SER vs. SEU: The Pitfalls and Secrets of Service Entrance Cables
What Is a Service Entrance Cable?
Service Entrance (SE) cables are electrical cables that bring power from electrical companies to residential buildings and our homes. The National Electric Code (NEC) indicates that service entrance cables are essentially used for services. SER and SEU are two common types of SE cables. These electrical cables are rated 600 volts and are suitable for both dry and moist applications. Both SER and SEU are flame-retardant and resistant to moisture. Both cables may have RHW, RHW-2, XHHW, XHHW-2, or THWN or THWN-2 conductors, depending on the particular product.
One noticeable issue that the customer wishing to purchase SER or SEU always stumbles upon is confusion about what those two abbreviations mean due to misinformation online. Luckily, distinguishing between the two types is relatively easy once you let go of all misinformation. So, let us settle the confusion once and for all.
Basically, SER is a round service electrical cable that typically has up to four conductors and a bare neutral. The cable is designed to use above the ground in feeder panels and branch circuits.
SEU is an unarmored Style U flat service electrical cable with two-phase conductors and a concentric neutral. SEU typically has an oval shape because of the stranded neutral conductors that wrap around the cable to create an oval shape. Like SER, The cable is mostly used as a panel feeder in multi-family residential buildings and branch circuits.
Important! SEU cable is sometimes called an underground service cable online, which is not true. Neither SEU nor SER is rated for use underground. The only similar cable that is suitable for the underground is USE.
Different Purposes of SER and SEU
So, both cables are used in feeder cables and branch circuits. Then, what is the real difference between their applications?
Despite their similarities, SER and SEU have different anatomy that determines that they should be used during different steps of your electrical project. SEU cable has a neutral conductor, but does not have a ground conductor. Since neutral conductors and ground conductors are connected at the point of service disconnect, SEU cables can only be used up to the service disconnect to avoid significant safety concerns. Meanwhile, SER cables are equipped with neutral and ground conductors, which makes them perfect for use after the service disconnect. The National Electrical Code requires neutral and ground wires to be separated when feeding a panel, so using service ground cables in the way indicated above is crucial to meet NEC's requirements.
The Installation of Service Entrance Cables: Things You Need To Know
It is generally required for a service cable to be installed by a professional. However, if you would like to know more about the installation, you should keep in mind a couple of things. The bare neutral conductor of a SER cable has to be fastened both at the end of the utility pole and the service pole. You can use the combination of an insulator and an archer bolt to attach it efficiently. As a result of this manipulation, the neutral cable and two hot conductors are left for splicing. The ends of the neutral conductor and the two hot conductors are then connected to the service entrance cable, which is pulled through a protective metal hood called "the waterhead." In the installation process, one should allow a 36-inches drip loop that prevents the water from entering. Please remember that the lack of a drip loop may result in corrosion or a short circuit.
