What is the difference between SER and SEU cable?

SER cable has a separate equipment grounding conductor making it a four-wire cable, while SEU has only two hots and a neutral without a separate ground. SER is needed for subpanel feeders that require an isolated ground.

Can SER cable be buried underground?

Standard SER cable is not rated for direct burial. Underground service lateral cable or conduit with individual conductors is used for underground runs.

What size SER cable do I need for a 200-amp panel?

A common choice is 4/0-4/0-2/0 aluminum SER cable for a 200-amp residential service, but local code and conductor temperature ratings should be confirmed with the authority having jurisdiction.

Does SER cable require conduit?

SER cable can be installed without conduit in many applications because its outer jacket provides mechanical protection. Some jurisdictions or specific installation conditions may still require conduit.

How long does SER cable last before it needs replacement?

SER cable can last decades when properly installed, but exposure to sunlight, physical damage, rodent activity, or moisture can shorten its lifespan and require earlier replacement.

SER Cable — Service Entrance Wiring and Replacement

An SER cable is a service entrance rated cable with two insulated hot conductors, a bare neutral, and a bare equipment grounding conductor bundled inside an overall outer jacket, used for panel feeder runs and service entrance wiring.

SER Cable diagram — labeled parts and installation context

What It Is

SER stands for Service Entrance Rated cable, and it is a type of aluminum or copper multi-conductor cable designed for carrying power between the meter base, main panel, or subpanel. It contains two insulated hot conductors, a bare concentric neutral wrapped around the assembly, and a bare equipment grounding conductor, all bundled inside a flame-retardant thermoplastic jacket rated for 600 volts per NEC Article 338.

Unlike standard NM cable used inside walls, SER cable is rated for exposed runs, direct connection to service equipment, and higher amperage loads. The four-conductor configuration makes SER cable the standard choice for subpanel feeders, where NEC Article 250.32 requires a separate equipment grounding conductor that is isolated from the neutral at the subpanel. The outer jacket is sunlight-resistant on most brands, allowing limited exterior exposure between the meter and the panel penetration point.

Types

Common aluminum configurations include 4/0-4/0-2/0 for 200-amp residential services, 2-2-4 for 100-amp feeder circuits, and 1/0-1/0-2 for 150-amp services. Copper SER cable is available for shorter, high-capacity runs where aluminum termination compatibility is a concern, though copper cable costs significantly more per foot and is heavier to work with.

Three-wire SER cable (two hots and a neutral without a separate ground) is designated SEU and is used only for service entrance runs where the neutral serves as the grounding path. Four-wire SER cable is standard for all subpanel feeders installed under current NEC rules. The conductors are typically XHHW-2 rated for wet and dry locations, and the jacket is marked with the cable type, conductor sizes, voltage rating, and UL listing information.

Where It Is Used

SER cable is used between the meter socket and main panel, between main panels and subpanels, and for large appliance feeders in some installations. It is the most common cable type for residential service upgrades from 100 to 200 amps and for feeding detached garage or workshop subpanels. In a typical residential garage subpanel installation, 2-2-4 aluminum SER cable feeds a 100-amp subpanel over a run of 30 to 50 feet.

SER cable is not rated for direct burial, so underground runs between buildings require either USE-rated cable or individual THWN conductors pulled through PVC or rigid conduit. Where SER cable must transition from an exterior meter to an interior panel, it typically enters the building through a weatherproof hub fitting and runs along the interior wall surface, secured with cable straps at intervals not exceeding 4-1/2 feet per NEC requirements.

How to Identify One

Look for a flat or oval gray or black multi-conductor cable with visible conductor markings printed on the outer jacket. The jacket text typically reads something like "2-2-4 AL SER 600V UL" followed by the manufacturer name. The cable has a distinctive flat profile because the conductors are arranged side by side rather than in a round bundle.

When the jacket is stripped, the two insulated hot conductors are black, the neutral is a bare concentric wrap of aluminum strands surrounding the assembly, and the equipment ground is a smaller bare conductor running alongside the hots. The concentric neutral wrap is the most recognizable feature of SE-type cables.

Replacement

Replacement is needed when the jacket is cracked or split, conductors show heat discoloration at terminations, insulation has deteriorated from age or rodent damage, or the cable no longer meets the ampacity requirements of a service upgrade. Signs of overheating include melted insulation, a burned smell at the panel, and discolored lug connections.

A permit is typically required for SER cable replacement work because it involves the service entrance or feeder circuits. The utility company may need to pull the meter during the work. When upgrading from 100-amp to 200-amp service, the SER cable, meter socket, and main breaker panel are usually replaced together as a coordinated upgrade.