I'm trying to determine the temperature rating of my service entry cable, so I can then determine its ampacity.

It is marked:


So I'm assuming its type is either UD or XLP. However neither of these are listed in the CA Electrical Code section 310.104: https://up.codes/viewer/california/ca-electric-code-2019/chapter/3/wiring-methods-and-materials#310.104

Is there an equivalent type that can be used for determining its temperature rating? If not, how should the temperature rating be determined?

Background [Updated]: This is an underground service entry to the main panel for a 1000 sqft house. The main breaker in panel is 100 amp. I'm trying to figure out whether I can either upgrade the panel or upgrade the main breaker in the panel without replacing the service entry. My understanding is that I need to start by determining the ampactiy of the cable, which starts with its temperature rating. But if there's a different way to answer the ampacity question I'm all ears. I do know about the '83 percent' rule, and may make use of it.

  • It may help to further explain why you need to determine its ampacity. There may be a different/better approach to achieving what you're after than the one you've chosen. Even if not, it's nice to have confirmation you're on the right track.
    – FreeMan
    Aug 31, 2022 at 12:30
  • @FreeMan good idea, thanks, added.
    – tom
    Aug 31, 2022 at 19:36

2 Answers 2


This question will probably need to be posed to your power company. As stated in the Robert Chapin's answer, type UD is Underground Distribution cable. CONALCO-S is mostly likely the brand/trade name. XLP refers to the insulation type, and the rest of the numbering indicates it's rated for 600V or less, cable size is 1/0, type is Aluminum. 1974 is most likely a footage marker.

See this PDF for the specs of a similar product: Ruggedized USE-2 and UD Cable

Unfortunately, the question of ampacity will go to your PoCo as they are responsible for the standards and practices on their side of the meter. NEC/CEC doesn't apply to them - they use their own set of codes - so that's why you don't see that cable type in your electrical code.

  • 1/0 Al is plenty large enough for a 100A service, even under NEC ampacity rules (heck, it's large enough to carry 100A at 60degC, which isn't a condition you need to worry about) Sep 1, 2022 at 1:38

XLP or XLPE is cross-linked polyethylene insulation. Also "X" as in XHH or XHHW, which can have different ratings. If this cable is from 1974 it might require more research.

UD is underground distribution. This is similar to Type USE cable, but I'm not sure how the ratings apply to older cables. Maybe someone else can fully answer that.

Here are some relevant links, indicating the modern approach to determining ampacity for underground cable is software driven.



Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.