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  1. #1
    Join Date
    Oct 2009
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    5

    Default When to replace old wiring?

    We recently bought a 1954 ranch house. This fall I began to pull out the old attic insulation and discovered several electrical wiring issues. The house has a mix of older wiring with a metallic jacket, newer NM wiring, and wiring run in conduit or BX. The wiring with the metallic jacket appears to be original to the house and is the source of my concerns.

    I found several instances where the metallic jacket on the older wiring appears to be damaged. I also found a few instances where the older wiring was laying over the newer NM wiring, and the NM wiring has been discolored. I can't tell if the discoloration is staining from the old jacket or actually burn marks from the wiring. I've included pictures to help illustrate. Do I need to replace all of this older wiring? If I don't, am I risking an electrical fire or simply just losing current through the poor jacketing.

    If I need to replace the wiring, how is this done without tearing apart the house? I assume all the wiring is tacked to the studs as it drops down the wall cavities. Can I simply replace the wiring in the attic to the point where it drops down the wall and then splice in a j-box? This eliminates half the problem but creates additional wire splices. Or is it possible to fish the wiring to each termination point?

    Our home inspector walked the attic and didn't mention any concerns with the older wiring, so I assumed it was safe. Any input or advice is appreciated. Thanks.
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  2. #2
    Join Date
    Feb 2009
    Posts
    693

    Default Re: When to replace old wiring?

    A couple thoughts.

    I doubt you will see any failure over the length of the cable assemblies or the conductors installed in conduit. In 30 plus years I have never seen that type of failure unless the conductors had way to much load on them with improperly sized OCPD’s (Breakers or fuses.)

    Where failure happens in most situations is at termination points and where lighting fixtures have been installed using improperly sized lamps frying the wire insulation or where terminals are loose at splices or connection points.

    I doubt that is a burn on the newer romex. Looks more to me like an insulation scrub-off from the older original wiring.

    I doubt any current is “leaking’ out of the older conductors.

  3. #3
    Join Date
    Oct 2009
    Posts
    5

    Default Re: When to replace old wiring?

    Thanks for the feedback NEC.

    It sounds like all I need to do is check all the electrical connections throughout the attic and secure anything loose. I may try to relocate a few j-boxes higher, so when I spray the new insulation over the attic floor, they'll be easier to find/access.

  4. #4
    Join Date
    Jun 2007
    Location
    Shamokin, Pa.
    Posts
    645

    Default Re: When to replace old wiring?

    Quote Originally Posted by NEC View Post
    A couple thoughts.

    I doubt you will see any failure over the length of the cable assemblies or the conductors installed in conduit. In 30 plus years I have never seen that type of failure unless the conductors had way to much load on them with improperly sized OCPD’s (Breakers or fuses.)

    Where failure happens in most situations is at termination points and where lighting fixtures have been installed using improperly sized lamps frying the wire insulation or where terminals are loose at splices or connection points.

    I doubt that is a burn on the newer romex. Looks more to me like an insulation scrub-off from the older original wiring.

    I doubt any current is “leaking’ out of the older conductors.
    I would agree with that
    SPAM on the board everywhere else, guess the mods are off today

  5. #5
    Join Date
    Feb 2009
    Posts
    693

    Default Re: When to replace old wiring?

    Quote Originally Posted by Ernie_Fergler View Post
    SPAM on the board everywhere else, guess the mods are off today
    Off today? They have been off since the new forum started.

    I do not get it. I admin a much smaller forum than this but me and one other guy hand approve new members and together view every post that comes through. It is not that hard and takes only a few minutes each day...... We have no spam.

    Brian, sounds to me like you have a sound plan.

  6. #6
    Join Date
    Sep 2009
    Location
    jersey
    Posts
    174

    Default Re: When to replace old wiring?

    You said a few things that leave me some concern
    Quote Originally Posted by brian_75 View Post
    We recently bought a 1954 ranch house. This fall I began to pull out the old attic insulation and discovered several electrical wiring issues. The house has a mix of older wiring with a metallic jacket, newer NM wiring, and wiring run in conduit or BX. I'll start here BX IS a problem and should be thoroughly investigated. Look for a seperate equipment ground within the jacket if it doesnt have one I would remove it or atleast re run it and and abandon it. DO NOT RELY ON THE JACKET AS AN EQUIPMENT GROUND I have seen with my very own beady little eyes bx that has broken or come "unwound" when it carries a fault current it heats up cherry red like an element in a stove. IMO bx can be far worse then knob and tube. The wiring with the metallic jacket appears to be original to the house and is the source of my concerns.I would be less concerned here but it wouldn't cost much to have a pro come out and put a megohm tester on it and know for sure, that wayif you do have individual branch circuits that are questionable you can replace just that branch circuit.

    I found several instances where the metallic jacket on the older wiring appears to be damaged. I also found a few instances where the older wiring was laying over the newer NM wiring, and the NM wiring has been discolored. I can't tell if the discoloration is staining from the old jacket or actually burn marks from the wiring. My guess is discoloration but look at the environment are the black marks next to a staple? Is the insulation worn through to the conductors? I've included pictures to help illustrate. Do I need to replace all of this older wiring? Once again the best way to tell is an isulation test with a meggarIf I don't, am I risking an electrical fire or simply just losing current through the poor jacketing.

    If I need to replace the wiring, how is this done without tearing apart the house? Pure skillI assume all the wiring is tacked to the studs as it drops down the wall cavities. Can I simply replace the wiring in the attic to the point where it drops down the wall and then splice in a j-box? By replacing only whats exposed your taking a out of site out of mind approach, I'll refer back to the meggar If your in doubt at all test everything replace what is questionable or at least manage the risk by limiting load and using arc fault on questionable circuits untill you can replace it This eliminates half the problem but creates additional wire splices. Or is it possible to fish the wiring to each termination point? I can, usually without destroying a house to bad but I have done one or two

    Our home inspector walked the attic and didn't mention any concerns with the older wiring, so I assumed it was safe. Most home inspectors are home inspectors because they were fired from the big box stores (most not all) The requirements for being a home inspector in most states are minimum at best Any input or advice is appreciated. Thanks.
    I'm not one of those guys that tells everyone to call a pro but in this case someone that knows how to really use a meggar could save you a bunch of money and show you exactly what does and doesnt need to be replaced.
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