In the land of electricity (NEC) there are many acronyms. Knowing what they stand for many times will dictate what is right or wrong with an installation.

I will be the first to admit this is a tough one to learn in all cases, but in conductors once you start getting a feel for it you can figure it out pretty quickly.

                                                 (SER top, SEU bottom)

I am going to start with two common above ground service entrance cable assemblies, SEU and SER.

The “SE” in both of these stands for “Service Entrance”. That is the cable that brings the power from the POCO (Power company) to you at your home.

Now, what does the “U” and “R” stand for? There is a bit of uncertainty on this, sometimes the exact meaning of these type of  designation can be lost,  but the consensus is the "U" stands for unarmored and the "R" stands for round.

Here lies knowing the difference.

SEU cable can only be used up to the the service disconnect (as a service entrance conductors). There is no grounding conductor (Ground) only a grounded conductor (Neutral). At the service disconnect this where the normal bonding of the grounding conductor and grounded conductor happens. After that point (at the service disconnect) SEU cannot be used since it has no grounding conductor (ground) and the neutral and ground are now to be forever apart (kind of sounds like a love lost).

Here is a good diagram showing their usage-

Here is a cable description from Southwire-

“CONSTRUCTION

Southwire Type SE cable is constructed with AlumaFlex AA-8000 series aluminum alloy, compact stranded conductors. The conductors are covered with a sunlight resistant Type XHHW-2 or Type THHN/THWN-2 insulation. A reinforcement tape is wrapped around the conductors for added strength and conformity. A gray sunlight resistant polyvinyl chloride (PVC) outer jacket covers the entire assembly.

Style SEU cable has two phase conductors surrounded by a concentric neutral while the SER style has two, three or four phase conductors and a bare neutral.”

http://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheet273

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