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Thread: Older 1/0 AWG RHW conductor ampacity

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    Older 1/0 AWG RHW conductor ampacity

    Greetings all.
    I am researching a 1/0 RHW conductor probably from the mid 60's.
    I cant make out all the printing on it.
    What I could read was " 1/0 Anaconda RHW 75C"
    Does anyone know if this had a dual rating such as RHH at that time?
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    I doubt that it's also rated RHH. I've seen plenty of RHW in old panels but I have never seen RHH or a dual rate RHW/RHH. What's the application?
    Rob

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    All responses based on the 2014 NEC unless otherwise noted

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    I'd say based on SKM's models for cable that it's 120 amps if aluminum and 150 amps if copper.

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    Thanks all, its a type of wire that was commonly used around here years ago for services, its tinned copper.
    This one in particular is a service entrance conductor coming from a meterbase on the right.
    And I am starting to see this more often and wondering if I am missing something?
    The small piece of buss between the lug and the breaker shows signs of overheating. The panel was recently replaced when the house was added on to. The electrician that replaced the panel did not want to mess with the meter and existing weatherhead as it is 1-1/2 conduit and recessed and just reused the existing service conductors.
    The work was done by a local company that has a good reputation and passed an inspection by a good inspector.

    My opinion is code requires a 175A breaker, that is if they really want to keep that wire as the residential service entrance.


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    Only thing a rating of RHH would have helped with is ampacity adjustments/correction factors, terminal temp rating was still going to be 75C.

    Or 310.15(B)(6) or whatever it was back then would have allowed you to protect at 175 where it applies.
    I live for today, I'm just a day behind.

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    Quote Originally Posted by kwired View Post
    Only thing a rating of RHH would have helped with is ampacity adjustments/correction factors, terminal temp rating was still going to be 75C.

    Or 310.15(B)(6) or whatever it was back then would have allowed you to protect at 175 where it applies.
    Yeah the old resi panels around here from the 60's and 70's era commonly were of the 'split buss' type with main lugs at the top feeding 6 mains with one main feeding a sub within the panel.
    The stickers on these do say '200Amps' and electricians think they are doing a 200A panel change, and somehow exempt from code because the wire is 'existing'.
    Comments based on 2017 NEC unless otherwise noted.

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    Quote Originally Posted by tortuga View Post
    Yeah the old resi panels around here from the 60's and 70's era commonly were of the 'split buss' type with main lugs at the top feeding 6 mains with one main feeding a sub within the panel.
    The stickers on these do say '200Amps' and electricians think they are doing a 200A panel change, and somehow exempt from code because the wire is 'existing'.
    I can see how many would think that.
    I live for today, I'm just a day behind.

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    Quote Originally Posted by tortuga View Post

    My opinion is code requires a 175A breaker, that is if they really want to keep that wire as the residential service entrance.


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    I agree, smaller CB or change the conductors.
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

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