Conduit Design Calculator is a software tool that aids in determining the most appropriate wall thickness of high-density polyethylene (HDPE) conduit installed via horizontal directional drilling (HDD) techniques.
- TN-48 Guidelines for Choosing Wall Thickness for HDPE Conduit Based on "Mini-HDD" (Horizontal Directional Drilling) – link
- PPI Conduit Design Calculator for mini-HDD applications – www.conduitcalc.com
- PPI eLearn™ Conduit Design Calculator – Short Course – link
How many power cables can be placed into a conduit?
It depends on the size and quantity of the cable. The NEC (National Electric Code) has guidelines on the number of conductors allowed in a HDPE Conduit. With one conductor, it can "fill" 53% of the inside diameter of the conduit. For 2 wires 31% and over 2 wires 40% fill ratio is allowed. Simply multiply the area of the conductors by the quantity and compare to the inside area of the conduit. For further discussion on the sizing of conduit based on cable fill and cable installation method, see:
- PE Handbook of PE Pipe – Chapter 14 on Duct and Conduit – Section 8.1 - link
- See external article Electrical Cable Basics and Selection (Water Well Journal, 10-19-23) - link
- PPI Statement AC - Operating 90 °C and 105 °C Rated Cables with HDPE Conduit - link
What is the maximum number of HDPE conduit innerducts in a casing?
This is highly dependent on the installation. The straighter and shorter the run, the more you can fill the casing. The longer and more complex the casing installation is, the less fill is applicable. Generally, the recommended percentage fills for all combined innerducts being considered, based on areas, is:
- 70% - max value recommended
- 50% - short straight runs
- 30% - longer and more complex runs
- Adjust values as needed per experience
Conduit Storage
How long can conduit be stored outdoors?
Black is recommended for any application where the conduit is exposed or stored over a long time period to sunlight (Carbon Black additive provides UV protection). Colors, even those with UV Stabilizers (other than black) cannot tolerate sunlight for extended periods of time without deterioration. ASTM F2160 specifies the stabilizers in colored conduit should protect it in outside storage for a minimum of one year. Contact the manufacturer for recommendations for storage. For more information, see:
- PE Handbook of PE Pipe – Chapter 14 on Duct and Conduit – Section 7.2 - link
- TR-18 Weatherability of Thermoplastic Piping Systems – link
Can conduit stored outdoors for more than one year still be used?
In some cases, yes, depending on storage conditions and location. Conduit can be recertified to meet the required standards for use in some situations. Please contact your manufacturer to see if they offer this service for the product you have a question about.
Conduit Installation
How do I avoid overstretching the conduit during installation?
HDPE conduit can be over-stressed during laying or pulling resulting in undesirable necking that may result in internal restriction that will later impede cable or innerduct pulling or blowing. For this reason, it is important to avoid over stressing the product during installation. The Safe Pull Strength is dependent on conduit dimensions, conduit temperature and conduit material. It is recommended to always use a breakaway link swivel, or similar, sized based on the Safe Pull Strength of the conduit being installed. PPI provides several references:
- PE Handbook of PE Pipe – Chapter 14 on Duct and Conduit – Section 9 - link – provides additional information on installation
- TN-63 Safe Pull Strength Calculations for Conduit – link
- TN-48 Guidelines for Choosing Wall Thickness for HDPE Conduit Based on "Mini-HDD" (Horizontal Directional Drilling) – link
- PPI Conduit Design Calculator for mini-HDD applications – www.conduitcalc.com
- PPI eLearn™ Conduit Design Calculator – Short Course – link
What do I do about HDPE Conduit Memory, Ovality and Coil-set?
Due to its flexible nature, HDPE conduit can become oval or out-of-round when it is wound onto reels or coils. Ovality is a packaging condition that occurs when conduit is coiled, whereby conduit flattens out as it is coiled. This is allowed and limits are specified in industry standards. Coil-Set is an inherent tendency for conduit to conform over time to the curved shape or bend radius of the coil or reel on which it has been stored. Both of these are sometimes termed “memory” as the conduit wants to hold its packaged shape; the conduit will have a memory from winding on the reel because the molecules align themselves during the manufacturing process of reeling, or "bending" the conduit. You can envision, one side of the conduit will be in tension, while the opposite is in compression. The molecules align themselves, relax and "remember" their position. Once uncoiled, they start to relax into the new positions. The rate of relaxation is temperature dependent, with relaxation occurring faster at higher temperatures.
For more information on ovality and coil-set, causes and methods for mitigations, see:
- TN-61 Coilable HDPE Conduit Ovality and Coil-Set – link
- TN-58 HDPE Conduit and Duct Handling Guide – link
For additional information on working safely with conduit, please see:
- PE Handbook of PE Pipe – Chapter 14 on Duct and Conduit – Section 9.1.3.3 - link – provides additional explanation regarding “coil memory”
- TN-63 Safe Pull Strength Calculations for Conduit– link
- TN-58 HDPE Conduit and Duct Handling Guide – link
What is the temperature range over which HDPE conduit can be installed?
HDPE conduit can be installed in ambient temperature ranging between -30 °F to 180 °F (-34 °C to 82 °C). At low temperature, care should be made in handling to avoid dropping the conduit. At high temperature, and particularly in conjunction with solar heating, HDPE conduit will have reduced Safe Pull Strength. Expansion/contraction of the conduit as a result of temperature changes should be considered in the design phase for above ground applications and, below ground, conduit should be allowed to stabilize with the ground prior to trimming and completing connections.
For additional information on thermal expansion/contraction, please see:
What is the impact of temperature on conduit length (thermal expansion/contraction)?
HDPE conduit has a high degree of thermal expansion/contraction, approximately 10 times that of metal pipe, with a coefficient of thermal expansion of 1 x 10-4 in/in/°F. As a “rule of thumb,” temperature change for unrestrained HDPE conduit is about “1/10/100,” that is, 1 inch for each 10 °F temperature change for each 100-foot of conduit. A temperature rise results in a length increase while a temperature drop results in a length decrease.
In aerial conduit applications due to the potential for significant temperature variations resulting from ambient fluctuations and solar heating, the effects of thermal expansion/contraction of the conduit must be carefully considered in the design process. In buried applications, temperature variations are significantly moderated in service; however, during installation, sufficient extra conduit should be laid to allow for thermal contraction that may occur once installed.
For additional information on thermal expansion/contraction, please see:
- PE Handbook of PE Pipe – Chapter 14 on Duct and Conduit – Section 11 - link
- PE Handbook of PE Pipe – Chapter 6 on Design of PE Piping Systems - link
- PE Handbook of PE Pipe – Chapter 8 on Above Ground Applications for PE Pipe - link
- PE Handbook of PE Pipe – Chapter 12 on Horizontal Directional Drilling - link
- TN-63 Safe Pull Strength Calculations for Conduit– Section 4.3 -link
Product Offering
What colors are available?
The National Public Works Association recommends
- Orange for Telecommunication conduit in the underground (see note below)
- Red or Black with three Red stripes are typical for power applications
- Black is recommended for any application where the conduit is exposed or stored over a long time period to sunlight (Carbon Black additive provides UV protection).
- PPI strongly recommends that Yellow NOT be used because this color is reserved for gas distribution piping
Colors, even those with UV Stabilizers (other than black) cannot tolerate sunlight for extended periods of time without deterioration. ASTM F2160 specifies the stabilizers in colored conduit should protect it in outside storage for one year. For more information, see:
- PE Handbook of PE Pipe – Chapter 14 on Duct and Conduit – Section 6.2 - link
- PPI Statement V - Recommended Color Code for Solid Wall Plastic Pipe and Conduit – link
Note: While modern gas pipe is yellow, when excavating existing piping infrastructure workers should be aware that certain older plastic gas pipe material was colored orange or tan. The American Gas Association has published a historical list of plastic gas pipe manufacturers which includes pipe colors where pertinent. Contact the local gas company for further information. See:
- American Gas Association Plastics Manufacturers Chart - link
Can conduit be ordered with more than one conduit and/or color per reel?
Yes. Most manufacturers provide special packaging called paralleling or segmenting. Conduit that is parallel packaged can have two or three different colors per reel. For more information, see:
- PE Handbook of PE Pipe – Chapter 14 on Duct and Conduit – Section 6.3 - link
- TN-50 Guide to Specifying Conduit – link
- MS-5 Model Specification for HDPE Solid Wall – link
What is the longest length that can be put on a reel?
That depends on the Outside Diameter of the conduit. The larger the conduit the less material will fit on a reel. See the PPI manufacturer's web sites for their standard reel configurations. For safety information related to handling of reels, see:
- TN-58 HDPE Conduit and Duct Handling Guide – link
Can the conduit be supplied in coils without a reel?
Yes. This type of packaging is usually for quantities of less than 1,000 feet per coil. Coils are generally secured at multiple points to keep them together and palletized for shipping. For safety information related to handling of coils, see:
- TN-58 HDPE Conduit and Duct Handling Guide – link
Can a pull tape be installed in the conduit at the factory?
Yes. Most manufacturers can install a wide range of pull tapes, from inexpensive polypropylene rope (PP Rope) to expensive Kevlar pull tapes that are pre-lubricated, measured and marked. The conduit is extruded over the pull line. The extruder has an opening in the back side of the extrusion die that forms the HDPE tube. The pull line is inserted into this opening at the same rate as the HDPE tube is extruded providing a continuous pull line inside the conduit. Depending on your project the manufacturer can suggest the pull line that is best for your application. See also:
- Specification Flow Chart of PPI TN-50 Guide to Specifying HDPE Conduit – link - for the various pull tapes available.
- MS-5 Model Specification for HDPE Solid Wall – link
Can cable be installed in the conduit at the factory?
Yes. This is called Cable in Conduit (CIC). Many types of cable, power or communications, can be installed in the conduit. ASTM D3485 and UL 1990 are the specifications for CIC for power applications. The requirements for the conduit used in these products are essentially the same as regular conduit.
What advantage does ribbed or lubricated conduit have?
Ribbed or lubricated conduit reduces the friction between cable and conduit to facilitate cable installation. The friction between the cable outer jacket and the conduit inner surface can be a limiting factor for the distance of cable installed. Friction can lead to excess heat that can damage conduit, cable or both. Reducing this friction can significantly increase the achievable cable install distance. Longitudinal ribs reduce the surface area reducing friction (note that these are still basically a smoothwall product). Lubricants are commonly added to cable surface during installation but conduit with the inner surface pre-lubricated at the factory may be available. It is important to consider the compatibility of the lubricant with the cable jacket and the installation method (pull or blown) when choosing a lubricant. For more on reducing the friction and selection of lubricants, see:
- PE Handbook of PE Pipe – Chapter 14 on Duct and Conduit – Section 10.5.2 - link
Why can't we get 4-inch Schedule 40 on a reel?
Theoretically, 4-inch schedule 40 conduit can be placed on a reel. However, it is not recommended. As the conduit is extruded, it is wound on a reel. As it is wound, the top of the conduit is in tension, while the bottom is in compression. This causes the conduit to ovalize. It is much more apparent in the larger diameters. ASTM F2160 acknowledges the effect and allows for it in the specification. As 4-inch Schedule 40 has a relatively thin wall, it (and Schedule 40 diameters above 4-inch) can have a tendency to buckle. That is why 4-inch Schedule 40 on a reel is not recommended. Those diameters are typically available in stick form. Heavier walls, such as SDR 13.5, can be put on reels. Six inch (6-inch) diameter conduit is typically the maximum diameter that is coilable. For more information on ovality and coil-set, causes and methods for mitigations, see:
- TN-61 Coilable HDPE Conduit Ovality and Coil-Set – link
- TN-58 HDPE Conduit and Duct Handling Guide – link
Conduit Materials
What is HDPE?
HDPE is the abbreviation for High Density Polyethylene, the preferred and most commonly used material to make conduit. HDPE is a polymer comprised primarily of ethylene and is different from polyvinyl chloride (PVC), polyethylene terephthalate (PET) and polypropylene (PP) plastics. HDPE is strong, tough, durable, flexible in all weather, and never gets brittle. These characteristics make it the ideal choice for conduit products. You may already be familiar with HDPE as it is successfully used in milk jugs and other consumer packaging products. In the case of conduit, a very specific durable grade of HDPE is selected to ensure appropriate long term performance in the application. For more information:
- PE Handbook of PE Pipe – Chapter 14 on Duct and Conduit – Section 7 – link – provides additional explanation about the material properties required for conduit.
What does the cell classification of HDPE mean?
The cell classification is a method of identifying and specifying the raw material properties of HDPE Conduit. It is a series of six numbers and one letter which describe the properties of the resin per ASTM D3350. The numbers, in order, represent the density, melt index, flexural modulus, tensile strength, slow crack growth, hydrostatic design basis, and the letter represents whether the material is black or colored. It is used in the industry standards to specify the minimum properties of acceptable materials to be used in the fabrication of conduit. As the cell classification is specified within these standards, it is typically not required to specify the cell classification of the material if you are already specifying conduit that conforms to any of the ASTM, NEMA, UL or CSA conduit standards. For more information:
- PE Handbook of PE Pipe – Chapter 14 on Duct and Conduit – Section 7 – link– provides additional explanation about the material properties required for conduit.
- TN-50 Guide to Specifying Conduit – link
- MS-5 Model Specification for HDPE Solid Wall – link
What is black or colored “masterbatch” concentrate?
In the manufacturing process for conduit, called extrusion, unpigmented polyethylene pellets are mixed with a small proportion of black or colored pellets. These black or colored pellets are also made of polyethylene but have had a high concentration of carbon black or colored pigments, and sometimes other additives, incorporated. These pellets are termed a “concentrate” or “masterbatch”. The extrusion process is specifically designed to melt and mix all the unpigmented and masterbatch pellets together distributing the black or color evenly throughout the entire material. Carbon black, color pigments and other additives are specifically selected to enhance the properties of the final product, such as outdoor weathering resistance.
Can I use conduit made with PE4710 material?
The standard HDPE resin used in the manufacture of conduit, and as specified in conduit standards, provides the ideal combination of strength and flexibility for most applications. Occasionally, a higher strength conduit may be desirable due to high anticipated installation or frictional forces, e.g., long difficult HDD run; in such cases, a heavier wall conduit may be selected or, alternatively, a higher strength material may be selected, such as a PE 4710 pressure pipe grade with approximately 15% greater tensile strength. The PE 4710 product will likely be stiffer and more expensive than standard industry conduit. Not all manufacturer’s supply PE 4710 based conduit and UL or CSA certified products may not be available. PE 4710 based pressure pipe may not conform to the conduit standards unless all specified conduit tests have been conducted and the printline includes the conduit standard reference.
PPI has a number of resources explaining the materials used in conduit, how to estimate the safe pulling strength of conduit and calculating the appropriate wall thickness for your installation:
- PE Handbook of PE Pipe – Chapter 14 on Duct and Conduit – Section 7.1.1 - link – provides additional explanation about the material properties required for conduit.
- TN-63 Safe Pull Strength Calculations for Conduit – link
- TN-48 Guidelines for Choosing Wall Thickness for HDPE Conduit Based on "Mini-HDD" (Horizontal Directional Drilling) – link
- PPI Conduit Design Calculator for mini-HDD applications – www.conduitcalc.com
- PPI eLearn™ Conduit Design Calculator – Short Course – link
What is regrind vs. recycle HDPE?
The use of regrind HDPE is permitted in most conduit standards (e.g. ASTM, UL, NEMA, CSA). As defined by ASTM D5033, regrind is "product... that has been reclaimed by shredding and granulating for in-house use." There are various sources of regrind from the manufacturing process. In all cases regrind is made from materials that are under the control of the conduit manufacturer and they are fully aware of the material composition of the regrind. Typically, regrind is used in combination with virgin resin anywhere from a 10 - 40% ratio. The use of regrind eliminates waste in the production process, avoiding material going to landfill unnecessarily, thus reducing the carbon footprint of the product.
Recycled HDPE are HDPE materials sourced from outside a manufacturer’s plant. This can be post-consumer, post-commercial or post-industrial material. The PPI Power & Communications division is developing requirements to ensure conduit made with recycled HDPE has the required durable, long-term performance needed for the application.
Codes, Standards & Certification
What standards exist for Conduit and where can I find them?
A number of standards bodies develop standards for conduit. Different standards may be intended for different end-uses and applications. Always read the scope of the standard to learn about its intended end-use. Standards are issued by:
- ASTM International (e.g., ASTM F2160, D3485)
- Underwriters Laboratories (UL & ULC) (e.g., UL651A, UL 1990)
- NEMA (e.g., TC7, TCB-4, TCB-3)
- Canadian Standards Association (CSA) (e.g., CSA C22.2 No. 327)
- American Association of State Highway and Transportation Officials (e.g., AASHTO R-63)
PPI provides several publications that may be helpful:
- PE Handbook of PE Pipe – Chapter 14 on Duct and Conduit – Section 3 - link
- TN-50 Guide to Specifying Conduit – link
- MS-5 Model Specification for HDPE Solid Wall – link
What does ASTM stand for?
ASTM was the American Society for Testing and Materials but has been renamed ASTM International to communicate the international scope and acceptance of its standards. It is an association of manufacturers, engineers, consultants and governmental officials who write standards for materials and products used in all types of construction, including conduit. ASTM Standards for conduit are ASTM F2160 and D3485.
ASTM F2160 vs. D3035, D2239 or D2447?
ASTM F2160 and D3485 are ASTM standards specifically written for conduit products. ASTM D3035, ASTM D2447, ASTM F714 and ASTM D2239 are ASTM water pipe specifications often referred to in conduit specifications. Dimensionally pipes conforming to ASTM F2160 and the various water pipe ASTM standards are the same, but the material specification for water pipes include pressure strength requirements and may not have been tested to all the standard conduit requirements. Using water pipe ASTM standards for conduit applications can raise the price significantly because pressure rated resin is more expensive than conduit non-pressure rated resins.
- See the PPI TN-50 Guide to Specifying Conduit – link - explains the differences in specifications and provides a Flow Chart to choose the proper specification for power or broadband conduit.
- MS-5 Model Specification for HDPE Solid Wall – link
What is UL or CSA Certification?
UL or CSA certified products are products that have been certified by a third party, in this case Underwriters Laboratories or Canadian Standards Association, to conform to a standard. Typically, it requires the manufacturer’s production facilities to be audited on a regular basis by the certifying agency and that samples from those facilities are tested periodically by the certifying agency to ensure conformance with the specified standards. UL or CSA certification may be required by certain customers or by code requirements in the power industry. In many applications third-party certification is not required as it adds cost. Not all products may be available with third party certification so check with the conduit manufacturer. Note that ASTM and NEMA do not provide certification services: In most cases, conduit manufacturers will attest to the fact that their products conform to one or more industry standards.
What is the difference between UL certified resin and ASTM F2160 resin?
Not much in reality. Resins can have either or both classifications. Both are quality resins and meet the same requirements; however, UL will independently test and certify the resin. A manufacturer is required to use a UL certified resin for UL certified product. Blending or mixing is not allowed by UL standards.
Why can't I get SDR 11, UL listed conduit?
SDR11 is not a wall thickness dimension ratio listed and therefore not allowed within the UL listing. UL, Underwriters Laboratories, has strict guidelines that require conduit manufacturers to manufacture exactly according to the UL specifications. UL 651A, Continuous Length HDPE Conduit, and UL 1990, Nonmetallic Underground Conduit with Conductors, have four categories of conduit wall thickness: EPEC A, EPEC B, Schedule 40 and Schedule 80. ASTM D3485, ASTM D2160 and NEMA TC7 include SDR11 conduit.
When HDPE conduit is used in directional drilling, a heavier walled conduit may be required. In 1¼-inch diameter through 3-inch diameter, a schedule 80 conduit will match up very closely to SDR 11 wall thickness and provide the extra pull strength required. Relevant PPI publications to assist in selecting wall thickness where the pulling forces may be of concern include:
- TN-63 Safe Pull Strength Calculations for Conduit – link
- TN-48 Guidelines for Choosing Wall Thickness for HDPE Conduit Based on "Mini-HDD" (Horizontal Directional Drilling) – link
- PPI Conduit Design Calculator for mini-HDD applications – www.conduitcalc.com
- PPI eLearn™ Conduit Design Calculator – Short Course – link
What are the NEC requirements for HDPE Conduit?
The US National Electric Code (NFPA 70) is the code regulating HDPE conduit use in power applications. Section 353 (2014 edition) specifies that conduit and fittings shall be listed and indicates conditions under which it can be used. Generally, conduit must be buried or encased and cannot be used in applications with an ambient temperature greater than 50 °C (122 °F). The cable fill limits are defined. Conductors or cables rated at a temperature higher than
The listed temperature rating of HDPE conduit are permitted to be installed in HDPE conduit, provided the conductors or cables are not operated at a temperature higher than the listed temperature rating of the HDPE conduit. For more information see:
- National Electrical Code NFPA 70 - link
- PPI Statement AC - Operating 90 °C and 105 °C Rated Cables with HDPE Conduit - link
Can 90C and 105C rated cables be used with HDPE Conduit?
Yes, the NEC (NFPA 7) permits the use of 90C and 105C rated conduit under specific conditions, provided the conductors or cables are not operated at a temperature higher than the listed temperature rating of the HDPE conduit. For more information see:
- PPI Statement AC - Operating 90 °C and 105 °C Rated Cables with HDPE Conduit - link